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Morphologic trends in Permo-Triassic gastropods: A theoretical morphology approach
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Morphologic trends in Permo-Triassic gastropods: A theoretical morphology approach
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MORPHOLOGIC TRENDS IN PERMO-TRIASSIC GASTROPODS: A THEORETICAL MORPHOLOGY APPROACH Copyright 2002 by Pedro Jose Marenco A Thesis Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE (GEOLOGY) December 2002 Pedro Jose Marenco Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: 1414849 UMI UMI Microform 1414849 Copyright 2003 by ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UNIVERSITY O F S O U T H E R N CALIFORNIA THE GRADUATE SCHOOL UNIVERSITY PARK LOS ANGELES, CALIFORNIA 9 0 0 0 7 This thesis, written by Pedro Jose Marenco under the direction of h is Thesis Committee, and approved by all its members, has been pre sented to and accepted by the Dean of The Graduate School, in partial fulfillment of the requirements for the degree of Dtan Date December^! 82002 T] MMITTEE / Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table Of Contents List Of Figures..................................................................................................................iii Abstract............................................................................................................................ vii Chapter 1: The Permo-Triassic Mass Extinction and Gastropod Evolution................. 1 Chapter 2: Theoretical Morphology..................................................................................7 SHELL MORPHOSPACE............................................................................................7 ORNAMENTATION SPACE....................................................................................14 Chapter 3: Methods..........................................................................................................52 FAUNAS STUDIED.................................................................................................. 52 STAGE LEVEL STRATIGRAPHY......................................................................... 53 HIGHER LEVEL CLASSIFICATION.....................................................................53 SELECTION OF SPECIES........................................................................................53 MEASUREMENTS.....................................................................................................55 Chapter 4: Results............................................................................................................61 CLASSIFICATION.................................................................................................... 61 FAUNAL TRENDS.................................................................................................... 62 GENERIC TRENDS................................................................................................... 69 Chapter 5: Interpretations............................................................................................. 106 FAUNAL TRENDS...................................................................................................106 GENERIC TRENDS..................................................................................................131 SOURCES OF ERROR............................................................................................ 132 Chapter 6: Conclusions..................................................................................................133 References.......................................................................................................................135 Appendix 1: Early Permian Measurement D ata......................................................... 138 Appendix 2: Late Permian Measurement Data............................................................140 Appendix 3: Early Triassic Measurement Data...........................................................143 Appendix 4: Middle Triassic Measurement Data....................................................... 144 ii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. List Of Figures Figure 1: Phanerozoic familial diversity curve....................................................................... 2 Figure 2: Permo-Triassic gastropod familial diversity curve................................................3 Figure 3: Raup’s WDT “cube” .................................................................................................8 Figure 4: Coordinate system used to model logarithmic spirals using Raup’s WDT model......................................................................................................................................10 Figure 5: SO measured on Alvania aurivillii.........................................................................17 Figure 6: SO measured on Calliostoma ligatum................................................................... 18 Figure 7: SO measured on Homalopoma luridum................................................................ 19 Figure 8: SO measured on Nerita versicolor....................................................................... 20 Figure 9: SO measured on Parviturbo francesae.................................................................21 Figure 10: SO measured on Turbo cailletti........................................................................... 22 Figure 11: CC measured on Epitonium humphreysi.............................................................24 Figure 12: Alvania aequisculpta.............................................................................................26 Figure 13: Calliostomafascinans...........................................................................................28 Figure 14: Tectarius muricatus...............................................................................................29 Figure 15: Triphora decorata................................................................................................. 30 Figure 16: Alvania montereyensis.......................................................................................... 31 Figure 17: Astraea tecta americana....................................................................................... 32 Figure 18: Rissoina stricta...................................................................................................... 33 Figure 19: Cymatium parthenopeum......................................................................................35 Figure 20: Solariella infundibulum........................................................................................ 36 iii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 21: Sthenorytispernobilis........................................................................................... 37 Figure 22: Ficus howelli ........................................................................................................38 Figure 23: Neptunea lyratalyrata........................................................................................... 39 Figure 24: Littorina albicarinata............................................................................................40 Figure 25: Mur ex beauii..........................................................................................................42 Figure 26: Littorina angustior................................................................................................ 44 Figure 27: SO-CC plot for Modem test fauna.......................................................................48 Figure 28: Stage level stratigraphy used for this study.........................................................54 Figure 29: Measuring for coiling geometry.......................................................................... 56 Figure 30: Spire index versus theta for Early Permian, Late Permian, Early Triassic and Middle Triassic.............................................................................................................. 63 Figure 31: W versus T for Early Permian, Late Permian, Early Triassic and Middle Triassic.................................................................................................................................. 64 Figure 32: SO-CC ornamentation space for Early Permian, Late Permian, Early Triassic and Middle Triassic................................................................................................66 Figure 33: Absolute and normalized SO frequencies for Early Permian, Late Permian, Early Triassic and Middle Triassic..................................................................... 67 Figure 34: Absolute and normalized frequencies for C C .................................................... 68 Figure 35: Percentage of species with SO and CC values that are both zero, one zero, and both non-zero for Early Permian, Late Permian, Early Triassic and Middle Triassic...................................................................................................................................70 Figure 36: Late Permian Worthenia species......................................................................... 72 Figure 37: Late Permian Worthenia species......................................................................... 74 Figure 38: Early Triassic Worthenia species........................................................................ 76 iv Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 39: Middle Triassic Worthenia species..................................................................... 78 Figure 40: Middle Triassic Worthenia species..................................................................... 80 Figure 41: Spire index versus theta for Worthenia............................................................... 82 Figure 42: W versus T for Worthenia.................................................................................... 83 Figure 43: SO-CC ornamentation space for Worthenia........................................................84 Figure 44: Permo-Triassic Strobeus....................................................................................... 85 Figure 45: Spire index versus theta for Strobeus.................................................................. 87 Figure 46: W versus T for Strobeus....................................................................................... 88 Figure 47: SO-CC ornamentation space for Strobeus...........................................................89 Figure 48: Early Permian Glabrocingulum species..............................................................91 Figure 49: Late Permian Glabrocingulum species................................................................93 Figure 50: Middle Triassic Glabrocingulum species........................................................... 95 Figure 51: Spire index versus theta for Glabrocingulum..................................................... 97 Figure 52: W versus T for Glabrocingulum.......................................................................... 98 Figure 53: SO-CC ornamentation space for Glabrocingulum............................................. 99 Figure 54: Permo-Triassic Glyptotomaria...........................................................................101 Figure 55: Spire index versus theta for Glyptotomaria...................................................... 103 Figure 56: W versus T for Glyptotomaria........................................................................... 