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The early Triassic recovery period: exploring ecology and evolution in marine benthic communities following the Permian-Triassic mass extinction

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The early Triassic recovery period: exploring ecology and evolution in marine benthic communities following the Permian-Triassic mass extinction

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THE EARLY TRIASSIC RECOVERY PERIOD: EXPLORING ECOLOGY
AND EVOLUTION IN MARINE BENTHIC COMMUNITIES
FOLLOWING THE PERMIAN-TRIASSIC MASS EXTINCTION
by
Elizabeth Petsios

A Dissertation presented to the
Faculty of the USC Graduate School
University of Southern California
In Partial Fulfillment of the
Requirements for the Degree
Doctor of Philosophy
In Geological Sciences

August, 2016
Acknowledgements
This work has been made possible through the support of several professors, students,
and staff in the Department of Earth Sciences at the University of Southern California and the
Davidson Molecular Biology Laboratory at the California Institute of Technology. Of the many
people whom I would like to acknowledge and thank for their role in furthering my studies and
career, the first and most important is undoubtedly my advisor, Dave Bottjer. The work
contained herein would not be possible without the scientific direction, support, and
contributions from Dave. I would like to thank Dave for the countless hours spent on discussion
of my scientific work and ideas, as well as his thoughtful career and professional advice. I am
grateful to Dave for providing opportunities for involvement in many different projects during
my time here, which have allowed me to develop many different skillsets.
I would like to thank Frank Corsetti and Will Berelson, who have been valuable sources
of constructive criticism and academic instruction, both in and out of the classroom. Frank and
Will, together with the other member of my qualifying committee, Luis Chiappe and Dave
Caron, have helped shape this dissertation.
I would like to thank my fellow students for assistance in the field and in the lab.
Specifically, I would like to thank Carlie Pietsch, who has been a mentor, collaborator, field
assistant and friend. Carlie instructed me in field and laboratory methods and safety, and has
been a valuable collaborator in our Permian-Triassic projects. I would also like to thank Jeffery
Thompson, a valuable collaborator in all things echinoid. Jeff has provided hours of insightful
discussion in topics concerning statistics, quantitative methods, evolutionary biology, and
taphonomy. I would also like to acknowledge my labmates, both senior and junior, who have
i
either accompanied me into the field or have provided support and instruction throughout my
years at USC: Lydia Tackett, Kathleen Ritterbush, Rowan Martindale, Scott Mata, Yadi Ibarra,
Joyce Yager, Dylan Wilmeth, and Katya Larina.
The geochemical data collected for this work would not have been possible without the
help of Lowell Stott and Will Berelson, who made their mass spectrometers available for me.
Additionally, I would like to thank Miguel Rincon and Nick Rollins, for their assistance in
preparing and running the samples.
For the mentoring I received in the theories and methods of echinoid molecular biology
in the Davidson Lab at the California Institute of Technology, I would like to thank Eric
Erkenbrach, Feng Gao, Erika Vielmas, Jon Valencia, Andy Cameron, Ping Dong, Roberto
Feuda, Jane Rigg, and the late Eric Davidson. I would especially like to thank Eric Davidson for
taking a chance on a paleontologist with no prior knowledge of molecular biology, and giving
me the opportunity to expand my skillsets by involving me in the projects of his lab.
I would like to thank the staff of the Earth Sciences Department at USC, for helping me
with administrative tasks, teaching assignments, and grant-writing efforts: Cindy Waite, Karen
Young, Barbara Grubb and Vardui Ter-Simonian.
The funding sources that have funded my field and lab work include the USC Earth
Sciences Department, the Geological Society of America, the Society for Sedimentary Geology,
and the Paleontological Society. Additionally, the Stauffer family and the Women in Science
and Engineering Campaign have provided financial support during my graduate career through
fellowship and summer support.
ii
Finally, I would like to thank my family for the financial, technical, and emotional
support they have provided during my graduate career. I would, specifically, like to thank my
fiancé John Yu, who, in addition to providing field and computer assistance, has supported my
career and academic endeavors throughout the years.

iii
Table of Contents

Acknowledgments............................................................................................................................i
Abstract...........................................................................................................................................ix
Chapter 1: Introduction to the Permian-Triassic mass extinction and the Early Triassic recovery
period: extinction causes and environmental perturbations ............................................................ 1
1 – Biotic consequences of the P-T extinction ............................................................................ 1
2 – Extinction causes and kill mechanisms ................................................................................. 2
3 – Dissertation purpose and significance ................................................................................... 4

Chapter 2: Quantitative analysis of the ecological dominance of benthic disaster taxa in the
aftermath of the end-Permian mass extinction................................................................................ 6
1 – Introduction ........................................................................................................................... 6
1.1 – End-Permian mass extinction and recovery ................................................................... 7
1.2 – Early Triassic disaster taxa ............................................................................................. 7
2 – Methods ............................................................................................................................... 11
2.1 – Quantitative recovery metrics ....................................................................................... 11
2.2 – Data sources .................................................................................................................. 12
3 – Results ................................................................................................................................. 14
4 – Discussion ........................................................................................................................... 17
5 – Conclusions ......................................................................................................................... 20
Figures and Tables .................................................................................................................... 21

Chapter 3: The effects of repeated environmental perturbations on community complexity and
faunal composition immediately after the Permian-Triassic extinction: A case study of faunal
shifts from the Induan of Panthalassa ........................................................................................... 41
1 – Introduction ......................................................................................................................... 41
1.1 – Environmental perturbations following the Permian-Triassic event ............................ 42
1.2 – Recovery dynamics in Early Triassic ........................................................................... 44
2 – Geologic setting................................................................................................................... 45
3 – Previous work on the Dinwoody Formation ....................................................................... 47
iv
4 – Methods ............................................................................................................................... 49
4.1 – Ecological sampling ..................................................................................................... 49
4.2 – Geochemical sampling ................................................................................................. 50
4.3 – Quantitative methods .................................................................................................... 51
5 – Results ................................................................................................................................. 52
5.1 – 
13
C
carb
excursions in the Dinwoody ............................................................................ 52
5.1.1 – Geochemical correlation with global excursions ............................................. 53
5.2 – Faunal composition....................................................................................................... 55
5.2.1 – Disaster taxa .................................................................................................... 55
5.2.2 – Microgastropods .............................................................................................. 57
5.2.3 – Microconchids ................................................................................................. 57
5.2.4 – Microfossils ..................................................................................................... 58
5.2.5 – Echinoids ......................................................................................................... 59
5.2.6 – Biostratigraphically informative taxa .............................................................. 60
5.2.7 – Trace fossils ..................................................................................................... 61
5.3 – Faunal shifts .................................................................................................................. 62
5.3.1 – Testing for taphonomic biases ......................................................................... 65
6 – Discussion ........................................................................................................................... 65
6.1 – Microconchida as a disaster taxon................................................................................ 65
6.2 – Chondrites occurrence in the Early Triassic ................................................................. 67
6.3 – Failed recovery attempt ................................................................................................ 69
7 – Conclusions ......................................................................................................................... 71
Figures and Tables .................................................................................................................... 73

Chapter 4: Tethyan ecological response to changing oxygen, temperature, and bathymetry after
the Permian Triassic crisis: Exploring the paleoecology of the Griesbachian to Smithian Werfen
Formation .................................................................................................................................... 107
1 – Introduction ....................................................................................................................... 107
2 – Werfen Formation geologic setting ................................................................................... 109
3 – Previous work on the paleoecology of the Werfen Formation.......................................... 114
4 – Methods ............................................................................................................................. 116
v
4.1 – Sample collection ....................................................................................................... 116
4.2 – The Uomo locality ...................................................................................................... 118
4.3 – The Bulla locality ....................................................................................................... 118
5 – Results ............................................................................................................................... 119
5.1 – Uomo facies and ecology ........................................................................................... 119
5.2 – Bulla facies and ecology ............................................................................................. 121
5.3 – 
13
C
carb
geochemistry and correlation ......................................................................... 122
5.4 – Faunal composition..................................................................................................... 124
5.4.1 – Community metrics ....................................................................................... 126
5.4.2 – Disaster taxa .................................................................................................. 127
5.5 – Ecological and geochemical correlations ................................................................... 128
6 – Discussion ......................................................................................................................... 129
6.1 – Upper Suisi Member failed recovery .......................................................................... 129
6.2 – Disaster taxa in the Werfen Formation ....................................................................... 132
6.3 – Cohesive fauna and phase shifts ................................................................................. 134
7 – Conclusions ....................................................................................................................... 135
Figures and Tables .................................................................................................................. 137

Chapter 5: Evolution and survivorship of crown group echinoids across the Permian-Triassic
biotic crisis .................................................................................................................................. 175
1 – Introduction to echinoid evolution .................................................................................... 175
1.1 – Cidaroid and euechinoid morphologies....................................................................... 177
2 – Permian and Triassic echinoids ......................................................................................... 181
2.1 – Eotiaris guadalupensis ............................................................................................... 182
2.2 – Eotiaris connorsi ........................................................................................................ 183
2.3 – Eotiaris keyserlingi ..................................................................................................... 184
2.4 – Other Middle and Late Permian echinoids ................................................................. 184
2.5 – Miocidaris pakistanensis ............................................................................................ 185
2.6 – Lenticidaris utahensis ................................................................................................. 186
2.7 – Miocidaris sp. from the Tesero Member .................................................................... 186
2.8 – Triadotiarid from the Dinwoody Formation ............................................................... 187
vi
2.9 – Early Triassic disarticulated occurrences ................................................................... 188
2.10 – Earliest euechinoid ................................................................................................... 190
3 – Methods ............................................................................................................................. 190
3.1 –Echinoid occurrences, diversity, rock record, and environmental distribution ........... 190
3.2 – Phylogenetic analysis ................................................................................................. 192
3.2.1 – Characters and character states ...................................................................... 194
4 – Results ............................................................................................................................... 195
4.1 – Phylogenetic analysis ................................................................................................. 195
4.2 – Environmental distribution ......................................................................................... 198
4.3 – Diversity and rock record biases ................................................................................ 201
5 – Discussion ......................................................................................................................... 203
5.1 – Permian-Triassic extinction survivors ........................................................................ 203
5.2 – Record bias and missing echinoids ............................................................................. 205
6 – Conclusions ....................................................................................................................... 207
Figures and Tables .................................................................................................................. 209

Chapter 6: Conclusions ............................................................................................................... 237
1 – Global mechanisms acting on local communities ............................................................. 237
2 – The importance of bathymetric stability to community sensitivity................................... 239
3 – Timing of global versus local recovery ............................................................................. 240
4 – Underestimating survivorship in poorly represented groups ............................................ 241
5 – Future studies .................................................................................................................... 242

References ................................................................................................................................... 243

Appendix: Locality information ................................................................................................. 270
Appendix Table 1 – Blacktail Creek ecology data ...................................................................... 271
Appendix Table 2 – Blacktail Creek ecology data ...................................................................... 272
Appendix Table 3 – Blacktail Creek carbon isotope data ........................................................... 273
Appendix Table 4 – Bulla ecology data... ................................................................................... 274
Appendix Table 5 – Bulla ecology data ...................................................................................... 275
vii
Appendix Table 6 – Bulla carbon isotope data............................................................................ 276
Appendix Table 7 – Uomo ecology data ..................................................................................... 277
Appendix Table 8 – Uomo ecology data ..................................................................................... 278
Appendix Table 9 – Uomo carbon isotope data .......................................................................... 279
Appendix Table 10 – List of echinoid specimens used for phylogenetic analysis ...................... 280
viii
Abstract
The Permian-Triassic mass extinction was the largest extinction of the Phanerozoic, and
led to significant taxonomic loss and ecological restructuring in both marine and terrestrial
ecosystems. Severe greenhouse gas induced climate change, sourced from extensive volcanic
outgassing during the emplacement of the Siberian Traps, is implicated as the source of the
various harmful environmental conditions that led to the extinction. Evidence from lithologic and
geochemical proxies suggests that episodes of thermal spikes in sea surface temperatures and
anoxia in the shallow shelf were conditions that were reoccurring in the marine realm during
both the initial extinction and subsequent Early Triassic interval. Recovery of marine
communities following the extinction was thought to be protracted due to the severity of
taxonomic loss, lasting the entirety of the Early Triassic. However, recent studies have shown
that progress of recovery in the Early Triassic is highly complex, differing between regions,
depositional environments, and community types. The importance of biotic (such as recruitment,
interspecies competition, and physiology) and abiotic (such as occurrence of anoxia, heat stress,
hypercapnia and acification) factors in the differential recovery following the extinction is not
well understood. Additionally, the manifestation of recovery progress is not well understood at
different geographic levels (global vs. local) using quantitative measures of recovery that reflect
community complexity. The aim of this body of work is to explore survival and recovery in the
marine realm in the Early Triassic following the Permian-Triassic mass extinction, through
quantitative analysis of the complexity of marine benthic communities. Two local-scale studies
of changes in community complexity associated with geochemical proxies of carbon cycle
perturbations are presented, one from a Panthalassic section, and one from two Tethyan sections.
Shallow-shelf benthic communities from the Panthalassic section show a trend of recovery
ix
relatively early in the Early Triassic, which subsequently fails in association with a large
negative carbon isotope excursion. A spike in sea surface temperatures, associated with a
recurrence of volcanic outgassing, is implicated as a shared causal mechanism between failed
recovery and carbon cycle excursions. In comparison, the two Tethyan sections show no clear
association of changes in community complexity and carbon isotope shifts, despite large positive
and negative excursions occurring within the section. The shallower setting of these sections, in
addition to frequent tectonically-induced bathymatry changes throughout, are likely masking
community sensitivity to larger global environmental conditions, such as the response to thermal
stress observed in the Panthalassic section. These studies demonstrate the importance of local-
scale conditions in producing disparate responses of communities to global-scale environmental
perturbations. An additional global scale database study of recovery of community complexity,
as reflected by decreasing ecological dominance of ‘disaster taxa’, shows a pattern of gradual
recovery throughout the Early Triassic. While studies focusing on individual sections can reveal
complexities in recovery due to local conditions, this global scale study shows an averaged and
generalized signal of recovery. These works highlight the importance of quantifying recovery at
both the local and global scale. In addition to these studies of recovery within benthic
communities, a study of extinction survival in echinoids, a poorly represented fossil group during
the Permian-Triassic, is presented herein. The evolutionary trajectory of modern echinoids has
been thought to be severely effected by a diversity bottleneck occurring at the Permian-Triassic
boundary. However, recent studies, including this study, suggest that a greater number of
lineages than previously thought survived the extinction. Phylogenetic relationships are used to
infer survival of multiple lineages into the Triassic that are poorly represented in the Permian,
due to a number of taphonomic problems. This study highlights the importance of phylogenetic
x
analyses in overcoming the limitations of a poor fossil record. The patterns of recovery and
survival following the Permian-Triassic mass extinction reveal the importance of quantitative
studies at different spatial and temporal scales, and highlight the complexity of biotic responses
to global climate crises.

xi
Chapter 1: Introduction to the Permian-Triassic mass extinction and the Early Triassic
recovery period: extinction causes and environmental perturbations

The Permian-Triassic boundary marks the transition between the Paleozoic and the
Mesozoic, as well as the largest biotic upheaval recorded in the fossil record. The severity of this
mass extinction was felt both in the marine and terrestrial realms, and led to a dramatic
restructuring of the ecosystem which ushered in the Modern Fauna (Sepkoski 1984), and modern
ecosystem structures (Bambach et al. 2002, Bush et al. 2007, Powell and Kowalewski 2002,
Wagner et al. 2006). Additionally, the recovery of ecosystems following the Permian-Triassic
mass extinction is the most delayed observed after any extinction event, at approximately 4
million years (Bottjer et al. 2008, Yin et al. 2007).
1 – Biotic consequences of the P-T extinction
The Permian-Triassic mass extinction saw the extinction of 96% of marine species (Raup
1979) and 70% of terrestrial vertebrates (Sahney and Benton 2008). Several prominent marine
Paleozoic groups become completely extinct, including blastoids, tabulate and rugose corals,
fusilinid foraminifera, fenestrate bryazoans, and trilobites (Hallam and Wignall 1997). Other
groups, such as brachiopods, crinoids, ammonoids, bivalves and gastropods experienced severe
reductions in diversity (Sepkoski 1982). In addition to causing the largest taxonomic loss of all
the ‘Big Five’ mass extinctions, the Permian-Triassic was also the most ecologically devastating
(McGhee et al. 2004). The extinction of reef building organisms ushered in a 5 million year reef
gap, save for microbial-sponge build-ups (Baud et al. 2007, Brayard et al. 2011; Griffin et al.,
2010; Pruss and Bottjer 2005), with severe selective extinction of reef-associated taxa. The
taxonomic loss of important constituents of the Paleozoic fauna, brachiopods and crinoids,
1
allowed for their eventual replacement, both ecologically and taxonomically, by members of the
Modern Fauna, such as bivalves and gastropods (Fraiser and Bottjer 2007, Gould and Calloway
1980). The Paleozoic Fauna are thought to have suffered disproportionally due to selective
extinction of taxa with poorly buffered respiratory physiology and highly calcified shells, which
include brachiopods, bryozoans, and crinoids (Clapham and Payne 2011, Knoll et al. 2007).
2 – Extinction causes and kill mechanisms
The synergistic effects of several different kill mechanisms, all thought to stem from the
eruption of the Siberian Traps, has been implicated as the cause of severe biotic and
environmental upheaval (Erwin 1993). The Siberian Traps unleashed an estimated 3-6 million
km
3
of flood basalts (Reichow et al. 2009), with an estimated release of 44,000 to 66,000 Gt of
CO
2
into the atmosphere (Saunders and Reichow 2009), thus triggering a large greenhouse
effect. Contact metamorphism of the basalts with evaporite, limestone, and coal-bearing host
rock is thought to have contributed an additional 114,000 Gt of CO
2
into the atmosphere, along
with other toxic gases such as HCl, HFl, and SO
2
(Black et al. 2012, Svensen et al. 2009). Some
evidence for the release of methane clathrates during this time has been put forth as well (Krull
et al. 2000), likely exacerbating greenhouse gas-induced warming. Geochemical evidence exists
for repeated outgassing from the Siberian Traps millions of years after the initial event,
throughout the Early Triassic (Payne and Kump 2007). This has been implicated as the cause for
continued environmental instability following the initial extinction event, leading to the
protracted recovery of Early Triassic ecosystems.
Lithologic and geochemical evidence exists for a plethora of environmental consequences
of the eruptions and resulting climate change. Evidence from 
18
O values of conodont apatite
2
shows warming in the oceans as high as 38
o
C in the surface waters at the P-T boundary (Sun et
al. 2012), which has the capacity to kill or severely inhibit metabolic function in many animal
groups (Song et al. 2014a). An additional thermal spike of 45
o
C is also observed 2 million years
later, in the Early Triassic (Galfetti et al. 2007). Ocean warming is implicated as the cause of the
Lilliput Effect observed in many groups, most famously in gastropods, following the Permian-
Triassic event (Payne 2005). Maximum body size in these taxa is severely reduced, likely to
compensate for higher metabolic requirements brought on by thermal stress.
Oceanic anoxia and euxinia are also likely significant kill mechanisms during the
extinction and subsequent recovery. Geochemical evidence from 
13
C values, pyrite framboids,
Th/U ratios, and redox sensitive trace metals suggests anoxic or euxinic events at the P-T
boundary and in the Early Triassic at several localities (Bond and Wignall 2010, Grasby et al.
2013, Grice et al. 2005, Song et al. 2014b, Wignall and Hallam 1992, Wignall and Twitchett
1996). It was initially proposed that stagnation of oceanic circulation due to global warming
caused complete anoxia of the deep ocean (Hotinski et al. 2001, Isozaki 1997). More recent
studies suggest that anoxic conditions were largely restricted to an expanded oxygen minimum
zone (OMZ), which would periodically incur onto shallow shelf environments (Algeo et al.
2011, Winguth and Maier-Reimer 2005). Coupled with this was upwelling of the chemocline,
bringing with it toxic sulfidic waters onto the shallow shelf (Algeo et al. 2008, Riccardi et al.
2006). OMZ expansion is linked to an enhanced biologic pump, brought about by increased
nutrient input into the oceans causing eutrophic conditions in the surface (Algeo et al., 2011).
Several other kill mechanisms are likely also at play at the P-T boundary, though likely have
a limited role following the extinction during the Early Triassic. Hypercapnia, due to increased
pCO
2
levels, is implicated for the selective extinction of taxa with poorly buffered respiratory
3
metabolisms, as these taxa would be unable to regulate intercellular pH as efficiently as well-
buffered taxa (Knoll et al. 2007). Associated with hypercapnia, ocean acidification may have
also played a role during the initial extinction event (Hinojosa et al. 2012), but the importance of
acidification during the P-T is less clear than during the Triassic-Jurassic extinction (Greene et
al. 2012, Hautmann et al. 2008). Toxic rain, brought about by the release of toxic gasses from
volcanic outgassing, has been implicated for terrestrial vegetation collapse in the terrestrial realm
(Foster and Afonin 2005, Retallack et al. 1996).
3 – Dissertation purpose and significance
The study of the Permian-Triassic biotic crisis and its aftereffects can help elucidate the
mechanisms at play in the modern-day crisis, both biological and environmental, brought about
by anthropogenic climate change (Payne and Clapham 2012). The injection of large amounts of
CO
2
into the atmosphere during the P-T is analogous to modern day CO
2
buildup, though the rate
of CO
2
input in the modern is approximately 400 time faster (Saunders and Reichow, 2009).
Several environmental conditions observed during the Permian-Triassic event have already
begun to manifest in the oceans today, including increased sea surface temperature, acidification,
and expanded OMZ’s (Hoegh-Guldberg et al. 2007, Stramma et al. 2008). The aim of my work
on this topic is to explore the tempo and mode of biotic recovery following the extinction event,
and disentangle the relative importance of biotic and abiotic mechanisms involved in differential
recovery patterns in post-extinction marine communities from different regions of the world. I
explore the behavior of marine invertebrate community constituents as recovery progresses
throughout the Early Triassic, both at a global and regional scale. I present a global overview of
the behavior of extinction opportunists, termed the ‘disaster taxa’, in Early Triassic marine
benthic communities (Chapter 2). I present two regional case studies of how post-extinction
4
recovery dynamics correlate with geochemical proxies of environmental instability in
Panthalassic (Chapter 3) and Tethyan (Chapter 4) shallow marine shelves. Finally, I present a
reevaluation of the extinction survivorship of echinoids, a group whose evolutionary history has
thought to have been significantly affected by the mass extinction event (Chapter 5).

5
Chapter 2: Quantitative analysis of the ecological dominance of benthic disaster taxa in the
aftermath of the end-Permian mass extinction

1 – Introduction

The end-Permian mass extinction, the largest extinction of the Phanerozoic, led to a
severe reduction in both taxonomic richness and ecological complexity of marine communities,
eventually culminating in a dramatic ecological restructuring of communities. During the Early
Triassic recovery interval, disaster taxa proliferated and numerically dominated many marine
benthic invertebrate assemblages. These disaster taxa include the bivalve genera Claraia,
Unionites, Eumorphotis, and Promyalina, and the inarticulate brachiopod Lingularia. The exact
nature and extent of their dominance remains uncertain. Here, a quantitative analysis of the
dominance of these taxa within the fossil communities of Panthalassa and Tethys benthic realms
is undertaken for the stages of the Early Triassic to examine temporal and regional changes in
disaster-taxon dominance as recovery progresses. Community dominance and disaster-taxon
abundance is markedly different between Panthalassic and Tethyan communities. In Panthalassa,
community evenness is low in the Induan stage but increases significantly in the Smithian and
Spathian. This is coincident with a significant decrease in the relative abundance and occurrence
frequency of the disaster taxa, most notably of the low-oxygen-affinity taxa Claraia and
Lingularia. While the disaster taxa are present in post-Induan assemblages, other taxa, including
two articulate brachiopod genera, outrank the disaster taxa in relative abundance. In the Tethys,
assemblages are generally more even than contemporaneous Panthalassic assemblages. I observe
an averaged trend toward more even communities with fewer disaster taxa in both Panthalassic
and Tethyan assemblages over time.
6
1.1 – End-Permian mass extinction and recovery

The end-Permian mass extinction saw the extinction of 78% of marine genera (Alroy et al.
2008) and more than 95% of marine species (Raup 1979) and the ecological restructuring of
marine communities (e.g. Dineen et al. 2014, Schubert and Bottjer 1995). This restructuring
included the initiation of the eventual decline of brachiopod ecological importance in favor of
bivalve dominance in the later Mesozoic (Fraiser and Bottjer 2007, Greene et al. 2011).
Environmental instability following the initial extinction pulse led to a series of failed recovery
attempts in some benthic marine environments (Grasby et al. 2013, Pietsch and Bottjer 2014,
Song et al. 2011) throughout the 5 Myr interval. This environmental instability has been linked
to temperature fluctuation (Joachimski et al. 2012, Romano et al. 2013, Sun et al. 2012),
reoccurring instances of oxygen minimum zone expansion onto shallow-shelf settings (Algeo et
al. 2011, Song et al. 2014a), and changing marine productivity and nutrient availability (Wei et
al. 2014). Many workers have found evidence of intervals of benthic faunal recovery relatively
early after the extinction event in which oxygen or temperature conditions are more favorable
(Hofmann et al. 2011, Twitchett et al. 2004), which subsequently ended due to onset of
unfavorable conditions. Recovery of pelagic taxa appears to have progressed more rapidly than
in benthic environments, with groups such as ammonoids and conodonts experiencing rapid
booms in diversity shortly after the extinction event (Brayard et al. 2006, Orchard 2007), some of
which also experienced busts in diversity shortly afterward (Stanley 2009).
1.2 – Early Triassic disaster taxa
The disaster taxa of the Early Triassic are a group of benthic invertebrate taxa that are
observed to become dominant and widespread in the aftermath of the end-Permian mass
7
extinction. This group was first recognized by and included the four bivalve genera Claraia,
Unionites, Eumorphotis, and Promyalina (Fig. 2.1). Rodland and Bottjer (2001) later observed
the ecological dominance, in terms of numerical abundance and frequency of occurrence across
multiple differing environments, of the inarticulate brachiopod “Lingula” (herein Lingularia
sensu Posenato et al. (2014)) in Lower Triassic western U.S. fossil assemblages (Fig. 2.1C).
Lingularia was later added to the group of Early Triassic disaster taxa in Benton (2003). These
five taxa are observed in Lower Triassic marine sections worldwide (Boyer et al. 2004, Fraiser
and Bottjer 2007, Komatsu et al. 2008, Schubert and Bottjer 1995), and commonly one or many
of these taxa are the most abundant within an assemblage (e.g., assemblages collected by
Schubert and Bottjer, 1995). These five genera have been deemed disaster taxa based on the
definition put forth by Fischer and Arthur (1977), who first coined the term, to refer to an
organism that becomes more abundant and widespread in response to a biotic crisis, whereas it
was only a minor component of communities before the crisis (Harries et al. 1996) (Fig. 2.2).
Following the end of the biotic crisis recovery interval, these disaster taxa are expected to be
competitively replaced by equilibrium taxa. Numerical dominance of an organism within a
community can have large ecological implications, as the most dominant taxa tend to control
many ecological processes, such as energy flow through a food web (Clapham et al. 2006).
Kauffman and Harries (1996) define disaster taxa as opportunistic, r-strategist organisms
uniquely adapted to the harsh conditions during and after a biotic crisis and therefore able to
proliferate in environments where other taxa are excluded.
Lingularia and Claraia have been hypothesized to be resilient to low-oxygen environments,
a condition that was reoccurring in some Early Triassic settings (Wignall 1993), based on the
occurrence of these taxa in dysoxic sediment types throughout the fossil record (Allison et al.
8
1995) and physiological studies (e.g. Hammen et al. (1962)) on modern representatives of the
group in the case of Lingularia. The modern lingulid brachiopod Lingula, deemed by some a
“living fossil” due to the morphological similarity of fossil and living forms (see (Emig 2003) for
discussion), is physiologically resilient in low-oxygen conditions. Modern lingulids live
infaunaully in organic-rich muddy nearshore environments that are susceptible to oxygen
depletion (Craig 1952, Worcester 1969), where resilience to low oxygen levels is advantageous.
Experiments by Hammen et al. (1962) and Shumway (1982) suggested that modern Lingula
consume less oxygen while sustaining normal metabolic functions when compared with
mollusks and articulate brachiopods, which likely lends them an advantage during low-oxygen
events. This potential physiological resilience may have allowed fossil lingulid brachiopods to
thrive in low-oxygen conditions in the past as well. Lingula-form brachiopods occur in
dysaerobic settings throughout the Phanerozoic, including within Cambrian matground facies
(e.g., wrinkle structures (Bailey et al. 2006)) and Paleozoic black shales (Craig 1952, Ferguson
1963), and seem to be restricted to either dysaerobic basinal settings or organic-rich intertidal
settings during these time intervals (Rodland and Bottjer 2001). In the Triassic, Lingularia are
categorized as shallow infaunal suspension feeders (Hofmann et al. 2014), similar in life mode to
modern Lingula (Craig 1952), and are found abundantly in Panthalassic and Tethyan collections
(Peng et al. 2007, Posenato et al. 2014, Rodland and Bottjer 2001, Wignall and Hallam 1993,
Zonneveld et al. 2007). Posenato et al. (2014) found postextinction Lingularia with smaller
shells and larger lophophoral cavities relative to pre-extinction forms, likely enabling resistance
to low-oxygen and high-temperature conditions due to a decreased body mass to lophophore
surface area ratio. Lingula-form brachiopods have long been a component of low-oxygen fauna
9
throughout the Phanerozoic (Allison et al. 1995), and their prevalence in these environments
indicated an evolutionarily long-lived physiological resilience to these conditions.
The paper pecten Claraia shares a common morphology with other thin-shelled bivalves that
tend to also occur in dysoxic sediment in the fossil record (Wignall 1993). These include the
bivalves Halobia and Paracyclas, which are also found in poorly oxygenated sediment
throughout the Phanerozoic (Allison et al. 1995, McRoberts 2000, Van Iten et al. 2013).
Additionally, Claraia shared a remarkably similar morphology with the Toarcian bivalves
Bositra and Pseudomytiloides, which act as opportunistic disaster taxa following the Early
Jurassic ocean anoxic event (Caswell and Coe 2013, Caswell et al. 2009). Claraia, a byssally
attached epifaunal suspension feeder (Allison et al. 1995), is found throughout Panthalassic,
Tethyan, and Boreal Lower Triassic collections in both carbonates and shales (e.g., Yin, 1981;
Boyer et al. 2004; Posenato 2008b). Claraia appears to become locally extinct in South China at
the Smithian–Spathian boundary (see Sun et al. (2012), but other workers (Fraiser and Bottjer
2007, McGowan et al. 2009, Tozer 1961) have reported a number of Claraia from Panthalassic
Spathian collections.
No specific physiological survival strategy has been proposed for the remaining disaster
genera Unionites, Eumorphotis, and Promyalina, but it is generally believed that a eurytopic life
strategy allowed them to proliferate in environments heavily affected by extinction and thus to
outcompete other survivors (Kashiyama and Oji 2004, Schubert and Bottjer 1995). It is possible
these taxa possessed advantageous adaptations, such as a resistance to low oxygen levels, high
temperature, or elevated acidity, but current understanding of the physiology of these extinct
clades is limited. A recent revision of the life modes of these genera by Hautmann et al. (2013)
and Hofmann et al. (2014) categorizes Eumorphotis as a byssally attached epifaunal suspension
10
feeder, similar to the bivalve Leptochondria, which is also found frequently in Lower Triassic
carbonate deposits (Schubert and Bottjer 1995). Promyalina has been described as an epifaunal
or semi-infaunal byssally attached suspension feeder (Hofmann et al. 2013c, McRoberts and
Newell 2005). These relatively “simple,” low-energy life modes may have lent an advantage to
these taxa in deleterious conditions (Aberhan and Baumiller 2003). Unionites is categorized as a
shallow infaunal suspension feeder (Hautmann et al. 2013), similar to Lingularia and modern-
day Lingula (Craig 1952).
2 – Methods

2.1 – Quantitative recovery metrics

Several workers have focused on different metrics to gauge the extent of recovery to pre-
extinction levels of community complexity in Early Triassic assemblages. Some metrics estimate
recovery extent based on the reappearance of complex communities consisting of diverse,
multitiered trophic webs and the presence of ecosystem-engineering organisms (Chen and
Benton 2012, Payne et al. 2006, Pietsch et al. 2014, Song et al. 2011). Other metrics base
recovery on the reappearance of diverse ichnocoenoses that include deep-tiering and low-
oxygen-sensitive ichnotaxa such as Thalassinoides (Hofmann et al. 2011, Pruss and Bottjer
2004). Hofmann et al. (2013) determined intervals of recovery in Panthalassic assemblages based
on changes in alpha and beta diversity. Functional diversity, or the disparity of life modes
represented in assemblages, has also been used as an indicator of ecological recovery following
the end-Permian mass extinction (Dineen et al. 2014, Foster and Twitchett 2014). All of these
metrics are similar in that the aim is to quantify the ecological complexity, and thereby the
recovery progression, of ancient communities. Communities that are highly uneven, low in
11
diversity, and highly simplistic in life mode are more susceptible to disturbances, temporally
unstable, and are indicative of an ecosystem under physical stress (Hillebrand et al. 2008).
Increasing community complexity, with a decrease of highly dominant taxa and increasing
evenness, can be used to quantify progression of recovery; thus, the measure of disaster-taxon
dominance is expected to track metrics of community complexity. An abundance of disaster taxa
in assemblages may indicate: (1) that overall evenness of the community is low, with lower
richness and alpha diversity and potentially less functional diversity and trophic-web complexity
represented; and (2) that certain abiotic stressors, such as low oxygen levels, may be present and
promoting the expansion of disaster taxa by excluding other taxa. This study aims to explore the
correlation of disaster-taxon occurrences and abundance with metrics for ecosystem complexity
and to assess the pace of recovery of complexity in benthic communities in the Early Triassic.
2.2 – Data sources

For this study, a quantitative analysis of dominance in Early Triassic marine benthic
communities in Panthalassa and Tethys was undertaken using abundance data from fossil
collections downloaded from the Paleobiology Database. Entries with abundance data reported
for brachiopod, bivalve, and gastropod genera were used to represent invertebrate assemblages.
Further filtering of collections was applied; entries were deemed suitable for inclusion in this
study if abundance counts of all bivalves, brachiopods, and gastropods were reported (e.g.,
brachiopod-only studies were excluded) and more than 20 individuals were counted. The cutoff
criteria of 20 individuals or more per collection was chosen to reduce noise introduced by
smaller collections and was found to increase statistical significance in the analysis. Other
biomineralizing benthic marine invertebrates groups, such as echinoderms, were not included,
due to the difficulty of assessing accurate counts of living individuals from disarticulated bioclast
12
counts and their lack of representation in Paleobiology Database abundance reports. Table 2.1
summarizes all collection references used. Western U.S. and western Canada collections were
used to represent the Panthalassic region, and collections from Italy, Pakistan, and South China
were used to represent the Tethys (Fig. 2.3). The data set was analyzed for three time bins
representing the Early Triassic stage or substage intervals: the Induan stage (including the
Griesbachian and Dienerian substages), the Smithian substage, and the Spathian substage.
Griesbachian and Dienerian substage collections were combined into the single Induan stage
time bin due to the limited number of collections available in some cases. The Tethyan analysis
included abundance counts from collections made by the authors and collaborators (Paleobiology
Database reference no. 54290). These counts were extracted using bulk sampling methods
whereby an equal volume of fossiliferous rock was collected and analyzed with the aid of a
dissecting microscope, and invertebrate taxa were identified to the genus level. A total of 179
abundance collections reporting 19,217 individuals were used in this analysis, with 140
collections representing Panthalassa and 39 representing Tethys. Smithian and Spathian Tethyan
collections were underrepresented compared with Panthalassa, but the large number of
individuals reported from this region (n = 2155) makes it possible to measure true biological
signals when normalizing metrics such as relative abundance are used.
Total abundance and average relative abundance were calculated for each collection, and
occurrence frequencies, or the percent of collections in which a genus occurs, were calculated
per time bin and region for all genera present. Clapham et al. (2006) advocated the use of
abundance data in addition to presence–absence data for evaluating ecological trends in the fossil
record, as taxonomic dominance (high diversity) is not necessarily reflective of ecological
dominance (high abundance). Ecological dominance of a taxon can be quantitatively identified
13
by high average relative abundance and a high occurrence frequency, and both were considered
in identifying periods of disaster taxon dominance. Traditionally, abundance data has not been
used in paleoecological studies due to concerns regarding the fidelity of the abundance record
and the time-consuming nature of bulk-sampling methods. However, many actuopaleontological
studies have shown that time-averaged death assemblages accurately reflect generalized
abundance relationships between taxa in living communities (Kidwell 2002, Kidwell and Flessa
1995). Here, I assume relative abundance of fossils accurately approximated the time-averaged
abundance distributions of the living benthic communities.
Simpson’s dominance index (D) (calculated using PAST, version 1.89 (Hammer et al.
2009)) and evenness (E
1/D
) were used as a metric of overall community evenness–dominance
independent of disaster-taxon abundance. Simpson’s D is a measure of taxonomic diversity that
is sensitive to highly abundant taxa, more so than other diversity indices such as Shannon’s H
(Hammer and Harper 2008). Evenness (E
1/D
) is calculated by normalizing the reciprocal of
Simpson’s D to taxonomic richness and thus represents evenness independent of diversity
(Magurran 2004). These two metrics are calculated as follows, where p
i
is the relative abundance
of the ith taxon in a given collection, and N is the total number of taxa in that collection:
Simpson’s dominance (D) = (p
i
)
2

Simpson’s evenness (E
1/D
) = (1/D)/N
3 – Results

Dominance and evenness in Early Triassic benthic assemblages exhibit some significant
differences between time bins and regions. Median Simpson’s dominance index is high in Induan
Panthalassic assemblages (Fig. 2.4 A) but decreases significantly in the Smithian (Mann-
14
Whitney U-test: p = 0.034, a = 0.05). Median dominance remains low in the Spathian of
Panthalassa when compared with the Induan, but a larger portion of the collections exhibit a
dominance of 0.5 or greater. However, no significant difference is observed between Smithian
and Spathian dominance values. Within Tethyan time bins, median dominance decreases
between Induan and Smithian assemblages, though not significantly (Fig. 2.4 B). However, there
is a significant increase in dominance between Tethyan Smithian and Spathian assemblages,
though sample size for these time bins is small (n = 4 and n = 8 collections, respectively). When
dominance is normalized to taxon richness (E
1/D
), there is no significant difference observed
between any time bins in either region (Figs. 2.4 B and 2.5 B), implying that changes in richness
significantly affect dominance in these time bins. Time bin comparisons between Panthalassa
and Tethys show significantly lower dominance in Tethyan Induan and Smithian assemblages
when compared with contemporaneous Panthalassic assemblages (Fig. 2.6 A-B; Mann-Whitney
U-test: p = 0.007 and p = 0.013, a = 0.05). Overall, Panthalassic assemblages exhibit declining
levels of dominance, whereas Tethyan assemblages sustain similar levels of dominance
throughout the three time bins. Tethyan assemblages are generally more even (less dominance)
then contemporaneous Panthalassic assemblages, except in the Spathian, though this difference
is not statistically significant and is likely skewed by the small number of collections in the
Tethys (n = 8) versus Panthalassa (n = 59) at this time.
Abundance tallies in Early Triassic assemblages show high relative abundance of the
previously hypothesized disaster-taxon genera relative to other biomineralizing marine benthic
invertebrates in the Induan of Panthalassic and Tethyan assemblages, with these disaster taxa
representing 79.1% and 54.6% percent of individuals reported, respectively (Fig. 2.7). Following
this high abundance in the Induan, the Smithian and Spathian assemblages exhibit a dramatic
15
decline in disaster-taxon relative abundance in both regions. This decline is most severe in
Panthalassa between the Induan and Smithian time bins, where the relative abundance is reduced
to 9.0%. Tethyan assemblages also exhibit a similar decline, with Smithian disaster taxa only
representing 26.2% of individuals. Spathian assemblages in both regions show low disaster-
taxon relative abundance, with 20.5% in Panthalassa and 25.4% in Tethys. Interestingly,
Smithian Panthalassic assemblages exhibit overall lower disaster-taxon abundance than is found
in the Spathian. This decline in disaster-taxon dominance after the Induan stage of the Early
Triassic coincides with a decrease of overall dominance (increased evenness) in Panthalassa.
This pattern is not as apparent in Tethyan assemblages, as dominance does not significantly
change between time bins, even though a decrease in disaster-taxon relative abundance is
observed.
Average relative abundances and occurrence frequencies of the disaster taxa reflect this
pattern of decreasing importance throughout the Early Triassic both within assemblages and
regionally. In Panthalassic Induan collections, the disaster taxa Unionites, Lingularia, and
Eumorphotis show the highest occurrence frequency and relative abundance of taxa present (Fig.
2.8 A-B), with the exception of the bivalves Pteria and Leptochondria, which are also highly
abundant in some Panthalassic Induan collections. In the Smithian, Unionites is the most
abundant disaster taxa but is outranked in abundance and occurrence frequency by
Leptochondria, Permophorus, and some gastropod genera (Fig. 2.7 C-D). In the Spathian, we see
a return of high abundance and occurrence frequency of a few disaster-taxon genera, with
Eumorphotis and Promyalina ranking highly (Fig. 2.8 E-F). However, other taxa, including the
articulate brachiopods Protogusarella and Piarorhynchella, are also highly abundant (Fig. 2.8
F). The disaster taxa occur in 20–70% of Panthalassic collections in the Induan (Fig. 2.8 B) but
16
are more limited in extent in the Smithian (Fig. 2.8 D). The Spathian of Panthalassa sees the
return of widely distributed Eumorphotis and Promyalina (Fig. 2.8 C), reflecting a reoccurrence
of disaster-taxon importance following the Smithian.
In Tethyan collections, the bivalve Unionites is the most frequently occurring and
abundant disaster taxon in the Induan time bin (Fig. 2.9 A-B), whereas in the Smithian and
Spathian, Eumorphotis also gains some importance. However, in the Smithian and Spathian, both
are outranked in terms of abundance by the bivalve Neoschizodus. In both Panthalassic and
Tethyan collections, Claraia and Lingularia only occur in high abundance during the Induan
time bin (Figs. 2.8 B and 2.9 B), after which they become only minor components of
assemblages. Compared with Panthalassic Spathian assemblages, where Eumorphotis and
Promyalina are more prevalent than other disaster taxa in Tethyan assemblages, Unionites
appears more important at this time. The patterns of changing relative abundance of the disaster
taxa are reflected in their regional distributions in Panthalassa and Tethys; as these taxa become
less frequently occurring regionally, they also become less abundant in those assemblages in
which they do occur.
4 – Discussion

There is a significant decrease in Simpson’s dominance in Panthalassic assemblages
between the Induan and Smithian time bins coincident with a dramatic decrease in the relative
abundance of the disaster taxa as a group, as well as an overall decline in dominance over time in
Panthalassa. A similar, though not as dramatic, decline in disaster-taxon abundance is observed
in Tethyan assemblages. The abundance of the so-called disaster taxa appears to track
dominance, a metric of community complexity, most clearly in Panthalassic assemblages.
17
While individual disaster taxa reoccur in high abundance at other times in the Early
Triassic, it is only in the Induan that we see the disaster taxa rank highest in terms of relative
abundance and occurrence frequency as a group; most clearly in Panthalassic collections.
Tethyan Induan assemblages are more even than contemporaneous Panthalassic collections, and
only the disaster taxon Unionites is highly abundant and widespread. Following the Induan stage,
disaster taxa overall become less important in terms of abundance and occurrence frequency in
both regions, as other taxa become more ecologically important and widespread. These more
abundant non–disaster taxa are associated with an overall decrease in community dominance and
an increase in diversity. Claraia and Lingularia occur in later stages of the Early Triassic, but the
peak of their ecological importance is limited to the Induan stage. Of all the disaster taxa,
Claraia and Lingularia are the only two with clear preferences for occurring in low-oxygen
conditions (Allison et al. 1995). Their prevalence in the Induan of Panthalassa may indicate an
increased role of low-oxygen conditions in biotic suppression in these environments, which
subsequently subsides in prevalence. Their dominance may also be a reflection of the direct
effects of the extinction event allowing these two physiologically adept genera to become
dominant and widespread, while the later dominance of Eumorphotis, Promyalina, and Unionites
may be a response to onset of different environmental conditions or normal competitive
interaction. Whatever the reason for the decline in Claraia and Lingularia abundance after the
Induan, it is clear that these two genera exhibit dissimilar patterns of dominance from the other
three taxa but act as true disaster taxa as defined by Kauffman and Harries (1996) following the
Permian–Triassic extinction. Further work is needed to clarify the status of the remaining three
genera as true disaster taxa.
18
The decline of disaster-taxon abundance after the Induan stage tracks increasing
community complexity in benthic assemblages, as overall dominance declines and diversity
increases. As recovery progressed following the Permian–Triassic extinction, rebounds and
resets in recovery of community complexity have been observed by many workers looking at
discrete sections or regions (Pietsch and Bottjer 2014). As some of these reported failed recovery
attempts occur within single substages, the temporal resolution of the data set used for this study
does not allow for direct identification of these intervals. However, the averaging of these short-
term recovery signals over the entirety of the Early Triassic reveals a pattern of overarching
recovery, starting in the Smithian and continuing into the Spathian. As this study samples
Panthalassic and Tethyan assemblages collected over a wide range of benthic environments with
varying energy levels, depositional settings, and oxygen conditions, the observed decrease in
dominance after the Induan stage reflects an averaged signal of recovery of ecosystem
complexity across these environments.
As complexity increased over the Early Triassic, larger-scale ecological restructuring was
already underway (Fraiser and Bottjer 2007). The end-Permian extinction marked the beginning
of the end for brachiopod ecological and taxonomic importance in marine communities, but the
transition from brachiopod-dominated Paleozoic Fauna assemblages to bivalve-dominated
Modern Fauna assemblages was not instantaneous. A rebound of Paleozoic faunal components
was observed in Panthalassic Middle Triassic assemblages by Greene et al. (2011) and is
attributed to the decoupling of taxonomic and ecological restructuring starting at the Paleozoic–
Mesozoic transition. In this study, an interval of increased articulate brachiopod ecological
importance is observed in the Spathian of Panthalassa, with reports of high abundance of
Protogusarella and Piarorhynchella. Rebounds in ecological importance of Paleozoic faunal
19
components such as brachiopods and crinoids (Boyer et al. 2004) in the Spathian of the Early
Triassic lends further evidence to the asynchronous nature of the Paleozoic to Modern faunal
transition.
5 – Conclusions

Dominance of disaster taxa in marine benthic assemblages reflects the status of
ecosystem complexity and therefore of progression of recovery following the end-Permian mass
extinction. We find that the Induan stage in both Panthalassic and Tethyan assemblages is when
disaster taxa occur at their highest abundance and widest distribution. This stage is also when
overall community dominance is at its peak in Panthalassic assemblages. Following the Induan
stage, we see a reduction of overall community dominance as well as disaster-taxon abundance
and distribution. The disaster taxa Claraia and Lingularia exhibit the most extreme decrease in
importance, and highly abundant occurrences of these two taxa are limited to the Induan stage.
Eumorphotis, Promyalina, and Unionites are found to occur in high abundance in some Smithian
and Spathian collections, but other non–disaster taxa join their ranks as well, including articulate
brachiopods in Panthalassa. The general decrease of disaster-taxon abundance observed tracks an
averaged signal of gradual recovery of benthic marine community complexity through the Early
Triassic.

20
Figures and Tables

Table 2.1 – Summary of Panthalassic and Tethyan Paleobiology Database collections used for
analysis, showing number of collections, total generic richness, and total number of individuals
reported per time bin and region. Also shown are the data source references and PaleobioDB
reference number, as well as the country the collections were made in.

21
Time Bins # Collections
Generic
Richness
#
Specimens
References
PaleobioDB
Ref #
Localities
Schubert and Bottjer 1995 8833 Western U.S.A.
Fraiser and Bottjer 2007 11667 Western U.S.A.
Hofmann et al. 2013a 44069 Western U.S.A.
Schubert and Bottjer 1995 8833 Western U.S.A.
Tozer 1961 11541 Canada
Fraiser and Bottjer 2007 11667 Western U.S.A.
Hautmann and Nützel 2005 15359 Western U.S.A.
Newell and Boyd 1975 11482 Western U.S.A.
Nützel and Schulbert 2005 28984 Western U.S.A.
Brayard et al. 2013 51090 Western U.S.A.
Hofmann et al. 2014 51103 Western U.S.A.
Schubert and Bottjer 1995 8833 Western U.S.A.
Fraiser and Bottjer 2007 11667 Western U.S.A.
McGowan et al. 2009 18152 Western U.S.A.
Hofmann et al. 2013b 38898 Western U.S.A.
Hautmann et al. 2013 44069 Western U.S.A.
Hofmann et al. 2014 51103 Western U.S.A.
Time Bins # Collections
Generic
Richness
#
Specimens
References
PaleobioDB
Ref #
Localities
Fraiser and Bottjer 2007 11667 Italy
Yin et al. 1994 13055 South China
Kaim et al. 2010 32961 South China
Pietsch and Bottjer 2015 54290 Italy
Fraiser and Bottjer 2007 11667 Italy
Wasmer et al. 2012 43119 Pakistan
Pietsch and Bottjer 2015 54290 Italy
Fraiser and Bottjer 2007 11667 Italy
Wasmer et al. 2012 43119 Pakistan
Induan
34 32
Panthalassa
Tethys
55 34 6625
1635
3641 27 43
Induan
Smithian
Spathian
11 18 286
Spathian 105 47 7317
16 17 437
Smithian
22
Figure 2.1 – Images of the five genera of Early Triassic disaster genera as summarized by
Benton (2003). (A) Unionites cf. canalensis, (B) Promyalina cf. putiatinensis, (C) Lingularia
borealis, (D) Eumorphotis cf. virginensis, and (E) Claraia aurita. Scale bar, 1 cm.

23
A
B
C
D
A
B
C
D
C
24
Figure 2.2 – Hypothetical behavior of disaster taxa and opportunistic taxa following a biotic
crisis. Thickness of line indicates relative abundance. Disaster taxa are opportunistic taxa that
experience booms of abundance shortly after a biotic crisis, in the survival interval, and after
which they are no longer abundant ecosystem components. Opportunistic taxa may experience
booms in abundance under normal shifting environmental conditions, not necessarily in response
to a biotic crisis. Modified from Kauffman and Harries (1996)

25
Extinction Repopulation
Survival Recovery
Disaster
Taxa
Somewhat abundant
Extremely abundant
Present, not abundant
Opportunistic
Generalists
26
Figure 2.3 – Simplified Early Triassic map of Pangea showing regions where abundance
collections reported in the Paleobiology Database were made, including western United States,
western Canada, Italy, Pakistan, and South China. Modified from Scotese (2001) and Pietsch and
Bottjer (2014).

27
Panthalassa
Paleo-Tethys
Neo-Tethys
28
Figure 2.4 – Simpson’s dominance index (D) calculated using PAST software (Hammer et al.
2009) for the Induan, Smithian, and Spathian of (A) Panthalassic and (B) Tethyan collections.
Mann-Whitney U-test p-values are reported between neighboring time bins. Bold values indicate
significant change between time bins (a= 0.05). Width of box plot represents relative number of
collections used in the analysis.

29
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Simpson’s Dominance (D)
Spathian
U =
p =
U =
p =
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Simpson’s Dominance (D)
Spathian
U =
A
B
U = 1012
p = 0.034
U = 1334
p = 0.698
84
p = 0.082
U = 2
p = 0.022
30
Figure 2.5 – Evenness (E
1/D
) calculated using PAST software (Hammer et al. 2009) for the
Induan, Smithian, and Spathian of (A) Panthalassic and (B) Tethyan collections. Mann-Whitney
U-test p-values are reported between neighboring time bins. Bold values indicate significant
change between time bins (a = 0.05). Width of box plot represents relative number of collections
used in the analysis.

31
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Simpson’s Dominance (D)
Spathian
U =
p =
U =
p =
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Simpson’s Dominance (D)
Spathian
U =
A
B
U = 1012
p = 0.034
U = 1334
p = 0.698
84
p = 0.082
U = 2
p = 0.022
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Evenness (E1/D)
Spathian
U = 711
p = 0.580
U = 977
p = 0.064
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Spathian
U = 54
p = 0.930
U = 12
p = 0.552
A
B
Evenness (E1/D)
32
Figure 2.6 – Regional comparison of dominance (D) and evenness (E
1/D
) between Panthalassic
and Tethyan assemblages. Dominance is shown in (A) Induan, (B) Smithian, and (C) Spathian
assemblages, and evenness is shown in (D) Induan, (E) Smithian, and (F) Spathian assemblages,
with width of box plot representing relative number of collections used in the analysis. Mann-
Whitney U-test p-values are reported between regions. Bold values indicate significant change
between regions (a = 0.05).

33
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Simpson’s Dominance (D)
Spathian
U =
p =
U =
p =
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Simpson’s Dominance (D)
Spathian
U =
A
B
U = 1012
p = 0.034
U = 1334
p = 0.698
84
p = 0.082
U = 2
p = 0.022
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Evenness (E1/D)
Spathian
U = 711
p = 0.580
U = 977
p = 0.064
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Spathian
U = 54
p = 0.930
U = 12
p = 0.552
A
B
Evenness (E1/D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Dominance (D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Dominance (D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Dominance (D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Evenness (E1/D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Evenness (E1/D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Evenness (E1/D)
A B C
D E F
U = 677
p = 0.007
U = 155
p = 0.013
U = 160
p = 0.159
U = 326
p = 0.299
U = 73
p = 0.646
U = 145
p = 0.905
34
Figure 2.7 – Overall relative abundance of all individuals reported from (A) Panthalassic and (B)
Tethyan collections. The relative abundance of disaster taxa is shown in black, with all other taxa
in white.

35
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Simpson’s Dominance (D)
Spathian
U =
p =
U =
p =
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Simpson’s Dominance (D)
Spathian
U =
A
B
U = 1012
p = 0.034
U = 1334
p = 0.698
84
p = 0.082
U = 2
p = 0.022
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Evenness (E1/D)
Spathian
U = 711
p = 0.580
U = 977
p = 0.064
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Spathian
U = 54
p = 0.930
U = 12
p = 0.552
A
B
Evenness (E1/D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Dominance (D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Dominance (D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Dominance (D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Evenness (E1/D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Evenness (E1/D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Evenness (E1/D)
A B C
D E F
U = 677
p = 0.007
U = 155
p = 0.013
U = 160
p = 0.159
U = 326
p = 0.299
U = 73
p = 0.646
U = 145
p = 0.905
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Leptochondria
Permophorus
Unionites
Neoschizodus
Myalina
Confusionella
Pleuronec ti tes
Strobeus
Eumorpho ti s
Promyalina
Promysidiella
Abrekopsis
Na ti copsis
Coelostylina
Lingularia
“Paullia”
Polygyrina
Worthenia
Omphaloptychia
Critt endenia
Entolioides
Ba tt enizyga
Chartronella
Soleniscus
Elegan ti nia
Sinbadiella
Zygopleura
Laubopsis
Claraia
My ti lus
Neritaria
Pernopecten
Semen ti concha
Unicardium
Occurrence Frequency
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Unionites
Promyalina
Lingularia
Claraia
Eumorpho ti s
Pteria
Myalina
Coelostylina
Neoschizodus
Leptochondria
Permophorus
“Spiriferina”
Orbicoelia
Dicellonema
Fletcherithyris
Heteropecten
Lepisma ti na
Lepisma ti na
My ti lus
“Paullia”
Pleuronec ti tes
Occurrence Frequency
Bivalves
Gastropods
Brachiopods
Disaster Taxa (Bivalves)
Disaster Taxa (Brachiopods)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Eumorpho ti s
Promyalina
Leptochondria
Protogusarella
Unionites
Piarorhynchella
Permophorus
Myalina
Chartronella
Na ti copsis
Neoschizodus
Coelostylina
Pleuronec ti tes
Pseudocorbula
Worthenia
Myophoria
Semen ti concha
Abrekopsis
Myoconcha
Omphaloptychia
“Paullia”
Pernopecten
Trigonodus
Claraia
Elegan ti nia
Entolium
Heminajas
Na ti ria
Obnixia
Rhynchonella
Arcomya
Chlamys
Discinisca
Entolioides
Homomya
Lingularia
Modiolus
Pleuromya
Protopis
Pseudomyoconcha
Vex
Occurrence Frequency
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Unionites
Lingularia
Eumorpho ti s
Pteria
Leptochondria
Claraia
Promyalina
Orbicoelia
Permophorus
“Spiriferina”
Myalina
Coelostylina
Dicellonema
Neoschizodus
Heteropecten
Fletcherithyris
“Paullia”
My ti lus
Lepisma ti na
Pleuronec ti tes
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Leptochondria
Confusionella
Permophorus
Promysidiella
Neoschizodus
Promyalina
Na ti copsis
Unionites
Abrekopsis
Strobeus
Sinbadiella
Myalina
Eumorpho ti s
Polygyrina
Laubopsis
Lingularia
Omphaloptychia
Entolioides
Worthenia
Pleuronec ti tes
Coelostylina
“Paullia”
Critt endenia
Chartronella
Ba tt enizyga
Pernopecten
My ti lus
Zygopleura
Elegan ti nia
Soleniscus
Claraia
Unicardium
Neritaria
Semen ti concha
Average Rela ti ve Abundance
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Protogusarella
Piarorhynchella
Promyalina
Leptochondria
Eumorpho ti s
Unionites
Permophorus
Pseudocorbula
Myalina
Obnixia
Pleuronec ti tes
Neoschizodus
Semen ti concha
Omphaloptychia
Coelostylina
Na ti copsis
Chartronella
Worthenia
Pernopecten
Myoconcha
Protopis
Elegan ti nia
Claraia
Rhynchonella
Vex
“Paullia”
Entolium
Myophoria
Na ti ria
Entolioides
Lingularia
Trigonodus
Abrekopsis
Heminajas
Modiolus
Homomya
Arcomya
Discinisca
Chlamys
Pleuromya
Pseudomyoconcha
Average Rela ti ve Abundance Average Rela ti ve Abundance Average Rela ti ve Abundance
A D
B E
C F
Average Rela ti ve Abundance
A B
C D
E F
Average Rela ti ve Abundance Average Rela ti ve Abundance
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Eumorphotis
Neoschizodus
Unionites
Coelostylina
Entolium
Pernopecten
Costatoria
Leptochondria
Myalina
Permophorus
Pecten
Battenizyga
Claraia
Lingularia
Naticopsis
Promyalina
Bakevellia
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Unionites
Neoschizodus
Claraia
Entolium
Eumorphotis
Myalina
Promyalina
Leptochondria
Permophorus
Pernopecten
Coelostylina
Lingularia
Pleuromya
Pseudomurchisonia
Pecten
Bakevellia
Scythentolium
Astartella
Astartopsis
Chartronella
Cylindrobullina
Dicellonema
Meishanorhynchia
Modiolus
Naticopsis
Neritaria
Palaeonarica
Pleuronectites
Promysidiella
Pseudocorbula
Trigonodus
Wannerispira
Bivalves
Gastropods
Brachiopods
Disaster Taxa (Bivalves)
Disaster Taxa (Brachiopods)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Scythentolium
Entolium
Eumorphotis
Leptochondria
Neoschizodus
Costatoria
Eobuchia
Palaeoneilo
Unionites
Cardinioides
Pinna
Promyalina
Pseudocorbula
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Unionites
Neoschizodus
Coelostylina
Pseudomurchsonia
Permophorus
Meishanorhynchia
Claraia
Eumorphotis
Lingularia
Entolium
Myalina
Pernopecten
Pecten
Pseudocorbula
Promyalina
Wannerispira
Pleuromya
Scythentolium
Leptochondria
Dicellonema
Naticopsis
Bakevellia
Neritaria
Astartella
Astartopsis
Chartronella
Cylindrobullina
Palaeonarica
Modiolus
Promysidiella
Trigonodus
Pleuronectites
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Neoschizodus
Unionites
Eumorphotis
Entolium
Coelostylina
Permophorus
Pernopecten
Claraia
Costatoria
Myalina
Pecten
Lingularia
Leptochondria
Promyalina
Battenizyga
Naticopsis
Bakevellia
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Neoschizodus
Unionites
Eobuchia
Palaeoneilo
Cardinioides
Eumorphotis
Scythentolium
Leptochondria
Entolium
Costatoria
Pseudocorbula
Pinna
Promyalina
Occurrence Frequency Occurrence Frequency Occurrence Frequency
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Induan Smithian Spathian
Abundance of all individuals
Other Benthic Taxa Disaster Taxa
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Induan Smithian Spathian
Abundance of all individuals
A
B
36
Figure 2.8 – Occurrence frequency and average relative abundance of each genus for
Panthalassic assemblages. Panthalassic occurrence frequency of genera is shown in the (A)
Induan, (B) Smithian, and (C) Spathian, and Panthalassic average relative abundance is shown in
the (D) Induan, (E) Smithian, and (F) Spathian. Disaster taxa are shown with open marks and all
other genera are shown with solid marks.

37
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Simpson’s Dominance (D)
Spathian
U =
p =
U =
p =
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Simpson’s Dominance (D)
Spathian
U =
A
B
U = 1012
p = 0.034
U = 1334
p = 0.698
84
p = 0.082
U = 2
p = 0.022
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Evenness (E1/D)
Spathian
U = 711
p = 0.580
U = 977
p = 0.064
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Spathian
U = 54
p = 0.930
U = 12
p = 0.552
A
B
Evenness (E1/D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Dominance (D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Dominance (D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Dominance (D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Evenness (E1/D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Evenness (E1/D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Evenness (E1/D)
A B C
D E F
U = 677
p = 0.007
U = 155
p = 0.013
U = 160
p = 0.159
U = 326
p = 0.299
U = 73
p = 0.646
U = 145
p = 0.905
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Leptochondria
Permophorus
Unionites
Neoschizodus
Myalina
Confusionella
Pleuronec ti tes
Strobeus
Eumorpho ti s
Promyalina
Promysidiella
Abrekopsis
Na ti copsis
Coelostylina
Lingularia
“Paullia”
Polygyrina
Worthenia
Omphaloptychia
Critt endenia
Entolioides
Ba tt enizyga
Chartronella
Soleniscus
Elegan ti nia
Sinbadiella
Zygopleura
Laubopsis
Claraia
My ti lus
Neritaria
Pernopecten
Semen ti concha
Unicardium
Occurrence Frequency
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Unionites
Promyalina
Lingularia
Claraia
Eumorpho ti s
Pteria
Myalina
Coelostylina
Neoschizodus
Leptochondria
Permophorus
“Spiriferina”
Orbicoelia
Dicellonema
Fletcherithyris
Heteropecten
Lepisma ti na
Lepisma ti na
My ti lus
“Paullia”
Pleuronec ti tes
Occurrence Frequency
Bivalves
Gastropods
Brachiopods
Disaster Taxa (Bivalves)
Disaster Taxa (Brachiopods)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Eumorpho ti s
Promyalina
Leptochondria
Protogusarella
Unionites
Piarorhynchella
Permophorus
Myalina
Chartronella
Na ti copsis
Neoschizodus
Coelostylina
Pleuronec ti tes
Pseudocorbula
Worthenia
Myophoria
Semen ti concha
Abrekopsis
Myoconcha
Omphaloptychia
“Paullia”
Pernopecten
Trigonodus
Claraia
Elegan ti nia
Entolium
Heminajas
Na ti ria
Obnixia
Rhynchonella
Arcomya
Chlamys
Discinisca
Entolioides
Homomya
Lingularia
Modiolus
Pleuromya
Protopis
Pseudomyoconcha
Vex
Occurrence Frequency
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Unionites
Lingularia
Eumorpho ti s
Pteria
Leptochondria
Claraia
Promyalina
Orbicoelia
Permophorus
“Spiriferina”
Myalina
Coelostylina
Dicellonema
Neoschizodus
Heteropecten
Fletcherithyris
“Paullia”
My ti lus
Lepisma ti na
Pleuronec ti tes
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Leptochondria
Confusionella
Permophorus
Promysidiella
Neoschizodus
Promyalina
Na ti copsis
Unionites
Abrekopsis
Strobeus
Sinbadiella
Myalina
Eumorpho ti s
Polygyrina
Laubopsis
Lingularia
Omphaloptychia
Entolioides
Worthenia
Pleuronec ti tes
Coelostylina
“Paullia”
Critt endenia
Chartronella
Ba tt enizyga
Pernopecten
My ti lus
Zygopleura
Elegan ti nia
Soleniscus
Claraia
Unicardium
Neritaria
Semen ti concha
Average Rela ti ve Abundance
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Protogusarella
Piarorhynchella
Promyalina
Leptochondria
Eumorpho ti s
Unionites
Permophorus
Pseudocorbula
Myalina
Obnixia
Pleuronec ti tes
Neoschizodus
Semen ti concha
Omphaloptychia
Coelostylina
Na ti copsis
Chartronella
Worthenia
Pernopecten
Myoconcha
Protopis
Elegan ti nia
Claraia
Rhynchonella
Vex
“Paullia”
Entolium
Myophoria
Na ti ria
Entolioides
Lingularia
Trigonodus
Abrekopsis
Heminajas
Modiolus
Homomya
Arcomya
Discinisca
Chlamys
Pleuromya
Pseudomyoconcha
Average Rela ti ve Abundance Average Rela ti ve Abundance Average Rela ti ve Abundance
A D
B E
C F
Average Rela ti ve Abundance
A B
C D
E F
Average Rela ti ve Abundance Average Rela ti ve Abundance
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Eumorphotis
Neoschizodus
Unionites
Coelostylina
Entolium
Pernopecten
Costatoria
Leptochondria
Myalina
Permophorus
Pecten
Battenizyga
Claraia
Lingularia
Naticopsis
Promyalina
Bakevellia
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Unionites
Neoschizodus
Claraia
Entolium
Eumorphotis
Myalina
Promyalina
Leptochondria
Permophorus
Pernopecten
Coelostylina
Lingularia
Pleuromya
Pseudomurchisonia
Pecten
Bakevellia
Scythentolium
Astartella
Astartopsis
Chartronella
Cylindrobullina
Dicellonema
Meishanorhynchia
Modiolus
Naticopsis
Neritaria
Palaeonarica
Pleuronectites
Promysidiella
Pseudocorbula
Trigonodus
Wannerispira
Bivalves
Gastropods
Brachiopods
Disaster Taxa (Bivalves)
Disaster Taxa (Brachiopods)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Scythentolium
Entolium
Eumorphotis
Leptochondria
Neoschizodus
Costatoria
Eobuchia
Palaeoneilo
Unionites
Cardinioides
Pinna
Promyalina
Pseudocorbula
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Unionites
Neoschizodus
Coelostylina
Pseudomurchsonia
Permophorus
Meishanorhynchia
Claraia
Eumorphotis
Lingularia
Entolium
Myalina
Pernopecten
Pecten
Pseudocorbula
Promyalina
Wannerispira
Pleuromya
Scythentolium
Leptochondria
Dicellonema
Naticopsis
Bakevellia
Neritaria
Astartella
Astartopsis
Chartronella
Cylindrobullina
Palaeonarica
Modiolus
Promysidiella
Trigonodus
Pleuronectites
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Neoschizodus
Unionites
Eumorphotis
Entolium
Coelostylina
Permophorus
Pernopecten
Claraia
Costatoria
Myalina
Pecten
Lingularia
Leptochondria
Promyalina
Battenizyga
Naticopsis
Bakevellia
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Neoschizodus
Unionites
Eobuchia
Palaeoneilo
Cardinioides
Eumorphotis
Scythentolium
Leptochondria
Entolium
Costatoria
Pseudocorbula
Pinna
Promyalina
Occurrence Frequency Occurrence Frequency Occurrence Frequency
38
Figure 2.9 – Occurrence frequency and average relative abundance of each genus for Tethyan
assemblages. Tethyan occurrence frequency of genera is shown in the (A) Induan, (B) Smithian,
and (C) Spathian, and Tethyan average relative abundance is shown in the (D) Induan, (E)
Smithian, and (F) Spathian. Disaster taxa are shown with open marks and all other genera are
shown with solid marks.

39
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Simpson’s Dominance (D)
Spathian
U =
p =
U =
p =
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Simpson’s Dominance (D)
Spathian
U =
A
B
U = 1012
p = 0.034
U = 1334
p = 0.698
84
p = 0.082
U = 2
p = 0.022
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Evenness (E1/D)
Spathian
U = 711
p = 0.580
U = 977
p = 0.064
Induan Smithian
0.0 0.2 0.4 0.6 0.8 1.0
Spathian
U = 54
p = 0.930
U = 12
p = 0.552
A
B
Evenness (E1/D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Dominance (D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Dominance (D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Dominance (D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Evenness (E1/D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Evenness (E1/D)
Panthalassa Tethys
0.0 0.2 0.4 0.6 0.8 1.0
Evenness (E1/D)
A B C
D E F
U = 677
p = 0.007
U = 155
p = 0.013
U = 160
p = 0.159
U = 326
p = 0.299
U = 73
p = 0.646
U = 145
p = 0.905
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Leptochondria
Permophorus
Unionites
Neoschizodus
Myalina
Confusionella
Pleuronec ti tes
Strobeus
Eumorpho ti s
Promyalina
Promysidiella
Abrekopsis
Na ti copsis
Coelostylina
Lingularia
“Paullia”
Polygyrina
Worthenia
Omphaloptychia
Critt endenia
Entolioides
Ba tt enizyga
Chartronella
Soleniscus
Elegan ti nia
Sinbadiella
Zygopleura
Laubopsis
Claraia
My ti lus
Neritaria
Pernopecten
Semen ti concha
Unicardium
Occurrence Frequency
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Unionites
Promyalina
Lingularia
Claraia
Eumorpho ti s
Pteria
Myalina
Coelostylina
Neoschizodus
Leptochondria
Permophorus
“Spiriferina”
Orbicoelia
Dicellonema
Fletcherithyris
Heteropecten
Lepisma ti na
Lepisma ti na
My ti lus
“Paullia”
Pleuronec ti tes
Occurrence Frequency
Bivalves
Gastropods
Brachiopods
Disaster Taxa (Bivalves)
Disaster Taxa (Brachiopods)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Eumorpho ti s
Promyalina
Leptochondria
Protogusarella
Unionites
Piarorhynchella
Permophorus
Myalina
Chartronella
Na ti copsis
Neoschizodus
Coelostylina
Pleuronec ti tes
Pseudocorbula
Worthenia
Myophoria
Semen ti concha
Abrekopsis
Myoconcha
Omphaloptychia
“Paullia”
Pernopecten
Trigonodus
Claraia
Elegan ti nia
Entolium
Heminajas
Na ti ria
Obnixia
Rhynchonella
Arcomya
Chlamys
Discinisca
Entolioides
Homomya
Lingularia
Modiolus
Pleuromya
Protopis
Pseudomyoconcha
Vex
Occurrence Frequency
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Unionites
Lingularia
Eumorpho ti s
Pteria
Leptochondria
Claraia
Promyalina
Orbicoelia
Permophorus
“Spiriferina”
Myalina
Coelostylina
Dicellonema
Neoschizodus
Heteropecten
Fletcherithyris
“Paullia”
My ti lus
Lepisma ti na
Pleuronec ti tes
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Leptochondria
Confusionella
Permophorus
Promysidiella
Neoschizodus
Promyalina
Na ti copsis
Unionites
Abrekopsis
Strobeus
Sinbadiella
Myalina
Eumorpho ti s
Polygyrina
Laubopsis
Lingularia
Omphaloptychia
Entolioides
Worthenia
Pleuronec ti tes
Coelostylina
“Paullia”
Critt endenia
Chartronella
Ba tt enizyga
Pernopecten
My ti lus
Zygopleura
Elegan ti nia
Soleniscus
Claraia
Unicardium
Neritaria
Semen ti concha
Average Rela ti ve Abundance
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Protogusarella
Piarorhynchella
Promyalina
Leptochondria
Eumorpho ti s
Unionites
Permophorus
Pseudocorbula
Myalina
Obnixia
Pleuronec ti tes
Neoschizodus
Semen ti concha
Omphaloptychia
Coelostylina
Na ti copsis
Chartronella
Worthenia
Pernopecten
Myoconcha
Protopis
Elegan ti nia
Claraia
Rhynchonella
Vex
“Paullia”
Entolium
Myophoria
Na ti ria
Entolioides
Lingularia
Trigonodus
Abrekopsis
Heminajas
Modiolus
Homomya
Arcomya
Discinisca
Chlamys
Pleuromya
Pseudomyoconcha
Average Rela ti ve Abundance Average Rela ti ve Abundance Average Rela ti ve Abundance
A D
B E
C F
Average Rela ti ve Abundance
A B
C D
E F
Average Rela ti ve Abundance Average Rela ti ve Abundance
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Eumorphotis
Neoschizodus
Unionites
Coelostylina
Entolium
Pernopecten
Costatoria
Leptochondria
Myalina
Permophorus
Pecten
Battenizyga
Claraia
Lingularia
Naticopsis
Promyalina
Bakevellia
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Unionites
Neoschizodus
Claraia
Entolium
Eumorphotis
Myalina
Promyalina
Leptochondria
Permophorus
Pernopecten
Coelostylina
Lingularia
Pleuromya
Pseudomurchisonia
Pecten
Bakevellia
Scythentolium
Astartella
Astartopsis
Chartronella
Cylindrobullina
Dicellonema
Meishanorhynchia
Modiolus
Naticopsis
Neritaria
Palaeonarica
Pleuronectites
Promysidiella
Pseudocorbula
Trigonodus
Wannerispira
Bivalves
Gastropods
Brachiopods
Disaster Taxa (Bivalves)
Disaster Taxa (Brachiopods)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Scythentolium
Entolium
Eumorphotis
Leptochondria
Neoschizodus
Costatoria
Eobuchia
Palaeoneilo
Unionites
Cardinioides
Pinna
Promyalina
Pseudocorbula
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Unionites
Neoschizodus
Coelostylina
Pseudomurchsonia
Permophorus
Meishanorhynchia
Claraia
Eumorphotis
Lingularia
Entolium
Myalina
Pernopecten
Pecten
Pseudocorbula
Promyalina
Wannerispira
Pleuromya
Scythentolium
Leptochondria
Dicellonema
Naticopsis
Bakevellia
Neritaria
Astartella
Astartopsis
Chartronella
Cylindrobullina
Palaeonarica
Modiolus
Promysidiella
Trigonodus
Pleuronectites
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Neoschizodus
Unionites
Eumorphotis
Entolium
Coelostylina
Permophorus
Pernopecten
Claraia
Costatoria
Myalina
Pecten
Lingularia
Leptochondria
Promyalina
Battenizyga
Naticopsis
Bakevellia
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Neoschizodus
Unionites
Eobuchia
Palaeoneilo
Cardinioides
Eumorphotis
Scythentolium
Leptochondria
Entolium
Costatoria
Pseudocorbula
Pinna
Promyalina
Occurrence Frequency Occurrence Frequency Occurrence Frequency
40
Chapter 3: The effects of repeated environmental perturbations on community complexity
and faunal composition immediately after the Permian-Triassic extinction: A case study of
faunal shifts from the Induan of Panthalassa

1 – Introduction

The following is a case study of the correlation between geochemical indicators of
environmental perturbations and faunal composition in marine benthic communities of the
Griesbachian of the Western. U.S. The aim of this study was to determine if ecological shifts, in
terms of taxonomic richness, evenness-dominance metrics, functional diversity, or disaster taxon
abundance can be observed coincident with large shifts in inorganic carbon isotopes at a bed-to-
bed scale. To accomplish this, high resolution geochemical and ecological sampling of the
Dinwoody Formation at Blacktail Creek in Southwestern Montana was conducted. Similar
methods were used by Caswell and Coe (2013), measuring bivalve size relative to geochemical
indicators of anoxia (such as [Mo], 
98/95
Mo, and 
13
C
org
) during the Toarcian ocean anoxia
events, as a means to track the direct effects of environmental anoxia on benthic biota. This
current study aims to incorporate more inclusive measures of benthic community health and
complexity, and compare shifts in these metrics to perturbations of the carbon cycle. In addition
to serving as a proxy for carbon cycle fluctuations, 
13
C
carb
was used as a means to constrain the
age of the Dinwoody through geochemical correlation to sections with better biostratigraphic
constraints. Bulk ecological samples from the Dinwoody at Blacktail Creek reveal shifts in
faunal composition and community complexity throughout the section corresponding to large
shifts in 
13
C
carb
values. The oldest fauna at the bottom of the section are low in diversity and
evenness, and dominated by rhynchonelliform brachiopods. These communities are coincident
with the end of a large 
13
C
carb
excursion. Above these, communities become more even and
41
diverse, with epifaunal bivalves becoming more abundant. Communities at the top of the section
return to low diversity and high dominance condition, with high abundance of the infaunal
disaster bivalve Unionites. This is also where the first definitive occurrence of Chondrites in the
Early Triassic is found. The high dominance and low evenness communities at the top and
bottom of the Blacktail Creek section are associated with major 
13
C
carb
shifts, implying a shared
abiotic cause. Our analysis shows that this biotic shift is independent of changes in siliciclastic
input throughout the section. Therefore, I attribute this faunal shift to a “failed” partial biotic
recovery in the Griesbachian of Panthalassa, whereby these communities experienced increases
in richness and evenness relative to older communities, but were still dominated by disaster taxa,
microconchids, and microgastropods. These partially recovered communities then “failed” as
deleterious conditions associated with large negative 
13
C
carb
shifts returned to these shelf
environments.
1.1 – Environmental perturbations following the Permian-Triassic event

Geochemical evidence exists for multiple episodes of unfavorable conditions both at the
Permian-Triassic boundary and throughout the Early Triassic that may be contributing to faunal
stress either at the local or global scale. Oxygen isotope data from conodont apatite reveals
fluctuations in global sea surface temperatures (Romano et al. 2013, Sun et al. 2012), with
thermal spikes occurring at the late Griesbachian and Smithian-Spathian boundary (Sun et al.
2012). Sea surface temperatures potentially reached 36
o
C during the late Griesbachian
temperature spike, likely inducing severe thermal stress in marine shelf environments. Thermal
shock and protein degradation has been demonstrated for marine invertebrates in temperatures
exceeding 45
o
C, but severe metabolic restriction can occur at temperatures of just 35
o
C (Somero
42
1995). These thermal spikes have been attributed to ongoing volcanism-induced greenhouse
conditions from Siberian Traps degassing (Payne and Kump 2007, Sobolev et al. 2011).
Additionally, ocean anoxic events or oxygen minimum zone expansion events onto the shallow
shelf have been indicated as potential recurring conditions. Song et al. (2012) find evidence from
conodont Ce and Th/U ratios for at least three ocean anoxia events starting in the latest
Changhsingian. Algeo et al. (2008) find evidence for deep anoxic-water upwelling onto the shelf
environment in South China at the Permian-Triassic boundary through concurrent excursions in

34
S
pyrite
and 
13
C
carb
. Large bathymetric gradients in 
13
C
DIC
have been reported from South
China, and have been attributed to severe ocean stratification and expanded ocean anoxia due to
climatic warming (Song et al. 2013b). All of these conditions are likely linked to ongoing
volcanism during the Early Triassic, and can lead to a number of environmental conditions with
an associated 
13
C
carb
signature.
The carbon cycle experienced extreme perturbations during the Permian-Triassic event
that continued into the Early Triassic, likely as a result of some combination of environmental
conditions described above. Evidence of large negative and positive excursions in carbonate
carbon isotopes have been reported globally (Corsetti et al. 2005, Horacek et al. 2007a, Horacek
et al. 2007b, Payne et al. 2004). Large negative excursions occur at the Permian-Triassic
boundary, near the Griesbachian-Dienerian boundary, and near the Smithian-Spathian boundary
(Korte and Kozur 2010). These negative carbon isotope excursions have been attributed to a
number of causes, including injection of light carbon from Siberian Traps volcanism, burning
through isotopically light coal and evaporite deposits (Sobolev et al. 2011). Large scale organic
material oxidation has also been indicated as a cause of some of these negative excursions
(Horacek et al. 2007a), as well as upwelling of deep anoxic and 
13
C-depleted waters (Algeo et
43
al. 2008). An extremely large positive excursion is reported near the Dienerian-Smithian
boundary, which has been attributed to wide-scale organic carbon burial due to high primary
productivity caused by continental nutrient influx to the oceans (Horacek et al. 2007a). Negative
excursions have been found in association with 
18
O
apatite
thermal spikes, corroborating the likely
volcanic-induced greenhouse conditions that caused these negative excursions (Sun et al. 2012).
The timing of ecological recovery in the marine benthic realm is therefore of great interest when
considering the fluctuating environmental conditions in the Early Triassic.
1.2 – Recovery dynamics in Early Triassic

Recovery in the marine realm after the Permian-Triassic mass extinction has been the
topic of numerous avenues of research in recent years (e.g. Twitchett (1999); Pietsch et al.
(2014)). Traditionally, global recovery following the Permian-Triassic mass extinction has been
thought to have been suppressed uniformly for the entirety of the Early Triassic (Hallam, 1991)
either due to the sheer volume of taxonomic loss at the extinction boundary (Schubert and
Bottjer 1995), or due to reoccurring environmental perturbations stemming from ongoing
Siberian Traps volcanism (Payne and Kump 2007). More recently it has come to light that the
nature of recovery following the Permian-Triassic extinction is highly complex, spatially and
temporally variable, and far from uniform in terms of ecological signature (Beatty et al. 2008,
Hofmann et al. 2011, Hofmann et al. 2014, Pietsch and Bottjer 2014, Zonneveld et al. 2010). But
what causes such variability in recovery patterns? Current explanations range from a purely
biotic explanation, whereby community interspecies competition and regional recruitment of
taxa determines the rate of recovery (Hofmann et al. 2014), to an abiotic explanation, whereby
increases in favorable conditions such as higher oxygen and cooler temperatures allows for swift,
almost immediate recovery (Twitchett et al. 2004). Likely, most communities experiencing
44
recovery have varying degrees of biotic and abiotic factors that determine the timing and degree
of recovery, and it is therefore necessary to consider both ecological and environmental
conditions simultaneously, as this study aims to do.
2 – Geologic setting

The Lower Triassic Dinwoody Formation is a marine mixed carbonate-siliciclastic ramp
deposit outcropping in areas of Southwestern Montana, Idaho, Northwestern Wyoming, and
Northern Utah (Fig. 3.1B), and represents some of the oldest post-Paleozoic rocks in North
America. The Dinwoody was deposited during the first transgressive event of the Early Triassic
across a flat plain, within the Phosphoria Basin/Dinwoody Sea epicontinental embayment on the
Eastern Panthalassic coast, (Newell and Kummel 1942, Paull and Paull 1994a, b) (Fig. 3.1A).
The depocenter of the basin is located in Southern Idaho today, where the maximum thickness of
the Dinwoody is recorded at 750 m (Kummel 1954). The Dinwoody deposits shallow to the east
and eventually grades into or are overlain by the marginal marine Woodside and Red Peak
Formations. The boundary between the Dinwoody and Woodside Formations is time
transgressive, occurring earlier in shallower parts of the basin (Carr and Paull 1983). The Late
Permian-aged Phosphoria Rock Complex, which is characterized by unfossiliferous cherts and
low-oxygen limestones, is believed to be Guadalupian in age. The contact between the
Dinwoody and underlying Phosphoria Rock Complex is thought to be unconformable, with the
latest Permian and Permian-Triassic extinction event not recorded. In fact, very little of the
uppermost Permian is preserved in North America, as it is believed that a large regressive event
during the Lopingian left the formerly flooded Guadalupian epicratonic sea subaereally exposed.
However, this has been challenged by new finding by Saltzman and Sedlacek (2013) which
suggest that at least one continuous shallow shelf Permian-Triassic section exists in North
45
America. Most Lopingian deposits in North America come from accretionary terranes or
tectonically uplifted deep basinal deposits, (e.g. Blome and Reed 1992, Gordon Jr and Merriam
1961), and as such, no Upper Permian marine shelf deposits are known. The Dinwoody and
Woodside/Red Peak Formations record shelf deposits of a single transgressive-regressive cycle,
after which another cycle resumes marine shelf deposition with the Olenekian-aged Thaynes
Formation that overlies the Woodside Formation in some localities (Paull and Paull 1994b,
Rodland 1999) The age of the Dinwoody Formation has so far only been constrained
biostratigraphically by limited occurrences of the Griesbachian conodont Isarcicella isarcica in
the basal mudstone unit (Carr and Paull 1983, Paull and Paull 1994a). Biostratigraphically
informative ammonoids are either absent from these sections, or are not preserved well enough
for species-level identifications to be made (Kummel 1954, Orchard and Tozer 1997).
Geochemical techniques for age constraint of the Dinwoody formation at Blacktail Creek are
detailed in this study.
The Dinwoody Formation at Blacktail Creek is exposed as 120 meters of mixed
carbonate and siliciclastic shelf deposits on the western side of Blacktail Rd. in Beaverhead Co.
(Fig. 3.1C). Underlying the Dinwoody Formation here, the Wordian to early Capitanian age
Blacktail Formation exhibits a clear Paleozoic brachiopod fauna (Schock 1981). In the field, the
boundary between the Blacktail and Dinwoody Formations is evident by a resistant, well-
exposed red-brown limestone bed with abundant, large, and ribbed rhynchonelliform
brachiopods, which is immediately and unconformably overlain by a covered interval of
approximately 10m, representing the basal mudstone unit of the Dinwoody Formation. This unit
is covered and inaccessible at Blacktail Creek. Paull and Paull (1994) interpreted this unit as
deposited during the early transgression and highstand of the first Early Triassic transgressive-
46
regressive event, and it is the deepest unit within the Dinwoody. The distal mudstone unit is
characterized by the inarticulate brachiopod Lingularia borealis and ammonoids found in float
(Rodland, 1999; this study). Previous work has dated this unit to Late Griesbachian in age
(Schock, 1981), but evidence from this current study suggest an older age (see section 5.1.1).
The first exposed beds of the Dinwoody Formation occur approximately 10m above the
boundary, consisting of mudstones with low fossil content, followed by rhynchonelliform
brachiopod “pavements” (Fig. 3.2). Fossiliferous wackestone and packstone deposits typify most
of the lower and middle part of the outcrop. A large covered interval of approximately 45 m
occurs in the middle of the section. Increased siliciclastic input is observed in the upper part of
the section, with increasing grain size and cross-bedding observed at the top of the section. This
evident shallowing is interpreted as recording the regression phase of this Early Triassic
transgressive-regressive event (Paull and Paull, 1994). An apparently intrusive spring-associated
carbonate breccia deposit was documented in this study in the upper part of the section, with
reworked Dinwoody Formation inclusions (Fig. 3.2). The overlying Woodside Formation is not
well exposed at Blacktail Creek.
3 – Previous work on the Dinwoody Formation

The first detailed ecological study of the Dinwoody Formation at Blacktail is reported in
Rodland (1999) and subsequently Rodland and Bottjer (2001), examining the facies distribution
of the disaster taxon Lingularia across multiple Dinwoody localities. In fact, it was this work
detailing the ecological dominance and distribution of Lingularia that led to the inclusion of
Lingularia as a disaster taxon in Benton (2003). Rodland (1999) assessed the distribution of
Lingularia across distal, mid-shelf, and proximal facies and interpreted this as evidence of the
47
ecological opportunism of this taxon, spreading into shelf facies from which it was formerly
excluded in the Paleozoic. Rodland (1999) found no sedimentary evidence of extended
dysaerobic conditions within the Dinwoody, based on sedimentary structures of high energy flow
(hummocky cross-stratification and cross bedding) likely injecting oxygen into the mid-shelf, as
well as trace fossil evidence of vertical burrows (Diplocriterion) that are normally excluded
during low-oxygen conditions. Rodland (1999) attributes the ecological success of Lingularia in
the wake of the end-Permian extinction as an indication of high dispersal rates and an r-selective,
opportunist life strategy.
A more recent study by Hofmann et al. (2013) explored the temporal and spatial patterns
of diversity and ecological structure between multiple Dinwoody Formation localities,
representing various bathymetries along the shelf. They found low diversity and high dominance
to be characteristic of earliest communities, both in distal and proximal sections, which they
attributed to the lingering effects of the mass extinction. Following these assemblages, they
observe a partial recovery interval in proximal settings, whereby communities increase in alpha
diversity and evenness. This early recovery is not observed in distal communities, but this is
interpreted to be reflective of normal onshore-offshore diversity patterns, and not an indication of
environmental suppression of recovery. Hofmann et al. (2013) describe the fauna of the
Dinwoody as overall low in beta diversity, which contributes to the delayed recovery of diversity
and generalized life habit of community constituents, as regional recruitment of new taxa and
interspecies interactions were limited.

48
4 – Methods

Measuring and sampling of the Dinwoody Formation at Blacktail Creek was conducted
during two field expeditions in 2012 and 2015. Exposed beds were measured and characterized
for lithology, grain size, bedding thickness, and fossil components. Surrounding float material
was surveyed for presence of macrofossils and ichnotaxa in sections where cover obstructed
direct observation of beds. The basal mudstone facies of the Dinwoody at Blacktail Creek were
inaccessible despite trenching efforts, but float material from the surrounding area was collected.
Bulk ecological samples and geochemical samples were collected in situ.
4.1 – Ecological sampling

Ecological bulk samples were taken from visibly fossiliferous beds, from the top 10 cm
of the bed, to constrain for time averaging of fossil deposits (Fig. 3.2). Approximately 10 kg of
rock was collected for each ecological sample, with a total of 15 samples taken over the section
amounting to 2,500 individual specimens. Bulk samples were disaggregated and cleaned, and a
dissecting microscope and calipers used to identify and measure all fossils recovered. Taxonomic
identification of fossil genera was accomplished with the aid of published descriptions and
figured specimens, summarized in Table 3.1. Size of fossil bivalves and brachiopods was
measured at the widest point for each taxon (e.g. ventral to dorsal for pectinid bivalves and
anterior to posterior for taxa such as Unionites). Fragmented specimens, where the full length of
the shell could not be determined, were not included in calculations of average size, but included
in occurrence counts. Gastropods were measured using the diameter of the terminal (body) whorl
as opposed to the height of the spire, to account for the often missing or obscured apex whorls of
high-spired taxa such as Coelostylina. Occurrences and size of echinoid material was recorded,
49
but estimations of living individuals from disarticulated remains are difficult in the case of multi-
element echinoderm taxa and were therefore excluded from abundance calculations. However,
presence or absence of echinoids was used in faunal composition NMDS analyses.
4.2 – Geochemical sampling

Samples for geochemical analysis were taken at < 0.5 m intervals over the section, or
where exposure allowed for sampling. 108 samples of approximately 3-5 g were collected for
geochemical and thin section analysis (Fig. 3.2). Carbonate samples were drilled for powder for

13
C
carb
measurements, from clean billet surfaces with care taken to avoid obvious signs of
alteration (i.e. weathering and stylolites). Replicates for some samples were drilled from
different areas of the billet, and no significant differences in 
13
C
carb
values were observed. Bulk
carbonate powder from the samples were analyzed for 
13
C
carb
using a Picarro G2131-i cavity
ring down spectrometer. An Automate device was used to acidify the sample. 3-5 mg of
powdered sample was pre-acidified with 1 mL of 10% phosphoric acid within an evacuated test
tube to release CO
2
gas (tubes were evacuated and filled if N
2
for 15 minutes). During analysis,
an additional 3 mL of 10% phosphoric acid was used. The standards used to normalize the data
for the inorganic carbon analyses were OPT Calcite ( 
13
C
VPDB
= 2.47 ± 0.01 and 12.002% C) and
USGS40 ( 
13
C
VPDB
= -26.39 +/- 0.04 and % carbon = 40.8). Several additional replicates were
run on an Isoprime isotope ratio mass spectrometer with dual inlet (DI-IRMS), which also
yielded no significant difference in values from samples run on the Picaro system.