104 Figure 57: SO-CC ornamentation space for Glyptotomaria...............................................105 Figure 58: SO-CC Breakdown for Permo-Triassic.............................................................108 Figure 59: Early Permian species in the zone of theoretical reticulation.........................110 v Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 60: Early Permian species in the zone of theoretical reticulation......................... 112 Figure 61: Late Permian species in the zone of theoretical reticulation...........................114 Figure 62: Late Permian species in the zone of theoretical reticulation...........................116 Figure 63: Late Permian species in the zone of theoretical reticulation...........................118 Figure 64: Late Permian species in the zone of theoretical reticulation........................... 120 Figure 65: Early Triassic species in the zone of theoretical reticulation..........................122 Figure 66: Middle Triassic species in the zone of theoretical reticulation.......................124 Figure 67: Middle Triassic species in the zone of theoretical reticulation.......................126 Figure 68: Most abundant Early Triassic species...............................................................129 v i Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Abstract Previous studies of Permo-Triassic gastropod morphology have focused on general morphotype and size trends across the boundary (Erwin 1990, Fraiser and Bottjer, in review). This study is an attempt to quantify trends in coiling geometry and ornamentation in Permo-Triassic gastropods using theoretical morphology. Shell coiling in gastropods can be modeled using four parameters developed by Raup (1966). Raup’s model was used here to investigate trends in shell coiling geometry through the Permo-Triassic boundary. A new theoretical morphology model is proposed in order to investigate broad scale trends in shell ornamentation. This new model has two parameters, one for spiral ornamentation and one for collabral ornamentation. The model was tested and developed on a subjectively chosen set of modem gastropods in order to fully examine its strengths and weaknesses and was then applied to Permo-Triassic gastropods. The results reported here quantify a decrease in ornamentation in the Early Triassic and the beginning of a return to pre-extinction ornamentation levels in the Middle Triassic. In particular the number of reticulate forms decreases drastically in the Early Triassic only to begin to return to normal in the Middle Triassic. Reticulation is likely an anti-predatory specialization since it effectively increases shell thickness with a minimum of material. The general absence of reticulation in the Early Triassic supports the hypothesis that Early Triassic gastropods exhibited vii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. opportunistic behavior (Fraiser and Bottjer, in review). Coiling geometry did not change significantly from the Early Permian through the Middle Triassic. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Chapter 1: The Permo-Triassic Mass Extinction and Gastropod Evolution The mass extinction at the end of the Permian was the largest extinction event in the history of multi-cellular animal life. An estimated 96% of marine animal species went extinct at this boundary (Raup 1979) with about 52% familial extinction (Raup and Sepkoski 1982) (fig. 1). The Gastropoda however, managed to weather the boundary with only 20% familial extinction (Erwin 1993) (fig. 2.) As such, it has been suggested that Permo-Triassic gastropods present an excellent opportunity to study the factors surrounding extinction and survival during a time of global biotic stress (Erwin 1990.) In 1973 Roger Batten discussed the nature of global gastropod faunas from Permian through Triassic time. He pointed out that the last “normal” marine gastropod faunas of the Paleozoic occurred in the Guadalupian (late Permian). These were followed by depauperate faunas consisting of low species diversity but large numbers of individuals in the latest Permian (Tatarian) and Early Triassic (Scythian). These stressed faunas consisted largely of Paleozoic gastropod genera considered to be conservative and long-ranging forms such as Worthenia, Euphemites, Glabrocingulum, Retispira, Bellerophon, Pseudozyglopleura and Donaldina in the latest Permian and Worthenia, Naticopsis, Marmolatella, Natiria, Pseudozygopleura and Hemizyga in the Early Triassic (Batten 1973). Although a few new genera evolved during the Early Triassic, Triassic taxa did not experience a significant radiation until the return of “normal” marine gastropod faunas in the Middle Triassic (Erwin 1990). It was not until this time that the modem gastropods truly began to radiate (Batten 1973, Erwin 1990). Batten also 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Number o f families 900 600 300 End Permian 52% familial extinction 200 0 600 400 Geological time (millions of years) Figure 1: Phanerozoic familial diversity curve (modified from Raup and Sepkoski 1982) 2 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Families 45 40 35 30 25 20 15 10 5 0 Early Triassic Middle Triassic Early Permian Late Permian 290 Ma 251 Ma Figure 2: Permo-Triassic gastropod familial diversity curve (modified from Erwin 1993) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. observed that there were genera that existed in the Guadalupian and in the Anisian but that were not found in the latest Permian and Early Triassic faunas. These taxa that only apparently went extinct, only to return, where later dubbed “Lazarus Taxa” by Jablonski (1986). In 1990, Erwin studied the effect of the End Permian extinctions on gastropod evolution by looking at taxonomic and broad morphologic trends from the Carboniferous to the end of the Triassic. During the late Paleozoic, gastropods experienced a significant radiation which largely increased both taxonomic and morphologic diversity, primarily due to the radiation of the Pleurotomarids. The resulting taxa were hit hard by the End Permian extinction but continued to radiate again during the Middle Triassic, only to be largely replaced by the modern gastropods towards the end of the Triassic. Erwin concluded that the End Permian extinction was not responsible for the changeover to the modem gastropod fauna, but rather served to turn back the evolutionary clock considerably. This agrees with Batten’s (1973) observations that early Triassic gastropods resembled Paleozoic gastropods rather than Permian gastropods and that Middle Triassic gastropods resembled Permian gastropods more than Jurassic gastropods. Erwin’s work on Permo-Triassic gastropods suggests that the mass extinction was not selective with regard to taxonomic structure, morphology or ecologic roles, but rather that survival was a function of geographic distribution, species richness and environmental tolerance, indicating that selectivity was very much a random process (Erwin 1985, Erwin 1989, Erwin 1990, Erwin 1993). Knowledge of Early Triassic gastropods largely comes from the faunas found in the Moenkopi formation of the Western United States, particularly the Sinbad Limestone 4 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. and Virgin Limestone members. Batten and Stokes (1986) described 16 genera and 26 species from the Sinbad Limestone which remains the most diverse described Early Triassic gastropod fauna. Almost all of described Sinbad species can be classified as microgastropods in that they measure less than 1cm. Fraiser and Bottjer (in review) studied the paleoecology of the Sinbad microgastropods and suggested that they are biotic recovery opportunists. The term opportunistic is defined as “having the ability to exploit newly available habitats or resources” (Lincoln et al. 1982). Biotic recovery opportunists are taxa that numerically dominate paleocommunities in a variety of different depositional environments around the world following a mass extinction event (Fraiser and Bottjer, in review). Part of the evidence that Early Triassic microgastropods exhibit biotic recovery opportunistic behavior is that although small gastropods exist during non-stressed times, they are never numerically dominant (Fraiser and Bottjer, in review). Fraiser and Bottjer (in review) studied this morphologic trend across the Permo-Triassic boundary. They found that gastropods were large in the Permian (only 28% of the species being smaller than 1cm), small in the Early Triassic (90% of the species being smaller than 1cm), and large again in the Middle Triassic (only 27% of the species being smaller than 1cm). In addition to the size trends quantified by Fraiser and Bottjer (in review), Early Triassic gastropods appear to be morphologically simpler relative to both Late Permian and Middle Triassic forms with regard to ornamentation (Batten 1973, Erwin 1990, Batten pers. comm. 2001) and whorl shape (pers. obs.). The goals of the current study are twofold: to document morphological trends with regard to gastropod coiling and ornamentation across the PT boundary with the hope of gaining insights into the mass 5 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. extinction selectivity and the paleoecology of the post-extinction recovery; and to propose a new method for quantifying ornamentation using the theoretical morphology approach. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Chapter 2: Theoretical Morphology SHELL MORPHOSPACE The discipline of theoretical morphology attempts to model morphologies using simple parameters with the hope of creating a morphospace in which all morphologies, both extant and unrealized, can be compared. The occupancy and vacancy of different areas of a morphospace help to elucidate evolutionary trends in morphology. The first attempt at creating a theoretical morphospace model for univalves was David M. Raup’s classic WDTS morphospace (McGhee 1999). Raup suggested that the shape of a spiral shell could be represented by four parameters (Raup 1962): S - the shape of the generating curve (e.g. the aperture of a gastropod); W - the rate of whorl expansion, namely, the increase in size of each successive whorl; D - the distance from the generating curve to the coiling axis; and T - the whorl translation rate, meaning the change in distance along the coiling axis of each successive whorl. With these four parameters, a computer can be used to produce every possible spiral shell that exhibits isometric growth, including those that have never existed in nature. Using the three parameters W, D, and T, Raup created a three dimensional morphospace which came to be known as the “Cube” (fig. 3). Using this “Cube,” Raup was able to plot the occurrences of the spiral shelled groups including the gastropods, brachiopods, pelecypods, and coiled cephalopods (Raup 1966). Equally important, the Cube graphically displayed which areas of the possible shell forms have never been realized. 