50
4.3 – Quantitative methods

Abundance data of brachiopods, gastropods, bivalves, and microconchids from in situ
ecological samples was tallied so that metrics of community ecological complexity can be
calculated. Firstly, generic richness and functional diversity was tallied for each sample.
Simpson’s Dominance index (D) and Shannon’s Diversity index (H) were calculated using the
software P.A.S.T ver. 1.89 (Hammer et al. 2009). Evenness (E
1/D
) was calculated by normalizing
Simpson’s Dominance to generic richness, for an independent measure of community evenness.
As in Chapter 2, these metrics were used as indicators of community complexity, as more
diverse and even communities tend to be 1) richer in functional diversity, 2) supporting more
complex interspecies interactions, and 3) more resistant to perturbation and therefore temporally
stable (Hillebrand et al. 2008). Functional group for each genus, including motility, feeding, and
life habit classifications, was determined from Paleobiology Database entries
Cluster analyses are a useful tool in ecology for visually differentiating between
assemblages based on faunal composition, by grouping assemblages with similar community
constituents and abundance distributions into clusters. In a hierarchical analysis, those clusters
are then grouped into larger clusters based on similarity (Hammer and Harper 2008). A
hierarchical cluster analysis was performed on abundance data using a constrained paired group
analysis with Bray-Curtis similarity index in P.A.S.T version 1.89 (Hammer et al. 2009). Bray-
Curtis Similarity was used in place of other distance measures (e.g. Euclidean) because it is more
appropriate for ecological abundance data (Clarke et al. 2006). A constrained analysis, whereby
clusters are forced into stratigraphic order, was used to visualize faunal shifts through the
section. However, this stratigraphic forcing sacrifices agreement between data and clusters, but
51
in this case the constrained analysis was used because stratigraphic position is informative.
Bootstrapping (N=1000) was used to determine cluster support.
Non-metric multidimensional scaling (NMDS) is an ordination technique, similar to
principle components analysis (PCA), whereby samples are positioned in multi-dimensional
space using rank order of taxa in place of Euclidian distances of differences in faunal
composition. NMDS techniques are preferable to PCA for ecological data due to the fact that no
assumption is made about the shape of the distribution (does not require normally distributed
data) (Minchin 1987), and that rank order comparisons are not sensitive to the overall size of a
collection (which may be variable due to collection size or taphonomic effects). NMDS analysis
was used to determine if partitioning occurs between siliciclastic and carbonate communities
based on community composition, and if, by extension, faunal shifts were merely a result of
increased siliciclastic deposits at the top of the section. The R package Vegan version 2.3-5
(Oksanen et al. 2016) was used to run the NMDS analysis.
5 – Results
5.1 – 
13
C
carb
excursions in the Dinwoody

The inorganic carbon isotope signature of the Dinwoody Formation at Blacktail Creek
records 2 major excursions at the bottom and top of the section, and several more minor
excursion in between (Fig. 3.3). At the bottom of the section, the minima of a large negative
excursion to values of -3.77
o
/
oo
is recorded, followed by a large positive excursion to values of
+0.32
o
/
oo
. Following this is another minor excursion, from approximately 0
o
/
oo
to -1
o
/
oo
, and
then back again to values near 0
o
/
oo
. These occur within the bottom half of the section, and it is
unclear if any excursions occur over the 40 meter covered interval. The top portion of the section
52
records 2 minor negative excursions and one major excursion at the very top of the section. The
minor excursions rage from -1
o
/
oo
to -2.5
o
/
oo
in magnitude, and the major excursion reaches
values of around -3.2
o
/
oo
. It is unclear if this negative excursion continues into more negative
values, as the topmost beds of the section are siliciclastic and therefore could not be sampled for
carbonate. The 
13
C
carb
values of the Blacktail Creek section are overall more negative than those
observed elsewhere (e.g. 
13
C
carb
at Dawen ranges from -2 to +8
o
/
oo
), which may be a result of
diagenetic effects, as recrystalization of carbonate within formational pore waters tends to
concentrate lighter carbon within the neomorphosed mineral (Marshall 1992, Tucker and Wright
2009). Despite this, direction and magnitude of shifts are likely primary, as carbonate isotope
values are usually rock-buffered and shift uniformly as a result of diagenesis (Scholle and Arthur
1980). In fact, the magnitude of these excursions is not outside the range of those observed
elsewhere, as carbon isotope excursions in the Early Triassic tend to be some of the largest
observed in the Phanerozoic (Corsetti et al. 2005).
5.1.1 – Geochemical correlation with global excursions

The major and minor excursions observed at Blacktail Creek can be correlated to those
observed in sections from South China, where conodont biostratigraphy is relatively well
constrained. The 
13
C
carb
profiles of the Dawen and Guandao sections of South China, from
Payne et al. (2004), were used for chemostratigraphic correlation of the Dinwoody at Blacktail
Creek (Fig. 3.3). Correlation between the timing of excursions between the Dawen and Guandao
sections is difficult, due to the diminished appearance of excursions at Guandao relative to
Dawen, but for the purposes of this study we rely on correlations established previously by
Payne et al. (2004). The beginning of the lowermost negative excursion in Dawen and Guandao
53
is correlated by Payne et al. (2004) to the base of the Early Triassic, following the last
appearance of the conodont Neogodolella changxingensis at the Guandao section and before the
first appearance of Hindeodus parvus (Fig.3.3). This lower Griesbachian negative excursion is
also observed in other sections globally, including in Italy and Iran (Horacek et al. 2007a;
Horacek et al. 2007b). Though the beginning of the basal negative excursion is not recorded in
our samples, (and likely occurs within the covered mudstone unit), we can correlate the apex of
the excursion to that observed at Dawen, suggesting that the age of this part of the section is
lowermost Griesbachian. This is significantly older than previously thought, as it has been
reported that the Dinwoody Formation only records late Griesbachian deposits due to an interval
of non-deposition during the Permian-Triassic and earliest Early Triassic (Schock 1981).
Following the covered interval, two successive minor negative excursions are observed at
Blacktail Creek, ranging from approximately -1.8
o
/
oo
to -2.4
o
/
oo
at their minima. In each case

13
C
carb
values then return to values of around 0
o
/
oo
before the next excursion occurs. The
minima and maxima of these two minor excursions, occurring between meter 80 and meter 105
at the Blacktail Creek section, can be linked to minor excursions occurring at the Dawen section
between meters 110 and 140 (Fig. 3.3). At the top of the Blacktail Creek section (meter 119), the
second largest negative excursion is recorded, reaching values of -3
o
/
oo
. This can be correlated to
the last of 3 successive negative excursions observed at the Dawen section. The magnitude of the
excursions are larger at Blacktail Creek than at Dawen, and overall values are more negative as
well. These differences in magnitude of excursion can be linked to localized processes. However,
the quick succession of the three negative excursions observed at both Blacktail Creek and
Dawen leads me to conclude that they are, in fact, the same events.
54
The end of the Griesbachian substage at the Dawen section is marked by positive
excursion of approximately +4
o
/
oo
magnitude which is preceded by three smaller negative
excursions which are correlated to those at Blacktail Creek. As the positive excursion is not
recorded at Blacktail Creek, I conclude that the Griesbachian-Dienerian boundary is not recorded
within the Dinwoody here.
5.2 – Faunal Composition

28 genera of invertebrates were recorded from the Dinwoody at Blacktail Creek,
spanning 18 orders and 9 life mode categories (Fig. 3.4). Table 3.2 summarized the taxa
recorded, their life mode and abundances. The most abundantly represented life mode is
stationary, suspension feeding epifauna, mostly due to the high abundance of rhynchonelliform
brachiopods in older samples and pectinid bivalves throughout the section.
5.2.1 – Disaster Taxa

The phosphatic “inarticulate” brachiopod Lingularia is the only taxon to occur in all
collections throughout the section, and occurs quite abundantly in several assemblages (Fig.
3.4e-f; Fig. 3.5). There is also evidence of Lingularia material in all thin sections (Fig. 3.6).
Community composition changes dramatically over the section, but Lingularia remains a
constant occurrence throughout. Preservation of apparently unaltered shell material is also
evident in many hand samples and thin sections. The Lingularia zone of the Dinwoody is
recognized as occurring in some Wyoming outcrops, in the lower part of the section, and is used
for correlation across outcrops of the Dinwoody (Newell and Kummel 1941). However, a clear
subdivision of the Lingula zones is lacking at Blacktail Creek, as has been reported to be typical
of some southwestern Montana sections (Ciriacks 1963, Hofmann et al. 2013, Rodland 1999).
55
Sample BTM20 represents a highly abundant Lingularia assemblage, and likely corresponds
with the Lingularia zone known from above the distal mudstone unit at other localities (Fig. 4.6).
The high occurrence frequency of Lingularia across multiple samples with differing depositional
environments, as well as high abundance in some samples, corroborates the classification of
Lingularia as a disaster taxon. In the Dinwoody at Blacktail Creek, Lingularia exhibits
particularly successful survival in the aftermath of the extinction.
Higher in the section, the disaster taxon Claraia (Fig. 3.4i) becomes more abundant (Fig.
4.5), likely corresponding to the Claraia zone of Newell and Kummel (1942), though a clear
zonation is again hard to distinguish in this section, as both Lingularia and Claraia are shown to
range throughout the section. This lack of clear zonation was also reported from other sections of
the Dinwoody in southwestern Montana, such as Hidden Pasture and Sandy Hollow, by
Hofmann et al. (2014). Still, Claraia exhibits high abundance in a few samples, but is not as
widely distributed as Lingularia in this section.
Of the remaining disaster taxa, Eumorphotis exhibits the highest abundance and
occurrence frequency within the middle of the section, while Unionites (Fig. 3.4 g) dominates
samples at the top of the section (Fig. 3.6). Eumorphotis (Fig. 3.4 k, p) is found to occur in a
dense, likely winnowed assemblage in sample BTM79, where it is found most abundantly
throughout the section. Promyalina (Fig. 3.4 a) does not exhibit high abundance relative to the
other disaster taxa in any sample. All samples exhibit high disaster taxon relative abundance
(>50%) throughout the section, except the basal-most three which are dominated by
rhynchonelliform brachiopod “pavements” (Fig. 3.6).

56
5.2.2 – Microgastropods
Gastropods represented a significant amount of fossil occurrences in bulk samples
BTM16 (79% total abundance) and BTM52 (15% total abundance), though some individuals
were recovered from other collections as well (Fig. 3.7). Three gastropod taxa were identified,
Coelostylina (Fig. 3.7 Dd), Strobeus (Fig. 3.7 D,a-b), and an as of yet indeterminate
vetigastropod (Fig. 3.7 Dc). In samples where gastropods are abundant (BTM16 and BTM52),
most are below 1mm in diameter (Fig. 3.7 A-B), and a few larger gastropods with diameters
greater than 1 mm were recovered from collections where gastropods were rare (BTM62,
BTM75, and BTM90, Fig. 3.7 C). The microgastropods appear partially or fully phosphatized in
both hand sample and thin section (Fig. 3.6h). Microgastropod occurrences are well documented
in the Dinwoody Formation (Marenco et al. 2013).
5.2.3 – Microconchids

Calcareous microconchid encrusters were observed in several collections, sometime
representing a significant amount of invertebrate abundance (~7% in sample BTM65). Sample
BTM65 also exhibits the highest encrusting frequency in the section, with approximately 10% of
shells encrusted with one or multiple planispiral microconchids (Fig. 3.8). Interestingly,
encrusting microconchids are found in equal amounts on both epifaunal (such as Eumorphotis)
and infaunal (such as Unionites) bivalve shells, but were not observed on any brachiopod shells
(e.g. Lingularia). Microconchids were also observed in multiple thin sections, mostly unattached
within the matrix (Fig. 3.6c). The only instances of non-planispiral morphologies are observed in
these unattached microconchids in thin section. Microconchids occur more frequently in thin
section, than in hand sample, and exhibit a higher degree of micro-structure preservation. The
57
sheet-like microstructure of the microconchid shells in thin section suggest similar taxonomy as
those found by He et al. (2012) in South China. A single occurrence of a microconchid
encrusting an echinoderm ossicle was observed in thin section (Fig. 3.8), though the preservation
is such that it is difficult to determine if it is planispiral or not.
5.2.4 – Microfossils

Fossils observed in thin section from Blacktail Creek ecological samples corroborate
faunal groups observed in hand samples. Echinoid spines and echinoderm fragments were
recorded throughout the section (Fig. 3.6 a-b) and appeared to be absent only in highly
siliciclastic collections, though this is likely a taphonomic effect. Thin phosphatic brachiopod
fragments, likely of the genus Lingularia, were observed in all thin sections throughout the
section. These fragments are likely of original shell material, as fine-scale details of internal
laminae and punctate fabrics are well preserved in many instances (Fig. 3.6e). Rhychonelliform
brachiopods also exhibit preservation of fine-scale fibrous fabrics within the shells (Fig. 3.6d),
though this is unlike what is observed in hand sample, where most are recrystallized and lacking
detailed external morphology.
An enigmatic microfossil composed of filamentous structures in a loosely radial
arrangement was observed in sample BTM31 in a micritic peloidal matrix (Fig. 3.6g). These
structures preserve no microstructure or internal morphology, and are approximately 200-300
m long and 5 m thick. There were no other occurrences of these microfossils. These structures
are potentially a type of filamentous microbe.
58

5.2.5 – Echinoids

Several disarticulated echinoid elements were recovered from multiple beds at Blacktail
Creek, in addition to a single partially articulated interambulacrum of a cidaroid echinoid (Fig.
3.4 l-o). Spines occurred in several collections, both in hand sample and thin section, but
definitive taxonomic identification of spine material alone is not possible. However, the straight,
non-ornamented nature of the spines is reminiscent of those found on the cidaroid triadotiarid
Lenticidaris utahensis of the Smithian-age Moenkopi Formation of Utah (Kier 1977b).
Additionally, a single interabulacral plate was recovered that is also likely triadotiarid in nature,
based on the relatively long width to height of the plate, the confluence of the areoles, and the
fact that the tubercle is perforate (Kroh and Smith, 2010). The partially articulated echinoid test
fragment of two interambulacral plates (Fig. 3.4o) cannot be identified to the same level, due to
the fact that plate boundaries are obscured and relative plate width and height cannot be
measured. However, this fragment is likely cidaroid in nature based on the perforation and
crenulation of the tubercle, and the relatively large size of the primary tubercle compared to the
scrobicular tubercles (Kroh and Smith, 2010). It is not possible to identify either of these
specimens to the species level, as a relatively complete and articulated test is required to observe
species-level traits such as plate suturing across the test. Cidaroids are the only order of
echinoids known from the Early Triassic (see Chapter 4 for additional discussion), and
triadotiarid cidaroids are the only family of echinoids definitively known from the Western U.S.
at this time, though they are often misidentified as belonging to the family Miocidaridae.
Disarticulated spines are known from many Western U.S. Lower Triassic deposits, but most are
Olenekian in age. The Griesbachian echinoid occurrences at Blacktail Creek represent some of
59
the oldest post-Paleozoic occurrences of echinoids (Kroh and Smith, 2010), and extend the
known occurrence of the Triadotiaridae, a Mesozoic cidaroid stem lineage, into the Induan.
5.2.6 – Biostratigraphically informative taxa

Biostratigraphic correlation of the Dinwoody in some localities is difficult, due to the
rarity of biostratigraphically informative ammonoids and conodonts (Paull and Paull, 1994) and
the lack of identifiable Lingularia and Claraia subzones. However, with this study we are able to
compliment the geochemical correlation made possible with the 
13
C
carb
profile, with newly
discovered ammonoid specimens from the basal units of the Dinwoody at Blacktail Creek.
Several ammonoid specimens (Fig. 3.9 a-c) were recovered from float near the lower few meters
of the outcrop, likely from the covered distal mudstone facies. This material was not used in
abundance calculations as it was not collected in situ, but represents a unique ammonoid-lingulid
assemblage (Fig. 3.9d) not observed elsewhere in the section, corroborating the interpretation of
these units as distal. These platycone ammonoids (Fig. 3.9a) are likely of the genus Ophiceras,
based on the relatively smooth outer shell morphology, evolute and laterally compressed form,
and wide umbilicus. The preservation quality of the specimens makes identification to the
species level difficult, as fine-scale details of shell ornamentation and septae shape are unknown.
Ophiceras species typify lower Griesbachian assemblages of the Otoceratan age (Kummel 1959,
1970, Orchard and Tozer 1997) in Idaho and Montana.
Additionally, biostratigraphically informative Claraia species, Claraia stachei and
Claraia extrema (Fig. 4.4i; Ciriacks 1963) occur throughout the middle part of the section, and
are co-occurring with ammonoids of the Otoceras zone at other localities (Kummel, 1959).
Additionally, Claraia stachei is concurrent with the Griesbachian conodont Isarcicella isarcica
60
(Carr and Paull, 1983). However, as these species have also been reported as ranging both above
and below the Otoceras zone at other Dinwoody localities (Newell and Kummel, 1942; Kummel,
1959), the usefulness of these taxa are limited to just indicators of Griesbachian strata. The
presence of Griesbachian and absence of Dienerian index taxa corroborates interpretation of the
Dinwoody section at Blacktail Creek as Griesbachian in age.
5.2.7 – Trace Fossils

Various ichnotaxa were recovered from both bulk samples and float material along the
section (Fig. 3.10). Specimens of the bedding plane locomotion trace Palaeophycus were
recovered throughout the section, some with a diagenetic dark halo surrounding the burrows
(Fig. 3.10a,d) and others with raised smooth walls on either side (Fig. 3.10g,f). These traces
occurred in both carbonate and siliciclastic collections, from the bottom of the section (likely
from the covered mudstone unit), to approximately meter 90 (Fig. 3.2).
Some Palaeophycus traces from siliciclastic deposits were found in association with
small vertical burrows of unknown classification (Fig. 3.10g). These burrows are shallow
(~5mm), small in diameter (~5mm), and puncture the bed in which they occur but not underlying
beds. The shallow depth of these traces and lack of multi-bed penetration excludes identification
as Skolithos or Lingulichnus, but may be representing similar behavior. Kummel and Teichert
(1970) report similar traces from the Griesbachian Mianwali Formation of the Salt Ranges in
Pakistan in association with planar traces, but these are simply described as behavior of “shallow
digging or resting”. Specimens of these traces were recovered from float from both the bottom
and middle of the section, over large intervals of cover potentially representing fine-grained,
61
non-resistant distal facies. Specimens from the bottom of the section occur with dense Lingularia
beds, while specimens from the middle cover interval are otherwise non-fossiliferous.
Several specimens of Chondrites from a single bedding plane were recovered from the
top of the section (BTM93, Fig. 3.10b-d). These specimens occur within a cross-bedded fine
grained sandstone, with abundant infaunal bivalves Unionites and Neoschizodus. The traces
occur on a darker surface underlying a layer of dense fossil bivalves, and are infilled with lighter
sediment from above. The vertical central shaft of the Chondrites trace is not preserved and was
likely reworked by wave action as evidenced by ripple marks on the overlying surface, so true
depth of this trace into the sediment cannot be measured. Indeed, these traces are only clearly
visible on the bedding plane. Despite this, the narrow, branching/dendritic structure is adequate
for identification. In some cases, a dark, possibly diagenetic halo is observed outlining some of
the burrows.
Notably absent from the Blacktail Creek section are Diplocraterion traces that are
prominent in other Dinwoody outcrops, such as Hidden Pasture. This is likely due to the more
basinal position of Blacktail Creek relative to Hidden Pasture, as the Diplocraterion traces there
tend to occur within more proximal and high-energy hummocky cross-stratified beds at Hidden
Pasture and elsewhere (Rodland, 1999).
5.3 – Faunal shifts

Rhynchonelliform brachiopods (i.e. “articulated” brachiopods) are present and
ecologically dominant at the bottom of the section, gradually decreasing in abundance and
diversity up section (3.11 A). There are no rhynchonelliform brachiopods present after sample
BTM31 at Blacktail Creek, though linguliform brachiopods continue to be an important
62
community constituent throughout (Fig. 3.11). In the bottommost samples BTM13 and BTM14,
the rhynchonelliform brachiopods produce a dense monospecific packstone pavement, described
previously by Newell and Kummel (1942) in the Dinwoody. This early Griesbachian resurgence
of rhynchonelliform brachiopods, representatives of the Paleozoic fauna that are displaced by the
Modern fauna beginning at the Permian-Triassic boundary (Fraiser and Bottjer 2007), has been
described from other Early Triassic sections as well (Chen et al. 2005). These taxa likely
represent extinction survivors that later give rise to a diverse Mesozoic brachiopod fauna.
Following the disappearance of rhynchonelliform brachiopods at Blacktail Creek (the
“lower fauna”), a more diverse fauna of epifaunal and infaunal bivalves typify assemblages in
the middle part of the section (the “middle fauna”; Fig. 3.11). These also exhibit high abundance
of disaster taxa mostly of the epifaunal pectinid bivalves Claraia and Eumorphotis. Additionally,
sporadic occurrences of abundant microgastropods and microconchids are observed (Fig. 3.2).
These assemblages typify most of the fossiliferous beds in the middle of the section at Blacktail
Creek. At the top of the section, assemblages shift to ones dominated by infaunal bivalves (the
“upper fauna”), mostly dominated by the disaster taxon Unionites. The constrained pair-group
cluster analysis clearly shows these three distinct faunal composition shifts across the section
(Fig. 3.11), comprised of the lower rhynchonelliform dominated group, the middle epifaunal
bivalve dominated group, and the upper infaunal bivalve dominated group. These assemblages
are relatively well supported by bootstrap values, of 64, 72, and 69 respectively (N=1000).
Sample BTM20 groups with the “lower fauna” samples in the cluster analysis, but generic
richness and evenness is higher in this sample, matching more so samples from above (Fig.
3.12). Therefore, for statistical testing, this sample is grouped with the “middle fauna”.
63
The “lower” (sample BTM13 and BTM14) and “middle” fauna (samples BTM20 to
BTM75) exhibit significantly different generic richness and dominance with “middle” fauna
samples with higher median richness and diversity and lower dominance (Wilcoxon signed-rank
test p values = 0.041 and 0.036, respectively. a = 0.05, Fig. 3.12). Additionally, the “middle” and
“upper” (BTM79 to BTM93) fauna exhibit statistically different richness and diversity, but not
dominance (Wilcoxon signed-rank test p values = 0.006 and 0.148, respectively; a = 0.05, Fig.
3.12).
These faunal shifts are observed to correlate with the timing of large excursions in

13
C
carb
values, which occur at the top and bottom of the section. “Lower” fauna samples BTM13
and BTM14, with low-richness and high dominance, occur immediately above the minima in

13
C
carb
values observed at the bottom of the section (Fig. 3.13). “Middle” fauna samples
correspond to a relatively quieter interval of 
13
C
carb
, though there are still minor isotope
excursions observed. The “upper” fauna, with low richness and high dominance, are again
associated with a large negative 
13
C
carb
excursion (Fig. 3.13). Correlation between magnitude of
carbon isotope shifts and generic richness is statistically significant (Pearson’s r = - 0.56, p value
= 0.028; a = 0.05), showing a negative correlation between large isotope shifts and high richness
(Fig. 3.15 A). There is also a significant negative correlation observed with Shannon’s diversity
index (Pearson’s r = - 0.54, p value = 0.038; a = 0.05. Fig. 3.15 D). Other metrics of community
health are also reported, including normalized evenness (E
1/D
), average body size, and functional
diversity, but none of these metrics show significant correlation with magnitude of carbon
isotope shifts. These correlations are, however, in the directions that would be expected if large
carbon isotope shifts are associated with poor community health. For example, there is a positive
correlation with isotope shifts and community dominance, and a negative correlation with
64
functional diversity and body size (Fig. 3.15 B, E, F). The correlation of timing of these faunal
shifts, changes in community health and complexity, and large 
13
C
carb
excursions implies a
shared causal mechanism.
5.3.1 – Testing for taphonomic biases

Of the total 15 ecological samples in this study, there are 8 carbonate and 7 siliciclastic
collections. There appears to be no significant partitioning of faunal composition and abundance
structures between carbonate and siliciclastic samples (Fig. 3.14A), despite siliciclastic deposits
becoming more common up-section (Fig. 3.2). Epifaunal bivalves are well represented in both
carbonate and siliciclastic deposits, despite an expected bias towards carbonate deposits
(Clapham et al. 2006). Similarly, infaunal bivalves and the infaunal Lingularia are well
represented between lithologies, despite an expected bias for siliciclastic environments (Clapham
et al. 2006). Rhynchonelliform brachiopods show the only clear lithologic preference, occurring
only in carbonate samples. Dominance and richness are not significantly different between
carbonate and siliciclastic environments (Wilcoxon signed-rank test p = 0.613 and 0.599,
respectively. a = 0.05; Fig. 3.14B). Additionally, rank-order NMDS shows no clustering of
collections based on lithologies (Fig. 3.14C). Therefore, it would appear that faunal shifts
observed across the section are indeed independent of lithologic change, and not simply an
artifact of substrate preference of the taxa or taphonomic biases.
6 – Discussion
6.1 – Microconchida as a disaster taxon

Microconchids, most likely a type of lophophorate (Taylor et al., 2010), have been
known to occur either free-living in microbial mat buildups or as encrusters on shelly fauna in
65
Early Triassic assemblages globally (He et al. 2012, Yang et al. 2011, Zatoń et al. 2013). He et
al. (2012) observed a high frequency of occurrence and abundance of Microconchida in
lowermost Triassic boundary sections in South China, within both distal and proximal facies.
Planispiral where found encrusting Claraia shells in the deep basinal facies, where Claraia
represented one of the few abundantly occurring macrofossils there. In proximal carbonate
microbial facies, they found the microconchids growing as spired forms, presumably to grow
above accumulating microbial mat material. We find similarly spired specimens of free-living
microconchids in micritic matrix in thin section (Fig. 4.6c), though these occur in non-
microbialitic wackestone deposits. The planispiral forms found encrusting on bivalve shells
resemble those found by He et al. (2012) in the Induan of South China, more so than the more
inflated forms found by Zatoń et al. (2013) in Spathian western U.S. collections. A clear
taxonomic identification of the planispiral encrusting microconchids found at Blacktail Creek is
not possible due to the moldic preservation of those specimens, but sheet-like microstructure
observable in thin section is similar specimens to identified as Microconchida by He et al.
(2012).
It has been postulated that these microconchids are disaster taxa, in that they proliferate
in normal marine facies, across multiple depositional environments, due to the opening of niche
space cause by the extinction and a physiological tolerance to deleterious conditions. The
microconchids observed at Blacktail Creek occur in a normal marine, mid to proximal ramp
setting in the Griesbachian of the western U.S., adding to the list of known occurrences of
microconchids across multiple depositional environments following the Permian-Triassic mass
extinction. Small-bodied invertebrates are generally less susceptible to thermal stresses than
larger taxa (Fenchel and Finlay 2008). It is likely that these Early Triassic microconchids
66
exhibited similar physiological resilience, and their distribution and abundance globally at this
time suggests that these are truly disaster forms.
6.2 – Chondrites occurrence in the Early Triassic

The Chondrites specimens recovered from Blacktail Creek represent one of the few
definitive occurrences of Chondrites in the Early Triassic, and the only one known from a
sandstone. Wignall and Hallam (1993) report Chondrites from more typical shale substrates of
the Mianwali Formation of the Salt Ranges in Pakistan. Hofmann et al. (2011) report a single
potential Chondrites specimen from the Werfen Formation of the Italian Dolomites, but such
identification is dubious as no clear branching or dendritic structure is evident.
The tracemaker of Chondrites has been postulated to have physiological adaptations to
resist low oxygen conditions, owing to the characteristic tiering depth of these trace fossils, as
well as the occurrence of Chondrites-only assemblages in low oxygen facies such as black shales
(Bromley and Ekdale 1984, Ekdale and Mason 1988, Savrda and Bottjer 1986). Chondrites has
been described as an indicator of anoxia (Ekdale 1985), but is more appropriately described as an
indicator of near-anoxia, as Chondrites traces disappear when complete water column anoxia is
present (Savrda and Bottjer, 1986). Additionally, Chondrites has been known to occur in
sediments with no evidence of oxygen limitation. Ekdale (1985) and Bromley (1990) describe
Chondrites as an opportunistic, r-selected ichnotaxon due to its propensity to occur in dense,
monospecific assemblages in low oxygen sediments, when other larger or more complex traces
are absent. It is hypothesized that the Chondrites behavior represents burrowing for the purposes
of accessing the organic-rich sediment below the sediment redox boundary, where pore waters
are often euxinic and poisonous to most invertebrates. With these adaptations, it is expected that
67
the Chondrites tracemaker would be able to proliferate and occur in great abundance in geologic
intervals marked by widespread seafloor anoxia, such as the OAE events associated with the
Permian-Triassic and Triassic-Jurassic events. Despite this, little evidence of this deep-tiering
ichnotaxon exists in the Early Triassic, even in fine-grained sections, like Spitsbergen where
preservation would be favorable and Chondrites has been reported from Permian deposits there
(Wignall et al. 1998).
The occurrence of Chondrites at Blacktail Creek within a cross-bedded fine-grained
sandstone suggests that the tracemaker was living proximally to shore, in an environment where
organic content in sediment is limited relative to more distal and lower-energy deposits.
Hertweck et al. (2007) report on Modern Chondrites-like traces from sandy tidal flats in the
German Wadden Sea, in association with Scoloplos armiger and Heteromastus filiformis,
polychaetes that live in well oxygenated, wave-mixed siliciclastic environments. Patches of
anoxic sediments are known to form within these deposits periodically (Freitag et al. 2003),
though no Chondrites-like traces have been reported from these areas. The appearance of
Chondrites in similar environments in the Griesbachian suggests a shift in strategies from both
Paleozoic and later Mesozoic occurrences of this ichnotaxon, perhaps as a response to oxygen
limitation present in deeper waters at this time. The Chondrites tracemaker may be excluded
from deeper facies, where it is most often found at other times, due to distal shelf complete
anoxia caused by OMZ incursions (Algeo et al. 2011). Interestingly, the tracemaker appears to
be restricted to inner shelf facies in the Early Triassic where thermal and wave stresses are
highest and organic content in sediment likely lowest. Lack of preservation of this trace fossil
within these environments due to wave reworking may also explain the apparent lack of
Chondrites during this time.
68
6.3 – Failed recovery attempt

Recorded within the Dinwoody Formation at Blacktail Creek is a potential ‘failed
recovery attempt’, whereby assemblages appear to gain in richness, evenness, and functional
diversity throughout the Griesbachian substage, only to return to high dominance, low-richness
conditions at the top of the section. This recovery attempt begins in the lower 15 m of the
section, following the replacement of rhynchonelliform-dominated communities with more
diverse bivalve communities. These “recovered” communities have higher richness and evenness
than those below, and represent more diverse life modes and niche space utilization. But still,
high dominance of disaster taxa, high occurrence frequency of Lingularia, microconchids and
microgastropods suggests that these communities are not fully recovered. Hofmann et al. (2014)
described the early recovery observed at other, shallower Dinwoody outcrops as “partial”, in that
alpha diversity increases throughout the section but overall regional beta diversity was still
limited. We believe that the assemblages at Blacktail Creek are also part of this “partially”
recovered fauna. However, we also observe a relapse of recovery that was not documented by
Hofmann et al. (2013). Our analysis suggests that this reduction in community complexity and
shift in faunal constituents is not an artifact of changing lithologies throughout the section, and
likely represents a real biological signal. It is not apparent why this relapse in recovery was not
observed in the proximal and distal sections surveyed by Hofmann et al. (2013), but could be due
to insufficient section sampling.
Evidence of “early” recovery has been found in several Early Triassic sections (Hofmann
et al. 2011, Hofmann et al. 2014, Song et al. 2011), where benthic communities experience
increased complexity (richness, evenness, ichnotaxon diversity, functional diversity, etc.) within
what has been traditionally considered the Early Triassic delayed recovery interval. However,
69
there has been very little documentation of a failure of these early recovery attempts within the
same section (Pietsch et al. 2014). The Permian to Dienerian Wadi Wasit Block of Oman is one
of these few examples of an initiated recovery attempt that subsequently failed. Benthic
communities exhibit increasing diversity and body size of gastropods up section, only to be
truncated by a drowning event in the Dienerian (Krystyn et al. 2003, Pietsch et al. 2014). Though
the circumstances of this failed recovery event are not similar to those at Blacktail Creek, which
records shallowing up section, we see that these incipient recovery attempts can be highly
dependent on environmental stability.
I find the timing of the faunal shifts observed at Blacktail Creek to be correlated with
major 
13
C
carb
excursions. These excursions are also observed globally, most significantly from
Tethyan sections in South China, Italy, and Iran (Payne et al. 2004; Horacek et al. 2007a,
Horacek et al. 2007b). The correlation of these events between multiple regions suggests a
common cause, and the coincidence of timing with the faunal shifts observed at Blacktail Creek
suggests a likely biotically disruptive condition linked to these events. Several conditions have
been proposed to produce the carbon isotope shifts observed during the Permian-Triassic and
Early Triassic interval. These include chemocline shallowing or oxygen minimum zone
expansion (Algeo et al. 2008; Algeo et al. 2011), causing euxinic 
13
C
carb
depleted waters to
incur onto shallow shelf environments. However, it is not likely that this is the direct abiotic
stressor occurring at Blacktail Creek, as no lithologic evidence of changing oxygen availability is
observed across the section, and a prevalence of pyrite was not found in any samples. The single
occurrence of Chondrites at the top of the section does not necessarily mean that low-oxygen
conditions were prevalent at this time, as this ichnotaxon is known as a ‘facies breaker’,
70
occurring in many different depositional facies of varying oxygen availability (Bromley and
Ekdale 1984).
It is more likely that these negative isotope excursions are caused by injection of
isotopically light carbon from Siberian Traps volcanism, and that greenhouse gas induced
warming at this time lead to the truncation of recovery ay Blacktail Creek. Yin et al. (2007)
proposed that the end-Permian extinction was a pulsed event, with the major extinction occurring
at the Permian-Triassic boundary, and a secondary extinction event occurring in the Late
Griesbachian. Yin et al. (2007) attributed this secondary extinction within the Griesbachian to
deleterious conditions caused by a second Siberian Traps outgassing event. In fact, we see
evidence of sea surface temperature spikes during the sampled interval, reported by Sun et al.
(2012), and attributed also to volcanic greenhouse effects. We believe the benthic fauna at
Blacktail Creek were able to experience temporary relief from thermal stressors and experienced
a partial recovery of community complexity, which was subsequently truncated due to extreme
temperature experienced by these communities through a shallowing event. Interestingly, the
abundance of the infaunal disaster bivalve Unionites during this time may be suggesting a
physiological resilience of this taxon to thermal stressors.
7 – Conclusions

A high resolution ecological survey of the Griesbachian Dinwoody formation at the
Blacktail Creek section in southwestern Montana reveals several interesting faunal shifts across
the section, correlated with large perturbations of the carbon cycle likely linked to Siberian Traps
volcanism. The latest Griesbachian volcanism event is correlated with a failed recovery within
the Blacktail Creek fauna, likely driven by greenhouse induced thermal spikes. Recorded herein
71
is one of a few examples of ‘early’ incipient recovery in benthic communities that is followed by
an apparent failure of recovery, and is the only event of this nature that has been attributed to
thermal stress. Additionally, this high resolution paleontological survey of Blacktail Creek
revealed several novel discoveries, including the first definitive occurrence of Chondrites in a
sandstone in the Early Triassic, an abundance of microconchid tubeworms of both free-living
and encrusting microconchids, and the oldest known occurrence of a triadotiarid echinoid.

72
Figures and Tables

Table 3.1 – List of publications used as references for taxonomic identifications of fossil taxa,
based on systematic descriptions and figures found therein. Groups, time period, and region of
taxa described are also listed.

73
Reference Group Time Span Region
Brayard et al., 2015 Gastropod Early Triassic Panthalassa (Western U.S.) and Boreal (Greenland)
Broglio Lorgia et al., 1986 Brachiopod, Bivalve, Gastropod Permian-Triassic Boundary Tethys (Italy)
Broglio Lorgia et al., 1986B Brachiopod, Bivalve, Gastropod, Echinoid Permian-Triassic Boundary Tethys (Italy)
Bruhwiler et al., 2008 Ammonoid Induan Tethys (South China)
Chen et al., 2005 Brachiopod Permian-Triassic Boundary Tethys (South China)
Ciriacks, 1963 Bivalve Permian to Triassic Panthalassa (Western U.S.)
Hautmann et al., 2011 Bivalve Induan Tethys (South China)
Hautmann et al., 2013 Bivalve, Ammonoid Olenekian Panthalassa (Western U.S.)
He et al., 2012 Microconchid Permian-Triassic Boundary Tethys (South China)
Hofmann et al. 2013 Bivalve, Gastropod, Ammonoid, Echinoid Olenekian Panthalassa (Western U.S.)
Hofmann et al. 2013B Brachiopod, Bivalve, Gastropod Olenekian Panthalassa (Western U.S.)
Hofmann et al. 2014 Brachiopod, Bivalve, Gastropod, Echinoid Induan Tethys (Italy)
Hofmann et al., 2011 Brachiopod, Bivalve, Gastropod Induan Panthalassa (Western U.S.)
Hoover, 1979 Brachiopod Induan Panthalassa (Western U.S.)
Kaim et al., 2010 Gastropod Induan Tethys (South China)
Kier, 1977 Echinoid Olenekian Panthalassa (Western U.S.)
Komatsu et al., 2006 Bivalve Induan Tethys (South China/ Vietnam)
Krystyn et al., 2003 Bivalve, Ammonoid Permian-Triassic Boundary Tethys (Oman)
Nutzel and Shulbert, 2005 Gastropod, Echinoid Olenekian Panthalassa (Western U.S.)
Yin, 1985 Bivalve Permian-Triassic Boundary Tethys (South China)
74
Table 3.2 – List of taxa found in samples, total abundance of each, order classifications, and life
mode classifications for motility, feeding, and life habit types. Life mode information was
extracted from the Paleobiology Database. Life mode for unknown bivalve taxon sp. A was
determined based on the morphology of the shell, and it’s similarity to other taxa with similar
outer shell morphology (e.g. Unionites, Neoschizodus). The life mode and systematics of
Unionites fassaensis has recently been revised (Foster et al., in press), and is classified as a
deposit feeder. This is reflected in the table entry for Unionites, but has not been used in
functional diversity calculations, pending further revision of the genus as a whole.

75
Genus Abundance Order Molity Feeding Life Habit
Bakevellia 9 Ostreida Staonary Suspension Feeding Semi-infaunal
Claraia 61 Pecnida Staonary Suspension Feeding Epifaunal
Coelostylina 566 Murchisoniina Facultavely Mobile Suspension Feeding Epifaunal
Entolium 13 Pecnida Facultavely Mobile Suspension Feeding Epifaunal
Eumorphs 627 Pecnida Suspension Feeding Epifaunal
Leptochondria 40 Pecnida Suspension Feeding Epifaunal
Lingularia 305 Lingulida Facultavely Mobile Suspension Feeding Infaunal
Myalina 18 Myalinida Facultavely Mobile Suspension Feeding Epifaunal
Naria 1 Euomphalina Mobile Carnivore Epifaunal
Neoschizodus 103 Trigoniida Facultavely Mobile Suspension Feeding Infaunal
Obnixia 242 Terebratulida Staonary Suspension Feeding Epifaunal
Permophorus 5 Cardiida Facultavely Mobile Suspension Feeding Infaunal
Pernopecten 6 Pecnida Facultavely Mobile Suspension Feeding Epifaunal
Promyalina 95 Myalinida Facultavely Mobile Suspension Feeding Epifaunal
Scythentolium 16 Pecnida Facultavely Mobile Suspension Feeding Epifaunal
Strobeus 9 Murchisoniina Mobile Carnivore Epifaunal
Towapteria 8 Ostreida Staonary Suspension Feeding Epifaunal
Unionites 219 Trigoniida Facultavely Mobile Suspension Feeding Infaunal
Bivalve indet. (Sp. A) 89 Trigoniida? Facultavely Mobile? Suspension Feeding? Infaunal
Pecten Indet. 29 Pecnida Facultavely Mobile Suspension Feeding Epifaunal
Microconchid indet. 30 Microconchida Staonary Suspension Feeding Encrusng
Vegastropod indet. 4 Vegastropoda Mobile Grazing Epifaunal
?Criendenia 1 Pecnida Staonary Suspension Feeding Epifaunal
?Ombonia 2 Orthoteda Staonary Suspension Feeding Epifaunal
?Trigonodus 1 Unionida Facultavely Mobile Suspension Feeding Infaunal
?Unicardium 1 Lucinida Facultavely Mobile Chemosymbioc Infaunal
Triadoatrid indet. - Cidaroida Mobile Grazing Epifaunal
Ophiceras sp. - Cerada Mobile Carnivore Nektonic
Staonary
Staonary
/Deposit
76
Figure 3.1 – A. Early Triassic paleogeographic position of the Blacktail Creek locality, on the
eastern coast of the Panthalassic Ocean (after Scotese, 2001). The Dinwoody is a ramp deposit
within the Phosphoria Basin, an epicontinental embayment on the western coast of Pangea. B.
Map of present-day position of the Blacktail Creek locality in southwestern Montana, just south
of the city of Dillon, with paleo-shoreline shown (after Paull and Paull, 1994). C. Simplified
geologic map of the Blacktail Creek outcrop, in the yellow undifferentiated Dinwoody/Woodside
Formation, after Lonn et al. (2000). Outcrops of the Permian and Triassic deposits are found on
the western side of Blacktail Rd. (Rodland, 1999).

77
UT
sdfhsag
200 km
© d-maps.com
ID
MT
WY
Blacktail Creek
Blacktail Rd
Tr
Dinwoody +
Woodside Fms
Quaternary
Deposits
P
Phosphoria
Fm
P
Quadrant
Fm
P
Snowcrest Range
Group
J-K
Ellis Group
500 m
A
B C
Panthalassa
Paleotethys
Neotethys
78
Figure 3.2 – Generalized stratigraphic column of the Dinwoody Formation at Blacktail Creek,
showing lithology and grain size. Measurement of the section began at the first beds exposed
above the top of the Phosphoria Formation, but the presence of the distal mudstone member is
assumed. Additional substantial cover of ~40 meters is encountered in the middle of the section
(~35 meters up). Samples for geochemical analysis (blue diamonds) and ecological analysis
(BTM) are shown next to sampled beds. Dominant faunal groups, ichnotaxa, and sedimentary or
fossil indicators of energy regime throughout the section are shown, including observations from
float material (indicated by asterisk*).

79
100
80
40
20
mud
wacke
pack
silt
vf
SAND
fm
SCALE (m)
0
-10
LIMESTONE
LITHOLOGY FOSSILS TRACES
STRUCTURES SAMPLES
SAMPLES
FOSSILS
TRACES
STRUCTURES
LITHOLOGY
* *
*
* *
*
* *
*
- Ammonoid
- Echinoid
- Pectinid Bivalve
- Infaunal Bivalve
- Gastropod
- Microchoncid
- Rhynchonelliform
brachiopod
- Linguliform
brachiopod
- Observed in float
- Geochemical sample
- Ecological sample
- Spring-seep brecca
- Chondrites
- Planar trace w/ halo
- Planar trace w/ walls
- Small planar burrows
- Conical burrows
*
- Ripples
- Cross bedding
- Articulated fossil
- Graded bedding
(coarsening)
- Laminated bedding
- Carbonate
- Siliciclastic
BTM13
BTM14
BTM16
BTM20
BTM31
BTM52
BTM55
BTM59
BTM62
BTM75
BTM79
BTM90
BTM93
BTM65
BTM85
BTM52
cover
80
Figure 3.3 – A- 
13
C
carb
of the Blacktail Creek section from carbonate samples, showing two
major excursions at the top and bottom of the section and other minor excursions in between.
The maxima and minima of these excursions are correlated with those from the Dawen section of
South China (B) from Payne et al. (2004). The Dawen section is correlated to the Guandao
section of South China (C), with reported conodont stratigraphy (D), and geochemical
correlations at the stub-stage level, by Payne et al. (2004). Geochemical correlations suggests
that the Dinwoody Formation at Blacktail Creek encompasses most of the Griesbachian stage,
with only the earliest and latest Griesbachian missing. We find no evidence that the Blacktail
Creek section records any excursions known from the Dienerian substage.

81
Ng. changxingensis H. parvus
Ns. dieneri
Ns. cristogalli
GRIESBACHIAN DIENERIAN SMITHIAN
GRIESBACHIAN
Blacktail
Creek
Dawen
China
Guandao
China
PERMIAN
02468
0 50 100 150
−2 0246
0 204060
150 200 250 300
80 100 120 140
−3 −2 −1 0
0 20 40 60 80 100
δ
13
Ccarb δ
13
Ccarb δ
13
Ccarb
100 120
INDUAN OLENEKIAN
EARLY TRIASSIC
Dinwoody Formation
m
mm
82
Figure 3.4 – Plate of fossil taxa recovered from Blacktail Creek. Scalebars are 1cm unless
otherwise denoted. a. Promyalina cf. spathi. b-c. Obnixia sp. d. Sp.A (infaunal bivalve species).
e-f. Lingularia sp. g. Unionites canalensis. h. Unionites sp. i. Claraia extrema. j. Permophorus
sp. k. Eumorphotis cf. multiformis. l. Triadotiarid interambulacral plate. m-n. Smooth, non-
ornamented echinoid spines. o. Partially articulated cidaroid echinoid interambulacral region. p.
Eumorphotis cf. mulleri. Preservation of most taxa recovered is moldic, with notable exception
of Lingularia specimens that often preserve apparently original shell material, as evidenced by
fine-scale details of growth lines visible on the shells.

83
84
Figure 3.5 – Disaster taxon (Lingularia, Claraia, Eumorphotis, Promyalina, Unionites) relative
abundance throughout the section, from each ecological bulk sample in stratigraphic order.

85
0 0.2 0.4 0.6 0.8 1
BTM13
BTM14
BTM16
BTM20
BTM31
BTM52
BTM55
BTM59
BTM62
BTM65
BTM75
BTM79
BTM85
BTM90
BTM93
Claraia
Eumorpho ti s
Promyalina
Unionites
Lingularia
Relative Abundance
Epifaunal Infaunal
86
Figure 3.6 – Photomicrographs of fossils found in thin section. (A) A cross section of an
echinoid spine, showing stereomic microstructure. (B) Echinoderm ossicles showing stereom
microstructure. Definitive identification of these occicles as echinoid in not possible. (C) Cross
section of microconchid shell, showing laminated-sheet texture (D) Rhynchonelliform
brachiopod shell showing fibrous fabrics. Cross-polarized light. (E) Thin, well-preserved
phosphatic lingulid brachiopod shell, likely Lingularia, showing punctae structure. Such well-
preserved microstructure is common for lingulid fragments in these thin section. (F) A bivalve
shell showing relatively well-preserved internal fabrics and hinge. (G) Unidentified filamentous
microfossil, potentially microbial. (H) Microgastropod with partial phosphotization of whorls.

87
88
Figure 3.7 – Microgastropod size and abundance distributions throughout the section. (A) Size
distribution from sample BTM16, which produced the highest abundance of gastropods from the
section, showing that the majority of gastropods (>85%) were less than 1 mm in diameter, and
are thus microgastropods. (B) Sample BTM52, with the second highest gastropod counts, and all
specimens recovered under 1mm in diameter. (C) Relative abundance and average size of
gastropods throughout the section. Most gastropod specimens were recorded from samples
BTM16 and BTM52, and average size for these samples is < 1.0 mm in diameter. Larger
gastropods (>1.5mm in diameter) were recorded from samples higher in the section, but these
amounted to just a few individuals (n<5). Still, larger gastropods represented relatively high
relative abundance in samples BTM90, due to the overall small nature of this sample (n = 20).
(D) Phosphatized microgastropods removed from matrix from samples BTM16 and BTM52,
many with preserved protoconch. (a-b) Strobeus sp. (c) Vetigastropod indet. (d) Coelostylina sp.

89
0 0.2 0.4 0.6 0.8 1
BTM13
BTM14
BTM16
BTM20
BTM31
BTM52
BTM55
BTM59
BTM62
BTM65
BTM75
BTM79
BTM85
BTM90
BTM93 Relative Abundance Average Size (mm)
Average Size (mm)
Relative Abundance
BTM16
Whorl size (mm)
Frequency
0.0 0.5 1.0 1.5 2.0 2.5 3.0
0 20 40 60 80
BTM52
Whorl size (mm)
Frequency
0.3 0.4 0.5 0.6 0.7 0.8 0.9
0 1 2 3 4 5 6 7
100
n = 184 n = 22
0.5 1.0 1.5 2.0 2.5 3.0
a b
c d
A B
C D
0.15mm
90
Figure 3.8 – (A) Microconchid encrusting frequency on macrofossils and microconchid counts
throughout the section. Sample BTM65 showed the highest frequency of encrusted shells at 10%
and highest occurrence of microconchids. (B) Photograph of Unionites shell encrusted with
multiple microconchids (shown by arrows), preserved as imprints. (C) Photomicrograph of
microconchid encrusting echinoderm ossicle.

91
1cm
0.00 0.04 0.08
% Encrusted Shells
0.1
Microconchid count
0 2 4 6 8 10 12 14
BTM13
BTM14
BTM16
BTM20
BTM31
BTM52
BTM55
BTM59
BTM62
BTM65
BTM75
BTM79
BTM85
BTM90
BTM93 - % encrusted - # microconchid
AB
C
92
Figure 3.9 – Ophiceras? sp. ammonoid specimens recovered from float material overlying basal
mudstone facies. (A) Ammonoid cast showing smooth, non-ornamented exterior, and wide
umbilicus. No septae are evident. (B) Two moldic ammonoid fossils, showing typical
preservation of these specimens. Large Promyalina associated with these fossils. (C) Ammonoid
specimen preserved as negative imprint, likely of the same genus as other specimens. (D)
Lingularia bedding plane in which several ammonoid specimens were found.

93
94
Figure 3.10 – Trace fossils found in bulk samples and float material. (a) Single Palaeophycus
burrow in a carbonate with dark, likely diagenetic halo and lighter interior.(b-d) Chondrites
specimens, showing dendritic branching structure, puncturing a darker surface within the cross-
bedded fine grained sandstone, and infilled with lighter sediment from above. Some show faint
dark halos (as in image d). (e) Single Palaeophycus burrow in a siliciclastic lithology with dark,
likely diagenetic halo and lighter interior. (f) Small branching burrows preserved in positive
relief on bedding plane, unknown affinity. (g) Dense bedding plane of small, conic, vertical
burrows, that puncture bed but do not continue into underlying bed. Some Palaeophycus or
Planolites burrows found on the same bedding plane, overprinting the top of the cones. Vertical
burrows are of unknown affinity. (h) Straight Palaeophycus, lined with smooth walls that
overprints conical vertical burrows.

95
96
Figure 3.11 – Transitions in faunal abundance distributions across the section, (A) showing
relative abundance of 6 major invertebrate groups occurring in bulk samples, and (B) showing
the results of a constrained paired-group cluster analysis using Bray-Curtis similarity with
bootstrap support shown at the nodes (N=1000). Two major faunal transitions between 3 faunal
associations are observed, one transition occurring as rhynchonelliform brachiopod-dominated
assemblages give way to epifaunal bivalve and gastropod dominated assemblages, and another as
these assemblages give way to infaunal bivalve-dominated assemblages at the top of the section.
These faunal groupings are well supported by bootstrap values (>50).

97
0% 20% 40% 60% 80% 100%
BTM13
BTM14
BTM16
BTM20
BTM31
BTM52
BTM55
BTM59
BTM62
BTM65
BTM75
BTM79
BTM85
BTM90
BTM93
Rhynchonelliform Brachiopod
Linguliform Brachiopod
Gastropod
Microconchid
Infaunal Bivalve
Epifaunal Bivalve
Abundance
91
64
84
20
1 0.5 0.75 0.25 0
Bray-Curs Similarity
Constrained Pair-group
Corr. coph = 8.8477
A B
58 100
59
36
16
26 48
72
69
94
91
64
69
94
Lower Fauna Middle Fauna Upper Fauna
98
Figure 3.12 – Statistical comparison of (A) generic richness, (B) Simpson’s dominance index,
and (C) Shannon’s diversity index, between samples from the bottom of the section (highlighted
by lower grey box in Fig. 3.11), middle of the section, and upper section (highlighted by upper
grey box in Fig. 3.11). Wilcoxon sum-rank test p-values shown below, with bold values
indicating significance (a = 0.05). Since the lower group consists of only two samples (BTM13
and BTM14), p-values derived from statistical tests involving these samples are not robust,
however values are still reported here denoted with an asterisk (*). Significant difference was
found between the middle and upper samples in both generic richness and Shannon’s diversity,
but not in Simpson’s dominance. Still, the middle group shows higher median richness, diversity
and lower median dominance than both groups below and above.

99
Lower Middle Upper
0 2 4 6 8 10 12 1.0
Richness (Genera)
Lower Middle Upper
0.0 0.4 0.8
Simpson's Dominance (D)
Lower Middle Upper
0.0 0.5 1.0 1.5 2.0
Shannon's H
p = 0.041* p = 0.006
p = 0.036* p = 0.148
p = 0.036* p = 0.019
A
B
C
100
Figure 3.13 – Side-by-side plots of 
13
C
carb
values and various ecological metrics across the
section. (A) 
13
C
carb
throughout the Blacktail Creek section as correlated with (B) generic
richness, (C) Simpson’s dominance index, (D) evenness, (E) Shannon’s diversity index (F)
average fossil size, and (G) diversity of life modes. Red boxes indicate parts of the section where
large 
13
C
carb
shifts are associated with low-richness communities, and highlight the groups used
in statistical tests, shown in Figure 3.12.

101
−4 −3 −2 −1 0
0 20406080 100 120
δ Ccarb
Meters
0 2 4 6 8 10 12 14
20 40 60 80 100 120
Richness (Genera)
Meters
0.0 0.2 0.4 0.6 0.8 1.0
20 40 60 80 100 120
Simpson's Dominance (D)
Meters
0.0 0.2 0.4 0.6 0.8 1.0
20 40 60 80 100 120
Evenness
Meters
0.0 0.5 1.0 1.5 2.0
20 40 60 80 100 120
Shannon's Diversity (H)
Meters
010 20 30 40
20 40 60 80 100 120
Avg. Body Size (mm)
Meters
13
Meters
Functional Diversity
AB C D
E
23456
20 40 60 80 100 120
FG
102
Figure 3.14 – Comparison of faunal composition between carbonate and siliciclastic samples.
(A) Faunal group relative abundances showing little difference between lithologies, except for
the presence of rhynchonelliform brachiopods in carbonates only. (B) Statistical comparisons of
Simpson’s dominance index and generic richness between lithologies, showing no significant
difference in either case (a = 0.05). (C) NMDS rank-order analysis, showing sample lithologies.
No clustering of samples based on lithology is observed.

103
Rhynchonelliform Brachiopod
Linguliform Brachiopod
Gastropod
Microconchid
Infaunal Bivalve
Epifaunal Bivalve
Carbonate Siliciclastic
Carbonate Siliciclastic
0.0 0.4 0.8
Simpson's Dominance
Carbonate Siliciclastic
048 12
Richness (Genera)
p = 0.613
p = 0.599
−1.5 −1.0 −0.5 0.0 0.5 1.0
−0.5 0.0 0.5 1.0
NMDS1
NMDS2
+
BTM13
BTM79
BTM93
BTM14
BTM75
BTM90
BTM52
BTM62
BTM20
BTM55
BTM16
BTM85
BTM59
BTM31
Carbonate
Siliciclastic
A
BC
104
Figure 3.15 – Blacktail Creek ecological samples, showing correlation between magnitude of
shifts of 
13
C
carb
values between successive ecological samples, and (A) generic richness, (B)
Simpson’s dominance index, (C) normalized evenness (E
1/D
) (D) Shannon’s diversity index. (E)
Average invertebrate body size (mm), and (E) functional diversity. Pearson’s product-moment
correlation coefficient (r) and p-values are shown. Statistically significant values are shown in
bold (a = 0.05).

105
4 6 8 10 12
0.5 1.0 1.5
Richness (Genera)
Dδ
13
C
0.2 0.4 0.6 0.8
0.5 1.0 1.5
Dominance (D)
Dδ
13
C
0.2 0.3 0.4 0.5 0.6 0.7
0.5 1.0 1.5
Evenness (E 1/D)
Dδ
13
C
0.5 1.0 1.5 2.0
0.5 1.0 1.5
Shannon’s Diversity (H)
Dδ
13
C
5 10 15 20 25 30 35
0.5 1.0 1.5
Average Body Size (mm)
Dδ
13
C
2 3 4 5 6
0.5 1.0 1.5
Functional Diversity
Dδ
13
C
A B C
D E
F
r = - 0.56 p = 0.028 r = 0.5 p = 0.061 r = - 0.03 p = 0.928
r = - 0.54 p = 0.038 r = - 0.21 p = 0.446 r = - 0.37 p = 0.173
106
Chapter 4: Tethyan ecological response to changing oxygen, temperature, and bathymetry
after the Permian Triassic crisis: Exploring the paleoecology of the Griesbachian to
Smithian Werfen Formation

1 – Introduction

Recovery in benthic marine invertebrate communities following the Permian-Triassic
crisis has been documented to be highly variable between Early Triassic localities (Pietsch and
Bottjer, 2014; Hofmann et al. 2014), likely influenced by local bathymetry, temperature,
oxygenation conditions, primary productivity, and available biodiversity. In Chapter 3 I
discussed a case study of an Induan Panthalassic section that exhibited incipient recovery,
followed by a collapse of recovery as geochemical indicators of carbon cycle instability resumed.
These changes were correlable to dramatic shifts in 
13
C
carb
values, potentially indicating a
common cause from environmental instabilities brought on by Siberian Traps degassing. Here, I
will discuss a case study from two Tethyan sections, spanning a similar time period from the
Induan and early Olenekian (Smithian) stages. These sections differ from the Panthalassic
section in that: 1) they span into the Smithian substage, allowing for observation of communities
2 Ma after the extinction event; 2) this stratigraphic interval spans multiple large 
13
C
carb

excursions, as well as the single largest excursion recorded in the Early Triassic; 3) these
sections represent widely variable depositional environments ranging from mid-ramp subtidal to
peritidal facies, that would allow for the observation of communities across various energy and
substrate regimens; and 4) these section occur in the silled Dolomite Basin of the Paleo-tethys
Ocean, which has been considered more restricted in circulation than the Panthalassic Ocean
(Winguth and Maier-Reimer 2005).
107
Reported below is a high resolution depositional facies, paleoecological, and carbon
isotope geochemistry analysis of two Werfen Formation sections, the Uomo and Bulla outcrops,
recording marine benthic invertebrate conditions from the Griesbachian to Smithian. I explore
changes in ecological complexity of these sections, and how the timing of these changes relates
to changes in depth, sediment influx, and 
13
C
carb
geochemistry. No evidence of significant
correlation between metrics of community complexity and magnitude of 
13
C
carb
shifts is
observed, unlike what was observed from the Blacktail Creek section. However, there is
evidence of incipient recovery with the occurrence of a high richness, low dominance fauna in
the Dienerian upper Suisi member in the Uomo section. This recovery is subsequently ended as
high terrigenous sedimentation begins in the Dienerian Campil Member. This short-lived
recovery is brief enough to not contribute to significant changes between metrics of community
complexity at the scale of Early Triassic substages, highlighting the necessity of high resolution
outcrop-based ecological studies to capture these events. Additionally, the high abundance and
frequency of occurrence of the infaunal bivalves Unionites and Neoschizodus throughout these
sections is reminiscent of the ecological dominance of Lingularia in the previously studied
Panthalassic section. I propose that the rapid sea level fluctuations leading to several shallowing
events inhibited benthic recovery, allowing for Unionites and Neoschizodus to proliferate while
macrofaunal composition remains relatively unchanged throughout the sections. These frequent
sea level changes also likely overpowered environmental forcings associated with carbon isotope
shifts as evidenced by the lack of correlation between isotope excursions and ecological shifts.
Generally, the paleoecological structure of these communities appears to be more dependent on
local bathymetric and sedimentary conditions as opposed to larger scale forcing such as
108
temperature, though the short-lived Dienerian failed recovery attempt could potentially be linked
to amelioration of thermal stress during a cooling trend (Sun et al. 2012).
2 – Werfen Formation geologic setting

The Werfen Formation is a mixed carbonate-siliciclastic shelf deposit on the western
coast of the Paleo-tethys ocean, outcropping today in the western Italian Dolomites and southern
Austrian Alps regions (Assereto et al. 1973). The Werfen Formation overlies the upper Permian-
aged (Wuchupingian to Changhsingian) Bellerophon Formation and is overlain by the Middle
Triassic (Anisian) aged Richthofenn Conglomerate or Serla Dolomite Limestone (Broglio Loriga
et al. 1985). The Bellerophon and Werfen Formations were deposited within the tectonically
active and expanding Dolomite Basin (Mostler 1982) a half-gra\ben basin that formed due to
rifting associated with the formation of the Neo-Tethys. The Bellerophon Formation consists
mainly of shallow marine carbonates and some evaporites, representing sabkah, lagoonal, and
fully marine conditions (Broglio Loriga et al. 1988). The overlying Werfen Formation spans
mid- to shallow marine carbonate and siliciclastic facies, and in several instances preserves
lagoonal and subaerially exposed peritidal facies. The rapidly changing bathymetry throughout
the Werfen Formation is attributed to third-order sea level change as a result of the tectonic
activity of the basin (Broglio Loriga et al. 1985, Gianolla 1998).
The Werfen Formation is subdivided into 8 lithostratigraphic members, which span from
the uppermost Changhsingian to the Olenekian stage (Spathian substage), and encompasses the
Permian-Triassic boundary and extinction event (Fig. 4.1). However, lithostratigrahic
identification alone is often insufficient for differentiating these units in the field, as facies repeat
and interfinger throughout the formation. Additionally, biostratigraphic constraint on the ages of
109
the units is difficult, as biostratigraphically informative conodonts and ammonoids are absent
over most of the section, only occurring at the top and bottom (Posenato 2008a). To circumvent
this, other means of age constraint are generally preferred in the Werfen, including identification
of Claraia, Eumorphotis, and Costatoria bivalve zones, geochemical correlation, and
magnetostratigraphy (see references and summary in Posenato, 2008). The Claraia zone
encompasses the Induan and lowermost Olenekian (lowermost Smithian), the Eumorphotis zone
encompasses the Smithian and lower Spathian, and the Costatoria zone is used to define
Spathian units. In this current study, a combination of lithologic characteristics, 
13
C
carb

correlation, and bivalve biostratigraphy have been used to identify the various Werfen Formation
members sampled.
The Tesero Oolite is the most basal member, which unconformably contacts the
Bellerophon Formation below, and represents a transgressive event. This member is
Changhsingian (uppermost Permian) in age, and encompasses the Permian-Triassic boundary
and extinction event (Fig. 3.1A), though some workers have argued that biological diversity
began to decrease prior to this in the upper Bellerophon Formation (Twitchett 1999). The Tesero
Oolite is commonly a thin oolitic layer, but can range from 2 – 30 m thick. The Tesero Member
is thickest in the area around the city of Trento, and thins towards the edges of the Dolomite
Basin, to the north and east (Broglio Loriga et al. 1985). It is composed of oolitic grainstones and
packstones containing laminated or micritized ooids, grapestones, intraclasts, and peloids,
representing a very proximal shoal environment. These oolitic facies grade upward into finer-
grained mudstone units that typify the overlying Mazzin Mamber. The so called ‘mixed fauna’,
(Posenato 2009) which includes Permian-holdover rhynchonelliform brachiopods species, have
been recorded from the lower Tesero member. These taxa have been described as stenohaline
110
Permian holdovers, and include Spirorbis (or potentially Microconchus) tubeworms, echinoids,
and brachiopods (Broglio Lorigia et al. 1985; Posenato, 2009). Additionally, the Tesero Oolite
also exhibits some characteristically Early Triassic fauna, including the disaster taxon
Eumorphotis (Posenato, 2009). These mixed fauna have been previously interpreted as
representing earliest Triassic reworking of underlying Permian material, but Broglio Lorigia et
al. (1985) and Posenato (2009) instead determine that these fauna are likely occurring in situ, and
therefore represent a transitional fauna living during the biotic crisis.
The overlying Griesbachian-aged Mazzin Member represents the earliest Early Triassic
deposits in the Dolomites region, and records the first appearance of the conodont Hindeodus
parvus (Perri (1991); though Posenato, (2009) reports occurrences in the upper Tesero Member.
and the bivalve Claraia wagni-griesbachi which indicate a Griesbachian age for the Member
(Broglio Lorigia et al. 1988; Posenato, 2008). The Mazzin Member is typified by thinly
laminated mudstone and alternating storm influenced bioclastic wackestone beds with micritic
intraclasts (Broglio Loriga et al. 1985, Pietsch et al. 2016), and has been interpreted as a subtidal,
mid-ramp setting, below fair-weather wave base but above storm wave base. There is evidence
for shifting levels of oxygenation throughout the unit, with evidence of low oxygen from
depleted Th/U ratios, limited bioturbation, and pyrite framboids found within the laminated
mudstone facies (Pietsch et al. 2016, Twitchett 1999, Wignall and Twitchett 1996). Pietsch et al.
(2016) report some instances of potentially oxygenated conditions within the Mazzin Member,
with evidence of highly abundant ostracod assemblages, which are usually regarded as highly
intolerant of low-oxygen conditions (Song et al. 2014b).
The Andraz Marl (or Andraz Horizon) is a thin marly horizon, typically orange or green
in color, which separates the limestones of the underlying Mazzin and overlying Suisi Members
111
(Posenato, 2008). This unit is often covered in the field due to its fissile texture, but trenching at
the Bulla section has allowed for excellent exposure of this unit there. This peritidal evaporitic
facies represents yet another shallowing event within the Dolomite Basin. Broglio Lorigia et al
(1985) use the upper contact of this unit to define the bottom of the Suisi Member. This unit is
unfossiliferous.
The Griesbachian to Dienerian Suisi Member unconformably overlies the Andraz
horizon, representing a deepening event with a well-defined erosional bottom contact (Brandner
et al. 2009). The Suisi Member contains variable lithologies, ranging from mudstones and
bioclastic wackestones, gastropod-oolitic grainstones, and siliciclastic cross-bedded facies,
which have been the subject of several redefinitions throughout the years (Brandner et al. 2009,
Broglio Loriga et al. 1985, Farabegoli and Perri 1998, Posenato 2008a). This study follows the
stratigraphy put forth by Brandner et al. (2009), whereby the lower gray limestone beds and
capping gastropod-oolite beds (formerly the Gastropod Oolite Member) are included within the
Suisi Member, and the overlying red siliciclastic beds are placed in the Campil Member. Using
this definition, the Suisi is typified by gray mudstones and bivalve dominated storm-bed
wackestones, as well as intermittent instances of the gastropod-oolite lithotype. Some instances
of red siliciclastic facies are also found below the topmost gastropod-oolite beds, making
differentiation of the Suisi and Campil Members difficult in the field. The Suisi is thought to
represent a third-order transgressive-regressive event, whereby the lower units were deposited in
a mid-ramp to offshore transition setting. Gradual shallowing is observed throughout the
member, which is eventually capped by the upper shoreface Gastropod-Oolite unit.
The Griesbachian-Dienerian boundary is problematic to define, in the Dolomites and
elsewhere, as this informal boundary is defined by the transition between Otoceran and
112
Gyronitidid ammonoid fauna, which is only clearly observable in Pakistani, Canadian, and
Himalayan outcrops (Ogg 2012). In South China, the boundary is placed at the end of recovery
to positive 
13
C
carb
values following the second major negative excursion after the PTB. This
inflection point precedes the large positive excursion that defines the Dienerian-Smithian
boundary, as well as the FAD of the conodont Neospathodus dieneri (Zhao et al. 2013).
However, a clear correlation of this point is not readily observable in 
13
C
carb
profiles of the
Italian sections, so the Griesbachian-Dienerian boundary is tentatively placed above the Andraz
Horizon and within the Suisi Member in an approximate position of this 
13
C
carb
excursion
(Horacek et al. 2007a; Posenato, 2008).
The Dienerian to Smithian Campil Member overlies the Gastropod-oolite horizon of the
Suisi Member, with red and brown marly siltstones and cross-bedded sandstones and occasional
limestone beds typifying the lower part of this unit. Further up section there is evidence of
shallowing conditions, with ripple marks and mudcracks (Borglio Lorigia, 1985; Brandner, 2009;
Pietsch et al. 2016). The Campil Member represents a transgressive-regressive event, from the
shallow subtidal/peritidal environments of the Gastropod-oolite horizon to hummocky cross-
stratified mid-ramp settings, followed by coarser-grained silt and sandstones with evidence of
subareal exposure. Brandner (2009) reports evidence of microbially influenced sedimentary
structures (MISS) in the shallower facies. The Campil Member represents a shift in
sedimentation regime in the Dolomites basin, with increased terrigenous input into the formerly
limestone-dominated ramp. The maxima of the large positive excursion that marks the
Dienerian-Smithian boundary is recorded within the limestones of the Campil Member. This
excursion, in addition to evidence of increase terrigenous input into marine settings, has been
interpreted as a continental shedding event, brought on by terrestrial vegetation decline and
113
precipitation increase due to global climate change (Horacek et al. 2007a). The positive
excursion has been interpreted as a large primary productivity spike, brought on by increased
nutrient input into the marine realm leading to increased organic carbon burial.
The Val Badia, Cencenighe, and San Lucano Members make up the remaining Werfen
Formation, and span the upper Smithian and Spathian substages. As these members were not
sampled in this current study, the details of their lithology are not discussed here. However, it is
worth mentioning that the remaining members represent three additional parasequence packages
(Giannolla et al. 2012), with the lower Val Badia Member composed of subtidal limestone facies
that give way to mud-cracked peritidal facies in the upper Val Badia, as well as oolitic and
lenticululated marl mud flat facies in the Cencenighe and San Lucano Members (Broglio Lorigia
et al., 1985).
3 – Previous work on the paleoecology of the Werfen Formation

The Werfen Formation had been the source of many studies on the paleoecology of the
benthic marine realm in the aftermath of the end-Permian extinction (Farabegoli et al. 2007,
Fraiser and Bottjer 2005, Fraiser et al. 2005, Hofmann et al. 2011, Hofmann et al. 2015, Pietsch
et al. 2016, Posenato 2008b, 2009, Twitchett 1999, 2007). Many of these studies have either
focused on trace fossil diversity (Twitchett and Wignall, Hofmann et al. 2011; Twitchett, 1999),
Lilliput microgastroopd assemblages (Friasier et al. 2005, Twitchett, 2007), or macroinvertebrate
diversity (Posenato, 2008a) as a means of gauging the extent of biotic upheaval in the wake of
the extinction. The timing of recovery found by these authors appears to differ depending on the
metrics used. Posenato (2008b) finds evidence of step-wise increase in bivalve diversity, with
114
lowest generic diversity observed in the Induan, followed by incremental increases in the
Olenekian and early Anisian.
Evidence of early recovery of communities following the Permian-Triassic extinction
was reported by Hofmann et al. (2011) and Hofmann et al. (2014). Through an ichnological
(Hofmann et al. 2011) and paleoecological (Hofmann et al. 2014) survey of several Werfen
Formation outcrops, including the Uomo section surveyed in this study, they concluded that a
failed recovery occurred in this tropical Tethyan region relatively early after the extinction event,
in the Griesbachian. This recovery was then subsequently truncated by the initiation of
terrigenous sediment influx in the Dienerian. Recovered communities reappear in the Spathian,
which are then sustained throughout the remainder of the Early Triassic. Hofmann et al. (2014)
attribute this pattern of delayed recovery in the Early Triassic to short-lived recovery attempts
thwarted by local facies effects that are highly region-specific.
Pietsch et al. (2016) explore the cohesiveness of these post-extinction communities as it
applies to the concept of phase shifts. They argue that the communities that form after the
Permian-Triassic mass extinction are a result of a threshold effect, brought on by large, repeated,
or sustained environmental perturbations associated with the extinction and Early Triassic. The
novel communities that form after this threshold effect constitute a cohesive fauna with novel
interspecies interactions (Hull and Darroch, 2013). Pietsch et al. (2016) argue that the Early
Triassic Werfen Formation records the advent of two such phase-shifted communities, with the
basal Griesbachian microbiolite-foraminifera-ostracod communities giving way to bivalve and
gastropod dominated communities in the Dienerian and Smithian. The sections sampled in the
Pietsch et al. (2016) study are the same as this current study, and the dataset collected by the
authors is used in this current study.
115
4 – Methods
4.1 – Sample collection

The Uomo and Bulla sections were measured and sampled during two field
expeditions in 2012 and 2014. Lithostratigraphic units were identified in the field from lithologic
characteristics and index fossil identification. The ecological and geochemical dataset used for
this study has been previously published in Pietsch et al. (2016). Separate and additional analyses
and interpretations using this dataset are presented herein.
Samples for ecological and thin section analysis were collected during a field expedition
to the Uomo and Bulla sections in the summer of 2012. Bulk samples for ecological analysis
were collected using similar methods as described in Chapter 3, at 5-10 meter intervals or where
conditions permitted. Fossiliferous carbonates and mixed-carbonate siliciclastic wackestones and
packstones were collected, as well as float siliciclastic material bearing sedimentary structures
and ichnofossils. Approximately 2-4 L of rock material was collected from each sample from the
Bulla section, and 1-2 L from the Uomo section. Later analysis of the recovered fossils from
these samples shows no bias in recorded diversity between samples of different size (see Pietsch
et al. 2016). Disaggregation of samples and identification of macrofossils were made both in the
field and in the lab, with the aid of a dissecting microscope. A total of 21 samples and 1015
individuals were recovered from the Uomo section, and 11 samples and 694 individuals from the
Bulla section. Figures and taxonomic descriptions from references outlines in Table 3.1 were
used for macrofossil identification to the genus level. Measurements of body size were made
along the longest axis of bivalve shells, and from base to apex of gastropod shells. Thin sections
were made from bulk samples for microfacies and microfossil identification, and were analyzed
using a petrographic microscope.
116
Geochemical samples for 
13
C
carb
were collected during a second field excursion in the
summer of 2014. Approximately 5 g of sample was collected at 20-100 cm intervals, or where
exposure allowed. A total of 92 samples were collected and analyzed for the Uomo section, and
16 were analyzed for the Bulla section. Laboratory methods used to process these samples are
the same as those outlined in Chapter 3. 
13
C
carb
was measured for samples collected during the
first field excursion as well. The 
13
C
carb
values from these samples, as well as lithostratigraphic
marker bed correlation, were used to determine the position of the geochemical samples relative
to the bulk samples that were collected previously.
Ecological analytical methods used are similar to those outlined in Chapter 3.
Constrained cluster analyses using Bray-Curtis Dissimilarity index were used to visualize faunal
shifts throughout the section, and were run using the software PAST ver. (Hammer et al. 2009).
Generic richness, Simpson’s dominance index (D), Shannon’s diversity index (H), average body
size, functional diversity and disaster taxon relative abundance were used as metrics of
community complexity. A non-metric multidimensional scaling (NMDS) analysis was run using
the software PAST to visualize faunal compositions from the sampled sections relative to others
from the Italian Dolomites region. Paleobiology Database collections were downloaded and
plotted for Changhsingian to Anisian aged brachiopod, gastropod, and bivalve Italian
assemblages, and compared to assemblages from the Uomo and Bulla sections. Significance of
correlation between magnitude of 
13
C
carb
shifts and metrics of ecological complexity were
calculated using Pearson’s product-moment correlation coefficient (r).

117
4.2 – The Uomo locality
The exposure at the Uomo section is located north of the town of Passo San Pelegrino, in
the Trento province (Fig. 1). This approximately 200 meter section (Fig.4.2) is exposed on the
southern slope of Cima Uomo, and can be accessed by a road leading to a ski lift at the top of the
section. The Bellerophon Formation and Tesero Oolite are poorly exposed on the lower slopes of
the section, but exposure quality increases up section into the Mazzin and cliff-forming Suisi and
Campil Members. The top of this exposure is truncated by intrusive igneous units (personal
observ.). Continued exposure of the Campil, Val Badia and Cencenighe Members can be found
at the neighboring Costabella section to the west of the Uomo outcrop. These two sections have
often been presented as a composite section in the literature (e.g. Horacek et al. 2007a; Hofmann
et al. 2014). The Costabella section was not sampled for this study.
4.3 – The Bulla locality

The Bulla section is exposed along an abandoned road leading to the town of Pufel/Bulla,
north of Ortesei/St. Ulrich in Val Gardena (Fig. 4.1; Fig. 4.3). The upper Bellerophon Formation
is exposed at this section as well as all lithostratigraphic units of the Werfen Formation ranging
from the Tesero Oolite to the Campil Member. The Val Badia Member has been previously
reported as exposed above the Campil Member in this section, but recent stratigraphic revisions
by Brandner (2009) include these beds within the Campil. This section is one of the better
studied sections of the Werfen of the Italian Dolomites (see Brandner, 2009), as there is
continuous exposure throughout, including the often covered Andraz Horizon.
118
5 – Results
5.1 – Uomo facies and ecology

Measuring and sampling of the Uomo section encompasses the Tesero to mid-Campil
Members (Fig. 4.2). The Tesero and Mazzin Members at Uomo are partially covered, so exact
placement of the boundary between these two members is difficult. The base of the section is
characterized by oolitic beds, oolite-stromatolite associations, micritic peloid and mudstone units
near the base. These ooids are round or oval, and have well developed laminations and are
partially micritized (Fig. 4.4). Thrombolitic/microbial fabric is present in between ooid grains in
some thin sections (Fig. 4.4 A). An ~60 cm thick stromatolite-ooid bed was sampled from the
near the base of the outcrop that showed ooids infilling between dendrite structures of the
stromatolites (Fig. 4.4 B). These microbialite-ooid associations also include rarer microgastropod
and bivalve clasts. These units likely represent the transitional facies between the Tesero and
Mazzin Members. Further up section, calcareous marls, mudstones and bioclastic wackestones
become more common, but ooid beds are still present. Lingularia is found in ecological samples
and thin section. Ostracods are found in thin section throughout this part of the section (Fig. 4.5
F), with one instance of a dense, ostracod-only assemblage recovered from an otherwise
unfossiliferuous mudstone (Fig. 4.5 F).
The Tesero to Mazzin transition is interpreted as a deepening event, with the Mazzin
Member representing a mid-ramp setting below fair weather wave base (Pietsch et al. 2016; this
study). There is evidence of low oxygen conditions at this time, including little bioturbation and
pyrite framboids found in thin section (Fig. 4.2). However, the presence of ostracods further up
section led Pietsch et al. (2016) to postulate that an interval of elevated oxygenation occurred
within the Mazzin, as modern ostracods are low-oxygen intolerant (Forel et al. 2013, Song et al.
119
2014a). A single bulk sample taken from the upper Mazzin shows numeric dominance of the
disaster taxa Lingularia and Unionites at the base of the Uomo section associated with these
ostracod accumulations. The overlying Andraz Member is not exposed at the Uomo section, but
trenching uncovered fissile orange marls at the top of the Mazzin units, likely belonging to this
peritidal member.
The base of the Suisi Member at Uomo exhibits lithologies similar to the upper Mazzin,
with occasional ooid-rich deposits with thrombolitic fabrics observable in thin section. These
give way to massive limestones, silty limestones, and bioclastic wackestones in the middle of the
Suisi Member. Micritic rip up clasts, cross-bedded silty limestones, and shelly hash become
more common in this part of the section. This is interpreted as a proximal subtidal environment
at the base followed by a deepening event into storm-bed dominated mid-ramp settings.
Microgastropods, microconchids, and foraminifera are found commonly in thin section (Fig. 4.5
A-B). Evidence of shallowing from the middle to upper Suisi Member is observed, with
coarsening of silt and sandstone beds, increased cross-bedding frequency, and more ooid-rich
beds. This is likely the part of the Suisi Member that was formerly known as the Gastropod-
oolite Member, but the lithologic distinction of these units is not as apparent in the field as it is
reported from other sections of the Werfen. The infaunal bivalves Neoschizodus and Unionites
were the two most abundant genera occurring in the upper Suisi Member, likely within the
Dienerian-aged units.
The Dienerian-aged lower Campil Member at the Uomo section is characterized by
increased terrigenous input, clearly visible in the field as the beginning of large red calcareous
siltstones and sandstones. Ooid grainstones and bivalve packstones also occur within the
dominantly siliciclastic Campil. Both siliciclastic and carbonate beds are commonly cross
120
bedded. Ripples, desiccation cracks, and micritic interclasts are evidence of very shallow
conditions, ranging from intertidal, lagoonal, and peritidal environments in the Campil.
Diplocraterion are found commonly in siliciclastic beds. The infaunal bivalve Unionites is by far
the most abundantly occurring genus in this part of the section.
The Smithian-aged upper Campil Member is likely truncated at the top of the section,
based on geochemical correlation with stratigraphy used by Horacek et al. (2007a). This part of
the Campil is typified by cross-bedded sandstones, rip-up clasts, and microgastropod mass
accumulations. Several beds of these dense microgastropod assemblages are found within red
limestone beds which are interbedded with the siliciclastic units. These microgastropods exhibit
a very distinct micritic envelope in thin section, likely as a result of occurring in a lagoonal
setting (Fig 4.6).
5.2 – Bulla facies and ecology

Measuring and sampling of the Bulla section encompasses the Tesero to Campil
Members (Fig. 4.3), with geochemical sampling spanning from the Tesero to Suisi Members.
General parasequence interpretations are similar as those discussed for the Uomo section, but
specific observations unique to the Bulla section are discussed in more detail here.
The Tesero Member at the Bulla section is well exposed, and is characterized by oolititc
grainstone beds. Unlike the Uomo section, no stromatolite-ooid beds where found at Bulla.
However, there is evidence of microbial and stromatolitic fabrics in thin section in the overlying
Mazzin Member. The lower Mazzin Member at the Bulla section is characterized by massive
mudstone beds with planar laminations (Fig. 4.3). Bioclastic components become more common
up section in the Mazzin, with bivalve wackestones and packstones becoming more frequent.
121
The Tesero to Mazzin transition is once again manifested as a deepening event followed by
shallowing into the upper Mazzin and Andraz Members at the Bulla section. The Andraz
Member is well exposed here, with teepee structures and lenticular bedding evident. Unionites,
Neoschizodus, and the microgastropod Pseudomurchisonia are common in the Mazzin at Bulla.
The Suisi Member at the Bulla section is characterized by biolcastic wackestones and
packstones throughout most of the section, with silty limestones and calcareous shales occurring
only in the upper part (Fig. 4.3). Infaunal bivalves such as Unionites and pectinid bivalves such
as Claraia and Eumorphotis are abundant in the Suisi here. Foraminifera, microconchids, and
echinoderms are found in thin section. Abundant microgastropods are found at the top of the
Suisi Member, corresponding to the Gastropod-oolite unit. Sedimentological indicators of
shallowing in the Suisi at Bulla is not as evident as in the Uomo section. However, shallower
conditions are clear in the Campil Member, with the occurrence of cross bedded sandstones and
packtstones at the transition between these units. The limited exposure (~15 m) of the Campil
Member at Bulla is interpreted as a high energy proximal subtidal setting.
Overall, the facies recorded at the Bulla section are generally deeper than corresponding
units at Uomo, with finer grained siliciclastic deposits occurring in the upper Suisi and Campil
Members at Bulla.
5.3 – 
13
C
carb
geochemistry and correlation

The 
13
C
carb
isotope profile measures from both the Uomo and Bulla sections are similar
to those of Horacek et al. (2007a) at these same sections (Fig. 4.7), and additionally, are similar
to other Tethyan carbon isotope profiles measured in Iran and China (Payne et al. 2004; Horacek
et al. 2007b). Though few carbonate carbon isotope profiles have been reported from
122
Panthalassic sections in this interval (see Chapter 3), the well-documented basal negative
excursion observed in the earliest Early Triassic is observable in both Tethyan localities and
Blacktail Creek. This basal negative excursion reaches minimum values of -1
o
/
oo
at Uomo and
-2
o
/
oo
at Bulla, before returning to more positive values. The end of this positive recovery is
coincident with the base of the Mazzin Member (Horacek et al. 2007a; this study). This point is
easily observable in the
13
C
carb
profiles of both the Bulla and Uomo localities, as well as in the
carbon isotope values of the Dawen section in South China (Payne et al. 2004).
Following this recovery to positive values, 
13
C
carb
values remain relatively stable,
hovering around values of +1
o
/
oo
, for several meters of section in both the Uomo and Bulla
localities. This interval of carbon isotope quiescence spans the Griesbachian-Dienerian boundary
in the Suisi Member. Interestingly, this interval in South China instead exhibits a gradual decline
of 
13
C
carb
values, followed by a gradual recovery to more positive values. This interval is
followed by rapidly occurring “micro-excursions”, ranging between values of 0
o
/
oo
and +3
o
/
oo
.
This interval is present in the South China Dawen section as well (Fig. 4.7). The exact number of
these micro-excursions is difficult to pinpoint without higher resolution sampling, but there
appears to be a minimum of 2 negative excursions in the Italian sections. These excursions span
the Dienerian upper Suisi Member.
The beginning of the well-documented large positive excursion that marks the Dienerian-
Smithian boundary occurs above this interval, coincident with the base of the Campil Member
(Fig. 4.7). The maxima of this excursion marks the Induan-Olenekian boundary within the
Campil Member. This maxima is recorded in the Uomo section as reaching values of + 6
o
/
oo
, in
the Bulla section (as sampled by Horacek et al. 2007a) at values of +5
o
/
oo
, and at the Dawen
123
section at values of +8
o
/
oo
(Payne et al. 2004). 
13
C
carb
values at the Uomo section show a steady
decline to values of -1
o
/
oo
at the top of the sampled section.
5.4 – Faunal Composition

The fauna of the Werfen Formation sampled at the Uomo and Bulla sections are similar
in many respects to Early Triassic fauna found elsewhere. Disaster taxa are widespread and
periodically dominant within assemblages. Overall, 27 genera of bivalves, gastropods, and
brachiopods were recorded from ecological samples, representing at least 6 different life modes
(summarized in Table 4.1). Many of these genera are globally distributed in the Early Triassic,
and found commonly in other Tethyan, Panthalassic, and boreal localities (e.g. Schubert and
Bottjer, 1995; Fraiser and Bottjer, 2007). The most abundantly occurring genera are the bivalves
Unionites and Neoschizodus, as well as the gastropod Pseudomurchisonia. The most commonly
occurring life modes are infaunal, facultatively mobile, suspension -feeders.
Unlike the Dinwoody Formation of the Western U.S., where rhynchonelliform and
linguliform brachiopods are common and abundant in the Induan (see Chapter 3), there are very
few brachiopods recovered from the Uomo and Bulla sections. Lingularia is only abundant in a
single bulk samples from the Griesbachian Mazzin of Uomo (Fig. 4.8), and is present but
uncommon in the Mazzin of Bulla (Fig. 4.9). The spiriferid brachiopod Crurythiris was
recovered from the Dienerian-aged upper Suisi and lower Campil of Uomo, but is again
uncommon. Rhychonelliform brachiopods, belonging to a Permian holdover fauna, have been
reported from the Tesero Member, but these have not been sampled for this study (Posenato,
2009).
124
Infaunal and epifaunal bivalves, as well as Murchisonid gastropods, are the most
common invertebrates found in bulk samples. In Uomo samples, a constrained cluster analysis
shows roughly 4 faunal group transitions though the section, starting with the basal Lingularia-
dominated assemblage in the Griesbachian-aged Mazzin. This assemblage is associated with
ostracods and oolitic-microbialite fabrics occurring in a mid-ramp setting, with likely
intermittent intervals of low oxygen. These assemblages then give way to gastropod and infaunal
bivalve dominated assemblages in the Dienerian-aged upper Suisi and lower Campil. Gastropods
occurring in these assemblages are small, ranging between 2 – 5 mm. These assemblages occur
during an interval of increasing energy, increasing terrigenous input, and shallowing in the
Uomo section. In the upper Dienerian Campil Member assemblages are dominated by infaunal
bivalves, mostly Unionites and Neoschizodus, followed by a transition to increased relative
abundance of epifaunal bivalves in the Smithian-aged Campil. These bivalve-dominated
assemblages are associated with high siliciclastic content in a shallow subtidal to intertidal
environment.
Faunal groups in the Bulla section show less variability than in the Uomo section, due to
the shorter stratigraphic interval that was sampled. Infaunal bivalves are generally dominant in
Bulla samples, with epifaunal bivalves and gastropods secondarily abundant. Gastropods of the
genus Coelostylina and Pseudomurchisonia become more abundant in the upper Suisi Member,
as is also observed in Uomo samples. These gastropod assemblages are associated with finer
grained calcareous shale beds in the upper Suisi Member at Bulla.
Faunal composition appears relatively conserved throughout the two studied sections,
with no major shifts between faunal group structure observed throughout the section. Infaunal
bivalves remain an important component of these communities throughout, with small
125
fluctuations in the relative importance of gastropods and epifaunal bivalves (Fig. 4.8 and Fig.
4.9). NMDS plotting of the sampled sections relative to other Italian abundance collections
spanning the Changhsingian and Anisian demonstrate this conserved faunal composition (Fig
10). Uomo and Bulla samples form smaller clusters within larger Induan and Olenekian clusters.
Changhsingian samples appear to plot closely to these Early Triassic assemblages as well, likely
due to the fact that these samples were collected from the Tesero Member, which exhibits mixed
Late Permian and Early Triassic faunal components (Posenato, 2009). Anisian assemblages show
clear differentiation in terms of faunal composition and structure.
5.4.1 – Community metrics

Metrics of ecological health such as Simpson’s dominance, richness, and Shannon’s
diversity were tabulated for the ecological samples, and compared between lithologic members
and time bins. Dominance ranges from 0.35 in the Mazzin, 0.28 in the Suisi, and is highest in the
Campil at 0.40. However, there is no significant change between these sampled members (Fig.
4.11A; Wilcoxon sum rank test, a = 0.05). Additionally, there are no significant changes
observed in Shannon’s diversity index (H) between these members, though the Suisi exhibits the
highest diversity at 1.6 (Fig. 4.11C). Mean generic richness ranges between 8.3 in the Mazzin,
8.8 in the Suisi, and 5.9 in the Campil, with the decline between Suisi and Campil richness being
significant (Wilcoxon sum rank test, a = 0.05). Comparing samples partitioned by time bin
yields similar results, with no significant differences in dominance, richness, or diversity
between Griesbachian, Dienerian, and Smithian samples, or between Indaun and Olenekian
samples (Fig. 4.12). Generally there is no significant change observed in ecological complexity
throughout this time in the Werfen, despite changing environmental conditions such as
bathymetry, energy levels, and terrigenous sediment influx.
126
5.4.2 – Disaster taxa

Disaster taxa represent the majority of individuals recovered from both Uomo and Bulla
samples, constituting an average of 74% of individuals at Uomo and 34% of individuals at Bulla.
Uomo Mazzin samples are dominated by Unionites and Lingularia, while later Suisi samples
show relatively less disaster taxon relative abundance (Fig. 4.13). Lower Campil samples from
Uomo show high overall dominance and relative abundance of Unionites. Upper Campil samples
exhibit relatively lower overall dominance and relative abundance of disaster taxa Unionites and
Eumorphotis, coinciding with generally lower disaster taxon abundance in Olenekian
assemblages as compared to Induan on average globally (see Chapter 2). Higher relative
abundance of Claraia is observed in middle Suisi Bulla samples relative to Uomo. Bulla samples
generally have fewer disaster taxa than Uomo samples.
Of the disaster taxa, Unionites occurs the most abundantly and frequently (Fig. 4.13),
occurring in 100% of samples from both sections (Fig. 4.14). The infaunal bivalve Neoschizodus
also exhibits similar behavior, with high average relative abundance and 100% occurrence
frequency in both sections. This genus is not considered a disaster taxon in the literature, but
seems to be similarly commonplace in many Early Triassic collections globally (see Chapter 2).
These two taxa are ubiquitous in Uomo and Bulla samples, while abundance distributions of the
other disaster taxa are more constrained in their stratigraphic distribution. Additionally, the
relative abundance of these two taxa does not seem to correspond with increasing siliciclastic
deposits up section, as would be the expected preferred living environment of infaunal bivalves
(Clapham et al. 2006).