7 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Most Gastropods 5 I Helicoid Forms Most Pelecypods Figure 3: Raup’s WDT “cube” (modified from McGhee 1999) 8 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. In 1990, Schindel argued that the WDTS morphospace is invalid because the parameters T and D were defined in terms of the third, W. His argument is based on a rearrangement of the equations used to describe a logarithmic curve in three dimensional space. In this space (Fig 4), there are three coordinate variables, 0, the position around a vertical line at the origin (the axis of coiling), r, the horizontal distance away from that vertical axis, and y the vertical distance down from the axis. Raup defined these coordinate variables in his landmark paper (Raup 1966) such that they mark points along a logarithmic curve defined by: where ro, yo, rc, W, T are all constant parameters and r© and y© are variables that are functions of 0 and the constant parameters, and represent the position of a point around the axis of coiling. These two equations generate the curve along which each point on the generating curve (aperture of a gastropod) spirals around the axis of coiling. However, it is important to note that W and T are constant parameters and not variables in the polar coordinate system so it is not correct to use these equations to say that T is a function of W. For example, since W and T are both constant parameters in this polar coordinate system they do not change in value during the generation of a curve in this space. That being said, Schindel’s suggested covariance in W and T can be visualized by using differential equations to describe W and T. For example, since W is the change in 0 / 2* •(1) y@=y,W@ /2n +rcTQV& /2’ 1 - \ ) .(2) 9 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Y {Coiling axis) W 2.0 initial Generating Curve (0 = 0) 2.0 1/3 (Y=0) Generating Curve after One Revolution <+) Point A is arbitrarily placed on generating curve. Increasing 0 Point B is the center of the the generating curve. Figure 4: Coordinate system used to model logarithmic spirals using Raup’s WDT model (modified from M cG hee 1999). 10 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. r with every change in 0 and T is the change in y with every change in r, they can be described by the following differential equations: dG T = d y _ dr The covariance lies in the fact that if you hold all else constant, a change in dr would cause a change in both W and T. Thus, T is not dependent on W, but may co-vary with it. However, note that a change in dr combined with a corresponding change in dy could result in a change in W but not in T. It is important to note that this implies that for any value of W there can be an infinite number of values for T and vice versa. Thus W and T can legitimately be plotted on a Cartesian coordinate system. Furthermore, W and T can be used to reproduce all logarithmically spiraled shell forms and therefore W-T morphospace occupancy still bears importance. SchindeFs criticism of the parameter D is indeed valid. He suggested that two shells whose generating curves moved away from the axis at the same rate would have different D values if they had different W values. This results from the fact that D is the ratio between the outer whorl margin and the inner whorl margin. Thus, if D is measured on corresponding whorls of two different shells whose inner margins are the same distance from the axis of coiling, but whose outer margins differ since one shell’s whorl is larger, than they would have different D values even though both whorls may move away from the axis at the same rate. Schindel suggests other very good reasons why Raup’s model is not ideal for studies of gastropod morphology. For one, there’s a lack of biological detail in this 11 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. model in that it ignores external features of shell morphology such as ornamentation. Second, there are a few logistical difficulties involving measurements. For example, in order to measure D, a gastropod must be axially sectioned (and thus destroyed) so that the axial margin of the whorl can be measured. Williamson (1981) addressed this issue by taking x-radiographs of specimens. However, as Schindel points out, sometimes there are mineral build ups on the interior of shells that can affect measurements on an x- radiograph. And lastly, Schindel argues that there is a lack of satisfying results when Raup’s model is applied to gastropods since such analyses rarely produce much variation among taxa. Schindel then proposes a new and more detailed morphospace that still requires axial sectioning. Even with the model’s problems, the WDTS morphospace, or variants thereof have been used with success on gastropods and other forms. An important example is a (1971) study of gastropod morphologic diversity by Vermeij. In his study, Vermeij was concerned with the shape of the aperture, S, rate of whorl translation T, and with the angle between the coiling axis and the plane of the aperture, E. By comparing these parameters between the Archaeograstropoda, Mesogastropoda, and Neogastropoda, Vermeij determined that the more primitive Archaeogastropods tended to have larger values of E and a corresponding small range of values of T. The two “higher” orders however experienced more morphologic range in T with their smaller values of E. These results were used to suggest that having a less elevated coiling axis allows for more potential forms in conispirally coiled shells. The purpose of the current study is to investigate any broad trends in gastropod morphology from the Late Permian to the Middle Triassic. A project of this scope 12 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. involves hundreds of described species housed in various museums around the world. Not only would it be difficult to gain access to all of these specimens, but it would be even more difficult to acquire permission to axially section these museum specimens. Furthermore, the microgastropods of the Sinbad fauna are much too small to section in any precise fashion. X-radiography works in theory, but once again the small size of the Early Triassic samples make this chore impractical, and furthermore, many of the specimens involved are internal or external casts that fail to preserve the internal architecture of the shell. Raup’s parameters W and T can be readily measured from properly oriented photographs and since this study involves previously described faunas, the Raup model was used for the analysis of shell coiling. In many gastropods, the distance from the aperture to the coiling axis, D, is zero or close to zero. For this reason and the fact that measuring for D requires axially sectioning museum specimens, D was not considered in this study. If it could be determined that a specimen had a low non-zero D value (a narrow umbilicus) the D value was assumed to be zero since any graphic reproduction of such forms using only W and T would be close approximations. If a specimen had an obvious large D value (wide umbilicus, or discoidal and planispiral forms) it was not considered for W and T since such forms can not be convincingly reproduced graphically without D values. Likewise, to measure the S parameter from a photograph, the picture must be very specifically oriented with the apertural plane in full view so that the generating curve can be measured. Since these photographs are relatively rare, S was not considered in this study. 13 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ORNAMENTATION SPACE This study introduces a new morphospace model for the quantification and analysis of shell ornamentation. Ornamentation comes in various forms and can be quite complex to describe. Following the principles of theoretical morphology, this new model reduces ornamentation space into two parameters, one representing spiral ornament, and the other representing collabral ornament. In this model, spiral ornament is considered to be any surficial feature of the whorl with relief that propagates continuously around the axis of coiling as the whorl grows. If flattened, such ornament would form a spiral on a plane. These are most often structures such as threads and cords. Since spiral ornaments propagate continuously around the coiling axis, their number and spatial distribution on the whorl remains constant. The simplified parameter SO, Spiral Ornaments, represents the number of spiral ornaments on the adult whorls of a specimen. The spatial distribution of spiral ornament on the whorl is not considered in this model. Collabral ornamentation is defined here as any surficial structure with relief that is discontinuous around the whorl and is secreted periodically with whorl growth. Often times these can be threads or cords that parallel the aperture and growth lines but they can also be nodes formed by the intersection of collabral elements with spiral elements as well as spines. The parameter CC, Collabral Cover, represents the percentage of whorl surface covered by collabral ornamentation for any given unit of spiral distance along a whorl. Direct counting like that done for Spiral Ornaments is not used for collabral ornamentation since it is difficult to see collabral elements near the periphery in photographs due to the curvature of the whorl surface. Usually CC is constant between different collabral elements, for example between cords and nodes, although CC becomes 14 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. variable when one form of collabral ornamentation is thicker, for example, large spines versus fine threads. Furthermore, it is understood that some features, such as spines or nodes, do not cover the entire vertical length of a whorl and as such, CC represents only the vertical section of the whorl that contains the ornamentation. Although this is a gross oversimplification of shell ornamentation, the purpose of this model is to quantify shell ornamentation in such a way that broad trends in ornamentation can be analyzed. This model can be used in conjunction with theoretical morphology models of shell shape in order to address the lack of biological detail pointed out by Schindel (1990). In order to develop and test this new ornament space model, the model was applied to twenty-two modem taxa using photographs and descriptions from Abbott (1974). The taxa were subjectively chosen based on ornamentation in order to fully explore the model’s strengths and weaknesses. The SO Parameter The SO parameter can often be determined directly from an author’s published description of a taxon. Such descriptions give the number of spiral ornamentations such as threads or cords found on the adult whorls. It is important to note that both parameters may vary between individuals within a species, a fact that must be kept in mind when discussing trends in ornamentation. Naturally, any shell ornamentation is best measured directly from the actual specimen, but these parameters can often be confidently determined from adequately oriented photographs. 15 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figures 5 through 10 show SO being measured from photographs of Alvania aurivillii, Calliostoma ligatum, Homalopoma luridum, Nerita versicolor, Parviturbo francesae, and Turbo cailletii respectively. Determining SO from these photographs is relatively straight forward and literally requires counting the number of spiral ornamentation present. These specimens are particularly simple and well suited for this model in that their ornamentations are uniform in size and shape and are readily visible in photographs. The CC Parameter Determining CC is somewhat less straightforward than determining SO. Once again, CC would be best measured by hand with the actual specimen, but can nonetheless be confidently determined using a favorable photograph. Two measurements are required to determine CC, both are measured parallel to the direction of whorl growth. First, CD (Cord Density) must be measured. CD represents the number of cords over the distance encompassing those cords. In these examples, CD is measured by measuring from the left edge of one collabral element to the right edge of the adjacent collabral element. Thus, CD is two elements over the distance containing both elements and gives a value in units of elements per unit measurement. Next, CW (Cord Width) must be measured. CW represents the distance containing one collabral element, in other words, the width of one collabral element in units of measurement per element. CC is then determined by multiplying CD by CW. The units of measurements and elements cancel, leaving a percentage representing the amount of collabral ornamentation cover in the distance containing two elements. 