127
5.5 – Ecological and geochemical correlations
Trends in ecological metrics of community health up-section are shown in Fig. 4.15 for
the Uomo section and Fig. 4.16 for the Bulla section. At Uomo, lowest richness and diversity,
and highest dominance are observed in samples from the lower Campil Member (Fig. 4.15).
These samples also exhibit low functional diversity, high disaster taxon relative abundance, and
largest bivalve average size, due to the high abundance of Unionites recovered from these
samples. This interval of low-richness, high-dominance fauna corresponds loosely with the end
of a period of “chaotic” 
13
C
carb
values, whereby small 2
o
/
oo
in magnitude excursions occur over
a relatively short stratigraphic interval. This period is also directly prior to the start of the
Dienerian-Smithian positive excursion. High-richness low-dominance fauna are found in
samples from the upper Suisi from Uomo, corresponding to an interval of relatively “chaotic”
carbon isotope values which record several rapid excursions. Generally, these metrics of
community health show a pattern of increasing complexity from the Mazzin to the Suisi, a
dramatic decline from the Suisi to the Campil, and a gradual increase into the remaining Campil
Member. However, there appears to be no statistically significant correlation between these
changes in ecological metrics and magnitude of shifts in 
13
C
carb
values (Fig. 4.17).
In the Bulla section, Mazzin samples are generally more diverse and even than in the
Mazzin of Uomo. Bulla ecological samples generally decrease in richness, diversity, and
evenness up section, with the exception of a single sample (BM16) from the upper Suisi (Fig.
4.16). Other ecological metrics show no clear trend up section, with the exception of a gradual
increase of disaster taxon relative abundance. An interval of low-richness high-dominance fauna
is observed in the upper part of the section, from the Dienerian-aged upper Suisi Member. This
interval is associated with an increase in finer grained calcareous shales in the Suisi. It is also
128
associated with an interval of relatively stable 
13
C
carb
values. There appears to be no significant
correlation between magnitude of carbon isotope shifts and measured ecological metrics in the
Bulla section (Fig. 4.18).
6 – Discussion
6.1 – Upper Suisi Member failed recovery

The two surveyed sections of the Werfen Formation span several Early Triassic
substages, depositional environments, substrate regimes, and carbon isotope excursions.
Ecological samples spanning the Griesbachian to Smithian Mazzin, Suisi, and Campil Members
do not exhibit a clear sustained pattern of benthic invertebrate community recovery in
dominance, diversity, or richness. These metrics remain statistically unchanged at the scale of
these lithostratigraphic members, with the exception of decreased richness observed in the
Campil. No significant changes are observed at the substage scale either. In the Uomo section, a
high-richness, low-dominance fauna occur in the Dienerian upper Suisi Member, which is then
followed by an interval of low-richness, high-dominance assemblages that occur in the Dienerian
lower Campil. These two intervals are separated by the initiation of terrigenous sedimentation
influx, termed the “Campil Event” (Pietsch et al. 2016). These intervals are also separated by
shallowing from an inner ramp subtidal setting into an intertidal lagoonal setting. This can be
considered a short-lived failed recovery, whereby upper Suisi communities experience some
increasing complexity relative to the Mazzin communities below, only to decline again. These
recovery fauna are short lived and do not amount to significant differences between the Suisi and
Campil Members average dominance. However, the significant decrease in generic richness
observed in the Campil is likely a result of the failure of these communities. There is no
observable occurrence of these high-richness low-dominance communities in the upper Suisi of
129
the Bulla section, save for a single sample in the upper Suisi Member (BM16) that records
elevated richness and diversity. In fact, communities in the upper Suisi member at Bulla tend to
exhibit the lowest richness, highest dominance, and highest relative abundance of disaster taxa in
that section.
The short-lived incipient recovery observed in Uomo samples does not appear to
correspond significantly to shifts in the carbon cycle, unlike what was observed in the Blacktail
Creek section in Chapter 3. In fact, this recovery interval occurs during a time of “chaotic”
carbon isotope shifts that occur before the beginning of the large Dienerian-Smithian positive
excursion, contrary to expectation that the causes of these excursions are also linked to disruptive
environmental conditions. The diversity decline following this recovery interval corresponds to
relatively more stable 
13
C
carb
values, again contrary to expectation, though there is still a small
magnitude excursion (~1.5
o
/
oo
) recorded at the end of this interval.
A lack of correlation between geochemical indicators of carbon cycle perturbations and
ecological metrics of community complexity throughout the sections indicates that local
conditions are likely far more important in shaping the timing of benthic recovery and recovery
failure in the Werfen Formation compared to the Blacktail Creek section. The sampled Werfen
sections span three parasequence packages, whereby depositional setting ranged from intertidal
and lagoonal to the mid-ramp offshore transition zone. By comparison, the Dinwoody Formation
exposed at the Blacktail Creek section records general shallowing, from distal offshore facies at
the base to proximal nearshore facies at the top. There are multiple units within the Werfen
Formation that have been interpreted as proximal subtidal or intertidal within the sampled span
of the Werfen Formation, including the Tesero Oolite, the Andraz Horizon, the Gastropod-oolite
unit of the upper Suisi Member, and parts of the Campil Member. These benthic communities
130
would be experiencing relatively rapid relative sea level changes, moving from mid-ramp fully
marine settings into shallower marginal marine settings. This follows the concept of the
‘Habitable Zone’, put forth by Beatty et al. (2008), that proposes the existence of a refugium for
benthic marine shelf communities living in the lower shoreface to offshore transition settings.
These communities are occurring above offshore anoxic or euxinic deep waters, but are still deep
enough to be shielded from high sea surface temperatures or disruption from wave action. Under
these conditions, these communities are able to achieve higher diversity that those occurring
more shallowly or deeper. The fluctuating bathymetric conditions occurring throughout the
Werfen Formation likely suppressed the progression of recovery for most of the section, but
allowed for a window of short lived recovery to occur when the right conditions were met.
The failed recovery attempt occurred during an interval of cooling temperatures in the
Dienerian (Sun et al. 2012). Despite shallowing conditions and increasing siliciclastic input in
the upper Suisi Member, these communities experienced some gain in complexity, potentially
due to the decreased thermal stress during this time. Additionally, these communities were
moving through lower shoreface facies as sea level was dropping, meaning that they were
occurring within the upper ‘Habitable Zone’ (Beatty et al. 2008). Likely both the cooling trend
and shallowing environment contributed to the increase in diversity and evenness observed in the
upper Suisi.
The initiation of the Campil terrigenous sedimentation event, as well as shallowing into
marginal marine intertidal settings, likely overpowered the reprieve brought on by cooling in the
Dienerian. This siliciclastic influx has been implicated by Hofmann et al. (2014) as the cause of
this observed decrease in diversity and evenness across multiple Werfen Formation outcrops. It
should be noted that Hofmann et al. (2014) report this failure of recovery as occurring in the
131
upper Suisi and not the lower Campil Member, but this is likely due to the different stratigraphic
schemes used. Additionally, they observed the height of diversity and evenness to occur in the
Griesbachian Mazzin Member and not the Dienerian Suisi Member as was observed at the Uomo
section in this study. It is possible that low sample numbers from the lower part of the Uomo
section obscured the observation of this initial recovery attempt in Uomo, as samples from the
Mazzin of the Bulla section corroborate an early recovery attempt in the Griesbachian as
observed by Hofmann et al. (2014). It would appear, however, that this transient recovery is
extremely dependent on local sedimentary and bathymetric conditions, even between sections of
the same formation. It is also possible that due to shifting oxygenation conditions occurring
within the Mazzin, that the ecological signal of recovery is highly variable within this unit, and
thus interpretations of recovery are highly dependent on sampling resolution.
6.2 – Disaster taxa in the Werfen Formation

Disaster taxa are important benthic invertebrate community constituents in the Werfen
Formation, and of the disaster taxa, the infaunal bivalve Unionites is the most prominent in these
sections. The abundance of Unionites in the Werfen Formation has been observed by other
workers as well (e.g. Hofmann et al. 2015), and is the most abundantly occurring fossil in
Werfen Formation abundance reports from the Paleobiology Database. Second to the numerical
dominance of Unionites is the infaunal bivalve Neoschizodus, which also exhibits high frequency
of occurrence in Werfen Formation abundance reports from the Paleobiology Database. The
abundance and distribution of these two genera across all samples of the Werfen Formation is
likely tied to the relatively unchanged faunal composition throughout these sections. Of the other
disaster taxa, only the epifaunal pectinid bivalves Claraia and Eumorphotis are prominent,
occurring in large numbers during certain intervals of the Uomo and Bulla sections.
132
Lingularia is observed to only occur in basal Griesbachian Mazzin Member samples.
Lingularia is highly abundant in a single sample from the Mazzin Member of the Uomo section,
and occurs but is not abundant in only a single sample from the lower Mazzin Member at Bulla.
This limited distribution of Lingularia in the Werfen is in contrast to what was observed in the
Dinwoody Formation, where Lingularia was common and abundant in multiple samples across
different depositional facies and substrates. In the Werfen Formation, it appears Lingularia is
limited to the mid-ramp and offshore carbonate facies of the Mazzin Member, which was likely
subject to intervals of low oxygen and microbial mat proliferation periodically (Wignall and
Hallam, 1992; Pietsch et al. 2016). Posenato et al. (2014) document the survival and proliferation
of the species L. yini and L. borealis in the Mazzin Member, as well as morphological
adaptations such as increased lophophore surface area and decreased shell size relative to their
Permian ancestors. They attribute their high abundance within this anoxic member to these
adaptive strategies for low oxygen resilience. While it is expected that Lingularia would be able
to survive and proliferate in these conditions, given its propensity to occur in low oxygen setting
at other times (Chapter 2; Allison, 1995), the facies limitation is unexpected. It is possible that
the prominence of shallow siliciclastic facies across the Werfen Formation instead favored the
proliferation of Unionites to the exclusion of Lingularia. While the preference of Unionites and
for shallow siliciclastic facies was observed in the upper Dinwoody Formation at Blacktail
Creek, Lingularia was abundant within these facies as well. Likely, the wide distribution if
Lingularia in both distal and nearshore settings is limited to Griesbachian strata, such as the
Dinwoody Formation and the Mazzin Member, and as such, is absent or uncommon in Dienerian
and Smithian units of the Werfen. This decrease in Lingularia abundance and distribution after
the Induan is documented across Panthalassic and Tethyan assemblages in Chapter 2.
133
Survival strategies have been proposed for the disaster taxa Lingularia and Claraia
suggesting that these two genera were likely resilient to low oxygen conditions. No such
adaptive strategies have yet been explored for Unionites and Neoschizodus, but it is clear from
the abundance and distribution of these taxa throughout the Werfen Formation that likely some
successful survival strategy was in use. Both Unionites and Neoschizodus have been classified as
mobile shallow infauna. Neoschizodus is described as a suspension feeder (Hautmann et al.
2013), while Unionites has been described as either a suspension feeder or a deposit feeder in the
case of “Unionites” fassaensis (now Austrotindaria fassaensis sensu Foster et al. in press). In
either case, the similarity in life mode between these two abundant taxa implies that their
infaunal life habit and motility allowed for their success in the Werfen Formation. Likely this
lifestyle was favored in the rapidly changing environment of the Werfen Formation, where an
ability to live within proximal and intertidal environments with high terrigenous sedimentation
rates and wave energy was advantageous.
6.3 – Cohesive fauna and phase shifts

The fauna of the Werfen Formation show little change in community constituents up-
section. In the macrofauna, a few genera are abundant and widespread throughout many different
depositional facies. In the microfauna, microgastropods occur throughout the section. The
organisms that appear to be restricted in their occurrence are the phosphatic brachiopod
Lingularia, ostracods, foraminifera, microconchids, and stromatolite-forming microbialites
which are limited to the Mazzin Member, and the tracemaker of Diplocraterion, which is
restricted to the Campil Member. Assemblage compositions from Uomo and Bulla samples show
clear overlap with other Werfen abundance collections (Fig. 4.10), as well as clear differentiation
from Italian Anisian assemblages.
134
Pietsch et al. (2016) proposed that these Early Triassic fauna constitute a phase shifted
community, whereby large or sustained environmental perturbations across a threshold result in
novel cohesive communities. Once formed, these communities exhibit ecological inertia, and are
thus sustained until another threshold is reached. Pietsch et al. (2016) argue that the basal
microbialite-ostracod-foraminiferal assemblages are one such phase shifted community, and are
sustained throughout the Mazzin Member despite fluctuations in oxygen levels. This current
study suggests that the inarticulate brachiopod Lingularia is also a member of this phase shifted
community. A second phase shifted community is encountered in the Suisi and Campil
Members, with the dominance of infaunal and epifaunal bivalves, as well as microgastropod
assemblages. This second phase shifted community is also corroborated by the results of this
current study, as little change in macrofaunal composition is observed throughout the section
despite changes in bathymetry. The cohesiveness of these phase shifted communities can be
attributed to ecological inertia, or to the frequency of environmental perturbation outpacing
ecosystem responses. I propose it is the latter in the case of the Werfen Formation communities,
with rapid changes in sea level sustaining the ecological dominance of a few infaunal disaster
taxa and stymieing major changes in faunal composition.
7 – Conclusions

The Werfen Formation records interplay between various environmental conditions on
the paleoecology of marine benthic communities following the Permian-Triassic mass extinction.
With outcrop-scale high resolution ecological and geochemical sampling, I am able to explore
what correlations exist between metrics of community complexity and environmental conditions
such as bathymetry, terrigenous sediment input, and 
13
C
carb
geochemistry. Unlike what was
found in the Panthalassic Dinwoody Formation, there was no correlation found between carbon
135
isotope shifts and community metrics in the Werfen Formation. The local conditions, such as
rapid sea level changes and terrigenous sediment influx recorded within the Werfen Formation
likely overpower ecological responses to carbon system perturbations that are occurring at the
global scale. This is also manifested in the relatively unchanged faunal composition throughout
these sections, with high occurrence frequencies of the disaster taxon Unionites and the infaunal
bivalve Neoschizodus. Despite a general trend of dominance of these eurytopic taxa, there is an
interval of low-dominance fauna exhibiting elevated richness within the upper Suisi Member. I
interpret these fauna as representing a transient recovery as communities move through the
‘Habitable Zone’ during a time of global cooling in the Dienerian. This recovery subsequently
fails as the terrigenous sedimentation influx of the ‘Campil Event’ begins. This paleoecological
reconstruction of the Werfen Formation highlights the importance of both local and global
environmental effects in shaping ecosystems following the Permian-Triassic mass extinction.

136
Figures and Tables

Table 4.1 – List of invertebrate genera found in ecological samples. Total abundance and life
mode classifications are shown. Life mode classifications after Paleobiology Database entries.

137
Genus Abundance Order Motility Feeding Life Habit
Aviculopecten 3 Pecti nida Stationary Suspension Feeding Epifaunal
Bakevellia 25 Ostreida Stationary Suspension Feeding Semi-infaunal
Chartronella 1 Trochoidea Mobile Grazer Epifaunal
Claraia 78 Pecti nida Stationary Suspension Feeding Epifaunal
Coelostylina 50 Murchisoniina Facultati vely Mobile Suspension Feeding Epifaunal
Costatoria 5 Trigoniida Facultati vely Mobile Suspension Feeding Infaunal
Crurithyris 1 Spiriferida Stationary Suspension Feeding Epifaunal
Cylindrobullina 3 Opisthobranchia ? ? Epifaunal
Entolium 52 Pecti nida Facultati vely Mobile Suspension Feeding Epifaunal
Eumorph otis 37 Pecti nida Stationary Suspension Feeding Epifaunal
Leptochondria
43 Pecti nida Stationary Suspension Feeding Epifaunal
Lingularia 17 Lingulida Facultati vely Mobile Suspension Feeding Infaunal
Myalina 21 Myalinida Facultati vely Mobile Suspension Feeding Epifaunal
Na ticopsis 8 Neritoidea Mobile Grazer Epifaunal
Neoschizodus 450 Trigoniida Facultati vely Mobile Suspension Feeding Infaunal
Permophorus 36 Cardiida Facultati vely Mobile Suspension Feeding Infaunal
Pernopecten 23 Pecti nida Facultati vely Mobile Suspension Feeding Epifaunal
Pleuromya 3 Pholadida Facultati vely Mobile Suspension Feeding Infaunal
Polygyrina 16 Murchisoniina Facultati vely Mobile Suspension Feeding Epifaunal
Promyalina 37 Myalinida Facultati vely Mobile Suspension Feeding Epifaunal
Pseudomurchisonia 162 Murchisoniina Facultati vely Mobile Suspension Feeding Epifaunal
Scythentolium 19 Pecti nida Facultati vely Mobile Suspension Feeding Epifaunal
Semen ticoncha 2 Cardiida Facultati vely Mobile Suspension Feeding Infaunal
Unionites 463 Trigoniida Facultati vely Mobile Suspension feeding / deposit feeding Infaunal
Bivalve sp. A 2 ? ? ? Infaunal
Bivalve sp. B 3 ? ? ? Infaunal
Brachiopod sp. A 1 Rhynchonelliform Stationary Suspension Feeding Epifaunal
Gastropod indet. 111 ? ? ? Epifaunal
Lucinid indet. 2 Lucinida Facultati vely Mobile Chemosymbio tic Infaunal
Pecti nid indet. 17 Pecti nida Stationary Suspension Feeding Epifaunal
138
Figure 4.1 – Overview of the Werfen Formation members and localities visited in this study. (A)
The 8 members of the Werfen Formation and their ages (the Gastropod-Oolite Member has here
been counted within the Suisi Member, after Brandner, 2009). The Werfen Formation spans the
uppermost Permian (Changhsingian stage) to the upper Early Triassic (Spathian substage). The
Dienerian-Smithian and Smithian-Spathian boundaries are easily defined based in 
13
C
carb

correlation or biostratigraphic correlation with sections in South China. However, the
Griesbachian-Dienerian is difficult to pinpoint due to the lack of biostratigraphically informative
fossils, obvious geochemical excursions or lithologic changes at this point. (B) Maps of the two
localities sampled, the Uomo and Bulla sections. The Uomo section is located in the town of
Passo San Pellegrino on route SS346. The Bulla section is located on an abandoned road south of
the city of Ortisei/St. Ulrich, leading to the town of Bulla/Puffels. (C) The paleogeographic
position of the Italian Dolomites region in the Early Triassic, on the western coast of the Paleo-
Tethys Ocean (Scotese, 2001). (D) A photograph of the 200 meter Uomo section, looking north
from the ski chalet at the base of the foothills. Cima Uomo is visible in the background. (E) A
photograph of part of the Suisi Member of the Bulla section, with C. Pietsch for scale.

139
Tesero Oolite
Bellerophon
Fm.
Mazzin
Mb.
Suisi
Mb.
Campil
Mb.
Val Badia
Mb.
Cencenighe
Mb.
San Lucano
Mb.
PERMIAN EARLY TRIASSIC
Andraz Hor.
Gastropod-ooilte Werfen Fm.
Griesbachian Dienerian Smithian Spathian
Induan Olenekian
Changh
-singian
Uomo
Panthalassa
Paleotethys
Neotethys
50 km
30 mi
Bolzano/
Bozen
A22
Ortisei/
St. Ulrich
Falcade
Moena
Uomo/Picol
Bulla/Puffels
SS242
SS346
Venice
Bolzano/
Bozen
Trento
Cortina
d’Ampezzo
-maps.com
100 km
AB C
D
E
140
Fig. 4.2 – Generalized stratigraphic section and depositional environment interpretations of the
Uomo section, showing Werfen Formation members and ages, common macro-, micro-, and
trace fossils, and sedimentary structures. Geochemical samples are shown in red, and ecological
samples and numbering are shown in blue.

141
40
60
50
70
80
90
100
170
180
190
200
210
0
10
30
220
20
160
And.
Mazzin
Tesero
S
u
i
s
i
C
a
m
p
i
l
140
M/Sh W/Si P/Sa G/Co
Dienerian Griesbachian Smithian
INDUAN OLENEKIAN
Timescale Members Lithology Samples Fossils Sed. Structures Ichno Dep. Environment
Supratidal/Intertidal
Proximal subtidal/Shoal
Intertidal (Andraz Marls)
Intertidal/Lagoonal
Mid-ramp/offshore
transition
Proximal subtidal/Shoal
Shallowing
UM01
UM02
UM03
UM04
UM05
UM06
UM07
UM08
UM09
UM10
UM11
UM12
UM14
UM15
UM16
UM13*
UM17
UM18
UM19
UM20
UM20
meters
- Cross-bedded sandstone
- Limestone
- Silty limestone
- Bioclastic limestone
- Geochem sample
- Bulk sample
- Gastropod
- Microconchid
- Ostracod
- Foraminifera
- Echinoderm ossicle
- Infaunal bivalve
- Pectinid bivalve
- Phosphatic brachiopod
- Diplocraterion
- Bioturbation indet.
- Stromatolite
- Micritic interclasts
- Cross bedding
- Mudcracks
- Ripples
- Shell hash
- Ooids
- Thrombolitic fabric
- Planar bedding
- Pyrite framboids
- Peloids
142
Fig. 4.3 – Generalized stratigraphic section and depositional environment interpretations of the
Bulla section, showing Werfen Formation members and ages, common macro-, micro-, and trace
fossils, and sedimentary structures. Geochemical samples are shown in red, and ecological
samples and numbering are shown in blue.

143
40
60
50
70
80
90
100
0
10
30
20
And.
Tesero
S
u
i
s
i
Campil
M/Sh W/Si P/Sa G/Co
Dienerian Griesbachian
INDUAN
Timescale Members Lithology Samples Fossils Sed. Structures Ichno Dep. Environment
110
M
a
z
z
i
n
Offshore
Proximal subtidal
Mid-ramp
Mid-ramp/
Proximal Subtidal
Intertidal?
Proximal subtidal
UM20
BM01
BM02
BM03
BM04
BM05
BM06
BM07
BM08
BM09
BM10
BM11
meters
- Cross-bedded sandstone
- Limestone
- Silty limestone
- Bioclastic limestone
- Geochem sample
- Bulk sample
- Gastropod
- Microconchid
- Ostracod
- Foraminifera
- Echinoderm ossicle
- Infaunal bivalve
- Pectinid bivalve
- Diplocraterion
- Bioturbation indet.
- Stromatolite
- Micritic interclasts
- Cross bedding
- Shell hash
- Ooids
- Planar bedding
- Pyrite framboids
- Oolitic limestone
- Calcareous shale
- Marls
144
Figure 4.4 – Photomicrographs of ooid-microbialite associations. (A) Ooids with thrombolytic
structure between grains. (B) Ooids within a stromatolite.

145
146
Figure 4.5 – Photomicrographs of various microfauna and clasts, showing (A-B) spiral
foraminifera. (C) a microconchid (D) an ostracod assemblage in micritic intraclasts, (E) cross-
section of a brachiopod shell, showing punctate structure, (F) a single ostracod with visible
hinge, and (G) micritic intraclasts.

147
148
Figure 4.6 – Photomicrographs of microgastropod assemblages with micrite envelope. (A)
Bivalve and gastropod recrystallized clasts, within a micrite matrix and with a micritic envelope.
(B) A microgastropod with clearly developed micrite envelope in a micrite matrix. (C) A
photomerged image of a microgastropod assemblage in a micrite matrix.

149
150
Fig. 4.7 – 
13
C
carb
profiles of (A) the Uomo section from this study, (B) the Uomo section
sampled by Horacek et al. (2007a), (C) the Bulla section from this study, (D) the Bulla section
sampled by Horacek et al. (2007a), and (E) the Dawen section from South China, as reported in
Payne et al. (2004). Werfen Formation lithostratigrahic units are shown correlated to carbon
isotope excursions as interpreted by Horacek et al. (2007a).

151
Griesbachian Dienerian
Uomo
This Study
Uomo
Horacek et al. 2007
Bulla
This Study
Bulla
Horacek et al. 2007
Dawen, China
Payne et al. 2004
Mazzin
Suisi Mb. Campil Mb.
Smithian
−1 12345
0 50 100 150 200
δ
13
Ccarb
Meters
−2 0246
0 50 100 150
δ
13
Ccarb
Meters
−2 −1 0 1
0 50 100
δ
13
Ccarb
Meters
−4 −2 0 2 4
0 50 100 150 200
δ
13
Ccarb
Meters
02468
0 50 100 150 200 250 300
δ
13
Ccarb
Meters
Tesero
AB
C
DE
152
Fig 4.8 – Uomo ecological samples, showing faunal distributions. (A) Faunal abundance
distributions from Uomo ecological samples, and (B) corresponding constrained cluster analysis
showing Bray-Curtis Dissimilarity index and bootstrap values (N = 1000). The high relative
abundance of infaunal bivalves is evident throughout the section.

153
0% 20% 40% 60% 80% 100%
UM01
UM02
UM03
UM04
UM05
UM06
UM07
UM08
UM09
UM10
UM11
UM12
UM14
UM15
UM16
UM17
UM18
UM19
UM20
Mazzin
Suisi Mb. Campil Mb.
Gries
Dienerian Smithian
INDUAN OLENEKIAN
A B
Rhynchonelliform Brachiopod
Linguliform Brachiopod
Gastropod
Infaunal Bivalve
Epifaunal Bivalve
Relative Abundance
Bray-Curtis Dissimilarity
47
37
31
32
53
76
50
53
77
90
87
59
55
95
62
89
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
coph corr. 0.6418
154
Fig. 4.9 – Bulla ecological samples, showing faunal distributions. (A) Faunal abundance
distributions from Bulla ecological samples, and (B) corresponding constrained cluster analysis
showing Bray-Curtis Dissimilarity index and bootstrap values (N = 1000).

155
0% 20% 40% 60% 80% 100%
B1
B2
B3
B4
B5
B6
B7
B8
B9
B10
B11
Rhynchonelliform Brachiopod
Linguliform Brachiopod
Gastropod
Infaunal Bivalve
Epifaunal Bivalve
Mazzin Mb. Suisi Mb.
Griesbachian Dienerian
INDUAN
A B
100
74
79
52
89
72
80
92
89
94
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
coph. corr = 0.356
Relative Abundance
Bray-Curtis Dissimilarity
156
Fig. 4.10 – NMDS analysis of faunal composition of Italian Permian-Triassic benthic marine
invertebrate assemblages. Assemblages downloaded from the Paleobiology Database are all from
the Dolomites region, and are color coded as Changhsingian, Induan, Olenekian, or Anisian in
age. Assemblages collected for this study from Uomo and Bulla are also shown. There is clear
overlap of Uomo and Bulla assemblages with other Italian Early Triassic assemblages.
Changhsingian assemblages, which are all collected from the Tesero Member, show slight
overlap, while Anisian communities show very distinct faunal composition.

157
-0.25 -0.20 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15
Coordinate 1
-0.15
-0.12
-0.09
-0.06
-0.03
0.00
0.03
0.06
Coordinate 2
PBDB Induan
PBDB Changhsingian
This Study - Uomo
PBDB Olenekian
This Study - Bulla
PBDB Anisian
Italy
158
Figure 4.11 – Comparing dominance, richness, and diversity between sampled members of the
Werfen Formation. Samples from the Bulla and Uomo sections have been combined. (A)
Comparison of Simpson’s dominance index between the Mazzin, Suisi, and Campil Members.
No significant difference in mean dominance is observed (Wilcoxon sum rank test, a = 0.05). (B)
Generic richness between sampled members shows no significant change between the Mazzin
and Suisi Members (Wilcoxon sum rank test, a = 0.05), but a significant decrease between the
Suisi and Campil Members (Wilcoxon sum rank test, a = 0.05). (C) Comparison of Shannon’s
diversity index sampled members. No significant difference in mean diversity is observed
(Wilcoxon sum rank test, a = 0.05).

159
Mazzin Mb. Suisi Mb. Campil Mb.
0.0 0.4 0.8
Simpson's D
Mazzin Mb. Suisi Mb. Campil Mb.
0 5 10 15 20
Richness (Genera)
Mazzin Mb. Suisi Mb. Campil Mb.
0.0 1.0 2.0 3.0
Shannon's H
W = 34
p = 0.412
W = 67
p = 0.389
W = 26
p = 1
W = 123
p = 0.049
W = 22
p = 0.692
W = 111
p = 0.182
A
B
C
160
Figure 4.12 – Comparison of ecological metrics across Early Triassic substages for combined
Uomo and Bulla samples. (A) Simpson’s dominance index (B) generic richness, and (C)
Shannon’s diversity index of combined Uomo and Bulla samples, comparing at the sub-stage
scale. No significant differences between sub-stages are observed for any of these metrics (a =
0.05). (D) Simpson’s dominance index (E) generic richness, and (F) Shannon’s diversity index of
combined Uomo and Bulla samples, comparing at the stage scale. No significant differences
between sub-stages are observed for any of these metrics (Wilcoxon sum rank test, a = 0.05).

161
Griesbachian Dienerian Smithian
0.0 0.4 0.8
Simpson's D
Induan Olenekian
0.0 0.4 0.8
Simpson's D
Griesbachian Dienerian Smithian
0 5 10 15 20
Richness (Genera)
Induan Olenekian
0 5 10 15 20
Richness (Genera)
Griesbachian Dienerian Smithian
0.0 1.0 2.0 3.0
Shannon's H
Induan Olenekian
0.0 1.0 2.0 3.0
Shannon's H
W = 44
p = 0.915
W = 76
p = 0.138
W = 51
p = 0.526
W = 43
p = 0.552
W = 46
p = 0.795
W = 33
p = 0.216
W = 93
p = 0.096
W = 54.5
p = 0.674
W = 39
p = 0.201
A
B
C
D
E
F
162
Figure 4.13 – Dominance and relative abundance distributions of the disaster taxa from (A)
Uomo and (B) Bulla samples. Unionites is most commonly the most abundant disaster taxon
throughout both sections. However, Eumorphotis becomes more abundant in Smithian samples
from the Uomo section, and Claraia becomes more abundant in Dienerian Suisi Member
samples from the Bulla section. Lingularia is only common in basal Griesbachian Mazzin
Member samples in both section, and is most abundantly found at the Uomo section. Simpson’s
dominance index exhibits the most pronounced changes in Dienerian Campil Member (formerly
Gastropod oolite member) samples from the Uomo section, where samples are high in
dominance and abundance of Unionites.

163
0 0.2 0.4 0.6 0.8 1
UM1
UM2
UM3
UM4
UM5
UM6
UM7
UM8
UM9
UM10
UM11
UM12
UM13
UM14
UM15
UM16
UM17
UM18
UM19
UM20
Lingularia
Claraia
Eumorphos
Promyalina
Unionites
Epifaunal Infaunal
Relave Abundance
Mazzin
Suisi Mb. Campil Mb.
Gries
Dienerian Smithian
INDUAN OLENEKIAN
Mazzin Mb. Suisi Mb.
Griesbachian Dienerian
INDUAN
0 0.2 0.4 0.6 0.8 1
B1
B2
B3
B4
B5
B6
B7
B8
B9
B10
B11
Relave Abundance
U’omo
Bulla
Simpson’s Dominance
0.0 0.2 0.4 0.6 0.8 1.0
Simpson’s Dominance
0.0 0.2 0.4 0.6 0.8 1.0
A
B
164
Fig. 4.14 – Comparison of ecological dominance of taxa occurring in combined Uomo and Bulla
samples. Rank plots of (A) average relative abundance, and (B) occurrence frequency of all
genera occurring in Uomo collections. (C) Average relative abundance and (D) occurrence
frequency are also shown for Bulla collections. In all cases, the infauna bivalves Unionites and
Neoschizodus are the highest rank in terms of these metrics.

165
0.00
0.08
0.16
0.24
0.32
0.40
0.00
0.24
0.48
0.72
1.00
0.00
0.08
0.16
0.24
0.32
0.40
0.24
0.48
0.72
0.96
0.00
Average Relative Abundance
Average Relative Abundance
Occurrence Frequency Occurrence Frequency
A
B
C
D
Unionites
Neoschizodus
Pseudomurchi.
Eumorphotis
Pectinid
Entolium
Lingularia
Coelostylina
Permophorus
Leptochondria
Myalina
Gastropod A
Claraia
Pernopecten
Promyalina
Bakevellia
Polygyrina
Costatoria
Aviculopecten
Pleuromya
Scythentolium
Cylindrobullina
Naticopsis
Crurithyris
Gastropod B
Gastropod C
Bivalve A
Brachiopod A
Unionites
Neoschizodus
Pseudomurchi.
Eumorphotis
Pectinid
Entolium
Lingularia
Coelostylina
Permophorus
Leptochondria
Myalina
Gastropod A
Claraia
Pernopecten
Promyalina
Bakevellia
Polygyrina
Costatoria
Aviculopecten
Pleuromya
Scythentolium
Cylindrobullina
Naticopsis
Crurithyris
Gastropod B
Gastropod C
Bivalve A
Brachiopod A
Unionites
Neoschizodus
Pseudomurchi.
Eumorphotis
Pectinid
Entolium
Lingularia
Coelostylina
Permophorus
Leptochondria
Myalina
Gastropod A
Claraia
Pernopecten
Promyalina
Bakevellia
Chartonella
Sementiconcha
Scythentolium
Cylindrobullina
Naticopsis
Gastropod B
Gastropod C
Bivalve A
Gastropod D
Lucinid
Unionites
Neoschizodus
Pseudomurchi.
Eumorphotis
Pectinid
Entolium
Lingularia
Coelostylina
Permophorus
Leptochondria
Myalina
Gastropod A
Claraia
Pernopecten
Promyalina
Bakevellia
Chartonella
Sementiconcha
Scythentolium
Cylindrobullina
Naticopsis
Gastropod B
Gastropod C
Bivalve A
Gastropod D
Lucinid
166
Fig. 4.15 – Trends in (A) 
13
C
carb
values, (B) generic richness, (C) Simpson’s dominance index,
(D) Shannon’s diversity index, (E) functional diversity, (F) disaster taxon relative abundance,
and (G) bivalve average size in mm from Uomo samples. The highlighted red region corresponds
to an interval of low-richness, high-dominance assemblages that occur in the lower Campil
Member.

167
−1 012345
0 50 100 150 200
δ
13
C
carb
Meter
2 4 6 8 10 12 14
50 100 150 200
Richness (Genera)
Meter
0.2 0.4 0.6 0.8
50 100 150 200
Dominance (D)
Meter
0.5 1.0 1.5 2.0
50 100 150 200
Diversity (H)
Meter
−1 012345
0 50 100 150 200
δ
13
C
carb
Meter
123456
50 100 150 200
Functional Diversity
Meter
0.4 0.6 0.8 1.0
50 100 150 200
Disaster Taxon Abundance
Meter
5 10152025
50 100 150 200
Bivalve Average Size (mm)
Meter
AB C D
AE F G
168
Fig. 4.16 – Trends in (A) 
13
C
carb
values, (B) generic richness, (C) Simpson’s dominance index,
(D) Shannon’s diversity index, (E) functional diversity, (F) disaster taxon relative abundance,
and (G) bivalve average size in mm from Bulla samples. The highlighted red region corresponds
to an interval of low-richness, high-dominance assemblages that occur at the top of the section in
the upper Suisi Member.

169
−2 0 1
20 40 60 80 100
δ
13
C
carb
Meter
610 14
20 40 60 80 100
Richness (Genera)
Meter
0.15 0.30 0.45
20 40 60 80 100
Dominance (D)
Meter
1.2 1.6 2.0
20 40 60 80 100
Diversity (H)
Meter
−2 0 1
20 40 60 80 100
δ
13
C
carb
Meter
23456
20 40 60 80 100
Functional Diversity
Meter
0.0 0.4 0.8
20 40 60 80 100
Disaster Taxon Abundance
Meter
68 10
20 40 60 80 100
Bivalve Average Size
Meter
A
B C D
E
F G H
−1
−1
18 2.4
12
170
Fig. 4.17 – Uomo samples, showing correlation between magnitude of shifts of 
13
C
carb
values
between successive ecological samples, and (A) generic richness, (B) Simpson’s dominance
index, (C) Shannon’s diversity index, (D) normalized evenness E
1/D
, (E) functional diversity, (F)
disaster taxon relative abundance, (G) bivalve size in mm, and (H) gastropod size in mm.
Pearson’s product-moment correlation coefficient (r) and p-values are shown. There are no
statistically significant correlations observed between magnitude of 
13
C
carb
changes and these
ecological metrics.

171
2 4 6 8 10 12 14
0.0 0.5 1.0 1.5
Richness (Genera)
Dδ
13
C
0.2 0.4 0.6 0.8
0.0 0.5 1.0 1.5
Dominance (D)
Dδ
13
C
0.5 1.0 1.5 2.0
0.0 0.5 1.0 1.5
Shannon’s Diversity (H)
Dδ
13
C
0.3 0.4 0.5 0.6 0.7 0.8
0.0 0.5 1.0 1.5
Evenness (E 1/D)
Dδ
13
C
123456
0.0 0.5 1.0 1.5
Functional Diversity
Dδ
13
C
0.4 0.6 0.8 1.0
0.0 0.5 1.0 1.5
Disaster Taxa Abundance
Dδ
13
C
5 10152025
0.0 0.5 1.0 1.5
Bivalve Size (mm)
Dδ
13
C
234567
0.0 0.5 1.0 1.5
Gastropod Size (mm)
Dδ
13
C
A
r = 0.03 p = 0.889
B
r = - 0.35 p = 0.146
C
r = 0.26 p = 0.284
D
r = 0.34 p = 0.154
E
r = - 0.03 p = 0.890
F
r = - 0.21 p = 0.380
G
r = - 0.41 p = 0.083
H
r = - 0.26 p = 0.423
172
Fig. 4.18 – Bulla samples, showing correlation between magnitude of shifts of 
13
C
carb
values
between successive ecological samples, and (A) generic richness, (B) Simpson’s dominance
index, (C) Shannon’s diversity index. (D) normalized evenness E
1/D
, (E) functional diversity, (F)
disaster taxon relative abundance, (G) bivalve size in mm, and (H) gastropod size in mm.
Pearson’s product-moment correlation coefficient (r) and p-values are shown. There are no
statistically significant correlations observed between magnitude of 
13
C
carb
changes and these
ecological metrics.

173
56789 10 11
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Richness (Genera)
Dδ
13
C
0.20 0.25 0.30 0.35 0.40 0.45
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Dominance (D)
Dδ
13
C
1.1 1.3 1.5 1.7
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Shannon’s Diversity (H)
Dδ
13
C
0.3 0.4 0.5 0.6
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Evenness (E 1/D)
Dδ
13
C
23456
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Functional Diversity
Dδ
13
C
0.1 0.2 0.3 0.4 0.5
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Disaster Taxa Abundance
Dδ
13
C
6 7 8 9 10 11
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Bivalve Size (mm)
Dδ
13
C
2.5 3.0 3.5 4.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Gastropod Size (mm)
Dδ
13
C

A
r = 0.42 p = 0.295
B
r = - 0.6 p = 0.116
C
r = 0.59 p = 0.125
D
r = 0.05 p = 0.906
E
r = - 0.56 p = 0.153
F
r = - 0.31 p = 0.457
G
r = 0.16 p = 0.698
H
r = - 0.11 p = 0.829
174
Chapter 5: Evolution and survivorship of crown group echinoids across the Permian-
Triassic biotic crisis

1 – Introduction to echinoid evolution
Echinoids are a diverse and ecologically important group in modern and ancient marine
benthic ecosystems. They experienced a severe bottleneck in diversity around the time of the
Paleozoic-Mesozoic transition, followed by a large radiation giving rise to the over 1000 species
of sea urchins today (Kroh and Mooi 2016, Kroh and Smith 2010). All modern echinoids belong
to two subclasses, the Cidaroida and Euechinoida (Fig. 5.1). Cidaroids, or pencil urchins, are
known for their large and broad spines, and have been called the more primitive of the two
groups due to their superficial resemblance to the Paleozoic Archaeocidarida (Kier 1977b).
Euechinoids are the more diverse subclass of modern echinoids, and include the Irregularia (e.g.
sand dollars and heart urchins). The post-Paleozoic radiation of echinoids was most profound in
the euechinoids, with the cidaroids maintaining limited diversity, in terms of both species and
morphologies, in the Modern (Kroh and Smith, 2010).
The origin of the modern crown group echinoids has been the subject of much discussion
in the literature (Erwin, 2000), particularly because of the proximity of the group’s origin to the
Permian-Triassic boundary and the Paleozoic-Mesozoic transition. Specifically, much interest
has been given to the notion that the Permian-Triassic extinction caused a severe bottleneck of
diversity within early crown group echinoids (Erwin 2000, Twitchett and Oji 2005), and lead to
the extinction of other Paleozoic groups, such as the Archaeocidaridae from which the crown
group evolved. Crown group cidaroids are known from before and after the Permian-Triassic
boundary, but are rare, and euechinoids do not appear in the fossil record until the Late Triassic.
Previously, it was thought that the euechinoids evolved from cidaroids in the early Mesozoic
175
(Kier, 1977). However, modern understanding of the origin of the crown group considers the
cidaroid and euechinoid lineages to have diverged cladogenically from a common ancestor, as
both groups retain different plesiomorphic morphologies found in the Archaeocidaridae, but also
share derived synapomorphies. Therefore, it can be inferred that with the appearance of one
lineage in the fossil record, that the other has also originated. It is therefore believed that despite
no fossil evidence of euechinoids in the Paleozoic, that at least two linages of echinoids must
have survived the Permian-Triassic extinction to give rise to the modern cidaroids and
euechinoids (Erwin, 2000), though how many representatives of each lineage survived is
unknown.
In this study, I explore the phylogenetic relationships of early cidaroids to elucidate the
survivorship of this group across the Permian-Triassic extinction. Fossil representation of this
group in the Permian and Triassic is poor, but understanding the phylogenetic relationships
amongst cidaroid species allows for inferences of lineage survivorship across the boundary to be
drawn. Additionally, I explore the environmental distribution of in situ echinoids from the
Permian to the Early Triassic, for the purposes of 1) determining if the Permian-Triassic
extinction had any effect on the range of distribution of the surviving echinoids, and 2) if the
environments in which these echinoids occur likely imposed some preservation bias, thus leading
to the poor record of Permian and Early Triassic echinoids. I explore the known and
phylogenetically inferred diversity of echinoids during this time and the frequency of occurrence
of disarticulated ossicles, as compared to rock record and sampling intensity. The results of this
study suggest that several echinoid lineages survived the Permian-Triassic extinction to give rise
to the modern crown group, and that the poor record of these early crown group echinoids likely
significantly masks true diversity and survivorship in this group. This study highlights the
176
importance of understanding phylogenetic relationships of a group across an extinction boundary
in order to assess true survivorship.
1.1 – Cidaroid and euechinoid morphologies
Modern living echinoids, belonging to the subclasses Cidaroida or Euechinoida, have
several defining characters relative to extinct archaeocidarid ancestors. All modern echinoids
exhibit five sets of two interambulacral columns separated by five sets of two ambulacral
columns, which constitute the twenty columns of the corona (Fig. 5.2; Fig. 5.3 A-B). Paleozoic
echinoids had varying numbers of columns, with some archaeocidarids possessing up to 19
interambulacral columns (in Nortonechinus) and 4 ambulacral columns (in Lepidocidaris).
Members of the genus Archaeocidaris had 4 columns of interambulacral plates, but had only 2
columns of ambulacral plates, thus making this ambulacral character state pleisiomorphic in
crown group echinoids (Smith 1984).
The fixation of the twenty column coronal arrangement occurred within the
archaeocidarid lineage that gave rise to the crown group, and is associated with a shift in growth
strategies (Smith, 2005). Coronal growth in Paleozoic echinoids was achieved through plate
addition, whereby new plates or columns of plates were added as the animal grew. In modern
echinoids, the adult column arrangement is reached shortly after metamorphosis (Gao et al.
2015), and additional growth thereafter is achieved by plate addition at the apex and primarily by
accretion of new stereom onto existing plates (Smith, 2005). This is first observed in the fossil
record in archaeocidarids, with some Archaeocidaris species showing evidence of growth
banding on interambulacral plates, as well as differentiation of plate forms from the apical to the
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oral end. This growth strategy is associated with the ability to produce larger and more
specialized interambulacral plates in archaeocidarids and later crown group echinoids.
An important synapomorphy of crown group echinoids is the presence of the perignathic
girdle, which constitutes five skeletal protrusions on the inner oral edge of the peristomal
opening (Fig. 5.3 C-D). The perignathic girdle is where the protractor and retractor muscles of
the Aristotle’s Lantern anchor to the test, and are thus important for providing strength to the jaw
apparatus. Archaeocidarids and other Paleozoic echinoids had no perignathic girdle, and it is
believed that the jaw muscles anchored directly to the inside of the test (Smith, 1984). Some
modern irregular echinoids have secondarily lost their perignathic girdle, following overall
specialization of the Aristotle’s Lantern to suit an infaunal, deposit feeding lifestyle (Kier 1974,
Mooi 1990). The presence of a perignathic girdle defines the crown group, but the specific
arrangement of the protrusions is an important subclass level synapomorphy (Durham and
Melville 1957, Jackson 1912, Mortensen 1928). Modern and fossil cidaroids have a perignathic
girdle that originates from the edge of the interambulacral zone, which are termed apophyses
(Fig. 5.3 C). Euechinoids have a perignathic girdle that is positioned on the edge of the
ambulacral zone, termed auricles (Fig. 3D). In euechinoids, the auricles are flanked by buccal
notches (Fig. 5.3 B,D), where the buccal sacs protrude from the test during feeding. These are
absent in all cidaroids (Kroh and Smith, 2010). Perignathic girdle organization has long been
recognized as the most important character for differentiating cidaroids and euechinoids
(Mortensen, 1928; Kroh and Smith, 2010), but observing the perignathic girdle in fossils can
prove challenging due to taphonomic obstructions, such as matrix infill or loss of the oral plates.
Some fossil Mesozoic genera defy characterization based on the perignathic girdle state alone.
For example, Middle Triassic Serpianotiaris exhibits well developed apophyses, but also has
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several test characters that are stereotypically euechinoid (Hagdorn 1995). The affinity of
Serpianotiaris has been problematic, as it has been placed as either a cidaroid or euechinoid in
previous phylogenetic analyses, depending on the importance assigned to the perignathic girdle
character (Kroh 2011, Kroh and Smith 2010, Smith 1994a, 2007). This highlights the importance
of using other additional test and lantern characters when determining the affinity of early crown
group echinoid taxa.
Phylogenetically important characters of the ambulacral and interambulacral zone are
also considered for cidaroid-euechinoid classification. Cidaroids are known for their large
primary tubercle that dominates each interambulacral plate, while euechinoids generally have
smaller, but more evenly sized tubercles per plate (Fig. 5.3 E-F). The mammelon of the tubercle
may be smooth or crenulate, which is typically a genus or family-level synapomorphy. Cidaroid
interambulacral plates generally have a scrobicular ring surrounding the primary tubercle (Fig.
5.3 E) made of scrobicular tubercles to which secondary spines attach. The regularity,
organization, confluence, and number of rings on an interambulacral plate are variable within
cidariod families. Euechinoid interambulacral plates generally have several large tubercles
surrounded by irregularly organized granules (Fig. 5.3 F). However, several Mesozoic
euechinoids are known that have ‘cidaroid-style’ interambulacral tubercles, such as the genus
Hemicidaris (Smith and Kroh 2000). The presence of a multitude of other euechinoid characters,
including characters of the perignathic girdle, ambulacral zone, lantern and apical disc, makes
Hemicidaris definitively euechinoid. Large primary interambulacral tubercles are the
pleisiomorphic state in crown group echinoids, as these are also present in archaeocidarids.
Likely, the large and robust tubercles allowed for the anchoring of large and robust spines that
are characteristic of many archaeocidarid and cidaroid groups (Smith, 2005). The crenulation of
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the tubercles also likely added additional support to the spine articulation, as these interlock with
crenulations on the base of the spine.
The plesiomorphic state of the ambulacral zone found in Archaeocidaris is one composed
of straight columns of simple ambulacral plates. Simple plates are a single skeletal element, with
one pore-pair and small perradial tubercles where secondary spines attach. Most cidaroids
exhibit the plesiomorphic ambulacral character state (Fig. 5.3 G), but a few cidaroid genera have
pseudocompound ambulacral plating (e.g. Procidaris), whereby some ambulacral plates are
enlarged, but there is no fusion of plates due to tubercle overgrowth (Kroh and Smith, 2010a).
Most euechinoids possess compound ambulacral plates, whereby multiple ambulacral elements
are fused into a single plate by overgrowth of one or more perradial tubercles (Fig. 5.3 H). A
single compound plate typically has multiple pore pairs. Pseudocompound plating is known from
basal euechinoids, such as Echinothurioids (Smith and Kroh 2000). Within the euechinoids, the
style of compound plating is an ordinal level trait, and is characterized by the number of fused
plates, as well as the order of fusion within the ambulacral columns.
Characters of the lantern are useful in differentiating modern cidaroids and euechinoids (Fig.
5.4), but as lantern elements are commonly disassociated from the test shortly after death of the
animal, use of these characters is limited in fossil taxa (Kier 1977a). Interestingly, for many
lantern morphologies, euechinoids tend to retain the plesiomorphic character state while
cidaroids exhibit the derived state, unlike what is observed for coronal characters. The cross-
sectional shape of the tooth of echinoids falls into one of 4 categories: flat, keeled, U-shaped, or
diamond shaped (Fig. 5.4 I-L). Archaeocidarids and basal euechinoids like Diademposis
(diadematoid) possess flat teeth (Fig. 5.4 L), while more derived euechinoids like
Strongylocentrotus (camarodont) have keeled teeth (Fig. 5.4 J). Irregular echinoids like
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clypeasteroids have specialized diamond-shaped teeth (Fig. 5.4 K). Cidaroids also have derived
tooth morphology, with U-shaped teeth (Fig. 5.4 I). In this instance euechinoids preserve the
plesiomorphic character state in some taxa while cidaroids exhibit a more derived state across all
taxa (Kroh and Smith, 2010). Additionally, euechinoids possess the plesiomorphic rotula
articulation (hinge form), while most cidaroids possess the derived ball-and-socket form (Fig. 5.4
E, G). The exception to this is the stem cidaroid genus Triadotiaris, which exhibits the
plesiomorphic character state (Kroh and Smith, 2010). Triadotiaris also exhibits the
plesiomorphic epiphysis shape, while other fossil and modern cidaroids and euechinoids share
the derived hatchet-shaped morphology (Fig. 5.4 F, H). The depth of the foramen magnum,
which is the indentation between the two hemipyramids that hold the tooth (Fig. 5.4 C-D), is
typically shallow in cidaroids (i.e. less than 1/3
rd
the height of the hepipyramid), and deep in
euechinoids (i.e. greater than 1/3
rd
the height of the hemipyramid). Archaeocidarids possess a
shallow foramen magnum, and thus the cidaroids exhibit the plesiomorphic state in this instance
(Kroh and Smith, 2010).
Additional characters of the peristomal membrane, tube feet, and apical disc distinguish
cidaroids and euechinoids, but as these characters are very rarely preserved in the fossil record,
they have limited usefulness in phylogenetic analyses using fossil specimens, and are thus not
considered in this study.
2 – Permian and Triassic echinoids
Diversity of echinoids in the Paleozoic is concentrated mostly in Carboniferous strata.
Echinoids in the Permian, however, are generally rare, with 9 known species from articulated
specimens. However, as the first crown group echinoids are known from the Permian, it is
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important to consider what few species are known from this time for phylogenetic reconstruction
of the early crown group. For the purposes of this study, I focus on echinoids known from the
Guadalupian (Middle Permian), Lopingian (Late Permian), and Early Triassic. The echinoids
that occur during this time include members of the families Archaeocidaridae, Proterocidaridae,
Miocidaridae, and Triadotiaridae. I also discuss Late Triassic occurrences of the first known
euechinoids from the family Pedinidae.
2.1 – Eotiaris guadalupensis
Thompson et al. (2015) describe the newly recognized oldest known cidaroid species
from the Guadalupian of Texas, known from partially articulated interambulacral plates with
attached spines (Fig. 5.5). This species, named Eotiaris guadalupensis, exhibits many crown-
group cidaroid characters, including an interambulacral zone composed of two columns only
(Fig. 5.5 B), a perignathic girdle composed of apophyses (Fig. 5.5 C), and a crenulate and
perforate primary interambulacral tubercle. The ambulacral zone of this species is unknown, but
it is assumed that there are only two columns of simple ambulacral plates that bevel under the
interambulacral region, which is consistent with the Archaeocidaris and later cidaroid character
state. Beveled edges on either side of the interambulacral columns of E. guadalupensis supports
the interpretation that these abutted directly to the ambulacral zone, and that there are truly only
two column of interambulacral plates. Additionally, it is assumed that, due to the nature of the
preservation, the ambulacral zone and apical interambulacral zone were not sutured rigidly to the
ambital interambulacral plates, as these regions are missing from all specimens. Non-rigid
suturing of the apical interambulacrum is consistent with what is observed in other miocidarids
(Kier, 1977). The spines of E. guadalupensis have two forms, one a straight spinous form, and
one a bulbous spinous form (Fig. 5.5 D-E). Spines intermediate to these two forms have also
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been found in the same collections. Only the straight form has been found in direct association
with test material (Fig. 5.5 B), but due to the similarity of the length and milled ring of the two
types of spines, it can be safely assumed to come from the same species. The oldest E.
guadalupensis specimens have been recovered from the Roadian-aged Road Canyon Formation
of the Glass Mountains, Texas. However, there are also occurrences of E. guadalupensis
elements known from the Wordian-aged Word Formation of the Glass Mountains and the
Capitanian-aged Bell Formation of the Guadalupian Mountain in Texas (Cooper and Grant 1972,
Thompson et al. 2015).
The occurrence of a true cidaroid in Roadian strata extends the known age of the crown
group to a minimum of 268.8 Ma old, which is a little more than 10 Ma older than previously
thought (Fig. 5.5 A), based on the occurrence of E. keyserlingi in the Wuchupingian (Smith and
Hollingworth 1990, Thompson et al. 2015). As an exact absolute date of the Roadian strata in
which E. guadalupensis occurs is unavailable, Thompson et al. (2015) conservatively place the
age of the occurrence at the top of the Roadian stage. Still, this is a significant change to the
estimated divergence age of the crown group, and has important implications for the calibration
of molecular clock phylogenies (Thompson et al. 2015). This also extends the inferred range of
the Euechinoida, sister clade of the Cidaroida, into the Middle Permian.
2.2 – Eotiaris connorsi
Eotiaris connorsi (Fig. 5.6 D) is known from the Capitanian-aged Bell Canyon Formation
(Kier 1965), and co-occurs with E. guadalupensis there. E. connorsi was figured by Kier (1965)
as a fully articulated (though collapsed) test, with articulated spines. Post-mortem deformation
has unfortunately obscured the ambulacral region in this original description, but several
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articulated interambulacral regions are preserved. Damage to the specimen since Kier’s initial
description has unfortunately resulted in further disarticulation, so that only individual
interambulacral zones remain. E. connorsi exhibits imbricated interambulacral plates throughout
the whole test, unlike E. guadalupensis. There are well-developed apophyses on the oral plates,
making this taxon definitively a cidaroid. The spines are straight and ornamented.
2.3 – Eotiaris keyserlingi
Eotiaris keyserlingi (Fig. 5.6 C) is known from the Wuchupingian-aged Ford Formation
from the United Kingdom, and is the youngest definitive occurrence of the genus Eotiaris. E.
keyserlingi is represented by multiple occurrences of articulated interambulacral zones and
disassociated spines (Smith and Hollingworth, 1991), from the Ford Formation of the U.K. and
the Zechstein Reef of Germany (Hollingworth and Pettigrew). Like E. guadalupensis, the apical
coronal plates and ambulacral plates are unknown, and are assumed to be non-rigidly sutured to
the rest of the test. E. keyserlingi and E. guadalupensis are remarkably similar in interambulacral
zone morphology, but are differentiated by spine morphology. The spines of E. keyserlingi and
straight and smooth, and show no variation of form as in E. guadalupensis. The teeth of E.
keyserlingi are the oldest definitive occurrence of the derived cidaroid-style U-shaped tooth
(Smith and Hollingworth, 1990).
2.4 – Other Middle and Late Permian echinoids
There are only two non-cidaroid echinoids known from the Middle and Late Permian, the
archaeocidarid Archaeocidaris selwyni and the proterocidarid Pronechinus anatoliensis.
Archaeocidaris selwyni occurs in the Roadian-aged Nowra Formation of Australia (Etheridge
1892), and is the youngest fully articulated occurrence of Archaeocidaris. One specimen is
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known, preserved as a fully articulated test but without spines. Younger Guadalupian silicified
archaeocidarid spines and plates are known but are considered indeterminate due to the
disarticulation of the remains. The occurrence of this archaeocidarid in the Guadalupian is
significant, as it demonstrates that the Archaeocidaridae survived and co-occurred with their
Miocidaridae descendants.
Pronechinus anatoliensis (Fig. 5.6 B) occurs in the Changhsingian-aged Gomaniibrik
Formation of Turkey (Kier, 1965). This taxon is also the youngest definitive occurrence of the
Paleozoic Proterocidaridae, which are thought to go extinct at the Permian-Triassic. The
Proterocidaridae are an anciently diverged group originating in the Devonian, and are not closely
related to the Archaeocidaridae (Kier, 1965; Smith, 1984). They are characterized by a flattened
test, with numerous specialized ambulacral plates, and presumably tube feet, on the oral side. It
has been hypothesized that these are specializations for living in fine-grained and deep
environments (Smith, 1984), or for filling a niche similar to modern-day sand dollars (Seilacher
1990), but detailed work on the ecology of these Paleozoic disc-shaped echinoids is lacking.
2.5 – Miocidaris pakistanensis
The miocidarid Miocidaris pakistanensis is known from the Dienerian-age Mittiwali
Member of the Mianwali Formation, formally known at the Lower Ceratite Limestone (Linck
1955). This is the oldest post-Paleozoic named species of echinoid, and one of two named Early
Triassic species. M pakistanensis is a relatively well-preserved specimen, with the whole test and
spines articulated in life position (Fig. 5.6 E). The oral size is obscured from view, and therefore
important phylogenetically informative characters are unknown despite its excellent
preservation. M. pakistanensis exhibits many miocidarid characters, including perforate and
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crenulate tubercles and a well-defined scrobicular ring. Unlike Eotiaris, however, it appears to be
flexible over the whole test, though the mode of preservation makes this difficult to determine
confidently. The spines of M. pakistanensis are large and clavate, and are unlike any seen in
older miocidarids.
2.6 – Lenticidaris utahensis
Lenticidaris utahensis is the best known Early Triassic echinoid yet found in terms of
morphology (Fig. 5.6 F). Over 200 specimens are known from the Spathian-aged Virgin
Limestone Member of the Moenkopi Formation in the Beaver Damn Mountains of Utah. These
specimens preserve articulated tests, with articulated primary and secondary spines, peristomal
membranes, lanterns, and apical discs, all of which are commonly lost and unknown in fossil
echinoids. This species has well developed apophyses, simple ambulacral plating, and large
interambulacral primary tubercles with a well-defined scrobicular area (Kier, 1965), which make
L. utahensis definitively cidaroid. The interambulacral area is imbricate throughout, which is
likely the reason Smith (2007) informally assigned this taxon to the family Triadotiaridae. L.
utahensis is the oldest known triadotiarid, though there exist older probable triadotiarid
disarticulated remains.
2.7 – Miocidaris sp. from the Tesero Member
Broglio Lorigia et al. (1985) report the occurrence of a partially articulated
interambulacral zone of an echinoid in the Tesero Member of the Werfen Formation. This
echinoid has been assigned to ?Miocidaris sp. by the authors, and further classification of the
specimen has not been possible as of yet. However, the specimen resembles E. keyserlingi in that
is has confluent areole orally, perforate and crenulate tubercles, and a well-defined scrobicular
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area. The loss of the ambulacral zone and apical interambulacral zone suggests non-rigid
suturing within these regions of the test, as is found in E. keyserlingi and E. guadalupensis. The
inner wall of the interambulacral zone is obscured by matrix, so the state of the perignathic girdle
cannot be assessed for this specimen currently.
The echinoid specimen was collected from the Tesero Member at the Tesero Section,
from approximately 2 meters above the base of the Werfen Formation there (Broglio Lorigia et
al. 1985). Perri and Farabegoli (2003) report the occurrence of H. parvus approximately 1.3
meters above the base of the Werfen Formation, within the Tesero Member at the Bulla Section.
It is not certain if the echinoid specimen was collected from the Changshingian or Griesbachian
portion of the Tesero Member, since the position of H. parvus is unknown from the Tesero
section. However, Posenato (2009) reports the occurrences of echinoid spines, plates, and teeth
within the uppermost Changhsingian Tesero Member, as well as spines from the underlying
Bulla Member of the Bellerophon Formation. These occurrences have also been assigned to the
genus Miocidaris by the author. It is therefore likely that the articulated echinoid specimen of
Broglio Lorigia et al. (1985) is in fact latest Permian in age. Posenato (2009) reports the echinoid
debris as occurring in a quite marginal marine setting within the Tesero Member, and includes
them as members of the Permian-Triassic boundary ‘mixed fauna’.
2.8 – Triadotiarid from the Dinwoody Formation
As discussed in Chapter 3, evidence of a triadotiarid occurring in the Griesbachian-aged
Dinwoody Formation was recovered from bulk samples taken at the Blacktail Creek outcrop (Fig
3.4 L). A single plate was recovered, which shows a large perforate and crenulate tubercle, a
poorly defined scrobicular ring, and a large width-to-height ratio. These are characteristic of the
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family Triadotiaridae, though further assignment is not possible due to the limited information
available from a single plate. Plates similar to this one are known from Olenekian strata (Nützel
and Schulbert 2005), but the occurrence of this plate in the Dinwoody extends the known fossil
range of the Triadotiaridae into the Induan, and is thus the oldest triadotiarid known. Many
authors have identified similar disarticulated plates and spines in the Early Triassic as
Lenticidaris utahensis, as this is the only triadotiarid known from this time. While this is the
most parsimonious assignment, true identification to the genus or species level is not possible
with the degree of disarticulation that is common with these occurrences, as several genus- level
traits are only observable on the whole test, and should therefore be used with caution.
A partially articulated interambulacral zone of a cidaroid echinoid was also recovered
from the Dinwoody Formation at Blacktail Creek, composed of at least two articulated
interambulacral plates (Fig 3.4 O). The orientation of the plates suggests that these represent a
single row. The tubercles are large, crenulate, and perforate. However, as the plate edges are
obscured, the dimension of the plates and the organization of the scrobicular ring are unclear. It
does appear that the area in between the two tubercles is composed of poorly organized
scrobicular tubercles, which is similar to what is found on Lenticidaris utahensis. Identification
of this specimen as a triadotiarid, however, remains dubious due to the poor exposure of the plate
margins.
2.9 – Early Triassic disarticulated occurrences
Disarticulated echinoid remains are somewhat common in the Early Triassic, but most
occurrences are of spines only. In Panthalassa, spines and plates are known from both the Induan
and Olenekian. Probable triadotiarid spines are known from several North American Early
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Triassic formations, including the Dinwoody Formation and Moenkopi Formation Virgin
Limestone and Sinbad Limestone (Ciriacks 1963, Moffat and Bottjer 1999, Nützel and Schulbert
2005). Straight, non-ornamented spines are also known from these formations. These
occurrences have often been assigned to Lenticidaris utahensis, as no other echinoid species is
known from the Early Triassic with this spine morphology. However, as there are few other
defining characteristics of the spines, assignment of this material to L. utahensis, should again be
done with caution.
Moffat and Bottjer (1999) describe a spine bed from the Spathian Virgin Limestone in
Nevada. The spines from this bed are large and clavate, and do not resemble the spines of L.
utahensis. Instead, these spines more closely resemble those known from the Tethyan Miocidaris
pakistanensis, and are thus named in the literature. The spines from this bed are one of the few
probable Miocidaris occurrences in Panthalassa, as most other spines and plates found in
Western U.S. Lower Triassic strata are more likely triadotiarid in origin.
Mata and Woods (2008) describe echinoid spines from the Smithian-age lower Union
Wash Formation of California. The spines are small but abundant, and are ornamented with faint
striations. The authors suggest that the shallow, intertidal source of this accumulation likely
represented a shallow water refugium for echinoids during the Early Triassic, as deeper shelf
facies were likely subject to periodic anoxia. The affinity of these spines is unknown, but they
are unlike the primary spines known from either L. utahensis and M. pakistanensis, and are not
smooth like the secondary spines known from L. utahensis. The uniformity of size of these small
spines raises the possibility that they are from a proterocidarid, like Pronechinus anatoliensis,
which are known to have only small spines across the whole test. This raises the possibility that
the Proterocidaridae survived into the Mesozoic, unlike what has previously been thought, but
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additional evidence from plates or other elements is needed to conclusively determine the
proterocidarid affinity of these spines.
2.10 – Earliest euechinoid
The earliest euechinoids are not known until the Norian (Late Triassic), at least 40
million years later than it is assumed the cidaroid-euechinoid divergence occurred (Thompson et
al. 2015). Smith (1994b) describes the pedinid Diademopsis herberti, from the Norian of Peru.
Several specimens of Diademopsis recovered from the Norian of Peru show articulated
ambulacral and interambulacral columns, well-developed auricles, buccal notches, and
compound ambulacral plating. The lantern from this species is unknown, but the lantern of the
later Rhaetian Diademopsis tomesii exhibits the plesiomorphic flat tooth cross-sectional shape,
which is the assumed state of the teeth of D. herberti as well. The Pedinidae are an extant family,
and are basal to other euechinoid families except for the echinothurioids and diadematoids. This
suggests that these lineages already diverged by the Norian, but no fossil evidence of them is yet
known.
3 – Methods
3.1 – Echinoid occurrences, diversity, rock record, and environmental distribution
The environmental distribution of echinoids living in the Middle Permian to Early
Triassic was reconstructed based on the depositional setting of articulated echinoid specimens.
Disarticulated remains were disregarded for this analysis, due to the likelihood of extensive
transport of these skeletal elements (Greenstein 1991, Kidwell and Baumiller 1990). Echinoid
occurrences were tallied from the literature, Paleobiology Database entries, museum and
personal collections. If available, data on the preservational state (e.i. whole test, partially
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articulated test, disarticulated material), lithology (e.i. carbonate or siliciclastic) and depositional
environment (i.e. lagoon, shoal, inner ramp, mid ramp, or outer ramp) were included. For in situ
occurrences (whole or mostly articulated tests), where depositional environment was not
discussed in the original literature, generalizations of depositional environments where made
from other sources for the highest available stratigraphic resolution (e.g. at the member scale). A
list of echinoid occurrences considered in this study is summarized in Table 5.1. Only fully
articulated occurrences were considered for phylogenetic analysis and diversity counts, but
disarticulated specimens were considered for occurrence counts. Several workers have, in the
past, defined new species based on disarticulated plates and/or spines (e.g. "Archaeocidaris
barroisi", Mathieu (1949)). This is particularly common in Paleozoic archaeocidarid specimens.
However, best practices for conservatively estimating echinoid diversity should rely only on
fully or partially articulated material, for two reasons: 1) several species-level homologies are
only apparent in fully articulated specimens (e.g. the articulation of the interambulacral region
adapically); and 2) morphological differentiation of elements along the test (e.i. apical vs. oral
spines; confluent ambital plates vs. non-confluent adapical plates) may erroneously overestimate
diversity.
Estimates for rock area and paleontological effort were made to compare to known
diversity of echinoids in the Guadalupian, Lopingian, and Early Triassic. Surficial exposure of
rock outcrops is difficult to calculate, and adequate estimates are only known for limited areas
(North America and Europe) at a very coarse temporal resolution. Therefore, number of marine
fossiliferous formations was used instead, as a proxy for available marine rock for study.
Number of marine formations were extracted from the Paleobiology Database, at the stage level.
Formations spanning more than one stage were counted for each stage. Number of marine
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Paleobiology Database collections were used as a proxy for paleontological effort per stage.
Presumably, known diversity of a group may be due to: 1) a true dearth of species;2) limited
preservation of species, or the environment in which they lived, due to global scale processes
such as sea level; and 3) lack of sampling or paleontological interest during a certain time
interval. Comparing the known diversity of echinoids from the Middle Permian to the Early
Triassic with proxies for rock record and paleontological effort can elucidate the relative
importance of these biases.
3.2 – Phylogenetic analysis
Specimens were used in phylogenetic analysis if sufficient articulated material was
available for study. Partially articulated test material was only considered if enough information
of character states of interest could be observed. For this reason, the Miocidaris species known
from the Tesero Member of the Werfen Formation was not included. Measurements and
observations of character states for phylogenetic analysis were collected in person from various
museum collections, with the aid of calipers and a dissecting microscope. Characters of the
whole test, interambulacral zone, ambulacral zone, apical disc, lantern and spines were
considered for this analysis.
Eleven Permian and Early Triassic species were used for this analysis (Fig. 5.6 and 5.7).
As there are no known euechinoids from the Permian or Early Triassic, only cidaroids are
included in this analysis, with the exception of Archaeocidaris whatlyensis, (Fig. 5.6 A) which
was used as the outgroup. A. whatlyensis, which occurs in the Mississippian, was chosen as the
outgroup in place of younger Permian archaeocidarids because it is one of the most well-known
Archaeocidaris species, due to excellent preservation of the articulated test, lantern, and spines.
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Additionally, preliminary unpublished phylogenetic analyses of the Archaoecidaridae suggest it
is one of the more derived species, closely related the eotiarids (Thompson et al. in prep). The
three Eotiaris species known from the Guadalupian and Lopingian were included, as well as the
two cidaroid species known from the Early Triassic, L. utahensis and M. pakeistanensis. The
?Miocidaris sp. reported from the Tesero Member of the Werfen Formation was not included, as
in-person observation of the specimen was not possible. Additional Jurassic stem cidaroids were
included in this analysis to elucidate the early evolution of the Early Triassic echinoids across the
Permian-Triassic boundary. These taxa included Procidaris edwardsi, Triadotiaris grandaeva,
Couvelardicidaris moorei, Couvelardicidaris dubari, and Procidaris lobatum.
The 22 characters used for phylogenetic analysis and their character states are listed
below. All characters are unordered, meaning that a change from a character state of 0 to a
character state of 1 is equally as parsimonious as a character state change from 0 to 2 or 1 to 0. A
heuristic maximum parsimony analysis was run using the software PAUP, version 4.0 (Swofford
2003), with 1000 random addition sequences (RAS) and tree bifurcation-reconnection (TBR).
Afterwards, the retention index of each character was calculated, and the search repeated using
the retention index as the character weight. This assigns a greater importance to characters that
are constant within clades, which likely represent true synapomorphies, and thus reduces the
noise created by homoplasy (Farris 1989). The retention index is calculated as follows, where G
represents the theoretical maximum number of steps that character could have in a given tree, M
represents the theoretical minimum number of steps, and S represents the actual number of
character state changes of that character.
RI = (G-S)/(G-M)
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3.2.1 - Characters and character states

1) Interambulacral plate dimensions (width:height ratio): (0) < 2.0 (1) > 2.0
2) Number of interambulacral plates per interambulacral column: (0) < 9 (1) > 9
3) Width of interradial extrrascrobicular area: (0) < 1/3 of plate width (1) >1/3 of plate
width
4) Number of interambulacral columns: (0) >2 (1) 2
5) Perradial tuberculation style: (0) Simple (1) Enlarged tubercles but not fully trigeminate
(2) Fully trigeminate
6) Coronal imbrication: (0) Imbricate throughout (1) Imbricate adapically only (2) Rigid
7) Perignathic girdle: (0) Absent (1) Composed of apophyses (2) Composed of auricles
8) Tooth cross-sectional shape: (0) Flat (1) U-shaped
9) Serration of tooth tip: (0) Absent (1) Present
10) Interambulacral tubercles crenulate? (0) No (1) Yes
11) Shape of ambital interambulacral plates: (0) Pentagonal (1) Hexagonal
12) Interambulacral tubercle boss undercut? (0) No (1) Yes
13) Interambulacral tubercle areoles confluent? (0) No (1) Yes, over whole test (2) Yes,
orally only
14) Scrobicular ring present? (0) No (1) Yes
15) All ambulacral plates in contact with perradius? (0) No (1) Yes
16) Ambulacral pore pairs: (0) Uniserial (1) Biserial
17) Imbrication of columns at ambitus: (0) Interradial imbrication (1) Adradial imbrication
(2) Rigid
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18) Ambulacral plating pseudocompound? (0) No (1) Yes adorally only (2) Yes over whole
test
19) Primary ambulacral tubercles perforate? (0) No (1) Yes
20) Spines hollow? (0) No (1) Yes
21) Spine sculpturing: (0) Smooth (1) Spinules
22) Spine shape: (0) Straight (1) Clavate
The character matrix for the 10 cidaroid taxa and the archaoecidarid outgroup is shown in Table
5.2.
4 – Results
4.1 – Phylogenetic analysis
The parsimony based phylogenetic analysis of the 10 cidaroid taxa results in two most
parsimonious trees (Fig. 5.8 A-B). These two trees show agreement between all nodes except for
the placement of E. connorsi. Two distinct clades are apparent in the analysis, which, for the
purposes of this discussion, have been termed the miocidarid and triadotiarid clades. The
miocidarid clade consists of E. guadalupensis and E. keyserlingi, the Miocidaris species, and
Couvalarocidaris. The triadotiarid clade consists of Lenticidaris utahensis, Triadotiaris
grandaeva, and Procidaris edwardsi. E. connorsi either places basal to the miocidarid clade or
basal to the triadotiarid clade. In the strict consensus tree (Fig. 5.8 C and Fig. 5.9), E. connorsi,
the triadotiarid clade, and the miocidarid clade form a polytomy. Bootstrap values greater than
50 are shown for a bootstrap analysis with 1000 repetitions. The miocidarid clade is relatively
well supported with a bootstrap value of 53, and the Lenticidaris-Triadotiaris branch within the
triadotiarid clade is very well supported with a bootstrap support of 83.
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The miocidarid clade is composed of the Permian Eotiaris species (except E. connorsi),
the Triassic to Jurassic Miocidaris species, and Couvelardicidaris moorei from the Jurassic (Fig.
5.7 B). E. guadalupensis and E. keyserlingi form a polytomy with the other groups, as it is not
clear if either is more basal than the other when compared to the Miocidaris-Couvelardicidaris
clade. Still, the eotiarids do not fall within this post-Paleozoic clade, supporting the idea that the
eotiarids are basal miocidarids. Couvelardicidaris moorei plots basal to the Miocidaris species.
Smith (2007) unofficially synonymizes Couvelardicidaris moorei and Couvelardicidaris dubarai
(5.7 D). However, this analysis suggests that these two taxa should be kept as separate species, as
they do not plot as sister groups to each other. The Induan Early Triassic species Miocidaris
pakistanensis plots as sister taxon to the Jurassic species Procidaris lobatum (previously
Miocidaris tenuispina, Smith (2015)), suggesting that Miocidaris pakistanensis is a relatively
derived miocidarid, and that several lineages of miocidarids may have already originated by the
time of the Permian-Triassic boundary (Fig. 5.9).
The results of the phylogenetic analysis suggest that the Triassic taxa Lenticidaris
utahensis and Triadotiaris grandaeva, as well as the Jurassic taxon Procidaris edwardsi
constitute a clade that is sister to the miocidarid clade, considered here as the triadotiarid clade
(Fig. 5.9). Lenticidaris utahensis is assigned to the Miocidaridae in older literature (Kier, 1977),
but Smith (2007) and Kroh and Smith (2010) informally assigned this genus to the Triadotiaridae
after Hagdorn (1995) erected the family. The results of this phylogenetic analysis corroborate
that assignment. Taxa of this family are characterized by imbricate plating throughout the test
and interambulacral plates with a large width-to-height ratio, which Lenticidaris utahensis
exhibits. However, the Triadotiaridae are also known to have pseudocompound ambulacral
plating, while Lenticidaris only has simple plating. This analysis suggests that pseudocompound
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plating is a derived trait within the Triadotiaridae, as Lenticidaris utahensis appears basal to the
other triadotiarids. P. edwardsi and T. grandaeva form a well-supported clade, suggesting that P.
edwardsi is also a triatotairid. P. lobatum is a miocidarid, but the results of this study suggest that
P. edwardsi should be assigned to the Triadotiaridae, as P. edwardsi and P. lobatum form a
paraphyletic group and should not be considered the same genus (Fig. 5.8).
E. connorsi is the only taxon that does not fall into either the miocidarid or triadotiarid
group in this analysis, and plots as either the most basal miocidarid or the most basal triadotiarid
in the two most parsimonious trees (Fig. 5.8 A-B). It shares many characteristics with the
Triadotiaridae, such as having interambulacral plates that have a large width-to-height ratio, and
being imbricate throughout the whole test, whereas miocidarids are generally imbricate
adapically only. The ambulacral region of E. connorsi, on the other hand, resembles the
miocidarids more so than the triadotiarids. As several character states of the ambulacral zone
appear to be derived within the Triadotiaridae, it may be that E. connorsi is actually a basal
triadotiarid with plesiomorphic ambulacral characters, such as are observed in Lenticidaris
utahensis. Additional phylogenetic analyses are needed, with additional characters and/or taxa, to
elucidate the affinity of E. connorsi.
The stratigraphic occurrence of these taxa suggests that many lineages of cidaroids were
already in existence in the Permian (Fig. 5.9). As the triadotiarids are basal to the miocidarids, it
is inferred that the ancestral triatotiarid lineage was already in existence by the first appearance
of a miocidarid in the fossil record in the Permian, despite no evidence of triadotiarids until the
Triassic. Additionally, the position of Miocidarid pakistanensis as a derived miocidarid suggests
that more basal miocidarid lineages existed, that eventually give rise to the Jurassic
couvalorocidarids. As miocidarids occur in the Induan, this suggests that these more basal
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miocidarid lineages were already in existence by at least the latest Permian. Therefore, in
addition to the currently unknown euechinoid ancestor, it appears that there were at least three
families of Paleozoic echinoids that survived into the Mesozoic, with one of these families, the
Miocidaridae, with potentially many lineages (Fig. 5.9).
4.2 – Environmental distribution
Articulated echinoid occurrences are rare in the Guadalupian, Lopingian, and Early
Triassic. Despite this, the record of articulated, presumably in situ echinoids from these time
intervals reveals preferential distribution in shallow settings. Specifically, the eotiarids are
known from reef platform settings (Fig. 5.10 A). In the Guadalupian, E. guadalupensis is known
from the Road Canyon, Word, and Bell Canyon Formations (Lamar Member), though
occurrences in the Word Formation are limited to spines only and are thus not considered in situ
(Thompson et al. 2015). E. connorsi is also known from the Bell Canyon Formation (Kier,
1965). The environmental settings in which these occur have been described as reef slope
deposits, with echinoid and other reefal faunal debris forming a course bioclastic packstone
deposited on the lower energy slope basinward of the reef (Babcock 1977). In the Lopingian, E.
keyserlingi has been reported from the Ford Formation of the United Kingdom, and the
Zechstein (Cycle 1) of Germany, which also represents reefal deposits, but in this case are
described as reef core or backreef debris (Hollingworth et al. 1988, Reich 2007, Smith and
Hollingworth 1990).
The environmental settings of the remaining Middle and Late Permian articulated
echinoid occurrences, Archaeocidaris selwyni and Proterocidaris anatoliensis, are likely a ramp
setting (Fig. 5.10 A). A. selwyni is known from the Nowra Sandstone (Etheridge , 1892),
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described as a middle to upper shoreface, inner ramp environment (Roux and Jones 1994). The
excellent preservation of this specimen, composed of articulated interambulacral and ambulacral
plates, suggests that burial in this high energy environment was rapid and with little
transportation. P. anatoliensis is known from the upper 2.5 meters of the Gomaniibrik
Formation, occurring in a bioclastic packstone (Kier, 1965). The two specimens are fully
articulated but without spines, and one specimen is in life position (apical side up), while the
other is positioned with the oral side up. This mode of preservation suggests some degree of
current influence, but the articulation of the delicate and non-rigidly sutured tests suggests that
transport was not extensive. The Gomaniibrik Formation represents a regressive-transgressive
cycle, with the bottom unit composed of dolomitic marine limestones, the middle unit composed
of fluvial-deltaic silts and interbedded coals, and the top unit composed again of fossiliferous
marine limestones, interbedded with shales and silts (Aydemir 2011, Nairn and Alsharhan 1997).
The coarse-grained bioclastic limestones and siliciclastic deposits interbedded with fine grained
argillaceous deposits suggests a storm-dominated mid-ramp setting below fair weather wave
base, though this assignment is pending a more detailed paleoenvironmental study of the unit.
The cidaroid reported from the Tesero Member of the Werfen Formation is the youngest
Permian echinoid known, and occurs in a wackestone unit that is described as a quiet, marginal
marine setting, backshore of an ooid shoal (Broglio Lorigia et al., 1985; Posenato, 2009). This
specimen likely occurs within less than one meter of the Permian-Triassic boundary, within the
boundary ‘mixed fauna’. These fauna are transitional between typical Permian and Early
Triassic fauna, but occur after the initial and most severe extinction horizon (Posenato, 2009).
For this reason, this specimen is considered post-extinction for the purposes of this study, despite
occurring in the uppermost Changhsingian.
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The oldest currently known echinoid in the Triassic is Miocidaris pakistanensis, which is
described as found from the “Lower Ceratite Limestone” of the Chhidru section (Linck, 1955) in
the Lower Triassic strata of the Salt Ranges. Detailed stratigraphic and environmental
information is not reported in the original literature on this specimen, making interpretation of
the depositional environment difficult. The Lower Ceratite Limestone is now assigned to the
base of the Mittiwali Member of the Mianwali Formation (Kaim et al. 2013, Wignall and Hallam
1993). The Mittiwali Member spans several lithologies and environments, including cross-
bedded sandstones, marls, organic-rich shales, and bioclastic limestones. The base of the
Mittiwali Member (the Lower Ceratite Limestone) at the Chhidru section where this specimen is
known from is predominantly composed of thick coarse-grained packstone beds interbedded
with thin mudstones (Wignall and Hallam, 1993), likely representing storm deposits within a
mid-ramp setting. Wignall and Hallam (1993) report an echinoid spine bed within this unit,
occurring in one of the mudstone units. Considering the degree of articulation of the whole test
and spines of the M. pakistanensis specimen, it is likely that this specimen came from these
mudstone units and was living in a mid-ramp environment (Fig. 5.10 B).
Lenticularis utahensis, known from the Virgin Limestone of the Moenkopi Formation,
occurs in a dense accumulation of hundreds of well-preserved specimens (Kier 1968), with
articulated primary and secondary spines, lanterns, peristomal membranes, and apical discs. The
echinoids occur throughout a thin (5 cm) sandstone unit, which grades-upwards in terms of
density of echinoid bioclasts. There is some faint evidence of cross bedding, but it is not
definitive (pers. obs). The echinoids on the bedding plane occur in either life position (apical side
up) or oral side up, and some spines are disarticulated from the test. This would suggest that
some agitation of the animals occurred during burial, but the overall excellent articulation of
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these specimens suggests that it was minimal. The Virgin Limestone is interpreted as spanning
from nearshore marine to lagoonal facies in the upper units (Poborski 1954). The exact
stratigraphic position of these specimens within the Virgin Limestone is unknown, but based on
the lithology, it is likely these echinoid lived in an inner ramp, nearshore setting (Fig. 5.10 B).
The distribution of Middle and Late Permian echinoids is predominantly in very shallow
settings, with several occurrences in reef or reef-associated facies, and one from an inner ramp
setting. Pronechinus is the only occurrence in a mid-ramp setting. In the Early Triassic,
echinoids are known from the inner ramp and mid-ramp, as there are no reefs in the Early
Triassic. It is not apparent that a restriction of environmental distribution occurred over the
Permian-Triassic boundary, as echinoids both before and after the boundary showed a preference
for shallower and higher energy environments (Fig. 5.10).
4.3 – Diversity and rock record biases
Echinoids in the Permian and Triassic are rare. Known species in Middle to Late Permian
and Early Triassic stages rarely exceed one known species per stage, with a maximum of two in
the Guadalupian (Fig. 5.11 B). Inferred fossil ranges from phylogenetic reconstructions,
however, suggest that there may have been at least 6 taxa in the Guadalupian and another 6 in the
Early Triassic. In the Roadian, the appearance of E. guadalupensis suggests the existence of 4
additional lineages: the triadotiarid lineage, the miocidarid lineage, the lineage leading to E.
connorsi, and the euechinoid lineage (Fig. 5.9 and Fig. 5.11 B). This is in addition to the inferred
range of proterocidarids through this stage (Fig. 5.12). An inferred diversity of 6 in the Induan is
based on the appearance of M. pakistanensis necessitating the existence of 3 additional lineages,
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leading to P. lobatum, C. moorei, and C. dubarai. This is in addition to the inferred triatodiarid
and euechinoid lineages at this time (Fig. 5.12).
Known diversity decreases from the Wordian to Capitanian, but this change is very small,
from two known species to one (Fig. 5.11 B). Likewise, inferred diversity decreases during this
same time interval from 6 inferred lineages to 5. Known diversity remains steady, while inferred
diversity increases again in the Induan. While a decrease in diversity is observed in the
Capitanian, the magnitude of change does not appear to constitute an extinction in echinoids.
There is no apparent dip in diversity at either the end-Guadalupian or Permian-Triassic
boundaries, either.
The scarcity of known echinoid species is likely heavily influenced by rock availability and
sampling intensity, but it appears that diversity is likely under sampled more in certain time
intervals than others. The Induan and Olenekian are represented by fewer fossiliferous
formations than other time intervals studied (Fig. 5.11 A). However, sampling intensity during
this time period is high. Conversely, rock availability in the Roadian, Wordian, and
Wuchupingian is relatively high, but sampling intensity is lower. Sampling intensity in the
Capitanian and Changhsingian is high, but rock availability is higher in the Capitanian and
somewhat limited in the Changhsingian.
Disarticulated echinoid occurrences are less common in the Permian than in the Early
Triassic, despite high sampling intensity in certain Permian time intervals (Fig. 5.11). Many
echinoid clasts are reported from the Early Triassic despite the rarity of named species during
this time. Little echinoid material is reported from the Capitanian and Changhsingian, despite
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high sampling intensity during this time. There appears to be no correlation with the abundance
of echinoids reported and known echinoid diversity over the time intervals studied.
5 – Discussion
5.1 – Permian-Triassic extinction survivors
Early cidaroid evolutionary relationships suggest that multiple lineages of cidaroids
survived the Permian-Triassic extinction (Fig. 5.12), contrary to the notion that there was only
one survivor (Erwin, 2000). Direct fossil evidence of only one genus, Eotiaris, is known from
before the boundary. Miocidaris occurs shortly after the boundary, in the Dienerian, but is
derived relative to Eotiaris. Echinoids more similar to Eotiaris persist into the Jurassic, in the
genus Couvalarocidaris. This suggests that this lineage differentiated from the Miocidaris
lineage before the appearance of Miocidaris pakistanensis in the fossil record, and that the
timing of this divergence was prior to the Dienerian. The proximity of Miocidaris pakistanensis
to the Permian-Triassic boundary suggests that this divergence could have been prior to the
boundary, and that therefore at least two miocidarid lineages survived the extinction. However,
the exact timing of the divergence is still uncertain, as no derived Miocidaris is yet known from
the Permian or Griesbachian. The echinoid specimen found in the uppermost Permian of Italy is
named “Miocidaris” in the literature, but is likely basal relative to M. pakistanensis, and
therefore does not help constrain the timing of this divergence. Nevertheless, considering the
scarcity of identifiable echinoid specimens in the Permian and Early Triassic, it is not surprising
that there is no echinoid known, despite phylogenetic reconstructions suggesting that there were
derived miocidarids early in the Triassic.
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Lenticidaris utahensis is known from at least the Spathian, but disarticulated plate
material suggests that triadotiarids were present in the Griesbachian. Phylogenetic analysis, both
from this study and prior studies (Kroh, 2011; Thomspon et al. 2015), placed the divergence of
miocidarids and triadotiarids in the Roadian or earlier, as this is the first appearance of the sister
group Miocidaridae in the fossil record. Therefore, at least one lineage of triadotiarids survived
the Permian-Triassic extinction to give rise to L. utahensis and others in the Triassic and
Jurassic. There is currently no fossil evidence of triadotiarids in the Permian, which constitutes
an approximately 17 Ma fossil gap. Such fossil gaps are not uncommon in the echinoid fossil
record. However, Eotiaris connorsi shares many characteristics with the Triadotiaridae, and the
uncertainty of the placement of this species in the phylogenetic analysis suggests the possibility
that it is a Permian triadotiarid. Further phylogenetic analyses are required to better contain the
affinity of E. connorsi, which should likely be assigned to a different genus.
The first appearance of a euechinoid in the fossil record is in the Norian, with the
occurrence of Diademopsis herberti, which is a pedinid. The inferred origination of the
euechinoids is dated to at least the Roadian, with the origination of the cidaroid sister-group.
This constitutes an approximately 40 million year fossil gap, in which no hint of a euechinoid is
known. However, at least one euechinoid must have survived the boundary, in order to give rise
to the modern euechinoids. The Pedinidae are more derived than other extant euechinoid families
such as the echinothurioids and diademopids. It would be expected that a representative of one of
these more basal groups would be the first to appear in the fossil record, but the preservation
potential of these groups is likely poor. Without the discovery of further paleontological
evidence of euechinoids prior to the Norian, the number of survivors and the timing of
divergence of these clades is difficult to constrain.
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5.2 – Record bias and missing echinoids
Large gaps between the inferred age of a lineage and its first appearance in the fossil
record are common in echinoids (Fig. 5.12). Part of this problem is taphonomic, as very few
species are known from more than one occurrence or from more than one time bin. E.
guadalupensis is the only species known from several occurrences across three Guadalupian
stages. The rarity of identifiable (i.e. articulated) echinoid occurrences no doubt contributes
heavily to the low diversity and large fossil gaps within lineages. Likely, the lack of clear
extinction horizons for echinoids over the end-Guadalupian or Permian-Triassic is a result of low
representation as well. Phylogenetic relationships allow us to infer what taxa should be present
but are not yet found, articulated or otherwise. The fact that these echinoids are ‘missing’ may be
a result of multiple taphonomic or ecological conditions, which vary temporally and between
groups.
In the Roadian, Wordian, and Wuchupingian, rock availability is high but sampling intensity
is low. Echinoid rarity during these times is likely a result of poor sampling, and inferred
diversity suggests that there are potentially 4 unsampled lineage during this time. In the
Changhsingian, sampling intensity is higher, but echinoid occurrences are low. This may be
reflecting true echinoid rarity prior to the Permian-Triassic mass extinction, though no dip in
diversity, inferred or known, is apparent prior to this interval. The scarcity of the record makes it
difficult to ascertain how significant the mass extinction at the end-Guadalupian and Permian-
Triassic were for echinoid diversity. Archaeocidarids are extinct by the Mesozoic, but since no
archaeocidarids are known from the Lopingian, they might have already been extinct by the end-
Guadalupian. Named Eotiaris species are not known from the Lopingian, but the echinoid
known from the Werfen Formation of Italy suggests that this genus survived until at least the
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latest Permian. Proterocidarids are known until the latest Permian and have been thought to
become extinct at the boundary, but the potential of protercidarid spines in the Early Triassic
makes this extinction uncertain as well. Even by using inferred diversity through phylogenetic
range inference, no apparent decline is observable at the Permian-Triassic boundary either.
The preservational style of many of these echinoid occurrences borders on Lagerstätte quality
(e.g. the Lenticidaris utahensis mass occurrence), especially in the case of fully articulated tests
and attached spines. The propensity of echinoids to disarticulate shortly after death, and the
necessity of full or partial articulation for accurate genus or species level identification
introduces a bias inherit to echinoids and lacking in other groups, such as bivalves. This bias in
preservational potential also varies within echinoid groups and across evolutionary time.
Paleozoic echinoids tend to have imbricate plating and a flexible test. This is present in the fossil
clades of archaeocidarids and triadotiarids, and in the modern echinothurioids. Plates that are
arranged imbricately lack significant stereomic interlocking between plates, and are instead held
together by soft tissue such as collagen (Smith, 1984). This makes the test flexible and easily
disarticulated after death. The first appearance of partially sutured tests is in the Miocidaridae,
with rigid articulation between adambital interambulacral plates. The potential for miocidarid
species to be preserved with sufficient articulation for species level identification is higher than
for the triadotiarids, and also potentially for basal euechinoids such as echinothurioids. The lack
of rigid articulation likely contributes significantly to the large fossil gap known in both
triadotiarid and euchinoid lineages.
The environmental distribution of echinoids across the Middle Permian to Early Triassic
may also be introducing a preservational bias. Low energy environments, on the outer ramp or
slope, can potentially more readily preserve fragile fossils. However, these environments are not
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as well represented in the rock record as shallower environments, and the environmental
distribution profile suggests echinoids preferred shallower environments. Shallower shelf
environments are more readily preserved, but are also higher energy and therefore fragile fossils
have a lower preservational potential in these environments. Echinoids in the Middle and Late
Permian are predominantly in shallow environments, with many Eotiaris species living in reefal
facies. There is a reef gap in the Early Triassic, but echinoids are known from shallow or
marginal environments during this time interval as well. This preference for shallower
environments appears to carry over from the Permian to the Early Triassic, despite the
disappearance of reefs. There is also no apparent restriction of echinoid environmental
distribution over the Permian-Triassic boundary, with echinoids ranging from mid-ramp to inner-
ramp facies in both time periods. However, this may be due to poor sampling of in situ
echinoids, for the myriad of reasons discussed above. If the echinoids were restricted to a
shallow refugium during the Early Triassic, as Mata and Woods (2008) suggest, then high energy
and transport could lead to the scarcity of articulated remains and the abundance of disarticulated
remains during this time. As it stands, the representation of articulated echinoid material is too
scarce to confidently determine if environmental preferences changed significantly over time,
and if those changes had any effect on echinoid preservational potential.
6 – Conclusions
Echinoids are a diverse group in the Modern, but are scarce in the late Paleozoic and early
Mesozoic. Study of the early evolution of the crown group, which originated during this time, is
difficult due to the myriad of factors that lead to poor representation of these taxa in the fossil
record. Despite this, we can reconstruct fossil ranges of these ‘missing’ echinoids using
phylogenetic relationships. The results of this study challenge the notion that the Permian-
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Triassic extinction was disastrous for echinoids, and that only one lineage, the Miocidaridae,
make it through the boundary. This study suggests that several, potentially as many as 4, cidaroid
lineages, at least one euechinoid lineage, and potentially a proterocidarid lineage survived the
Permian-Triassic mass extinction. Environmental distribution of echinoids across the Permian-
Triassic boundary shows no significant reduction in bathymetric range, but instead shows that
echinoids retained a preference for shallow, high energy environments despite the disappearance
of reefs in the Early Triassic. Echinoids are poorly represented in the Early Triassic, despite
higher sampling efforts compared to the Permian, which may stem from this preference for
higher energy environments and the poor preservational potential of these delicate early crown
group taxa. There remains a high potential for new discoveries in the Permian, as this is a time
that is generally poorly sampled with respect to echinoids.

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Figures and Tables

Table 5.1 – Summary of Middle Permian, Late Permian, and Early Triassic echinoid species
known from articulated material. Mode of preservation, location, lithology, and environmental
interpretations are also shown. Environmental interpretations are made from the literature and
from in-person observation of matrix material.

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Identification Preservation Location Formation Age Lithology
Depositional
Environment Source
Early Triassic
Lenticidaris utahensis Full test + spines USA Moenkopi Fm (Virgin Lm) Spathian Siliciclastic (sandstone) Inner Ramp Kier, 1977
Miocidaris pakistanensis Full test + spines Pakistan Mianwali Fm (Mittiwali Mb) Dienerian Carbonate (packstone?) Mid-ramp Linck, 1955
Miocidaris? Indet Interambulacrum no spines Italy Werfen Fm (Tesero Mb)
Changshingian
(*post-extinction) Carbonate (oolite) Shoal/Lagoon
Broglio Lorigia et al.
1983
Lopingian
Pronechinus anatoliensis Full test no spines Turkey Gomaniibrik Fm (upper Mb) Changhsingian Carbonate (biopackstones) Mid ramp? Kier, 1965
Eotiaris keyserlingi Interambulacrum UK Ford Formation (ZC 1) Wuchupingian Carbonate (reefal) Reef
Smith and
Hollingsworth, 1990
Eotiaris keyserlingi Interambulacrum Germany Zechstein Wuchupingian Carbonate (reefal) Reef
Hollingworth and
Pettigre, 1988
Guadalupian
Eotiaris guadalupensis Interambulacrum + spines USA Bell Canyon Fm (Lamar Mb) Capitanian Carbonate (reefal) Reef slope
Cooper and Grant, 1972;
Thompson et al. 2015
Eotiaris connorsi Interambulacrum + spines USA Bell Canyon Fm Capitanian Carbonate (reefal) Reef slope Kier, 1965
Eotiaris guadalupensis Interambulacrum USA Road Canyon Fm Roadian Carbonate (reefal) Reef slope
Cooper and Grant, 1972;
Thompson et al. 2015
Archaeocidaris selwyni Full test no spines Australia Nowra Fm. Roadian Sandstone Inner Ramp Etheridge , 1892
210
Table 5.2 – A summary of the characters and character states for the 11 echinoid taxa used in the
phylogenetic analysis, which was run using the software P.A.U.P. (Phylogenetic Analysis Using
Parsimony; Swofford, 2003).