16 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 5: SO measured on Alvania aurivillii (modified from Abbot 1974) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 6: SO measured on Calliostoma ligatum (modified from Abbot 1974). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 7: SO measured on Homalopoma luridum (modified from Abbot 1974) 19 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 8: SO measured on Nerita versicolor (modified from Abbot 1974) 20 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 9: SO measured on Parviturbo francesae (modified from Abbot 1974) 21 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 10: SO measured on Turbo cailletti (modified from Abbot 1974). 22 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 11 shows CC being determined for Epitonium humphreysi. The white box in the figure surrounds two black lines. The longer line is the distance used in CD and the shorter line is the distance of CW. It is important to select an area of the last whorl that is in the forefront of the picture in order to facilitate more accurate measurements since depth related artifacts can lead to erroneous measurements. For E. humphreysi, a CC value of 0.48 means that 48% of the length of the longer black line consists of collabral elements, costae in this case. Assuming that both the rate of growth of CW and the rate of growth of the spacing between elements is the same and remains constant, then CC can be used to recreate the pattern of collabral ornamentation for the whole whorl and indeed for the whole shell. Another assumption is that the two elements measured are the same size or very close to it. Of course, the element further along in the direction of whorl growth is going to be larger. If this assumption does not hold true, or more precision is required, then CC can also be determined more accurately by measuring the widths of both elements, summing them and then dividing that value by the distance they both occupy. The math involved for both techniques is identical, but the first method assumes both elements are the same size. The reason the first method was used in this study is that for the vast majority of specimens measured, two adjacent elements are similar enough in size to be considered equal at the level of precision of the measuring device used. This rarely holds true for planispiral forms with large rates of whorl expansion in which adjacent collabral elements are significantly larger than their immediate predecessors. A more detailed discussion of how both of these parameters can be used to reproduce ornamentation occurs later in this paper. 23 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. so=o 1 ■ CD=2cords/9.73units CW=2.34u n its/cord CC=0.48 Figure 11: CC measured on Epitonium humphreysi (modified from Abbot 1974). 24 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reticulation and Related Issues Reticulation occurs when a shell contains both spiral and collabral ornamentation such that they intersect and form a web-like pattern. Figure 12 shows the SO and CC measurement for Alvania aequisculpta, a gastropod with reticulate ornamentation. In general, shells with non-zero values for both SO and CC will exhibit reticulation if the elements in question span the width and height of the whorl respectively such as with the spiral and collabral cords of A. aequisculpta. However, this generality brings up two important issues when looking at trends in reticulation and when applying the model in general. The first is that of spatial distribution of elements. For example, if there are 7 spiral cords on the base of the shell, and collabral cords or nodes cover 78% of the whorl along the upper whorl face, the spiral and collabral elements would not intersect and thus no reticulation results. Thus any study looking at trends in reticulation must look at spatial distribution of the elements on the shells in question in order to determine if it is actually reticulation being observed. Spatial distribution is discussed further in a subsequent section. The other issue that reticulation brings up is that of multiple forms of collabral ornamentation on one shell. In reticulated shells, commonly nodes form at the intersection between spiral and collabral elements. These nodes then form another set of collabral elements. Since nodes tend to be thicker than the cords that form them, their CC values will be larger than that of the interspaces between nodes. Indeed in A. aequisculpta small nodes can be seen at the intersections and those could have been measured for CC instead. This requires one to ask, “which set of collabral elements is to be measured?” This question is best answered within the context of the study being 25 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. S0=7 CD=2cords/2.93units CW=0.76units/cord CC=0.52 Figure 12: Alvania aequisculpta (modified from Abbott 1974). 26 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. undertaken. If the study is looking at the function of ornamentation, then perhaps the most protruding or visible set of collabral ornamentation should be considered. A similar issue is raised in forms such as Calliostoma fascinans, Tectarius muricatus, and Triphora decorata as seen in figures 13 through 15 respectively. Abbot (1974) described C. fascinans as having “strongly beaded cords” and T. decor ata and T. muricatus as having “rows of...beads.” Are these beads to be considered as spiral ornaments since they occur in rows, or are they collabral ornaments because they are discontinuous? Indeed, this question is raised by various forms of ornamentation including spines and nodes. Once again, the solution to this dilemma lies in the focus of the study. The model can be used to reproduce this ornamentation either way, so the issue really becomes not one of modeling, but one of data interpretation. For example, if these beads form a similar function to nodes formed by reticulation, then perhaps these structures should be treated as intersections of collabral and spiral ornaments with the interspaces between the intersections significantly reduced. In fact, both C. fascinans and T. decorata seem to have spiral and collabral cords connecting the beads. As can be seen in figures 13 through 15 , in this test study these structures were considered as both spiral and collabral ornamentation for illustrative purposes. Spatial Distribution One of the major shortcomings of this model is that it does not take spatial distribution into account. Figures 16 through 18 show three specimens (Alvania montereyensis, Astraea tecta americana, and Rissoina stricta) that illustrate the effect of spatial distribution on shell ornamentation. A. tecta americana shows a whorl surface 27 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD=2nodes/3.46units CW=1.53units/node CC=0.88 S 0= 14 Figure 13: Calliostoma fascinans (modified from Abbott 1974). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. S0=11 CD=2nodes/4.04units CW=1.74units/node CC=0.86 Figure 14: Tectarius muricatus (modified from Abbott 1974). 29 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. S0=3 CD=2nodes/3.82 CW=1.69u nits/node CC=0.88 Figure 15: Triphora decorata (modified from Abbott 1974). 30 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SO— 11 CD=2cords/1.76units CW=0.40u n its/cord CC=0.45 Figure 16: Alvania montereyensis (modified from Abbott 1974). 31 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD=2cords/3.50units CW=1.38units/cord CC=0.79 Figure 17: Astraea tecta americana (modified from Abbott 1974). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. S0=15 CD=2cords/1.90units CW=0.60units/cord CC=0.63 Figure 18: Rissoina stricta (modified from Abbott 1974). 33 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. that for the whole of the outer whorl face has no spiral ornamentation but only has collabral ribs. However, the base is completely different with a set of very finely fimbriated spiral cords. As mentioned above, an SO value of 5 and a CC of 0.79 often indicate reticulation. However, obviously in A. tecta americana there is no reticulation. Thus the model does not accurately describe the ornamentation on this shell. Once again the solution to this problem may be context sensitive. For example, since A. tecta americana has such a flat base, it may be argued that only the outer whorl face would ever be exposed and thus only the outer whorl face should be considered, in which case A. tecta americana would have an SO of 0 and a CC of 0.79. A. montereyensis and R. stricta offer a different challenge. A. montereyensis exhibits a reticulated outer whorl surface and a non-reticulated base, R. stricta exhibits a non-reticulated outer whorl surface and a reticulated base. Once again, the model parameters would suggest that both of these shells are entirely reticulate. The Trouble With Photographs As mentioned above, it is always best to do morphologic studies on actual specimens instead of photographs. However, the scope of some studies may require measuring samples from photographs. Figures 19 through 24 show six specimens (Cymatium parthenopeum, Solariella infundibulum, Sthenorytis pernobilis, Ficus howelli, Neptunea lyratalyrata, and Littorina albicarinata) that are difficult to accurately measure using photographs alone. L. albicarinata and N. lyratalyrata both contain ornamentation that is not visible in the photographs. In the case of L. albicarinata, the text can be used to supplement the 34 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD=2cords/5.90units CW=2.13units/cord CC=0.72 S0=8 Figure 19: Cymatium parthenopeum (modified from Abbott 1974). 35 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. S0=6 CD=2cords/1.82units CW=0.39units/cord CC=0.43 Figure 20: Solariella infundibulum (modified from Abbott 1974). 36 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CD=2cords/6.62units CW=2.12units/cord CC=0.64 Figure 21: Sthenorytis pernobilis (modified from Abbott 1974). 37 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. h=63.15units CD(spirai)— 2cords/1.46units SO ~hX C D {spiral) SO~87cords CD=2cords/1.12units CW=0.35 units CC=0.63 Figure 22: Ficus howelli (modified from Abbott 1974). 38 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 23: Neptunea lyratalyrata (modified from Abbott 1974). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. S0=12 CC=0 Figure 24: Littorina albicarinata (modified from Abbott 1974). 