211
# 1 # 2 # 3 # 4 # 5 # 6 # 7 # 8 # 9 # 10 # 11 # 12 # 13 # 14 # 15 # 16 # 17 # 18 # 19 # 20 # 21 # 22
Mississippian Archaeocidaridae Archaeocidaris whatlyensis 0 10000001 0000010000011
Permian Miocidaridae? Miocidaris connarsi 1 1110011 ? 1002010010011
Permian Miocidaridae Miocidaris keyserlingi 0 0 1 1 ? 1 1 1 0 10120 ? ? 01 ? ? 11
Permian Miocidaridae Eotiaris guadalupensis 0 0 1 1 ? 1 1 ? ? 10120 ? ? 01 ? ? 11
Triassic Miocidaridae Miocidaris pakistanensis 0 ? 0100 ? ? ? 1 ? 0 ? 110010000
Triassic Triadotiaridae Triadotiaris grandaeva 1 11110110 1001101002000
Triassic Triadotiaridae Lenticidaris utahensis 1 11100110 1002010000010
Jurassic Miocidaridae Couvelardicidaris moorei 0 0 1 1 ? 1 ? ? ? 1112010121 ? ? 0
Jurassic Miocidaridae Miocidaris dubari 0 0 1 1 ? 1 1 ? ? 11121 ? ? 01 ? ? ? ?
Jurassic Miocidaridae Miocidaris tenuispina 0 00111 ? ? ? 1111110 ? 12 ? 00
Jurassic Triadotiaridae Procidaris edwardsi 1 10120 ? 1 ? 1 0 0 ? 000002100
Characters
Family Genus Age
212
Figure 5.1 – Phylogenetic relationships of modern echinoid groups, recreated from molecular
and morphologic data from Smith et al. (2006) and Kroh and Smith (2010). Echinoids shown
from right to left are the cidaroid Cidaris cidaris, echinothurioid Hapalosoma pellucidum,
arbacoid Arbacia lixula, clypeasteroid Clypeaster rosaceus, and spatangoid Spatangus
purpureus. Photos modified from the Echinoid Directory (Smith and Kroh, 2000).

213
Cidaroids Euechinoids
Regular Echinoids Irregular Echinoids
Histocidaridae
Psychocidaridae
Cidaridae
Echinothuriods
Diadematoids
and Pedinoids
Camarodonts
Arbacoids
Stomopneustids
Salenioids
Cassiduloids
Clypeasterines
Scutellines
Holasteroids
Spatangoids
Archaeocidarids †
214
Figure 5.2 – Modern echinoid (Eucidaris tribuloides) showing the terminology for regions and
orientations of the test. Modified from Smith and Kroh (2000).

215
Adoral
(Oral)
Adapical
(Anal / Aboral)
Interradial
Suture
Interambulacral
Zone
Ambulacral
Zone
Perradial
Suture
Adradial
Suture
Ambitus
216
Figure 5.3 – Morphological difference between cidaroid and euechinoid tests and plates. (A) A
cidaroid test (Eucidaris tribuloides), oral view, showing two columns of interambulacral plates
and two columns of ambulacral plates (modified from Smith and Kroh, 2000). (B) An euechinoid
test, oral view, showing two columns of interambulacral plates and two columns of ambulacral
plates, as well as the buccal notches on the periphery of the peristome in the interambulacral
zone (modified from Smith and Kroh, 2000). (C) Internal view of a cidaroid test, showing the
peristomal membrane and apophyses (labeled ap). (D) An internal view of a euechinoid test,
showing buccal notches and auricles (labeled au). (E) A cidaroid interambulacral plate, showing
the components of the primary tubercle. (F) The euechinoid interambulacral zone, showing
multiple large and small tubercles. (G) Cidaroid ambulacral zone, showing ambulacral plates.
(H) Euechinoid interambulacral zone, showing compound ambulacral plates. All images
modified from Smith and Kroh (2000).

217
Buccal
Notches
Cidaroid Euechinoid
Pore-pair
Perradial
Suture
Adradial
Suture
Perradial
Tubercle
Pore-pair
Perradial
Suture
Adradial
Suture
Perradial
Tubercle
Simple
Plate
Compound
Plate
Buccal
Notches
Scrobicular
Ring
Areol
Boss
Mammelon
Perforation
Parapet
Adoral/Adapical
Suture
Peristomal
Membrane
Ambulacral
Zone
Interambulacral
Zone
Interambulacral
Zone
Ambulacral
Zone
Mammelon
Boss
Tubercle
Adradial
Suture
Tubercle
AB
C D
E F
G
H
218
Figure 5.4 – Morphological differences between cidaroid and euechinoid Aristotle’s Lantern. (A)
General anatomy of a single pyramid, lateral view. (B) Ventral view showing the 5 pyramids
arranged radially to form the Aristotle’s Lantern jaw apparatus (adapted from Kroh and Smith,
2010b). (C) A cidaroid-style pyramid, with a shallow foramen magnum (less than 2/3 of the
height of the hemipyramid) (adapted from Kroh and Smith, 2010). (D) A euechinoid-style
pyramid, showing a deep foramen magnum (more than 2/3 of the height of the hemipyramid).
(E) A cidaroid-style rotula, with ball-and-socket morphology (Stylocidaris; modified from Kroh
and Smith, 2010a). (F) A cidaorid-style epiphysis (Stylocidaris; modified from Kroh and Smith,
2010a). (G) A euechinoid-style rotula, with hinge morphology (Arbacia; modified from Kroh
and Smith, 2010a). (H) A euechinoid-style epiphysis (Arbacia; modified from Kroh and Smith,
2010a). (I) A cidaroid-style tooth (Stylocidaris) in cross section, with a distinct U-shape (Smith,
1981; Markel and Titschack, 1969). (J) A keeled euechinoid-style tooth (Stomopneustes,
stirodont) in cross section (Smith, 1981). (K) A diamond-shaped euechinoid-style tooth
(Echinocyamus, clypeasteroid) in cross section (Smith, 1981). (L) A flat euechinoid-style tooth
(Diademopsis; pedinid) in cross section (Smith, 1981).

219
Cidaroid Euechinoid
Hemipyramid
Rotula
Foramen
Magnum
Tooth
Hemipyramid
Epiphysis
Tooth
A
B
C D
E
G
IJ K
L
H
F
220
Figure 5.5 –The oldest known crown group cidaroid known from the fossil record. (A) A
reconstruction of phylogenetic relationships between stem cidaroid and euechinoid clades and
their stratigraphic ranges in the Permian and Triassic, after Kroh and Smith (2010) and Kroh
(2011). Bold lines indicate actual fossil range, while thin lines indicate inferred range. The blue
line indicates the new fossil range of Eotiaris guadalupensis, and the dashed area indicates the
difference between the previous oldest known definitive cidaroid (E. keyselingi) and the oldest
occurrences of E. guadalupensis. This also indicates the difference between the previously
estimated minimum age of divergence between cidaroids and euechinoids, and the new
divergence estimate based on the oldest occurrence of E. guadalupensis. (B) The holotype of E.
guadalupensis (USNM 610600), composed of an articulated interambulacral zone and attached
spine. (C) The inner surface of the interambulacral zone of E. guadalupensis of paratype USNM
610602 showing apophyses. (D) A bulbous spine form of E. guadalupensis, ornamented with
small spinules. (E) A straight spine form, ornamented with small spinules. Scale bar is 1 cm.
Figure modified from Thompson et al. (2015).

221
Archaeocidaris
Miocidaridae
Polycidaridae
Serpianotiaridae
Triadotiaridae
Echinothurioida
Other crown
euechinoids
Previous divergence estimate
(Smith and Hollingworth, 1990)
Cidaroidea
Diplocidaridae,
Rhabdocidaridae,
crown cidaroids
Euechinoidea
New divergence estimate
252.2
259.8
254.2
265.1
272.3
237.0
247.1
250.0
241.5
268.8
279.3
290.1
228.4
209.5
201.3
PERMIAN
Lopigian
Guada-
lupian
TRIASSIC
Middle
Early
Late
Cis-
uralian
Artin-
skian
Kung-
urian
Roadian
Wordian
Capit-
anian
Wuchia-
pingian
Changh-
singian
Induan
Olenekian
Anisian
Ladinian
Carnian
Norian
Rhaetian
Fossil range
Inferred ranges
E. guadalupensis n.sp.
fossil range
Eotiaris guadalupensis n.sp.
Miocidaridae
Diademopsis heberti Smith, 1994
Pedinidae
A
BC D E
222
Figure 5.6 – Plate of Permian and Triassic echinoid specimens discussed or used in the
phylogenetic analysis. (A) Archaeocidaris whatelyensis. (B) Pronechius anatoliensis. (C)
Eotiaris keyserlingi. (D) Eotiaris connorsi. (E) Miocidaris pakistanensis. (F) Lenticidaris
utahensis. Scale bar is 1 cm unless otherwise marked.

223
224
Figure 5.7 – Plate of Permian and Triassic echinoid specimens discussed or used in the
phylogenetic analysis. (A) Procidaris edwardsi. (B) Couvelardicidaris moorei. (C) Triadotiaris
grandaeva. (D) Couvelardicidaris dubarai. (E) Procidaris lobatum. Scale bar is 1 cm unless
otherwise marked.

225
226
Figure 5.8 – Results of a phylogenetic analysis with 10 Permian to Jurassic cidaroid species and
an Archaeocidaris outgroup, run in the program P.A.U.P. (Phylogenetic Analysis Using
Parsimony; Swofford, 2003). (A) and (B) show the resulting two most parsimonious trees. (C)
shows the consensus between these two trees. Eotiaris connorsi is the only taxon that shows
inconstant placement between the two trees, and thus forms a polytomy with the two major
clades in the consensus tree. Bootstrap (N=1000) values are shown for nodes with a bootstrap
support of greater than 50.

227
A. whatleyensis
T. grandaeva
E. connorsi
P. edwardsi
E. keyserlingi
C. dubari
P. lobatum
C. moorei
E. guadalupensis
L. utahensis
M. pakistanensis
A. whatleyensis
T. grandaeva
E. connorsi
P. edwardsi
E. keyserlingi
C. dubari
P. lobatum
C. moorei
E. guadalupensis
L. utahensis
M. pakistanensis
M. pakistanensis
E. connorsi
P. lobatum
T. grandaeva
C. moorei
E. keyserlingi
E. guadalupensis
A. whatleyensis
L. utahensis
C. dubari
P. edwardsi
AB
C
53
83
228
Figure 5.9 – The consensus phylogenetic tree, with species shown in stratigraphic context. The
two major clades represented in the phylogenetic analysis are labeled here as the Triadotiaridae
and the Miocidaridae. Procidaris edwardsi is not currently known as a triadotiarid, but the
results of this analysis show that the placement of Procidaris edwardsi as sister group to
Triadotiaris grandaeva is well supported. The timing of divergence events is hypothetical.
Minimum time of divergence is constrained by the first appearance of that lineage in the fossil
record, but there are no constraints for maximum divergence.

229
A. whatleyensis
T. grandaeva
E. connorsi
P. edwardsi
E. keyserlingi
C. dubari
P. lobatum
C. moorei
E. guadalupensis
L. utahensis
M. pakistanensis
Permian Triassic Jurassic
Early Early E Middle Middle Mid Late Late Late
Miocidaridae Triadotiaridae
230
Figure 5.10 – Reconstruction of paleoenvironmental distribution of echinoid species known from
the (A) Middle and Late Permian, and (B) Early Triassic. Bathymetry on the shelf is determined
from the literature. Where detailed stratigraphic information is not available from the original
literature, additional sources were consulted on the formation or member in which that species is
known.

231
Archaeocidaris selwyni
FWWB
SWB
Outer Ramp Mid Ramp Inner Ramp
Shoal
Lagoon
Miocidaris sp.
Lenticidaris utahensis
FWWB
SWB
Outer Ramp Mid Ramp Inner Ramp Reef Lagoon
Eotiaris guadalupensis
Eotiaris keyserlingi
Middle and Late Permian
Early Triassic
Eotiaris connorsi
Pronechinus anatoliensis
Miocidaris pakistanensis
A
B
232
Figure 5.11 – Comparison of quality of the rock record during stages of the Middle-Late Permian
and Early Triassic as compared to known echinoid diversity and echinoid clast occurrences (A)
Counts of marine fossiliferous formations (blue) and paleontological collections (pink) for all
stages of the Middle Permian, Late Permian, and Early Triassic. Counts of formations and
collections are downloaded from the Paleobiology Database (March, 2016). (B) Counts of
disarticulated echinoid occurrences (grey), reported in the Paleobiology Database for all stages
of the Middle Permian, Late Permian, and Early Triassic. Echinoid species known from each
stage are shown with the blue line, and inferred species, determined from inferred ranges from
the phylogenetic relationships, are shown with the red line.

233
0
20
40
60
80
100
120
140
160
0
500
1000
1500
2000
2500
3000
3500
0
5
10
15
20
25
30
35
40
45
Echinoid occurrences
0
1
2
3
4
5
6
7
Known Species
Inferred Species
Occurrences
Diversity
Collections
Formations
Collecons (PBDB)
Marine Formaons (PBDB)
Guadalupian Lopingian Early Triassic
Roadian Wordian Capitanian Wuchiapin. Changhsin. Induan Olenekian
A
B
Guadalupian Lopingian Early Triassic
Roadian Wordian Capitanian Wuchiapin. Changhsin. Induan Olenekian
234
Figure 5.12 – Summary of echinoid groups known from the Middle Permian to Early Triassic,
with thick lines denoting fossil range, and thin lines denoting inferred range. Cidaroid and
euechinoid lineages are outlined as belonging to the crown group. The range of Eotiaris is
tentatively shown to reach the Permian-Triassic boundary, based on the echinoid found in the
Tesero Member of the Werfen Formation by Broglio Lorigia et al. (1983). The Proterocidaridae
are tentatively shown to cross the Permian-Triassic boundary based on the spines described by
Mata and Woods (2008).

235
Eotiaris
Miocidaris and other miocidarids
Lenticidaris and other triadotiarids
Pedinid euechinoids
Other euechinoids
?
?
?
?
Permian Triassic
Proterocidarids
Archaeocidarids
Crown group
Induan Olenek. Anisian Ladinian Car. Nor. Rhae.
Early Middle Late Cisuralian Guadalupian Lopingian
As. Sa. Ar. Ku. Ro.
Wo. Cap. Wuch. Chang.
?
236
Chapter 6: Conclusions

The results of this work demonstrate the complex relationships between biotic recovery
of marine benthic invertebrate communities, disaster taxon ecological dominance, and various
environmental conditions in the aftermath of the Permian-Triassic extinction. Additionally, the
evolutionary relationships and survivorship of early crown group echinoids, an important and
diverse constituent of modern ecosystems, is elucidated in this study. New details of the tempo
and mode of recovery in the Early Triassic, both at the global and regional scale, are presented
along with high resolution correlation of ecological patterns with changes in bathymetry, carbon
isotope geochemistry, and substrate type. This research highlights the importance of studying
ecological recovery at different scales for capturing important local variation, but also
understanding the averaged global patterns. Outcrop-scale studies are important for
differentiating the relative importance of local and global environmental forcings on the mode of
recovery of the local fauna. The complexity of recovery from the Permian-Triassic mass
extinction is apparent when considering differential recovery patterns from outcrop or regional-
scale studies from around the world. However, it is important not to overlook the large scale
patterns of progressive recovery that are apparent in global database studies.
1 – Global mechanisms acting on local communities

The timing of incipient recovery and subsequent crash recorded in the Dinwoody
Formation of the Blacktail Creek section correlated significantly with the timing of large shifts in
carbon isotope chemistry in the oceans. The low-diversity high-dominance fauna that occur at
the base and top of the section occur during times of large negative carbon isotope excursions,
and changing lithology is found to not be correlated with changes in community composition and
237
structure throughout the section. The carbon isotope profile of the Blacktail Creek section is
reflective of the global carbon isotope curve of the Early Triassic, and this suggest a common
causal mechanism operating at the global scale that affects both the carbon cycle and benthic
marine communities concurrently. Explanations for the negative 
13
C
carb
carbon excursions
observed in the Early Triassic invoke chemocline upward excursions or expansion and incursion
of the OMZ onto the shallow shelf (Algeo et al. 2008, Algeo et al. 2011, Riccardi et al. 2006,
Song et al. 2013a). While these events would leave a depleted carbon isotope signature in
carbonate rock forming under these conditions, there is no lithologic evidence of an anoxic or
euxinic water column at Blacktail Creek during the interval in question. Additionally, it is hard
to imagine a scenario where these incursions are synchronous across Panthalassic and Tethyan
sections, creating similar carbon isotope signatures in locations with differing basin
configurations and current circulation. Another explanation of the negative shifts invokes
periodic injections of isotopically light carbon into the atmospheres and oceans from continued
Siberian Traps outgassing. This outgassing has also been linked to thermal events in ocean
surface waters (Payne and Kump 2007, Sun et al. 2012). The global nature of these shifts points
to volcanic outgassing as the most likely cause, and the associated heating as the most likely
mechanisms for benthic community recovery collapse as a consequence of this.
No independent or direct geochemical or lithologic evidence for warming is forthcoming
from the Blacktail Creek section, as conodonts, the most reliable source of 
18
O values in the
Early Triassic, are uncommon there. The possibility exists to extract 
18
O values from Lingularia
shells from this section, as they are both abundant and appear unaltered in some instances.
However, a more thorough determination of the nature of preservation of the phosphatic shells is
needed first.
238
2 – The importance of bathymetric stability to community sensitivity

The Panthalassic Blacktail Creek section spanned outer ramp to inner ramp facies, with
no evidence of intertidal or subaerial exposure at any point. On the other hand, the Tethyan Bulla
and Uomo sections span mid-ramp to peritidal facies, with several shallowing events into shoal
or intertidal environments. The Werfen Formation communities show no correlation to carbon
isotope shifts, and maintain high relative abundance of disaster taxa throughout the sections,
whereas the Blacktail Creek sections appears to be sensitive to global-scale mechanisms
affecting ocean carbon chemistry. If the likely cause for community collapse in the Dinwoody
Formation is ocean warming, it would be expected that the communities of the Tethyan section
experience the same conditions and respond similarly, given the global nature of the warming.
Moreover, it would be expected that the Tethyan communities would be even more drastically
affected, as these communities are shallower and presumably experiencing more intense
warming. However, the opposite is observed whereby these Tethyan communities show no
apparent response to the timing of negative carbon isotope shifts tied to volcanic outgassing and
warming.
I propose that the lack of response observed in the Tethyan sections is likely a
consequence of the already unstable nature of these communities, due to rapid changes in
bathymetry and terrigenous sedimentation influx. Several shallowing events into shoal or
marginal marine settings record communities already stressed, either due to proximity to high
energy environments such as an ooid shoal, or due to living in restricted settings such as a lagoon
or intertidal mudflats. This likely overprints whatever effect global-scale climate change may be
having on communities in deeper settings. The sustained paucity of these communities is
interpreted as a consequence of a threshold effect, whereby sustained environmental stressors, in
239
this case rapid bathymetric and terrigenous sedimentation changes, pushes communities into a
stable ‘phase shifted’ state. This may explain the decreased sensitivity of these Tethyan
communities to shifts in the oceanic carbon isotope chemistry relative to the communities of a
similar time period in the Dinwoody Formation in Panthalassa.
3 – Timing of global versus local recovery

The timing and expression of recovery at the local scale is highly dependent on local
conditions in the Early Triassic, as demonstrated by this body of work, as well as several other
authors (Hofmann et al. 2011, Hofmann et al. 2013, Hofmann et al. 2015, Pietsch and Bottjer
2014, Twitchett et al. 2004, Twitchett 1999). This leads to nonsynchronous recovery patterns
observable in different sections or regions. Some authors interpret these patterns as evidence for
early recovery following the Permian-Triassic event when conditions, such as oxygen or
temperature, are favorable. Indeed, many sections worldwide show signs of benthic community
recovery relatively early after the initial extinction event. However, this current body of work
demonstrates the importance of disentangling conditions that are a direct consequence of
extinction-associated environmental perturbations, such as anoxia, euxinia, and thermal stress,
from otherwise ‘ordinary’ conditions, such as lithology change or changing bathymetry.
While single outcrop or regional-scale studies show evidence of incipient recovery early
in the Early Triassic, it is important to understand the timing of recovery at the global scale
through averaging of ecological metrics from sections worldwide. The global signal, as explored
in this work through quantification of disaster taxon dominance, shows steady recovery
throughout the stages of the Early Triassic. While interest is given to these early recoveries in the
240
Induan, it is important to understand the global context in which these recovered communities
occur, which is one of overall impoverished diversity and high dominance.
4 – Underestimating survivorship in poorly represented groups

Extinction rates in almost all groups of marine calcifying taxa are dramatically high
across the Permian-Triassic boundary. Particularly affected are members of the so called
‘Paleozoic fauna’, which exhibit poorly buffered respiratory systems and include the crinoids
and blastoids. Extinction in the echinoids has been traditionally viewed as equally severe, given
only one known survivor at the time (Erwin 2000). However, this work demonstrates that the
paucity of the fossil record of echinoids both before and after the Permian-Triassic mass
extinction makes it exceptionally difficult to truly asses the severity of extinction in this group,
and that lineage survivorship was likely higher than originally thought. Phylogenetic
reconstructions can be used to infer ‘boundary crossers’, by estimated time of divergence
between two sister groups. This method has been applied to echinoids across the boundary, and
shows no clear evidence of significant lineage loss across the Permian-Triassic extinction. In
fact, several lineages that survive into the Jurassic are all inferred to be present in the Permian.
Echinoid extinction rate appears to be exceptionally low at the Family level across the Permian-
Triassic.
This method can be applied to groups with inconsistent fossil representation to infer
‘boundary crosser’ diversity across all time periods. Current methods of using first and last
appearances are likely underestimating diversity significantly in poorly represented groups,
since, as it is demonstrated with echinoids, the first appearance of a taxon in the fossil record
could be tens of millions of years after its origination. This method is best applied to poorly
241
represented groups with resolved phylogenies, such as crinoids, which face many of the same
preservational difficulties as echinoids and are also likely underrepresented during this interval.
5 – Future studies

The results of this work demonstrate the complex nature of ecological recovery in marine
benthic communities in the aftermath of the Permian-Triassic mass extinction. This variation can
be attributed, in many instances, to different environmental stressors acting on the communities
that are spatially and temporally variable. Sometimes, the stressor(s) at play are not entirely
clear, due to a lack of direct geochemical or lithologic evidence, as is the case at Blacktail Creek.
I propose ways to circumvent this by comparing aspects of community structure of these fossil
assemblages with what is observed in modern ecosystems under various anthropogenic or natural
stressors, such as anoxia, thermal stress, eutrophication and sediment influx (Dauer 1993,
Gilman et al. 2010, Norkko et al. 2001, Wernberg et al. 2013). Comparing community taxon
abundance distributions (Death 1996, Wagner et al. 2006), as well as functional group abundance
distributions, of ancient and modern communities can elucidate and help predict responses to
various environmental stressors. There is still much left to decipher regarding ancient community
behavior in the wake of the largest mass extinction of the Phanerozoic, the study of which can be
aided with the application of modern ecological observation and comparison.

242
References

Aberhan, M., and T. K. Baumiller. 2003. Selective extinction among Early Jurassic bivalves: a
consequence of anoxia. Geology 31(12):1077-1080.
Algeo, T., Y. Shen, T. Zhang, T. Lyons, S. Bates, H. Rowe, and T. Nguyen. 2008. Association of
34S ‐depleted pyrite layers with negative carbonate δ13C excursions at the Permian ‐
Triassic boundary: Evidence for upwelling of sulfidic deep ‐ocean water masses.
Geochemistry, Geophysics, Geosystems 9(4).
Algeo, T. J., Z. Q. Chen, M. L. Fraiser, and R. J. Twitchett. 2011. Terrestrial–marine
teleconnections in the collapse and rebuilding of Early Triassic marine ecosystems.
Palaeogeography, Palaeoclimatology, Palaeoecology 308(1):1-11.
Allison, P. A., P. B. Wignall, and C. E. Brett. 1995. Palaeo-oxygenation: effects and recognition.
Geological Society, London, Special Publications 83(1):97-112.
Alroy, J., M. Aberhan, D. J. Bottjer, M. Foote, F. T. Fürsich, P. J. Harries, A. J. Hendy, S. M.
Holland, L. C. Ivany, and W. Kiessling. 2008. Phanerozoic trends in the global diversity
of marine invertebrates. Science 321(5885):97-100.
Assereto, R., N. F. Sestini, A. Bosellini, and W. Sweet. 1973. The Permian-Triassic boundary in
the Southern Alps (Italy).
Aydemir, A. 2011. Comparison of Mississippian Barnett Shale, Northern-Central Texas, USA
and Silurian Dadas Formation in Southeast Turkey. Journal of Petroleum Science and
Engineering 80(1):81-93.
Babcock, J. 1977. Calcareous algae, organic boundstones, and the genesis of the upper Capitan
Limestone (Permian, Guadalupian), Guadalupe Mountains, west Texas and New Mexico.
Upper Guadalupian Facies, Permian Reef Complex, Guadalupe Mountains, New Mexico
243
and West Texas: Society of Economic Paleontologists and Mineralogists, Permian Basin
Section, Publication:77-16.
Bailey, J. V., F. A. Corsetti, D. J. Bottjer, and K. N. Marenco. 2006. Microbially-mediated
environmental influences on metazoan colonization of matground ecosystems: evidence
from the Lower Cambrian Harkless Formation. Palaios 21(3):215-226.
Bambach, R. K., A. H. Knoll, and J. J. Sepkoski. 2002. Anatomical and ecological constraints on
Phanerozoic animal diversity in the marine realm. Proceedings of the National Academy
of Sciences 99(10):6854-6859.
Baud, A., S. Richoz, and S. Pruss. 2007. The lower Triassic anachronistic carbonate facies in
space and time. Global and Planetary Change 55(1):81-89.
Beatty, T. W., J. Zonneveld, and C. M. Henderson. 2008. Anomalously diverse Early Triassic
ichnofossil assemblages in northwest Pangea: a case for a shallow-marine habitable zone.
Geology 36(10):771-774.
Benton, M. J. 2003. When life nearly died: the greatest mass extinction of all time. Thames &
Hudson London.
Black, B. A., L. T. Elkins-Tanton, M. C. Rowe, and I. U. Peate. 2012. Magnitude and
consequences of volatile release from the Siberian Traps. Earth and Planetary Science
Letters 317:363-373.
Blome, C. D., and K. Reed. 1992. Permian and Early (?) Triassic radiolarian faunas from the
Grindstone terrane, central Oregon. Journal of Paleontology 66(03):351-383.
Bond, D. P., and P. B. Wignall. 2010. Pyrite framboid study of marine Permian–Triassic
boundary sections: a complex anoxic event and its relationship to contemporaneous mass
extinction. Geological Society of America Bulletin 122(7-8):1265-1279.
244
Bottjer, D. J., M. E. Clapham, M. L. Fraiser, and C. M. Powers. 2008. Understanding
mechanisms for the end-Permian mass extinction and the protracted Early Triassic
aftermath and recovery. GSA Today 18(9):4-10.
Boyer, D. L., D. J. Bottjer, and M. L. Droser. 2004. Ecological signature of Lower Triassic shell
beds of the western United States. Palaios 19(4):372-380.
Brandner, R., M. Horacek, L. Keim, and R. Scholger. 2009. The Pufels/Bulla Road Section:
Deciphering Environmental Changes Across The Permian-triassic Boundary to the
Olenekian by Integrated Litho-, Magneto-and Isotope Stratigraphy. A Field Trip Guide.
Geo. Alp 6:116-132.
Brayard, A., H. Bucher, G. Escarguel, F. Fluteau, S. Bourquin, and T. Galfetti. 2006. The Early
Triassic ammonoid recovery: paleoclimatic significance of diversity gradients.
Palaeogeography, Palaeoclimatology, Palaeoecology 239(3):374-395.
Brayard, A., E. Vennin, N. Olivier, K. G. Bylund, J. Jenks, D. A. Stephen, H. Bucher, R.
Hofmann, N. Goudemand, and G. Escarguel. 2011. Transient metazoan reefs in the
aftermath of the end-Permian mass extinction. Nature Geoscience 4(10):693-697.
Broglio Loriga, C., C. Neri, and M. Pasini. 1988. Marine Fossil, Assemblages from Upper
Permian to Lowermost Triassic in the Western Dolomites (Italy). Società geologica
italiana.
Broglio Loriga, C., C. Neri, and R. Posenato. 1985. The early macrofaunas of the Werfen
Formation and the Permian-Triassic boundary in the Dolomites (Southern Alps, Italy).
Studi trentini di scienze naturali. Acta geologica 62:3-18.
Bromley, R. 1990. Trace Fossils. Biology and Taphonomy. 280 pp. Un win & Hyman, London.
245
Bromley, R. G., and A. Ekdale. 1984. Chondrites: a trace fossil indicator of anoxia in sediments.
Science 224(4651):872-874.
Bush, A. M., R. K. Bambach, and G. M. Daley. 2007. Changes in theoretical ecospace utilization
in marine fossil assemblages between the mid-Paleozoic and late Cenozoic. Journal
Information 33(1).
Carr, T. R., and R. K. Paull. 1983. Early Triassic stratigraphy and paleogeography of the
Cordilleran miogeocline. Rocky Mountain Section (SEPM).
Caswell, B. A., and A. L. Coe. 2013. Primary productivity controls on opportunistic bivalves
during Early Jurassic oceanic deoxygenation. Geology 41(11):1163-1166.
Caswell, B. A., A. L. Coe, and A. S. Cohen. 2009. New range data for marine invertebrate
species across the early Toarcian (Early Jurassic) mass extinction. Journal of the
Geological Society 166(5):859-872.
Chen, Z. Q., and M. J. Benton. 2012. The timing and pattern of biotic recovery following the
end-Permian mass extinction. Nature Geoscience 5(6):375-383.
Ciriacks, K. W. 1963. Permian and Eotriassic bivalves of the Middle Rockies. Columbia
University.
Clapham, M. E., D. J. Bottjer, C. M. Powers, N. Bonuso, M. L. Fraiser, P. J. Marenco, S. Q.
Dornbos, and S. B. Pruss. 2006. Assessing the ecological dominance of Phanerozoic
marine invertebrates. Palaios 21(5):431-441.
Clapham, M. E., and J. L. Payne. 2011. Acidification, anoxia, and extinction: A multiple logistic
regression analysis of extinction selectivity during the Middle and Late Permian. Geology
39(11):1059-1062.
246
Clarke, K. R., P. J. Somerfield, and M. G. Chapman. 2006. On resemblance measures for
ecological studies, including taxonomic dissimilarities and a zero-adjusted Bray–Curtis
coefficient for denuded assemblages. Journal of Experimental Marine Biology and
Ecology 330(1):55-80.
Cooper, G., and R. Grant. 1972. Dating and correlating the Permian of the Glass Mountains in
Texas. Bulletin of Canadian Petroleum Geology 20(4):727-741.
Corsetti, F. A., A. Baud, P. J. Marenco, and S. Richoz. 2005. Summary of Early Triassic carbon
isotope records. Comptes Rendus Palevol 4(6):473-486.
Craig, G. Y. 1952. A comparative study of the ecology and palaeoecology of Lingula.
Transactions of the Edinburgh Geological Society 15(1):110-120.
Dauer, D. M. 1993. Biological criteria, environmental health and estuarine macrobenthic
community structure. Marine Pollution Bulletin 26(5):249-257.
Death, R. 1996. The effect of habitat stability on benthic invertebrate communities: the utility of
species abundance distributions. Hydrobiologia 317(2):97-107.
Dineen, A. A., M. L. Fraiser, and P. M. Sheehan. 2014. Quantifying functional diversity in pre-
and post-extinction paleocommunities: A test of ecological restructuring after the end-
Permian mass extinction. Earth-Science Reviews 136:339-349.
Durham, J. W., and R. Melville. 1957. A classification of echinoids. Journal of
Paleontology:242-272.
Ekdale, A. 1985. Paleoecology of the marine endobenthos. Palaeogeography, Palaeoclimatology,
Palaeoecology 50(1):63-81.
Ekdale, A., and T. Mason. 1988. Characteristic trace-fossil associations in oxygen-poor
sedimentary environments. Geology 16(8):720-723.
247
Emig, C. C. 2003. Proof that Lingula (Brachiopoda) is not a living-fossil, and emended
diagnoses of the Family Lingulidae.
Erwin, D. H. 1993. The great Paleozoic crisis: life and death in the Permian. Columbia
University Press.
Erwin, D. H. 2000. The permo-triassic extinction. Shaking the Tree: Readings from Nature in the
History of Life 189.
Etheridge, R. 1892. A Monograph of the Carboniferous and Permo-carboniferous Invertebrata of
New-South Wales: Echinodermata, Annelida, and Crustacea. Charles Potter.
Farabegoli, E., and M. Perri. 1998. Permian/Triassic Boundary and Early Triassic of the Bulla
section (Southern Alps, Italy). ECOS VII Southern Alps Field Trip Guidebook. Giornale
di Geologia, Series 3(60):292-311.
Farabegoli, E., M. C. Perri, and R. Posenato. 2007. Environmental and biotic changes across the
Permian–Triassic boundary in western Tethys: the Bulla parastratotype, Italy. Global and
Planetary Change 55(1):109-135.
Farris, J. S. 1989. The retention index and homoplasy excess. Systematic Biology 38(4):406-407.
Fenchel, T., and B. Finlay. 2008. Oxygen and the spatial structure of microbial communities.
Biological Reviews 83(4):553-569.
Ferguson, L. 1963. The paleoecology of Lingula squamiformis Phillips during a Scottish
Mississippian marine transgression. Journal of Paleontology:669-681.
Fischer, A. G., and M. A. Arthur. 1977. Secular variations in the pelagic realm. SEPM Special
Publications (25):19-50.
Forel, M. B., S. Crasquin, S. Kershaw, and P. Y. Collin. 2013. In the aftermath of the end ‐
Permian extinction: the microbialite refuge? Terra Nova 25(2):137-143.
248
Foster, C., and S. Afonin. 2005. Abnormal pollen grains: an outcome of deteriorating
atmospheric conditions around the Permian–Triassic boundary. Journal of the Geological
Society 162(4):653-659.
Foster, W. J., and R. J. Twitchett. 2014. Functional diversity of marine ecosystems after the Late
Permian mass extinction event. Nature Geoscience 7(3):233-238.
Foster, W. J., Danise, S., and R. J. Twitchett. Accepted In Press. A silicified Early Triassic
marine assemblage from Svalbard. Journal of systematic Palaeontology.
Fraiser, M. L., and D. J. Bottjer. 2005. Restructuring in benthic level-bottom shallow marine
communities due to prolonged environmental stress following the end-Permian mass
extinction. Comptes Rendus Palevol 4(6):583-591.
Fraiser, M. L., and D. J. Bottjer. 2007. When bivalves took over the world. Paleobiology
33(3):397-413.
Fraiser, M. L., R. J. Twitchett, and D. J. Bottjer. 2005. Unique microgastropod biofacies in the
Early Triassic: indicator of long-term biotic stress and the pattern of biotic recovery after
the end-Permian mass extinction. Comptes Rendus Palevol 4(6):543-552.
Freitag, T. E., T. Klenke, W. E. Krumbein, G. Gerdes, and J. I. Prosser. 2003. Effect of anoxia
and high sulphide concentrations on heterotrophic microbial communities in reduced
surface sediments (Black Spots) in sandy intertidal flats of the German Wadden Sea.
FEMS microbiology ecology 44(3):291-301.
Galfetti, T., P. A. Hochuli, A. Brayard, H. Bucher, H. Weissert, and J. O. Vigran. 2007.
Smithian-Spathian boundary event: Evidence for global climatic change in the wake of
the end-Permian biotic crisis. Geology 35(4):291-294.
249
Gao, F., J. R. Thompson, E. Petsios, E. Erkenbrack, R. A. Moats, D. J. Bottjer, and E. H.
Davidson. 2015. Juvenile skeletogenesis in anciently diverged sea urchin clades.
Developmental biology 400(1):148-158.
Gianolla, P. 1998. Triassic sequence stratigraphy in the Southern Alps (Northern Italy):
definition of sequences and basin evolution.
Gilman, S. E., M. C. Urban, J. Tewksbury, G. W. Gilchrist, and R. D. Holt. 2010. A framework
for community interactions under climate change. Trends in Ecology & Evolution
25(6):325-331.
Gordon Jr, M., and C. Merriam. 1961. Late Permian ammonoids in the Inyo Range, California
and their significance. US Geological Survey Professional Paper:238-239.
Gould, S. J., and C. B. Calloway. 1980. Clams and brachiopods-ships that pass in the night.
Paleobiology:383-396.
Grasby, S., B. Beauchamp, A. Embry, and H. Sanei. 2013. Recurrent Early Triassic ocean
anoxia. Geology 41(2):175-178.
Greene, S. E., D. J. Bottjer, H. Hagdorn, and J.-P. Zonneveld. 2011. The Mesozoic return of
Paleozoic faunal constituents: A decoupling of taxonomic and ecological dominance
during the recovery from the end-Permian mass extinction. Palaeogeography,
Palaeoclimatology, Palaeoecology 308(1):224-232.
Greene, S. E., R. C. Martindale, K. A. Ritterbush, D. J. Bottjer, F. A. Corsetti, and W. M.
Berelson. 2012. Recognising ocean acidification in deep time: An evaluation of the
evidence for acidification across the Triassic-Jurassic boundary. Earth-Science Reviews
113(1):72-93.
250
Greenstein, B. J. 1991. An integrated study of echinoid taphonomy: predictions for the fossil
record of four echinoid families. Palaios:519-540.
Grice, K., C. Cao, G. D. Love, M. E. Böttcher, R. J. Twitchett, E. Grosjean, R. E. Summons, S.
C. Turgeon, W. Dunning, and Y. Jin. 2005. Photic zone euxinia during the Permian-
Triassic superanoxic event. Science 307(5710):706-709.
Griffin, J., P. J. Marenco, M. L. Fraiser, and M. E. Clapham. 2010. Stromatolite-sponge-
tubiphytes reefs in the Virgin Limestone Member of the Moenkopi Formation, Nevada:
Implications for biotic recovery following the end-Permian mass extinction. 2010 Annual
Meeting of the Geological Society of America. Conference Paper no. 21-16.
Hagdorn, H. 1995. Die Seeigel Des Germanischen Oberen Muschelkalks. Geologische und
Palaontologische Mitteilungen, Innsbruck 20: 245-281.
Hallam, A., and P. B. Wignall. 1997. Mass extinctions and their aftermath. Oxford University
Press.
Hammen, C. S., D. P. Hanlon, and S. C. Lum. 1962. Oxidative metabolism of Lingula.
Comparative biochemistry and physiology 5(3):185-191.
Hammer, Ø., D. Harper, and P. Ryan. 2009. PAST-PAlaeontological STatistics, ver. 1.89.
University of Oslo, Oslo.
Hammer, Ø., and D. A. Harper. 2008. Paleontological data analysis. John Wiley & Sons.
Harries, P. J., E. G. Kauffman, and T. A. Hansen. 1996. Models for biotic survival following
mass extinction. Geological Society, London, Special Publications 102(1):41-60.
Hautmann, M., M. J. Benton, and A. Tomašových. 2008. Catastrophic ocean acidification at the
Triassic-Jurassic boundary. Neues Jahrbuch für Geologie und Paläontologie-
Abhandlungen 249(1):119-127.
251
Hautmann, M., A. B. Smith, A. J. McGowan, and H. Bucher. 2013. Bivalves from the Olenekian
(Early Triassic) of south-western Utah: systematics and evolutionary significance.
Journal of Systematic Palaeontology 11(3):263-293.
He, L., Y. Wang, A. Woods, G. Li, H. Yang, and W. Liao. 2012. Calcareous tubeworms as
disaster forms after the end-Permian mass extinction in south China. Palaios 27(12):878-
886.
Hertweck, G., A. Wehrmann, and G. Liebezeit. 2007. Bioturbation structures of polychaetes in
modern shallow marine environments and their analogues to Chondrites group traces.
Palaeogeography, Palaeoclimatology, Palaeoecology 245(3):382-389.
Hillebrand, H., D. M. Bennett, and M. W. Cadotte. 2008. Consequences of dominance: a review
of evenness effects on local and regional ecosystem processes. Ecology 89(6):1510-1520.
Hinojosa, J. L., S. T. Brown, J. Chen, D. J. DePaolo, A. Paytan, S.-z. Shen, and J. L. Payne.
2012. Evidence for end-Permian ocean acidification from calcium isotopes in biogenic
apatite. Geology 40(8):743-746.
Hoegh-Guldberg, O., P. J. Mumby, A. J. Hooten, R. S. Steneck, P. Greenfield, E. Gomez, C. D.
Harvell, P. F. Sale, A. J. Edwards, and K. Caldeira. 2007. Coral reefs under rapid climate
change and ocean acidification. Science 318(5857):1737-1742.
Hofmann, R., N. Goudemand, M. Wasmer, H. Bucher, and M. Hautmann. 2011. New trace fossil
evidence for an early recovery signal in the aftermath of the end-Permian mass
extinction. Palaeogeography, Palaeoclimatology, Palaeoecology 310(3):216-226.
Hofmann, R., M. Hautmann, A. Brayard, A. Nützel, K. G. Bylund, J. F. Jenks, E. Vennin, N.
Olivier, and H. Bucher. 2014. Recovery of benthic marine communities from the end ‐
252
Permian mass extinction at the low latitudes of eastern Panthalassa. Palaeontology
57(3):547-589.
Hofmann, R., M. Hautmann, and H. Bucher. 2013. A new paleoecological look at the Dinwoody
Formation (Lower Triassic, western USA): intrinsic versus extrinsic controls on
ecosystem recovery after the end-Permian mass extinction. Journal of Paleontology
87(05):854-880.
Hofmann, R., M. Hautmann, and H. Bucher. 2015. Recovery dynamics of benthic marine
communities from the Lower Triassic Werfen Formation, northern Italy. Lethaia
48(4):474-496.
Hofmann, R., M. Hautmann, M. Wasmer, and H. Bucher. 2013c. Palaeoecology of the Spathian
Virgin Formation (Utah, USA) and its implications for the Early Triassic recovery. Acta
Palaeontologica Polonica 58(1):149-173.
Hollingworth, N. T., T. H. Pettigrew, and P. Association. 1988. Zechstein reef fossils and their
palaeoecology. Palaeontological Association.
Horacek, M., R. Brandner, and R. Abart. 2007a. Carbon isotope record of the P/T boundary and
the Lower Triassic in the Southern Alps: evidence for rapid changes in storage of organic
carbon. Palaeogeography, Palaeoclimatology, Palaeoecology 252(1):347-354.
Horacek, M., S. Richoz, R. Brandner, L. Krystyn, and C. Spötl. 2007b. Evidence for recurrent
changes in Lower Triassic oceanic circulation of the Tethys: the δ 13 C record from
marine sections in Iran. Palaeogeography, Palaeoclimatology, Palaeoecology 252(1):355-
369.
Hotinski, R. M., K. L. Bice, L. R. Kump, R. G. Najjar, and M. A. Arthur. 2001. Ocean stagnation
and end-Permian anoxia. Geology 29(1):7-10.
253
Hull, P. M., and S. A. Darroch. 2013. Mass extinctions and the structure and function of
ecosystems. Ecosystem Paleobiology and Geobiology, The Paleontological Society
Papers 19:1-42.
Isozaki, Y. 1997. Permo-Triassic boundary superanoxia and stratified superocean: records from
lost deep sea. Science 276(5310):235-238.
Jackson, R. T. 1912. Phylogeny of the Echini: With a Revision of Palaeozoic Species. The
Society.
Joachimski, M. M., X. Lai, S. Shen, H. Jiang, G. Luo, B. Chen, J. Chen, and Y. Sun. 2012.
Climate warming in the latest Permian and the Permian–Triassic mass extinction.
Geology 40(3):195-198.
Kaim, A., A. Nützel, M. Hautmann, and H. Bucher. 2013. Early Triassic gastropods from Salt
Range, Pakistan. Bulletin of Geosciences 88:505-516.
Kashiyama, Y., and T. Oji. 2004. Low-diversity shallow marine benthic fauna from the Smithian
of northeast Japan: paleoecologic and paleobiogeographic implications. Paleontological
Research 8(3):199-218.
Kauffman, E. G., and P. J. Harries. 1996. The importance of crisis progenitors in recovery from
mass extinction. Geological Society, London, Special Publications 102(1):15-39.
Kidwell, S. M. 2002. Time-averaged molluscan death assemblages: palimpsests of richness,
snapshots of abundance. Geology 30(9):803-806.
Kidwell, S. M., and T. Baumiller. 1990. Experimental disintegration of regular echinoids: roles
of temperature, oxygen, and decay thresholds. Paleobiology 16(03):247-271.
Kidwell, S. M., and K. W. Flessa. 1995. The quality of the fossil record: populations, species,
and communities. Annual Review of Ecology and Systematics:269-299.
254
Kier, P. M. 1965. Evolutionary trends in Paleozoic echinoids. Journal of Paleontology:436-465.
Kier, P. M. 1968. The Triassic echinoids of North America. Journal of Paleontology:1000-1006.
Kier, P. M. 1974. Evolutionary trends and their functional significance in the post-Paleozoic
echinoids. Memoir (The Paleontological Society):1-95.
Kier, P. M. 1977a. The poor fossil record of the regular echinoid. Paleobiology 3(02):168-174.
Kier, P. M. 1977b. Triassic echinoids. Smithsonian Institution Press.
Knoll, A. H., R. K. Bambach, J. L. Payne, S. Pruss, and W. W. Fischer. 2007. Paleophysiology
and end-Permian mass extinction. Earth and Planetary Science Letters 256(3):295-313.
Komatsu, T., D. T. Huyen, and C. Jin-Hua. 2008. Lower Triassic bivalve assemblages after the
end-Permian mass extinction in South China and North Vietnam. Paleontological
Research 12(2):119-128.
Korte, C., and H. W. Kozur. 2010. Carbon-isotope stratigraphy across the Permian–Triassic
boundary: a review. Journal of Asian Earth Sciences 39(4):215-235.
Kroh, A. 2011. Echinoids from thE triassic of st. cassian–a rEviEw. Geo. Alp 8:136-140.
Kroh, A., and R. Mooi. 2016. World Echinoidea Database. Accessed at
http://www.marinespecies.org/echinoidea on 2016-04-28.
Kroh, A., and A. B. Smith. 2010. The phylogeny and classification of post-Palaeozoic echinoids.
Journal of Systematic Palaeontology 8(2):147-212.
Krull, E., G. Retallack, H. Campbell, and G. Lyon. 2000. δ13Corg chemostratigraphy of the
Permian ‐Triassic boundary in the Maitai Group, New Zealand: Evidence for high ‐
latitudinal methane release. New Zealand journal of geology and geophysics 43(1):21-32.
255
Krystyn, L., S. Richoz, A. Baud, and R. J. Twitchett. 2003. A unique Permian–Triassic boundary
section from the neotethyan Hawasina basin, Central Oman Mountains. Palaeogeography,
Palaeoclimatology, Palaeoecology 191(3):329-344.
Kummel, B. 1954. Triassic stratigraphy of southeastern Idaho and adjacent areas. US
Government Printing Office.
Kummel, B. 1959. Lower Triassic ammonoids from western Southland, New Zealand. New
Zealand journal of geology and geophysics 2(3):428-447.
Kummel, B. 1970. Stratigraphic boundary problems: Permian and Triassic of West Pakistan.
Edited by Bernhard Kummel and Curt Teichert.
Kummel, B., and C. Teichert. 1970. Stratigraphy and paleontology of the Permian-Triassic
boundary beds, Salt Range and trans-Indus ranges, West Pakistan. University Press of
Kansas.
Linck, O. 1955. Ein bemerkenswerter seeigel-rest (Miocidaris pakistanensis n. sp.) aus der
Unter-Trias der Salt Range (Pakistan). N. Jb. Geol. Paläont., Mh:489-195.
Lonn, J. D., Skipp, Ruppel, Janecke, Perry, Sears, Bartholemew, Stickney, Frtiz, Hur;pw, and
Thomas. 2000. Geologic map of the Lima 30′ × 60′ quadrangle, southwest Montana.
Open File Rep. 408, Mont. Bur. of Mines and Geol., Butte, Mont.
Magurran, A. E. 2004. Measuring biological diversity. African Journal of Aquatic Science
29(2):285-286.
Marenco, P. J., M. Fraiser, M. Clapham, and H. Gatz-Miller. 2013. Extreme microgastropod
size-limitation in Early Triassic shallow marine settings, Hidden Pasture, Montana:
Implications for environmental conditions following the end-Permian mass extinction. P.
88. Geol. Soc. Am. Abstr. Progr.
256
Marshall, J. D. 1992. Climatic and oceanographic isotopic signals from the carbonate rock record
and their preservation. Geological magazine 129(02):143-160.
Mata, S. A., and A. D. Woods. 2008. Sedimentology and paleoecology of the Lower Member of
the Lower Triassic (Smithian-Spathian) Union Wash Formation, east-central California.
Palaios 23(8):514-524.
Mathieu, G. 1949. Contribution à l'étude des monts troglodytes dans l'extrême Sud-Tunisien:
géologie régionale des environs de Matmata medenine et Foum-Tatahouine. Imprimerie
SAPI.
McGhee, G. R., P. M. Sheehan, D. J. Bottjer, and M. L. Droser. 2004. Ecological ranking of
Phanerozoic biodiversity crises: ecological and taxonomic severities are decoupled.
Palaeogeography, Palaeoclimatology, Palaeoecology 211(3):289-297.
McGowan, A., A. Smith, and P. Taylor. 2009. Faunal diversity, heterogeneity and body size in
the Early Triassic: testing post-extinction paradigms in the Virgin Limestone of Utah,
USA ∗. Australian Journal of Earth Sciences 56(6):859-872.
McRoberts, C. A. 2000. Paleobiology of the Triassic" flat clam" Halobla in oxygen-deficient
marine facies. P. 8. Geological Society of America, Northeastern Section.
McRoberts, C. A., and N. D. Newell. 2005. Marine Myalinidae (Bivalvia: Pterioida) from the
Permian of West Texas. American Museum Novitates:1-15.
Minchin, P. R. 1987. An evaluation of the relative robustness of techniques for ecological
ordination. Pp. 89-107. Theory and models in vegetation science. Springer.
Moffat, H. A., and D. J. Bottjer. 1999. Echinoid concentration beds: two examples from the
stratigraphic spectrum. Palaeogeography, Palaeoclimatology, Palaeoecology 149(1):329-
348.
257
Mooi, R. 1990. Paedomorphosis, Aristotle's lantern, and the origin of the sand dollars
(Echinodermata: Clypeasteroida). Paleobiology 16(01):25-48.
Mortensen, T. 1928. A Monograph Of The Echinoidea. Reitzel & Oxford University Press,
Copenhagen & London
Mostler, H. 1982. Bozener Quarzporphyr und Werfener Schichten. Exkursionsführer zur 4:43-
79.
Nairn, A., and A. Alsharhan. 1997. Sedimentary basins and petroleum geology of the Middle
East. Elsevier.
Newell, N. D., and B. Kummel. 1941. Permo-Triassic Boundary in Idaho, Montana, and
Wyoming. American Journal of Science 239(3):204-208.
Newell, N. D., and B. Kummel. 1942. Lower Eo-Triassic stratigraphy, western Wyoming and
southeast Idaho. Geological Society of America Bulletin 53(6):937-996.
Norkko, A., J. E. Hewitt, S. F. Thrush, and T. Funnell. 2001. Benthic ‐pelagic coupling and
suspension ‐feeding bivalves: linking site ‐specific sediment flux and biodeposition to
benthic community structure. Limnology and Oceanography 46(8):2067-2072.
Nützel, A., and C. Schulbert. 2005. Facies of two important Early Triassic gastropod
lagerstätten: implications for diversity patterns in the aftermath of the end-Permian mass
extinction. Facies 51(1-4):480-500.
Ogg, J. 2012. Chapter 25, Triassic. The Geologic Time Scale 2012:681-730.
Oksanen, J., F. G. Blanchet, R. Kindt, P. Legendre, P.R. M., R. B. O'Hara, G. L. Simpson, P.
Solymos, M. H. H. S. and, and H. Wagner. 2016. Vegan: Community Ecology Package.
R package version 2.3-5. https://CRAN.R-project.org/package=vegan.
258
Orchard, M., and E. Tozer. 1997. Triassic conodont biochronology, its calibration with the
ammonoid standard, and a biostratigraphic summary for the Western Canada
Sedimentary Basin. Bulletin of Canadian Petroleum Geology 45(4):675-692.
Orchard, M. J. 2007. Conodont diversity and evolution through the latest Permian and Early
Triassic upheavals. Palaeogeography, Palaeoclimatology, Palaeoecology 252(1):93-117.
Paull, R. K., and R. A. Paull. 1994a. Lower Triassic transgressive-regressive sequences in the
Rocky Mountains, eastern Great Basin, and Colorado Plateau, USA. Rocky Mountain
Section (SEPM).
Paull, R. K., and R. A. Paull. 1994b. Shallow marine sedimentary facies in the earliest Triassic
(Griesbachian) Cordilleran miogeocline, USA. Sedimentary Geology 93(3):181-191.
Payne, J. L. 2005. Evolutionary dynamics of gastropod size across the end-Permian extinction
and through the Triassic recovery interval. Paleobiology 31(2):269-290.
Payne, J. L., and M. E. Clapham. 2012. End-Permian mass extinction in the oceans: An ancient
analog for the twenty-first century? Annual Review of Earth and Planetary Sciences
40:89-111.
Payne, J. L., and L. R. Kump. 2007. Evidence for recurrent Early Triassic massive volcanism
from quantitative interpretation of carbon isotope fluctuations. Earth and Planetary
Science Letters 256(1):264-277.
Payne, J. L., D. J. Lehrmann, J. Wei, and A. H. Knoll. 2006. The pattern and timing of biotic
recovery from the end-Permian extinction on the Great Bank of Guizhou, Guizhou
Province, China. Palaios 21(1):63-85.
259
Payne, J. L., D. J. Lehrmann, J. Wei, M. J. Orchard, D. P. Schrag, and A. H. Knoll. 2004. Large
perturbations of the carbon cycle during recovery from the end-Permian extinction.
Science 305(5683):506-509.
Peng, Y., G. R. Shi, Y. Gao, W. He, and S. Shen. 2007. How and why did the Lingulidae
(Brachiopoda) not only survive the end-Permian mass extinction but also thrive in its
aftermath? Palaeogeography, Palaeoclimatology, Palaeoecology 252(1):118-131.
Perri, M. 1991. Conodont biostratigraphy of the Werfen Formation (Lower Triassic), Southern
Alps, Italy. Bollettino della Società Paleontologica Italiana 30(1):23-46.
Pietsch, C., and D. J. Bottjer. 2014. The importance of oxygen for the disparate recovery patterns
of the benthic macrofauna in the Early Triassic. Earth-Science Reviews.
Pietsch, C., S. A. Mata, and D. J. Bottjer. 2014. High temperature and low oxygen perturbations
drive contrasting benthic recovery dynamics following the end-Permian mass extinction.
Palaeogeography, Palaeoclimatology, Palaeoecology 399:98-113.
Pietsch, C., E. Petsios, and D. J. Bottjer. 2016. Sudden and extreme hyperthermals, low-oxygen,
and sediment influx drove community phase shifts following the end-Permian mass
extinction. Palaeogeography, Palaeoclimatology, Palaeoecology 451:183-196.
Poborski, S. J. 1954. Virgin Formation (Triassic) of the St. George, Utah, area. Geological
Society of America Bulletin 65(10):971-1006.
Posenato, R. 2008a. Global correlations of mid Early Triassic events: the Induan/Olenekian
boundary in the Dolomites (Italy). Earth-Science Reviews 91(1):93-105.
Posenato, R. 2008b. Patterns of bivalve biodiversity from Early to Middle Triassic in the
Southern Alps (Italy): regional vs. global events. Palaeogeography, Palaeoclimatology,
Palaeoecology 261(1):145-159.
260
Posenato, R. 2009. Survival patterns of macrobenthic marine assemblages during the end-
Permian mass extinction in the western Tethys (Dolomites, Italy). Palaeogeography,
Palaeoclimatology, Palaeoecology 280(1):150-167.
Posenato, R., L. E. Holmer, and H. Prinoth. 2014. Adaptive strategies and environmental
significance of lingulid brachiopods across the late Permian extinction. Palaeogeography,
Palaeoclimatology, Palaeoecology 399:373-384.
Powell, M. G., and M. Kowalewski. 2002. Increase in evenness and sampled alpha diversity
through the Phanerozoic: comparison of early Paleozoic and Cenozoic marine fossil
assemblages. Geology 30(4):331-334.
Pruss, S. B., and D. J. Bottjer. 2004. Early Triassic trace fossils of the western United States and
their implications for prolonged environmental stress from the end-Permian mass
extinction. Palaios 19(6):551-564.
Pruss, S. B., and D. J. Bottjer. 2005. The reorganization of reef communities following the end-
Permian mass extinction. Comptes Rendus Palevol 4(6):553-568.
Raup, D. M. 1979. Size of the Permo-Triassic bottleneck and its evolutionary implications.
Science 206(4415):217-218.
Reich, M. 2007. Linguaserra spandeli sp. nov.(Echinodermata: Ophiocistioidea) from the Late
Permian (Zechstein) of Thuringia, Germany. Pp. 317-330. Annales de paléontologie.
Elsevier.
Reichow, M. K., M. Pringle, A. Al'Mukhamedov, M. Allen, V. Andreichev, M. Buslov, C.
Davies, G. Fedoseev, J. Fitton, and S. Inger. 2009. The timing and extent of the eruption
of the Siberian Traps large igneous province: Implications for the end-Permian
environmental crisis. Earth and Planetary Science Letters 277(1):9-20.
261
Retallack, G. J., J. J. Veevers, and R. Morante. 1996. Global coal gap between Permian–Triassic
extinction and Middle Triassic recovery of peat-forming plants. Geological Society of
America Bulletin 108(2):195-207.
Riccardi, A. L., M. A. Arthur, and L. R. Kump. 2006. Sulfur isotopic evidence for chemocline
upward excursions during the end-Permian mass extinction. Geochimica et
Cosmochimica Acta 70(23):5740-5752.
Rodland, D. L. 1999. Paleoenvironments and paleoecology of the disaster taxon Lingula in the
aftermath of the end-Permian mass extinction. Master Thesis, University of Southern
California.
Rodland, D. L., and D. J. Bottjer. 2001. Biotic recovery from the end-Permian mass extinction:
behavior of the inarticulate brachiopod Lingula as a disaster taxon. Palaios 16(1):95-101.
Romano, C., N. Goudemand, T. W. Vennemann, D. Ware, E. Schneebeli-Hermann, P. A.
Hochuli, T. Brühwiler, W. Brinkmann, and H. Bucher. 2013. Climatic and biotic
upheavals following the end-Permian mass extinction. Nature Geoscience 6(1):57-60.
Roux, J. L., and B. Jones. 1994. Lithostratigraphy and depositional environment of the Permian
Nowra Sandstone in the southwestern Sydney Basin, Australia. Australian Journal of
Earth Sciences 41(3):191-203.
Sahney, S., and M. J. Benton. 2008. Recovery from the most profound mass extinction of all
time. Proceedings of the Royal Society of London B: Biological Sciences 275(1636):759-
765.
Saltzman, M. R., and A. R. Sedlacek. 2013. Chemostratigraphy indicates a relatively complete
Late Permian to Early Triassic sequence in the western United States. Geology
41(4):399-402.
262
Saunders, A., and M. Reichow. 2009. The Siberian Traps and the End-Permian mass extinction:
a critical review. Chinese Science Bulletin 54(1):20-37.
Savrda, C. E., and D. J. Bottjer. 1986. Trace-fossil model for reconstruction of paleo-
oxygenation in bottom waters. Geology 14(1):3-6.
Schock, W. W. 1981. Stratigraphy and paleontology of the Lower Dinwoody Formation and its
relation to the Permian-Triassic boundary in western Wyoming, southeastern Idaho and
southwestern Montana.
Scholle, P. A., and M. A. Arthur. 1980. Carbon isotope fluctuations in Cretaceous pelagic
limestones: potential stratigraphic and petroleum exploration tool. AAPG Bulletin
64(1):67-87.
Schubert, J. K., and D. J. Bottjer. 1995. Aftermath of the Permian-Triassic mass extinction event:
Paleoecology of Lower Triassic carbonates in the western USA. Palaeogeography,
Palaeoclimatology, Palaeoecology 116(1):1-39.
Scotese, C. R. 2001. Atlas of Earth History. PALEOMAP Project, Arlington, Texas.
Seilacher, A. 1990. The sand-dollar syndrome: A polyphyletic constructional breakthrough.
Evolutionary Innovations:3-18.
Sepkoski, J. J. 1982. Mass extinctions in the Phanerozoic oceans: a review. Geological Society
of America Special Papers 190:283-290.
Sepkoski, J. J. 1984. A kinetic model of Phanerozoic taxonomic diversity. III. Post-Paleozoic
families and mass extinctions. Paleobiology 10(02):246-267.
Shumway, S. E. 1982. Oxygen consumption in brachiopods and the possible role of punctae.
Journal of Experimental Marine Biology and Ecology 58(2):207-220.
263
Smith, A. 2015. British Jurassic Regular Echinoids. Part 1. Paleontographical Society
Monograph:1-67.
Smith, A.. 2005. Growth and form in echinoids: the evolutionary interplay of plate accretion
versus plate addition. In: Briggs, D.E.G (Ed.), Evolving form and function – fossils and
development. Yale University Press. New Haven, CT. 181-194.
Smith, A., and N. Hollingworth. 1990. Tooth structure and phylogeny of the Upper Permian
echinoid Miocidaris keyserlingi. Pp. 47-60. Proceedings of the Yorkshire Geological and
Polytechnic Society. Geological Society of London.
Smith, A. B. 1984. Echinoid palaeobiology. Special Topics in Paleontology. Vol. 1 Allen and
Unwin, London.
Smith, A. B. 1994a. Rooting molecular trees: problems and strategies. Biological Journal of the
Linnean Society 51(3):279-292.
Smith, A. B. 1994b. Triassic echinoids from Peru. Palaeontographica Abteilung A:177-202.
Smith, A. B. 2007. Intrinsic versus extrinsic biases in the fossil record: contrasting the fossil
record of echinoids in the Triassic and early Jurassic using sampling data, phylogenetic
analysis, and molecular clocks. Paleobiology 33(02):310-323.
Smith, A. B., and A. Kroh. 2000. The echinoid directory. Natural History Museum.
Sobolev, S. V., A. V. Sobolev, D. V. Kuzmin, N. A. Krivolutskaya, A. G. Petrunin, N. T. Arndt,
V. A. Radko, and Y. R. Vasiliev. 2011. Linking mantle plumes, large igneous provinces
and environmental catastrophes. Nature 477(7364):312-316.
Somero, G. N. 1995. Proteins and temperature. Annual review of physiology 57(1):43-68.
Song, H., J. Tong, T. J. Algeo, M. Horacek, H. Qiu, H. Song, L. Tian, and Z.-Q. Chen. 2013a.
Large vertical δ 13 C DIC gradients in Early Triassic seas of the South China craton:
264
implications for oceanographic changes related to Siberian Traps volcanism. Global and
Planetary Change 105:7-20.
Song, H., P. B. Wignall, Z.-Q. Chen, J. Tong, D. P. Bond, X. Lai, X. Zhao, H. Jiang, C. Yan, and
Z. Niu. 2011. Recovery tempo and pattern of marine ecosystems after the end-Permian
mass extinction. Geology 39(8):739-742.
Song, H., P. B. Wignall, D. Chu, J. Tong, Y. Sun, H. Song, W. He, and L. Tian. 2014a.
Anoxia/high temperature double whammy during the Permian-Triassic marine crisis and
its aftermath. Scientific reports 4:4132.
Song, H., P. B. Wignall, D. Chu, J. Tong, Y. Sun, H. Song, W. He, and L. Tian. 2014b.
Anoxia/high temperature double whammy during the Permian-Triassic marine crisis and
its aftermath. Scientific reports 4.
Song, H., P. B. Wignall, J. Tong, D. P. Bond, H. Song, X. Lai, K. Zhang, H. Wang, and Y. Chen.
2012. Geochemical evidence from bio-apatite for multiple oceanic anoxic events during
Permian–Triassic transition and the link with end-Permian extinction and recovery. Earth
and Planetary Science Letters 353:12-21.
Song, H., P. B. Wignall, J. Tong, and H. Yin. 2013b. Two pulses of extinction during the
Permian-Triassic crisis. Nature Geoscience 6(1):52-56.
Stanley, S. M. 2009. Evidence from ammonoids and conodonts for multiple Early Triassic mass
extinctions. Proceedings of the National Academy of Sciences 106(36):15264-15267.
Stramma, L., G. C. Johnson, J. Sprintall, and V. Mohrholz. 2008. Expanding oxygen-minimum
zones in the tropical oceans. Science 320(5876):655-658.
265
Sun, Y., M. M. Joachimski, P. B. Wignall, C. Yan, Y. Chen, H. Jiang, L. Wang, and X. Lai.
2012. Lethally hot temperatures during the Early Triassic greenhouse. Science
338(6105):366-370.
Svensen, H., S. Planke, A. G. Polozov, N. Schmidbauer, F. Corfu, Y. Y. Podladchikov, and B.
Jamtveit. 2009. Siberian gas venting and the end-Permian environmental crisis. Earth and
Planetary Science Letters 277(3):490-500.
Swofford, D. L. 2003. PAUP*: Phylogenetic Analysis Using Parsimony, version 4.0 b10.
Taylor, P. D., O. Vinn, and M. A. Wilson. 2010. Evolution of biomineralization in
‘Lophophorates’. Special Papers in Palaeontology 84:317-333.
Thompson, J. R., E. Petsios, E. H. Davidson, E. M. Erkenbrack, F. Gao, and D. J. Bottjer. 2015.
Reorganization of sea urchin gene regulatory networks at least 268 million years ago as
revealed by oldest fossil cidaroid echinoid. Scientific reports 5.
Tozer, E. T. 1961. The sequence of marine Triassic faunas in western Canada. Department of
Mines and Technical Surveys, Canada.
Tucker, M. E., and V. P. Wright. 2009. Carbonate sedimentology. Blackwell Publishing.
Twitchett, R., L. Krystyn, A. Baud, J. Wheeley, and S. Richoz. 2004. Rapid marine recovery
after the end-Permian mass-extinction event in the absence of marine anoxia. Geology
32(9):805-808.
Twitchett, R. J. 1999. Palaeoenvironments and faunal recovery after the end-Permian mass
extinction. Palaeogeography, Palaeoclimatology, Palaeoecology 154(1):27-37.
Twitchett, R. J. 2007. The Lilliput effect in the aftermath of the end-Permian extinction event.
Palaeogeography, Palaeoclimatology, Palaeoecology 252(1):132-144.
266
Twitchett, R. J., and T. Oji. 2005. Early Triassic recovery of echinoderms. Comptes Rendus
Palevol 4(6):531-542.
Van Iten, H., V. P. Tollerton, C. A. Ver Straeten, J. De Moraes Leme, M. G. Simoes, and S. C.
Rodrigues. 2013. Life mode of in situ Conularia in a Middle Devonian epibole.
Palaeontology 56(1):29-48.
Wagner, P. J., M. A. Kosnik, and S. Lidgard. 2006. Abundance distributions imply elevated
complexity of post-Paleozoic marine ecosystems. Science 314(5803):1289-1292.
Wei, H., J. Shen, S. D. Schoepfer, L. Krystyn, S. Richoz, and T. J. Algeo. 2014. Environmental
controls on marine ecosystem recovery following mass extinctions, with an example from
the Early Triassic. Earth-Science Reviews.
Wernberg, T., D. A. Smale, F. Tuya, M. S. Thomsen, T. J. Langlois, T. De Bettignies, S.
Bennett, and C. S. Rousseaux. 2013. An extreme climatic event alters marine ecosystem
structure in a global biodiversity hotspot. Nature Climate Change 3(1):78-82.
Wignall, P. 1993. Distinguishing between oxygen and substrate control in fossil benthic
assemblages. Journal of the Geological Society 150(1):193-196.
Wignall, P., and A. Hallam. 1992. Anoxia as a cause of the Permian/Triassic mass extinction:
facies evidence from northern Italy and the western United States. Palaeogeography,
Palaeoclimatology, Palaeoecology 93(1):21-46.
Wignall, P., and A. Hallam. 1993. Griesbachian (Earliest Triassic) palaeoenvironmental changes
in the Salt Range, Pakistan and southeast China and their bearing on the Permo-Triassic
mass extinction. Palaeogeography, Palaeoclimatology, Palaeoecology 102(3):215-237.
267
Wignall, P., R. Morante, and R. Newton. 1998. The Permo-Triassic transition in Spitsbergen: δ
13 C org chemostratigraphy, Fe and S geochemistry, facies, fauna and trace fossils.
Geological magazine 135(01):47-62.
Wignall, P. B., and R. J. Twitchett. 1996. Oceanic anoxia and the end Permian mass extinction.
Science 272(5265):1155.
Winguth, A. M., and E. Maier-Reimer. 2005. Causes of the marine productivity and oxygen
changes associated with the Permian–Triassic boundary: a reevaluation with ocean
general circulation models. Marine Geology 217(3):283-304.
Worcester, W. S. 1969. Some aspects of the ecology of Lingula (Brachiopoda) in Kaneohe Bay,
Hawaii. University of Hawai'i, Honolulu.
Yang, H., Z. Chen, Y. Wang, J. Tong, H. Song, and J. Chen. 2011. Composition and structure of
microbialite ecosystems following the end-Permian mass extinction in South China.
Palaeogeography, Palaeoclimatology, Palaeoecology 308(1):111-128.
Yin, H. 1981. Palaeogeographical and stratigraphical distribution of the Lower Triassic Claraia
and Eumorphotis (Bivalvia). Acta Geological Sinica 3:000.
Yin, H., Q. Feng, X. Lai, A. Baud, and J. Tong. 2007. The protracted Permo-Triassic crisis and
multi-episode extinction around the Permian–Triassic boundary. Global and Planetary
Change 55(1):1-20.
Zatoń, M., P. D. Taylor, and O. Vinn. 2013. Early Triassic (Spathian) post-extinction
microconchids from western Pangea. Journal of Paleontology 87(01):159-165.
Zhao, L., Y. Chen, Z.-Q. Chen, and L. Cao. 2013. Uppermost Permian to Lower Triassic
conodont zonation from Three Gorges area, South China. Palaios 28(8):523-540.
268
Zonneveld, J.-P., T. W. Beatty, and S. G. Pemberton. 2007. Lingulide brachiopods and the trace
fossil Lingulichnus from the Triassic of western Canada: Implications for faunal recovery
after the end-Permian mass extinction. Palaios 22(1):74-97.
Zonneveld, J.P., M. K. Gingras, and T. W. Beatty. 2010. Diverse ichnofossil assemblages
following the PT mass extinction, Lower Triassic, Alberta and British Columbia, Canada:
evidence for shallow marine refugia on the northwestern coast of Pangaea. Palaios
25(6):368-392.