40 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. photograph since it says that between the two carinae on the outer whorl surface are six fine spiral threads (Abbott 1974). For N. lyratalyrata the text only mentions that there are also faint small spiral threads but it does not say how many. Thus L. albicarinata can be adequately described by the model from the photograph whereas N. lyratalyrata cannot unless one is to ignore the less prominent ornamentation. S. infundibulum and F. howelli both contain ornamentation that is too fine to accurately measure from photographs. The collabral threads of S. infundibulum can be seen and measured from the photograph, but the small size of the threads makes it very difficult to accurately measure. The spiral threads of F. howelli are so fine and numerous that in places they can not be seen in the photograph. An approximation is offered for SO for F. howelli in which the spiral thread density is multiplied by the apparent height of the whorl in order to approximate the number of spiral threads in the whorl. Flowever, this method is not very precise and should only be used as an approximation. S. pernobilis contains bladelike collabral ribs that are difficult to measure from the photograph since it is difficult to determine where the base of the ribs begin. Nevertheless, an attempt at a measurement was made. C. parthenopeum is a shell that seems to have some collabral undulations which are very difficult to define from the photograph. Although an attempt was made to measure them here, this type of specimen is best excluded from photograph based studies. More Complex Forms Some shell ornamentations are just too complex to be done justice using this model. Shells with large and irregular spines are one such type of shell that is best left untouched by this model. Figure 25 shows Murex beauii which, in addition to 41 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. S0=12 CD=2cords/3.43units CW=0.95 units/cord CC=0.55 Figure 25: Murex beauii (modified from Abbott 1974). 42 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. reticulation by spiral and collabral cords, has large spiny varices with wavy webs hanging from them. Although the reticulation can be readily described using this model, the varices are far beyond the reach of the model. Coloration Although not thoroughly explored here, the SO-CC model may be used for quantifying color patterns. Figure 26 shows Littorina angustior which in addition to its spiral undulations has collabral color bands. These were measured for CC in order to suggest this alternate use of the model. Modeling Ornamentation The SO-CC model can be used in conjunction with a shell coiling model to reproduce ornamented shells using a computer. Although the software needed for this purpose has not been implemented by the author as of the time of this paper, the necessary algorithms are quite commonly used in computer graphics and can be readily adopted to implement this model. Drawing ornamentation on a computer drawn shell can be readily accomplished using a procedure called texture mapping. Texture mapping is a process in which a two-dimensional image is drawn (i.e. “mapped”) onto a three- dimensional surface. In the case of ornamentation, a pattern of ornamentation would be mapped onto the surface of a modeled shell. The trick then becomes how to draw the pattern to be mapped. A very simple method for designing ornament patterns true to the intricacies of the SO-CC parameters is proposed here. As such, shells drawn with this method will have the same shortcomings 43 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CDC 0|0r — 2bands/2.87units C W ^olor=0*81 C C co!or=0.56 W Figure 26: Littorina angustior (modified from Abbott 1974). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. as those discussed for the SO-CC model above. For every unit of whorl generation, an image map will be created. The map for this unit of whorl will span the entire vertical height of the whorl and will span whatever fraction of the whorl width specified by the unit. The smaller the unit of whorl width defined for image mapping, the better the resolution of the ornamentation will be. This unit is a fraction of the whorl width and as such grows in absolute size as the whorl grows. For each unit of whorl area mapped, spiral cords will be drawn such that SO number of cords are equally sized and evenly spaced vertically on the map. As the whorl grows, the cords will grow in thickness in subsequent maps as well according to the rate of growth specified by the shell coiling model used since the unit of mapping grows as the whorl grows. Two collabral cords will be drawn for each unit by spacing them away from the margins such that their combined area covers CC of the total map width. Now a complete ornamentation unit has been created. This unit is then mapped onto the corresponding area of the modeled shell surface. If the mapping unit is too coarse, then the spiral ornaments between units will appear discontinuous since subsequent spiral cords will be significantly larger. Thus the spiral cords on a unit can be drawn such that during the course of one unit they grow to the size of the starting edge of the cords on the subsequent unit. This correction is preferred to making too fine a resolution of units since the smaller the unit, the smaller the absolute size and the larger the absolute amount of collabral ornamentation per whorl. This of course brings up a drawback of both the model and the drawing procedure. SO and CC do not specify size of ornamentation, but only address the number of ornamentation. For example, an SO of 3 can come from a shell with three very large 45 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. and closely packed spiral costae and also from a shell with three very small and openly spaced spiral threads. Likewise, a CC of 0.50 could come from a whorl with one hundred small cords and also from a whorl with two very broad spiral ribs. Furthermore, as discussed above, there are many forms of spiral and collabral ornamentation beyond spiral and collabral threads. The issue of reticulation comes up here again. Using this drawing method, any form with non-zero SO and CC values will appear reticulated even though the shells these values came from may not necessarily exhibit reticulation as discussed previously. Despite these shortcomings, the SO-CC model can produce ornamentation very similar to many shells in the fossil record. The model can be augmented with other parameters to reproduce more realistic patterns. For example, a parameter can be introduced to relate collabral cord width to whorl width so that collabral ornamentation can be scaled accordingly during drawing. Also, generalized ornamentation types can be defined such that nodes, spines, or ribs can be used instead of cords. Parameters may be introduced to specify spatial distribution of spiral and collabral elements to overcome the reticulation issue. Indeed, many parameters can be added to the SO-CC model to make it more realistic, but at some point the resulting model will leave the realm of theoretical morphology in that it will no longer seek to highlight broad scale morphologic trends, but rather will focus on highly detailed trends. The more detailed the model becomes, the more difficult it will be to apply to large numbers of specimens. One advantage of theoretical morphospace models is that they are general enough to be applied to large 46 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. scale projects involving large numbers of forms. Thus there is a trade off between the scope of applicability and realism. Interpretation o f the Test Data The data from this test study can be analyzed by making a plot such as that in figure 27. This plot shows the distribution in SO-CC space of the test fauna. This model was designed for looking at trends in ornamentation through time, but given that this data represents only one fauna from one time period, nothing can be said about changes in ornamentation. However, the data can be used to gauge how adequately the SO-CC model represents the taxa in question. It must be reemphasized that figure 27 represents a subjectively chosen set of modem taxa and is not meant to convey trends in any real modem fauna. Note first that two shells have the same SO-CC values, Calliostoma ligatum and Turbo cailletii, with an SO of 17 and a CC of 0. Comparing figures 6 and 10 it is reasonable to suggest that the two do in fact have very similar ornamentation. The next striking quality of the plot is that F. howelli alone occupies the high region of SO values with an estimated SO of 87. F. howelli does not have an unsual density of spiral ornamentation, but its large vertical whorl surface area and small spiral ornamentation make for a very high SO value. This brings up an important point when modeling using SO-CC and WDTS: modeled ornamentation is more realistic when the whorl shape (the S parameter) is taken into account. Another important feature of the plot are the two shells that plot along the SO equal to zero line, Epitonium humphreysi and Sthenorytis pernobilis with a CC of 0.48 47 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Modern Test Fauna SO-CC 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 ♦ ♦ 100 0 20 40 60 80 SO Figure 27: SO-CC plot for Modern test fauna. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. and 0.64 respectively. These CC values are somewhat similar and considering that they both have an SO of zero, their shells should show some similarity. Figures 11 and 21 show these two shells along with their similarities and differences. In terms of amount of ornamentation, these shells are indeed very similar. However, in terms of type of ornamentation, these shells are quite different. Does this invalidate the usefulness of the model? Perhaps the fact that they have similar number but different types of ornamentation is of ecological significance and can be the focus of some ornamentation study. The data also shows that there are 11 shells that may be reticulate according to the general rule discussed above. Of these, A. tecta americana does not truly exhibit reticulation, and both A. montereyensis and R. strict a contain only partial reticulation. T . decorata and C. fascinans are heavily beaded forms but have visible spiral cords that intersect at those beads and thus are in fact subtly reticulate. However, the CC values for these two forms represent the beads and thus the degree of reticulation is not accurately represented in this plot as can be said for A. montereyensis and R. stricta. T. muricatus contains rows of beads but no collabral elements joining them and as such is not reticulate. L. angustior was used as an example for modeling color and as such is not a reticulate shell. Likewise, C. parthenopeum was an example of a difficult photograph and as such nothing can be said about its collabral ornamentation from the data here. A. aequisculpta, M. beauii, S. infundibulum, and F. how elli (the lone shell in the high SO region with 87) are in fact reticulate forms although M. beauii has other ornamentation as well. 49 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Due to the nature of ornamentation modeling using the SO-CC paradigm, the region of SO-CC space off of the axes can be considered a zone of “theoretical reticulation” since values in this zone produce reticulated simulations using the method described above. Therefore, theoretical reticulation bears a different significance than actual reticulation. Actual reticulation is a descriptive term describing a pattern of ornamentation. Theoretical reticulation refers to the amount of ornamentation coverage on a shell. The further a point moves from the SO-CC origin off of the axes, the higher the amount of spiral and collabral ornamentation that point represents. Thus distance from the origin off of the axes implies more shell surface area covered by ornamentation. Any trends in such ornamentation coverage may be of functional, ecological and evolutionary significance. It is interesting to note that the area of theoretical reticulation between CC values greater than 0 and less than about 0.30 is unoccupied in this data set. Indeed, it seems qualitatively that no gastropods in Abbott (1974) contain shells that would exhibit CC values in that range (pers. obs.). Although no investigation of this has been undertaken, it can be suggested that CC values in that range are not biologically useful since they would have a minimal collabral ornament cover and the costs of secretion may outweigh the benefits of such a small amount of coverage. Summary There are many assumptions made by the SO-CC model and a number of shortcomings related to detail. However, in terms of quantifying the amount of ornamentation, the model seems to be more than adequate. Furthermore, in theoretical 50 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. morphology studies, changes in morphospace are most important. Changes in the amount of ornamentation are indeed important trends to look for in that they may have significant ecological and evolutionary implications. Of course changes in the types of ornamentation are very important as well, but that is an endeavor that may be too complicated for the realm of theoretical morphology given the vast range of ornamentation types. 