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Appendix: Locality Information
Blacktail Creek Outcrop: (44°45'7.35"N; 112°17'50.10"W)
The Blacktail Creek outcrop of the Dinwoody Formation is exposed on the eastern side of
Blacktail Road, approximately 35 miles southeast of Dillon in Beaverhead County, Montana.
The outcrop is accessible via a gravel road either from the north or south. The northern route is
accessible from the city of Dillon, where State Highway 91 intersects Blacktail Road, and takes
approximately 1 hour. This route is well maintained. The southern route is accessible from the
town of Monida, via S Valley Road, which intersects Blacktail Road on the eastern side of the
Lima Reservoir. This route takes approximately 1.5 hours. The routes from the towns of Lima or
Dell are inaccessible due to gates and private property.

Uomo Outcrop: (46°23'44.19"N; 11°47'54.62"E)
The Uomo outcrop of the lower Werfen Formation is exposed on the southern foothills of Cima
Uomo, approximately 1.5 miles north of San Pellegrino Pass, which is 16 miles east of the city of
Moena, Trento Province. From the Hotel Chalet Cima Uomo, it is a 1.5 hour hike to the top of
the outcrop. A dirt road, inaccessible to cars due to gates, can be followed to a ski lift, which is
near the bottom of the section.

Bulla Outcrop: (46°34'11.18"N; 11°37'50.59"E)
The Bulla outcrop of the lower Werfen Formation is exposed on the southern side of an
abandoned road leading from the city of Ortisei, Bolzano Province, to the town of Bulla/Pufels.
The road can be accessed via route SP64 south of Ortisei. It is a well maintained gravel path.
Park signage based on the work of Brandner et al. 2009 demarks their interpretations of the
various Werfen Formation Members along the outcrop.
270
BTM13 BTM14 BTM16 BTM20 BTM31 BTM52 BTM55 BTM59 BTM62 BTM65 BTM75 BTM79 BTM85 BTM90 BTM93
?Crittendenia 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
?Ombonia 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0
?Trigonodus 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0
?Unicardium 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0
Bakevellia 0 0 0 7 0 0 0 0 0 1 1 0 0 0 0
Claraia 0 0 0 0 5 0 49 2 4 1 0 0 0 0 0
Coelostylina (full) 0 0 184 2 0 0 0 0 0 0 3 0 0 0 0
Entolium 0 0 0 0 0 0 0 0 3 0 6 0 0 0 4
Eumorphotis 0 4 25 10 16 79 23 26 41 11 44 347 1 0 0
Coelostylina (partial) 0 0 361 2 0 10 0 0 1 0 0 0 0 3 0
Leptochondria 0 0 0 3 0 3 7 0 2 0 25 0 0 0 0
Lingularia 8 8 19 119 29 21 1 16 12 40 13 2 11 4 2
Microconchid 1 0 0 0 1 8 0 0 0 12 0 8 0 0 0
Myalina 0 0 1 0 1 0 0 6 2 3 5 0 0 0 0
Natiria 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0
Neoschizodus 0 0 7 1 10 0 7 8 1 22 0 0 4 3 40
Obnoxia 83 62 89 5 3 0 0 0 0 0 0 0 0 0 0
Pecten Indet 0 1 0 9 0 10 0 0 0 0 0 0 0 0 0
Permophorus 0 0 0 0 0 0 0 0 0 0 0 2 0 0 3
Pernopecten 0 0 0 0 0 0 0 0 0 5 1 0 0 0 0
Promyalina 0 0 4 8 10 8 17 9 0 37 0 0 2 0 0
Bivalve indet (Sp. A) 0 0 0 11 75 0 0 3 0 0 0 0 0 0 0
Scythentolium 0 0 0 0 0 1 0 9 5 0 0 0 1 0 0
Strobeus 0 0 0 0 0 8 0 0 0 0 0 0 0 1 0
Towapteria 0 0 0 0 0 0 0 0 4 4 0 0 0 0 0
Unionites 0 0 0 5 22 1 21 15 2 21 4 3 13 9 103
Vetigastropod indet 0 0 0 0 0 4 0 0 0 0 0 0 0 0 0
Collections
Appendix Table 1 - Blacktail Creek Ecology Data
Genus
271
Collection Outcrop Meter Richness (Genus) Abundance Dominance (D) Evenness (E 1/D) Shannon's H % Encrusted Gastropod Size (mm) % Disaster Abundance
BTM13 16.00 3.00 92.00 0.82 0.41 0.35 0.01 NA 0.09
BTM14 17.00 4.00 75.00 0.70 0.36 0.61 0.00 NA 0.16
BTM16 19.00 10.00 693.00 0.36 0.28 1.29 0.00 0.65 0.07
BTM20 23.50 13.00 183.00 0.44 0.18 1.44 0.00 0.93 0.78
BTM31 30.00 10.00 172.00 0.25 0.40 1.71 0.01 NA 0.48
BTM52 78.50 11.00 153.00 0.30 0.30 1.67 0.03 0.55 0.71
BTM55 82.00 8.00 134.00 0.21 0.58 1.75 0.00 NA 0.83
BTM59 85.00 10.00 95.00 0.16 0.63 2.01 0.00 NA 0.72
BTM62 89.00 11.00 77.00 0.32 0.28 1.63 0.00 3.00 0.29
BTM65 91.00 11.00 157.00 0.17 0.53 1.96 0.11 NA 0.56
BTM75 103.00 9.00 102.00 0.27 0.41 1.61 0.00 NA 0.60
BTM79 105.50 5.00 362.00 0.92 0.22 0.22 0.01 NA 0.97
BTM85 111.00 7.00 33.00 0.29 0.50 1.48 0.00 NA 0.82
BTM90 115.00 5.00 20.00 0.29 0.69 1.40 0.00 2.35 0.65
BTM93 118.50 5.00 152.00 0.53 0.38 0.85 0.00 NA 0.69
Appendix Table 2 - Blacktail Creek Ecology Data
272
Appendix Table 3 - Blacktail Creek carbon isotope data
Meter d13Ccarb o/oo Meter d13Ccarb o/oo Meter d13Ccarb o/oo Meter d13Ccarb o/oo
0.75 -3.62 30.00 -0.42 87.40 -0.01 103.50 -0.51
2.75 -3.77 30.00 -0.35 87.50 -0.61 103.70 -0.58
12.55 -2.34 33.35 -0.38 87.70 -0.68 103.90 -0.83
12.85 -2.03 33.45 -0.59 87.80 -0.57 104.60 -0.79
13.15 -1.08 34.50 -0.51 88.05 -0.95 105.50 -1.30
13.25 -0.72 77.65 -0.44 88.20 -0.57 108.85 -1.70
13.55 -1.30 77.80 -0.59 88.30 -0.42 109.15 -1.24
13.80 -1.11 77.90 -0.55 88.40 -0.83 109.35 -1.64
16.00 -0.99 78.00 -0.58 88.60 -1.21 109.65 -1.89
16.00 -0.77 78.10 -0.15 88.70 -0.92 112.40 -2.01
16.20 -0.40 78.25 -0.29 88.80 -1.01 112.60 -1.75
16.50 -0.14 78.45 -0.84 89.00 -0.79 112.75 -1.87
16.60 0.32 78.50 -0.56 89.00 -0.56 114.75 -3.13
16.90 0.03 78.65 -0.68 89.20 -0.86 115.00 -2.23
17.00 0.13 79.55 -0.60 89.40 -1.12 115.55 -3.15
17.05 -0.31 79.70 -0.69 89.50 -0.37
17.15 -0.09 79.85 -0.72 89.70 -1.21
17.40 0.00 79.95 -0.73 95.70 -1.62
18.30 -0.18 80.15 -0.88 95.80 -1.93
18.55 -0.58 80.25 -0.88 98.80 -2.02
18.70 -0.67 80.45 -0.92 99.10 -2.29
18.90 -0.49 80.65 -0.92 101.60 -1.61
19.00 -0.79 80.75 -1.24 101.85 -1.47
19.10 -0.85 82.00 -0.67 102.10 -1.16
19.20 -0.83 83.90 -1.55 102.20 -0.89
19.35 -0.91 85.00 -1.73 102.50 -0.37
23.05 -0.79 85.70 -1.62 102.80 0.03
23.50 -0.93 85.90 -1.10 103.00 -1.51
28.85 -0.10 86.10 -0.90 103.00 -1.40
29.05 0.03 86.90 -0.51 103.05 -0.53
29.55 0.13 87.05 -0.41 103.25 -0.34
273
BM1 BM2 BM3 BM4 BM5 BM6 BM7 BM8 BM9 BM10 BM11
Bakevellia 1 2 0 0 0 0 15 0 0 0 0
Claraia 2 1 0 0 2 6 28 3 0 1 0
Entolium 0 3 2 1 1 2 0 1 1 0 3
Eumorphotis 2 0 1 0 1 0 1 0 0 0 1
Leptochondria 9 1 3 0 0 0 11 0 0 0 0
Myalina 6 0 0 0 3 0 7 0 0 1 1
Pectinid 0 1 0 0 0 0 0 0 0 0 0
Pernopecten 0 1 0 1 2 2 1 1 0 2 1
Promyalina 1 0 1 0 1 0 18 0 0 0 0
Scythentolium 0 3 3 0 0 1 6 0 3 0 0
Chartronella 0 0 0 0 0 0 0 0 0 1 0
Coelostylina 0 0 0 3 3 0 5 11 0 10 0
Cylindrobulina 0 0 0 0 0 0 0 0 0 1 0
Gastropod Sp. A 0 0 0 0 0 0 33 0 0 0 0
Gastropod Sp. B 0 0 0 0 0 0 5 0 0 0 0
Gastropod Sp. C 0 0 0 0 0 0 2 0 0 0 0
Gastropod indet 0 0 0 0 0 0 0 0 3 0 0
Naticopsis 0 0 0 0 0 0 7 0 0 0 0
Pseudomurchisonia 14 0 0 0 0 0 34 0 0 0 0
Sementichoncha 0 2 0 0 0 0 0 0 0 0 0
Lucinid indet 0 0 0 0 0 0 2 0 0 0 0
Neoschizodus 20 37 22 6 9 9 59 7 18 6 3
Permophorus 8 1 0 0 0 0 0 0 0 0 0
Unionites 39 15 6 11 10 3 72 4 3 5 9
Lingula 1 0 0 0 0 0 0 0 0 0 0
Bivalve Sp. A 0 0 3 0 0 0 0 0 0 0 0
Genus
Collections
Appendix Table 4 - Bulla Ecological Data (also published in Pietsch et al. 2016)
274
Collection Richness (Genus) Dominance (D) Shannon's H Evenness (E 1/D) Functional Diversity % Disaster Abundance Bivalve Size (mm) Gastropod Size (mm)
BM1 11 0.22 1.82 0.42 6.00 0.44 10.10 2.50
BM2 11 0.36 1.47 0.25 6.00 0.24 5.50 NA
BM3 8 0.33 1.52 0.38 4.00 0.20 8.40 NA
BM4 5 0.35 1.25 0.58 3.00 0.50 11.60 4.00
BM5 9 0.21 1.84 0.54 5.00 0.44 10.90 2.70
BM6 6 0.26 1.54 0.65 3.00 0.39 9.70 NA
BM7 17 0.13 2.28 0.44 6.00 0.39 10.70 3.50
BM8 6 0.27 1.49 0.62 4.00 0.26 11.40 3.20
BM9 5 0.45 1.12 0.45 2.00 0.11 5.60 2.70
BM10 8 0.23 1.70 0.54 6.00 0.22 6.80 3.60
BM11 6 0.31 1.43 0.53 4.00 0.56 9.60 NA
Appendix Table 5 - Bulla Ecology Data (also published in Pietsch et al. 2016)
275
Appendix Table 6 - Bulla carbon isotope data (also published in Pietsch et al. 2016)
Meter d13Ccarb o/oo
15.03 -2.26
22.93 -2.01
33.03 -0.59
37.91 -1.09
39.28 0.88
40.98 0.70
57.64 1.08
60.61 0.52
64.49 1.35
67.24 0.78
70.68 1.52
80.69 0.85
95.62 0.59
97.78 1.15
276
UM01 UM02 UM03 UM04 UM05 UM06 UM07 UM08 UM09 UM10 UM11 UM12 UM14 UM15 UM16 UM17 UM18 UM19 UM20
Aviculopecten 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Bakevellia 0 0 0 1 3 1 1 0 0 0 0 0 0 0 0 1 0 0 0
Bivalve sp. A 0 0 0 0 0 0 0 0 0 0 0 0 2 0 0 0 0 0 0
Brachiopod indet 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0
Claraia 0 12 19 2 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0
Coelostylina 0 1 0 0 0 0 0 0 0 0 0 0 0 1 1 2 11 0 2
Costatoria 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 3 0 0
Crurithyris 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0
Cylindrobullina 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Entolium 0 7 1 0 3 4 2 0 0 4 0 0 2 0 1 7 6 1 0
Eumorphotis 0 7 0 3 0 0 0 2 0 0 0 0 0 0 8 5 1 5 0
Gastropod sp. A 0 0 54 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Gastropod sp. B 0 0 8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Gastropod sp. C 0 0 6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Leptochondria 0 5 2 1 2 1 1 0 0 0 0 1 1 1 1 0 2 1 0
Lingularia 13 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Myalina 1 7 1 1 0 0 4 0 0 3 1 0 0 0 1 2 0 0 0
Naticopsis depresispirus 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0
Neoschizodus 0 33 28 12 43 15 17 0 7 12 1 2 12 3 26 12 26 2 3
Pectinid 0 0 0 0 0 0 3 0 0 0 0 0 8 0 0 0 0 4 1
Permophorus 0 10 2 2 0 0 0 0 0 0 0 0 5 0 0 0 7 0 1
Pernopecten 0 0 0 0 0 0 0 0 0 6 0 0 0 0 2 2 2 0 0
Pleuromya 0 1 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Polygyrina 0 0 16 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Promyalina 0 2 9 0 0 1 2 0 0 0 0 0 0 0 0 2 0 0 0
Pseudomurchsonia 0 0 0 0 5 61 16 30 0 0 0 0 2 0 0 0 0 0 0
Scythentolium 0 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Unionites 10 19 27 29 11 10 27 9 33 32 17 18 3 5 13 10 10 1 2
Collections
Genus
Appendix Table 7 - Uomo Ecology Data (also published in Pietsch et al. 2016)
277
Collection Meter Richness (Genus) Dominance (D) Shannon's H Evenness (E 1/D) Functional Diversity % Disaster Abundance Bivalve Size (mm) Gastropod Size (mm)
UM01 13.00 3.00 0.47 0.83 0.71 3.00 0.96 8.30 NA
UM02 61.00 13.00 0.16 2.08 0.47 4.00 0.72 8.20 2.00
UM03 72.00 14.00 0.17 2.08 0.43 6.00 0.49 9.50 4.20
UM04 77.00 9.00 0.39 1.31 0.29 3.00 0.93 14.50 NA
UM05 79.00 9.00 0.38 1.43 0.29 6.00 0.83 12.70 7.20
UM06 81.00 9.00 0.45 1.19 0.25 6.00 0.33 9.50 4.30
UM07 83.50 10.00 0.24 1.69 0.42 4.00 0.66 7.20 4.80
UM08 95.00 3.00 0.59 0.71 0.57 3.00 0.71 9.60 3.20
UM09 106.00 2.00 0.71 0.46 0.70 1.00 1.00 20.20 NA
UM10 106.50 5.00 0.38 1.23 0.53 3.00 0.78 13.10 NA
UM11 113.00 4.00 0.81 0.41 0.31 3.00 0.90 26.20 NA
UM12 116.00 3.00 0.75 0.50 0.45 2.00 0.96 16.30 NA
UM14 155.00 8.00 0.21 1.79 0.60 4.00 0.69 4.40 2.50
UM15 167.00 4.00 0.36 1.17 0.69 3.00 0.80 8.90 5.50
UM16 173.00 8.00 0.33 1.40 0.38 4.00 0.90 9.70 3.30
UM17 183.00 12.00 0.16 2.06 0.52 5.00 0.62 9.20 5.00
UM18 194.00 9.00 0.22 1.80 0.51 4.00 0.54 10.10 3.30
UM19 202.50 6.00 0.24 1.57 0.68 3.00 0.80 7.10 NA
UM20 205.00 5.00 0.23 1.52 0.85 4.00 0.50 4.30 3.40
Appendix Table 8 - Uomo Ecology Data (also published in Pietsch et al. 2016)
278
Appendix Table 9 - Uomo carbon isotope data (also published in Pietsch et al. 2016)
Meter d13C carb o/oo Meter d13C carb o/oo Meter d13C carb o/oo
3 -0.62 60.5 1.52 166 5.70
4.5 -1.21 63 2.03 167 5.63
6 1.17 64 1.79 169 5.12
8 1.20 66 2.15 170 5.02
9.5 1.05 68 1.86 173 5.50
11 1.15 71.5 1.21 175 4.55
13 1.03 72.5 2.64 180 4.73
29 1.46 75 0.95 186 3.78
30 1.55 76 2.08 187 3.19
31 1.33 77 0.26 188 3.23
32.5 1.09 78 0.16 189 3.05
35 1.22 78.5 0.19 192 3.15
36.5 1.48 82.5 -0.15 194 2.58
38 1.57 83.5 0.55 198 2.12
40 1.22 84 0.41 200 1.97
41 1.20 85 1.24 211 0.00
42 1.52 86 0.70 213 -0.80
44 1.78 86.5 2.94 219 -0.65
45 1.40 87 2.75
45.5 1.33 90.5 2.86
46.5 1.55 94.5 1.69
49 1.10 112 1.76
49.5 1.42 115 2.69
51.5 1.39 116 2.30
54.5 0.93 117 1.83
55.5 0.54 118 2.51
56.5 1.57 153 4.05
58 1.36 155 4.05
60 1.45 164 4.59
279
Appendix Table 10 - List of echinoid specimens used for phylogenetic analysis
Taxonomic ID Label ID Specimen(s) Coded Location
Archaeocidaris whatleyensis Archaeocidaris whatleyensis BMNH Pal. PI E 76887; BMNH Pal. E 76888 (holotype) British Museum of Natural History
Couvelardicidaris dubari Miocidaris dubari BMNH E76720 British Museum of Natural History
Couvelardicidaris moorei Miocidaris moorei BMNH E 1536 (Holotype); BMNH E37723 British Museum of Natural History
Eotiaris connorsi Miocidaris connorsi USNM 144195; USNM 144194 Smithsonian Institution National Museum of Natural History
Eotiaris guadalupensis Miocidaris connorsi USNM 610600 (Holotype); USNM 610601-610605 Smithsonian Institution National Museum of Natural History
Eotiaris keyserlingi Miocidaris keyserlingi G3.04a; G3.04b Hancock Museum; British Museum of Natural History
Lenticidarus utahensis Lenticidaris utahensis USNM 247926 (Holotype) Smithsonian Institution National Museum of Natural History
Miocidaris pakistanensis Miocidaris pakistanensis IGP 1058/1 (Holotype) Museum of the University of Tübingen MUT
Procidaris edwardsi Procidaris edwardsi BMNH Pal. 75689 British Museum of Natural History
Procidaris lobatum Miocidaris tenuispina E82513; E42178; 38512 British Museum of Natural History
Triadotiaris grandaeva Triadotiaris grandaeva MHI 1149; MHI 571; MHI 572; SMNS 24843 Muschelkalk Museum, Ingelfingen; State Museum of Natural History Stuttgart
280

Abstract (if available)

Abstract The Permian-Triassic mass extinction was the largest extinction of the Phanerozoic, and led to significant taxonomic loss and ecological restructuring in both marine and terrestrial ecosystems. Severe greenhouse gas induced climate change, sourced from extensive volcanic outgassing during the emplacement of the Siberian Traps, is implicated as the source of the various harmful environmental conditions that led to the extinction. Evidence from lithologic and geochemical proxies suggests that episodes of thermal spikes in sea surface temperatures and anoxia in the shallow shelf were conditions that were reoccurring in the marine realm during both the initial extinction and subsequent Early Triassic interval. Recovery of marine communities following the extinction was thought to be protracted due to the severity of taxonomic loss, lasting the entirety of the Early Triassic. However, recent studies have shown that progress of recovery in the Early Triassic is highly complex, differing between regions, depositional environments, and community types. The importance of biotic (such as recruitment, interspecies competition, and physiology) and abiotic (such as occurrence of anoxia, heat stress, hypercapnia and acification) factors in the differential recovery following the extinction is not well understood. Additionally, the manifestation of recovery progress is not well understood at different geographic levels (global vs. local) using quantitative measures of recovery that reflect community complexity. The aim of this body of work is to explore survival and recovery in the marine realm in the Early Triassic following the Permian-Triassic mass extinction, through quantitative analysis of the complexity of marine benthic communities. Two local-scale studies of changes in community complexity associated with geochemical proxies of carbon cycle perturbations are presented, one from a Panthalassic section, and one from two Tethyan sections. Shallow-shelf benthic communities from the Panthalassic section show a trend of recovery relatively early in the Early Triassic, which subsequently fails in association with a large negative carbon isotope excursion. A spike in sea surface temperatures, associated with a recurrence of volcanic outgassing, is implicated as a shared causal mechanism between failed recovery and carbon cycle excursions. In comparison, the two Tethyan sections show no clear association of changes in community complexity and carbon isotope shifts, despite large positive and negative excursions occurring within the section. The shallower setting of these sections, in addition to frequent tectonically-induced bathymatry changes throughout, are likely masking community sensitivity to larger global environmental conditions, such as the response to thermal stress observed in the Panthalassic section. These studies demonstrate the importance of localscale conditions in producing disparate responses of communities to global-scale environmental perturbations. An additional global scale database study of recovery of community complexity, as reflected by decreasing ecological dominance of ‘disaster taxa’, shows a pattern of gradual recovery throughout the Early Triassic. While studies focusing on individual sections can reveal complexities in recovery due to local conditions, this global scale study shows an averaged and generalized signal of recovery. These works highlight the importance of quantifying recovery at both the local and global scale. In addition to these studies of recovery within benthic communities, a study of extinction survival in echinoids, a poorly represented fossil group during the Permian-Triassic, is presented herein. The evolutionary trajectory of modern echinoids has been thought to be severely effected by a diversity bottleneck occurring at the Permian-Triassic boundary. However, recent studies, including this study, suggest that a greater number of lineages than previously thought survived the extinction. Phylogenetic relationships are used to infer survival of multiple lineages into the Triassic that are poorly represented in the Permian, due to a number of taphonomic problems. This study highlights the importance of phylogenetic analyses in overcoming the limitations of a poor fossil record. The patterns of recovery and survival following the Permian-Triassic mass extinction reveal the importance of quantitative studies at different spatial and temporal scales, and highlight the complexity of biotic responses to global climate crises.

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Creator Petsios, Elizabeth (author)

Core Title The early Triassic recovery period: exploring ecology and evolution in marine benthic communities following the Permian-Triassic mass extinction

School College of Letters, Arts and Sciences

Degree Doctor of Philosophy

Degree Program Geological Sciences

Publication Date 07/27/2016

Defense Date 05/25/2016

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag echinoid,end-Permian mass extinction,Fossils,invertebrate,marine,OAI-PMH Harvest,paleoecology,paleontology,phylogenetic analysis,quantitative ecology

Format application/pdf (imt)

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Bottjer, David J. (committee chair), Caron, David (committee member), Corsetti, Frank (committee member)

Creator Email epetsios@gmail.com,petsios@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c40-283042

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Legacy Identifier etd-PetsiosEli-4643.pdf

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Document Type Dissertation

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Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the a...

Repository Name University of Southern California Digital Library

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