51 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Chapter 3: Methods FAUNAS STUDIED Specimens for this study came from three previously described faunas. Gastropods from the Lower and Upper Permian (Wolfcampian through Guadalupian) of the Western United States were described in a series of publications by Yochelson (1956, 1960), Batten (1958, 1989), and Erwin (1985). Early Triassic specimens from the Moenkopi Formation of the Western United States were described by Batten and Stokes (1986.) Middle Triassic (Anisian through Ladinian) specimens from the Guizhou province of China were described by Yin and Yochelson (1983a, 1983b,1983c). These three Permo-Triassic gastropod faunas are the only described faunas for the interval in question. However, there are a number of undescribed Latest Permian and Early Triassic faunas that would likely alter the trends observed in this study. Although much of the Latest Permian and Early Triassic faunas, including the Moenkopi fauna used here, have been described as “stressed” faunas with morphologically simple forms (Batten 1973, Erwin 1990), these other undescribed faunas are said to contain more “normal” morphologically complex forms (Batten pers. comm. 2001). The latest Permian faunas are one from the very latest Chanxingian and another from the latest Dzulfian of Greece. In Alaska, there is said to be Permian through Middle Triassic sequences of volcanics with limestone lenses containing undescribed gastropods of complex and unusual forms (Batten pers. comm. 2001). 52 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. STAGE LEVEL STRATIGRAPHY The stage-level and Epoch assignment used in this study is that described by Erwin (1993)(fig. 28). In this classification, the Late Permian consists of the Guadalupian and Tatarian stages while the Early Permian consists of the Stages and series (namely the Wolfcamp series in the United States) below the Guadalupian, beginning with the Leonardian. Stage level data per species was determined either from direct range descriptions in the literature or by finding the stages corresponding to the formations in which the species occurred. Using this stage level data, irregardless of the ranges before the Permian and after the Triassic, the individual species were classified by epoch either as Early Permian, Late Permian, Early Triassic, or Middle Triassic. HIGHER LEVEL CLASSIFICATION The higher-level classification for the Gastropoda is currently under revision. Tracey et al. (1993) published a preliminary approximation of the new classification in the Fossil Record 2. For the sake of consistency pending the formal reclassification, the higher level classification used by the authors of each work was used in this study. SELECTION OF SPECIES All species assigned a species name were included in the database. Specimens from uncertain specific affinities (usually classified as “species a” etc. within a genus) were excluded. 53 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Age Period Epoch Stge Alternate Stages Jurassic zU U Late R haetian Norian *tn to C O Carnian Middle Ladinian Anisian n r i _ Early Scythian ZD 1 “ Tatarian Dorshamian Changxingian Late Djulfian Longtanian Guadalupian Capitanian Kazanian (Zechstein) Wordian Ufimian Kungurian Roadian Leonardian Artinskian C ro • mm— E <v Cl Early (Rotliegendes) Sakmarian Asselian oon - ZyU Carboniferous Figure 28: Stage level stratigraphy used for this study (modified from Erwin 1993). 54 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. MEASUREMENTS The majority of specimens were measured directly from photographs. Photographs were selected in which the axis of coiling could be confidently determined. Ideal photographs are ones in which the shell is oriented with the axial plane parallel to the focal plane and with the aperture showing so that the inner margin of the whorl is apparent. In these photographs, the axis of coiling is estimated as being a line connecting the apex of the shell with the portion of the columella visible through the aperture (fig. 29). Less than ideal photographs, those where the precise location of the axis is difficult to determine, could still be used but with a lesser degree of certainty. Thus it must be reemphasized that only broad-scale trends would be considered as significant in this study. The parameter T was measured following the lead of Vermeij (1970) and Thompson (1942) before him by taking the cotangent of the angle between the axis of coiling and a line (the hypotenuse) connecting two points on consecutive landmarks of adjacent whorls. This angle is referred to as theta in this study. Both Vermeij and Thompson actually used an angle a which was defined as half of the apical angle. Elowever, this angle is less precise since one side of the axis will be larger than the other depending on the direction of coiling (mostly dextral). The left side was used for dextral shells and the right side was used for sinistral shells. T represents the ratio between the distance the whorl moves down over the distance it moves out. A line perpendicular to the axis of coiling (d) drawn to the hypotenuse forms a right triangle, and since the cotangent of theta gives the ratio of adjacent over opposite, T can be exactly determined in this fashion (fig 29). These landmarks could be any whorl feature whose position on 55 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Axis Of Coiling Figure 29: Measuring for coiling geometry (modified from Batten 1958). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. the whorl remains constant during whorl growth. Typical landmarks include the middle of the selenizone, prominent spiral ornamentation, or prominent angulations forming the periphery. For forms with a high degree of whorl overlap, landmarks on preceding whorls are covered. In these instances, the suture at the periphery was chosen as the landmark. These same landmarks are then used to determine W. To do this, the line d to the axis is measured for each of the two whorls. The ratio of the distances of the larger whorl over the smaller whorl gives the rate of whorl expansion (fig. 29). Because many forms exhibit anisometric growth, only the bottom two adult whorls were measured. Largely discoidal, planispiral, largely globose and bilaterally symmetrical forms were not measured for spiral geometry. Likewise, forms where landmarks on the periphery are obscured by ornamentation, such as large spines, were not measured for spiral geometry. Ornamentation was determined from a combination of photographs and the descriptions given of the species. Commonly spiral ornamentation occurred on the base of the whorl as well as on the other whorl surfaces. When both basal and side views were available, a good estimate for SO could be drawn from the photographs. However, in some instances, the pictures did not give a complete view of ornamentation, either because not all surfaces were shown, preservation was bad and ornament did not show well on the photograph, or because the ornament was too small to be visible on a photograph. The style of description varied significantly between authors, and sometimes they described the amount of ornamentation fully. If this was the case, the data from the description was used. More often, the descriptions gave value ranges (e.g. 57 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. base contains 10-15 spiral threads) since ornamentation varies to a certain degree between individuals within a species. In these situations the median number in the range was used assuming it may likely represent an average individual. In cases where the description of ornamentation was lacking, direct counts from photographs were used. The CC parameter was determined from photographs in two parts. First a line containing two full collabral elements was measured from the leftmost edge of the leftmost element to the rightmost edge of the rightmost element. The number of elements, two, divided by the distance of the line was then determined and termed, CD, the collabral-omament density. Then the width of an individual element was measured. This number was termed, CW, the collabral-omament width. These two numbers were then multiplied together to give the percentage of the measured line that was covered by collabral elements. This dimensionless number, CC, then is the percentage of whorl covered by collabral ornamentation per unit area. The measurements from photographs were made on precise tracings of the outlines of the photographs with axis of coiling and landmarks marked. Measurements of © were made with a protractor to the tenth of a degree. Line measurements were made with a caliper to one hundredth of a millimeter. The spire indices of each species were determined from the published measurements by dividing the height by the width of each specimen. If more than one individual had been measured per species, up to five spire indices were chosen at random from the available measurements and averaged to give a representative approximation for the species. 58 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. The Early Triassic fauna from the Moenkopi Formation was studied both from the published description and from the collection at the American Museum of Natural History. Some forms were too miniscule to measure by hand, being that they were less than a few mm themselves! These tiny specimens had to be measured from the photographs. Indeed, a few could not be measured at all do to poor orientation in the photograph. All were too small to measure with calipers, but those that were not less than 2-3 mm were measured using a petrographic microscope. The samples were carefully oriented with the axial plane horizontal by noting the center of the base and orienting it at the same height with the apex. This orientation was maintained by embedding the sample in play-dough. The samples were then examined under the microscope by first aligning the vertical axis of the crosshairs with the axis of coiling and the origin at the apex. The tray was then rotated until the vertical crosshair was aligned with a line connecting two landmarks on successive whorls as was described above. The angle theta was then read directly off of the stage. The sample was then oriented such that the perpendicular connecting the landmark and the axis of coiling was aligned with the horizontal ruled axis of the crosshairs and with the origin of the crosshairs on the intersection between the axis of coiling and the perpendicular. The distance to the landmark was then measured and scaled to the hundredth of a mm using the horizontal crosshair. This was repeated for the earlier whorl. Ornamentation for these species was determined from the publication as described above. As should be apparent from the preceding methodology, the measurements used in this study were not very precise. This is a function of the nature and scope of the project. For example, it would seem obvious that the best way to do morphologic studies 59 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. is to visit the actual museum samples. This was done for the Early Triassic fauna. However, these gastropods are so small that even hands on measuring, which involved hands but a microscope, could not be very precise. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Chapter 4: Results The measurement data for Permo-Triassic gastropods used in this study can be found in the appendix. CLASSIFICATION Two hundred and thirty-six species from sixteen superfamilies of gastropods were included in this study. These superfamilies consist of the Acteonancea, Anomphalacea. Bellerophontacea, Cerithiacea, Craspedostomatacea, Euomphalacea, Loxonematacea, Murchisoniacea, Neritacea, Platyceratacea, Pleurotomariacea, Pseudophoracea, Pyramidellacea, Subulitacea, Trochacea, and the Trochonematacea. Of these, ten were represented in the Early Permian, nine in the Late Permian, six in the Early Triassic, and six in the Middle Triassic. In this data set, only the Pleurotomariacea were present in all four epochs. Of the 236 species in this database, 158 have coil geometry data, 187 have complete ornamentation data, and 135 have both ornamentation and coil data. One hundred and eighty-six have spire index data and 139 have both spire index and coil geometry data. Of the 91 genera in this data set, only one, Worthenia, is present in the Permian (Late), Early Triassic and Middle Triassic. One genus, Strobeus, was present in both the Late Permian and in the Early Triassic. Two genera, Glabrocingulum and Glyptotomaria, were present both in the Late Permian and Middle Triassic, but not in the Early Triassic and thus are considered Lazarus taxa. 61 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. FAUNAL TRENDS Coiling Geometry Spire Index and Theta Figure 30 shows spire index versus theta for 139 species grouped among the four epochs. These two measurements are not independent since they are both a function of shell height and width. Nonetheless, spire indices and theta values are plotted together for illustrative purposes. Overall, the points very closely fit a logarithmic curve, showing the relationship between the spire index and the angle theta. The curve shows that each of the four groups are distributed along the curve with significant overlap especially in the range of theta between 20 and 40 degrees. The two exceptions to this are the very low angled high spired forms which are predominantly Early Permian and the very high angled, low spired forms which are predominantly Middle Triassic. The late Permian group has the most restricted range being clustered around thetas of 20-40 degrees. W andT Figure 31 shows W versus T for the 158 species with coiling data. The data follows a power curve. Once again, each group is distributed along most of the curve with the exception of the high T low W species from the Early Permian and the low T high W species from the Middle Triassic. Most species are clustered between W values of 1 and 3. The late Permian group is very much restricted to this range. 62 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Spire Index versus Theta ♦ Early Permian ■ Late Permian a Early Triassic xJVIiddle Triassic y = -1.1929Ln(x) + 5.4592 R2 = 0.8299 0 20 40 60 80 Theta Figure 30: Spire index versus theta for Early Permian, Late Permian, Early Triassic and Middle Triassic. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. W versus T 35 30 25 20 15 10 5 0 ♦ ♦ Early Permian * Late Permian t t a Early Triassic A x Middle Triassic A v v ........ ..— .. ....... I , , . , . , . , , . . . . ! , ,................ » « J 0 y = 10.794x ■3.1959 w R = 0.6197 Figure 31: W versus T for Early Permian, Late Permian, Early Triassic and Middle Triassic. 64 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Ornamentation SO and CC Figure 32 shows SO versus CC for the 187 species with ornamentation data. Most species are located along either axis, but the middle area is predominantly Late Permian with a high degree of Early Permian and Middle Triassic forms as well. Early Triassic forms are only represented by two species in the area with both spiral and collabral ornamentation. Because of the amount of clustering on each axis, the data becomes difficult to see, so the absolute and normalized frequencies were computed for SO (fig. 33) and CC (fig. 34). Figure 33 shows that most species in three of the four groups fall into the first bin with SO values at or near zero. The exception is the Late Permian where the highest occurrence of species exhibit SO values near 20. Of the Early Permian forms that have SO values significantly greater than zero, the highest occurrence of species exhibit SO values near fifteen. For the Early Triassic species, the second highest occurrences of species exhibit either SO values near 15 or SO values near twenty. For the Middle Triassic, the second highest occurrence of species exhibits SO values near ten. Only the late Permian contains SO values higher than 30, with the highest being forty. The highest for the Early Permian is 30, for the Middle Triassic 25, and for the Early Triassic 20. Figure 34 shows the frequency data for CC. The highest occurrence for all four groups is a CC value at or close to 0. The second highest for the Early Permian is 0.7, for the Later Permian 0.5, for the Early Triassic is 0.4, 0.5, and 0.7, and 0.6 for the Middle 65 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SO versus CC 1 0.9 0.8 0.7 0.6 8 0.5 0.4 0.3 0.2 0.1 0 X ♦ ^ H * % X * ♦ X v * i . 10 20 30 SO 40 50 ♦ Early Permian ■ Late Permian A Early Triassic X Middle Triassic 60 Figure 32: SO-CC ornamentation space for Early Permian, Late Permian, Early Triassic and Middle Triassic. 66 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SO Frequency #Species 35 30 25 20 15 10 □ Early Perm ian ■ Late Perm ian ■ Early Triassic □ Middle Triassic Ik iL lflJ 0 0 5 10 15 20 25 30 35 40 45 50 □ Early Permian 29 10 5 13 8 2 2 0 0 0 0 ■ Late Permian 16 8 8 9 18 8 5 3 2 0 0 ■ Early Triassic 13 3 1 2 3 0 0 0 0 0 0 □ Middle Triassic 27 4 8 1 5 4 0 0 0 0 0 SO bins Normalized SO Frequencies 0.8 I Early Perm ian I Late Perm ian % Species ■ Early Triassic □ Middle Triassic 0.4 0.2 40 45 0.4 0.2 0.2 19 Early Permian ■ Late Permian 0.6 ■ Early Triassic 0.6 0.2 □ Middle Triassic SO Bin Figure 33: Absolute and normalized SO frequencies for Early Permian, Late Permian, Early Triassic and Middle Triassic. Bin increment is 5. 67 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CC Frequency ( 0 03 O 03 Q . ( / > I J O 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 ■ Early Permian 45 0 0 1 0 2 1 5 1 2 3 ■ Late Permian 30 0 0 4 4 12 7 4 4 2 1 ■ Early Triassic 14 0 0 0 2 2 0 2 0 1 0 □ Middle Triassic 23 0 0 0 0 2 6 2 5 2 3 CC Bin Normalized CC Frequencies < 0 . 2 2 o « a. (0 1 0.9 0.8 0.7 0.6 0.5 ■ 0.4 ; 0.3 4 0.2 I 0.1 - j | 0 | 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 □ Early Permian 0.75 0.44 o o 0 0.02 0 0.03 0.02 0.08 0.02 0.03 0.05 0.01 0 ■ Late Permian 0 0.06 0.06 0.18 0.1 0.06 0.06 0.03 0.05 ■ Early Triassic 0 6 7 0 0 0 0.1 0.1 0 0.1 0 □ Middle Triassic 0.53! 0 0 0 0 0.05 0.14 0.05 0.12 0.05 0.07 CC Bin ■ Early Permian ■ Late Permian ■ Early Triassic □ Middle Triassic B Early Permian ■ Late Permian ■ Early Triassic □ Middle Triassic Figure 34: Absolute and normalized frequencies for CC. Bin increment is 0.1. 68 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Triassic. The maximum CC value for the Early Permian, Late Permian and Middle Triassic is close to 1 and for the Early Triassic is close to 0.9. To further compare the distribution of SO and CC data among the four groups, figure 35 shows the percentage of species from each group that have SO and CC values that are both equal to zero, those that have one zero and one non-zero, and those that have both non-zero. Most Early Permian species have SO and CC values that are both zero. Most Late Permian forms have SO and CC values that are both non-zero. Most Early Triassic groups have either both values as zero or one value as non-zero. Most Middle Triassic species have one non-zero although a significant amount have both as zero. GENERIC TRENDS In order to evaluate morphologic changes in long-ranged taxa, survivor taxa and Lazarus taxa, trends within survivor and Lazarus genera were studied. Note that for each plot described below, only a fraction of the total species in each genus are shown due to the inability to acquire measurements from some of the photographs. Worthenia Worthenia is the only genus in this dataset that is present in the Permian (Late), Early Triassic and Middle Triassic. Thus, Worthenia presents an excellent opportunity to examine morphological trends within a taxon across the PT boundary and through the beginning of the recovery period. There are a total of 26 Worthenia species in this database. Of these, 13 are from the Late Permian, 11 with ornamentation data, 12 with coil geometry data, and 10 with both. Two are from the Early Triassic and both have 69 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. % S p ecies Percent Species with Degree of Ornamentation 0.6 Both 0 O ne 0 CC and SO v alu es Both > 0 ■ Early Permian ■ Late Permian ■ Early Triassic □ Middle Triassic Figure 35: Percentage o f species with SO and CC values that are both zero, one zero, and both non zero for Early Permian, Late Permian, Early Triassic and Middle Triassic.Triassic. 70 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ornamentation data but only one has coil data. Eleven are from the Middle Triassic, of which seven have ornamentation data, eight have coil data and six have both. The Worthenia species from the Late Permian, Early Triassic and Middle Triassic are shown in figures 36 through 40. Figures 41 and 42 show theta versus spire index and W versus T respectively for the species of Worthenia. No trends can be deduced from the one Early Triassic data point. However, it can be seen from the plot that the Permian Worthinids have a broader range of variation in both dimensions on both plots than that of the Middle Triassic forms. Figure 43 shows SO versus CC for Worthenia. Although all three groups exhibit a wide range of spiral ornamentation, the two Early Triassic forms have no collabral ornamentation. The Permian and Middle Triassic forms have a sub-equal number of species that lie on the horizontal axis without any collabral ornamentation. Strobeus In this database, Strobeus occurs both in the Late Permian and the Early Triassic with one species in each. Figure 45 and 46 show theta vs. SI and W versus T respectively for Strobeus. As can be seen from this plot, the Early Triassic form is somewhat higher spired than its Permian counterpart. Figure 47 shows the two species in SO-CC space. As can be seen in this plot, the Permian form has a significant amount of spiral ornamentation while the Early Triassic form has no ornamentation whatsoever. The two Strobeus species are shown in figure 44. 71 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 36: Late Permian Worthenia species (modified from Batten 1989): a. Worthenia alticarinata b. Worthenia arizonensis c. Worthenia bialveozona d. Worthenia bicarinata e. Worthenia corrugata f. Worthenia crenulata g. Worthenia kingi h. Worthenia latialveozona i. Worthenia multilineata Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 37: Late Permian Worthenia species (modified from Batten 1989) a. Worthenia pilula b. Worthenia planalveozona c. Worthenia speciosa d. Worthenia tabulata Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 75 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 38: Early Triassic Worthenia species (modified from Batten and Stokes 1986): a. Worthenia canalifera b. Worthenia windowblindensis Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A 77 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 39: Middle Triassic Worthenia species (modified from Yin and Yochelson 1983a): a. Worthenia conica b. Worthenia ecki c. Worthenia esinensis d. Worthenia extensus e. Worthenia gigas f. Worthenia hausmanni g. Worthenia ligylirae h. Worthenia nuda Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 40: Middle Triassic Worthenia species (modified from Yin and Yochelson 1983a): a. Worthenia tuberculifera b. Worthenia xui c. Worthenia zardini Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SI Vs. Theta for Worthenia ♦ Late Permian j ■ Early Triassic ! ▲ Middle Triassic 0 10 20 30 40 50 60 Theta Figure 41: Spire index versus theta for Worthenia. 1 .o 1.6 ♦ 1.4 ♦ Aa A ▲ ▲ 1.2 4 * ♦ ♦ ▲ A ♦ a ♦ 1 w 0.8 " ♦ ♦ ♦ ♦ ♦ 0.6 0.4 0.2 n 82 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. W vs. T for Worthenia Figure 42: W versus T for Worthenia. ♦ Late Permian ■ Early Triassic ▲ Middle Triassic 83 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SO vs. CC for Worthenia 1.2 1 0.8 g 0.6 0.4 0.2 0 0 5 10 15 20 25 30 35 SO Figure 43: SO-CC ornamentation space for Worthenia. ♦ Late Permian ■ Early Triassic ▲ Middle Triassic Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 44: Permo-Triassic Strobeus a. Late Permian Strobeus girtyina (modified from Erwin 1985). b. Early Triassic Strobeus paludinaeformis (modified from Batten and Stokes 1986). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. B Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SI Vs. Theta for Strobeus 10 15 20 Theta 25 30 35 ■ Late Permian A Early Triassic 40 Figure 45: Spire index versus theta for Strobeus. 87 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. W vs. T for Strobeus 2.5 1.5 ■ Late Permian ▲ Early Triassic 0.5 1.5 W 2.5 Figure 46: W versus T for Strobeus. 88 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SO Vs. CC for Strobeus ■ Late Permian A Early Triassic Figure 47: SO-CC ornamentation space for Strobeus. 89 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Glabrocingulum Glabrocingulum occurs in the Early Permian, Late Permian and Middle Triassic and as such constitutes a Lazarus taxon. There are nine Glabrocingulum species in the database, three from the Early Permian, one has ornamentation data, another has coiling data, but none has both. Three occur in the Late Permian, two have ornamentation data, two have coiling data, and two have both. Three occur in the Middle Triassic, two with ornamentation data, three with coiling data, and two with both. The Early Permian, Late Permian and Middle Triassic Glabrocingulum species are shown in figures 48 through 50. Figures 51 and 52 show theta versus spire index and W versus T for Glabrocingulum respectively. With such a small data set, no trends can be observed. However, all the points are fairly well clustered together. Figure 53 shows Glabrocingulum in SO-CC space. All the species exhibit spiral ornamentation, but collabral ornamentation is restricted to the Permian forms. It should be noted that the third Middle Triassic species of Glabrocingulum, G. regulocostata, is not shown because its spiral ornamentation could not be measured. It does however have ornament in the form of threads and costae like its contemporaries (fig. 50c). It does not have collabral ornamentation. Likewise, the Early Permian G. texanum is not shown because its collabral ornamentation is too fine to measure from a photograph. However, it would likely have a high CC value and is very much reticulated (fig. 48c). 90 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 48: Early Permian Glabrocingulum species (modified from Batten 1989): a. Glabrocingulum diablo b. Glabrocingulum lupis c. Glabrocingulum texanum Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 92 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 49: Late Permian G labrocingulum species (modified from Batten 1989): a. Glabrocingulum alveozonum b. Glabrocingulum carlsbadensis c. Glabrocingulum coronatum Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 94 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 50: Middle Triassic Glabrocingulum species (modified from Yin and Yochelson 1983a): a. Glabrocingulum joannis-austriae b. Glabrocingulum laevilineata c. Glabrocingulum regulocostata Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SI Vs. Theta for Glabrocingulum (0 Theta ♦ Early Permian ■ Late Permian ▲ Middle Triassic Figure 51: Spire index versus theta for Glabrocingulum. 97 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. W Vs. T for Glabrocingulum Figure 52: W versus T for Glabrocingulum. ♦ Early Perm ian ■ Late Perm ian ▲ Middle Triassic 98 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SO Vs. CC for Glabrocingulum 0.8 0.7 0.6 0.5 8 0.4 0.3 0.2 0.1 0 0 10 20 30 40 50 60 SO Figure 53: SO-CC ornamentation space for Glabrocingulum. ♦ Early Perm ian ■ Late Perm ian ▲ Middle T riassic 99 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Glyptotomaria Like Glabrocingulum, Glyptotomaria was present in the Early Permian, Late Permian and Middle Triassic and is thus also a Lazarus taxon. There are three species of Glyptotomaria in the dataset, one for each of the three epochs. The Early and Late Permian species have both ornamentation and coiling data, but the Middle Triassic species only has ornamentation data. The three Glyptotomaria species are shown in figure 54. Figures 55 and 56 give the coiling data for Glyptotomaria (the two samples with coiling data.) These plots show that the two Permian forms had similar general morphologies. Figure 57 plots the three Glyptotomaria species in SO-CC space. Both of the Permian forms have similar ornamentation. The Middle Triassic form has a higher degree of collabral ornamentation but less spiral ornamentation. 100 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 54: Permo-Triassic Glyptotomaria: a. Early Permian Glyptotomaria marginata (modified from Batten 1958). b. Late Permian Glyptotomariapistra (modified from Batten 1958). c. Middle Triassic Glyptotomaria triassica (modified from Yin and Yochelson 1983a). 101 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. B a ✓ * ' f * v > * • * w ■ 102 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SI Vs. Theta for Glyptotomaria 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 10 20 30 40 50 60 Theta Figure 55: Spire index versus theta for Glyptotomaria. ♦ Early Permian ■ Late Permian i Middle Triassic 103 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. W Vs. T for Glyptotomaria ♦ Early Permian ■ Late Permian Figure 56: W versus T for Glyptotomaria. 104 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SO Vs. CC for Glyptotomaria 8 SO 10 ♦ Early Permian ■ Late Permian ▲ Middle Triassic 12 14 16 Figure 57: SO-CC ornamentation space for Glyptotomaria. 105 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Chapter 5: Interpretations FAUNAL TRENDS Coiling Geometry The coiling data shows that the Gastropoda during Late Permian time occupied a wide range of shell morphotypes. The subsequent faunas continued to fill this subset of morphospace both during the post extinction stressed phase and the recovery phase. These results agree with those of Erwin (1990) who found that the mass extinction was not selective on general shell morphology. The Early Permian high spired data (high T and low theta) comes from the Subtuloida, Streptacididae, and Turritellidae (Paleozoic forms reclassified as Acanthonematidae; Tracy et al. 1993) of the United States described by Erwin (1985.) These families were hit hard by the PT mass extinction. The last occurrence of the Subtuloida is Strobeus paludinaeformis from the Sinbad Limestone of the Early Triassic (Tracey et al. 1993). Likewise the last occurrence of the Turritellidae (Acanthonematidae) is in the Middle Triassic (Anisian/Ladinian.) Lastly, the last occurrence of the Streptacididae is in the Permian of the United States. Thus, these high spired forms were decimated by the extinction whether they went extinct at the boundary or survived into the Triassic before they went extinct. It is not surprising therefore that these families are not represented in the Early and Middle Triassic faunas studied here. Subsequently, this region of morphospace went unoccupied during the Triassic intervals. The sole occupancy of the low spired morphospace by Middle Triassic forms is more likely an artifact of the measuring techniques used here. Forms with high values of 106 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. W are very difficult to measure without sectioning since subsequent whorls tend to obscure the earlier whorls. Thus, many forms with height W’s were unable to be measured and left off of the plot. These forms occurred in all of the faunas studied. Likewise, the T=0 and W>0 regions of W-T morphospace are unoccupied. This is a result of the exclusion of planispiral and bilaterally symmetrical forms described during the Permian. Some bilaterally symmetrical bellerophonts have been reported from the Early Triassic, but none have been described yet. These forms were omitted because they cannot be accurately measured from photographs. However, these forms did contribute to ornamentation data when available. Ornamentation As one travels through morphospace with higher CC coincident with higher SO, the degree of theoretical reticulation of shell ornamentation increases. The results of this study show that the theoretical reticulation morphospace was occupied during the Permian and Middle Triassic, but to the highest degree in the Late Permian (fig. 58). The Early Triassic is noticeably devoid of these morphotypes, with the exception of two species. Figures 59 through 66 show the specimens that occupied the zone of theoretical reticulation for the four epochs studied. As can be seen from the photographs, many of these shells are actually reticulate. All of them, however, bear a significant amount of both collabral and spiral ornamentation. The high degree of reticulation evidenced in the Late Permian may have been a response to predation pressures. It has been suggested that ornamentation decreases the chance of successful predation by durophagous predators since it increases the chance 107 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 58: SO-CC Breakdown for Permo-Triassic. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Early Permian SO v ersus CC ♦ Early P erm ian Late Permian SO versus CC 1 0.9 0.8 0.7 0.6 I 0.5 1 0.4 0.3 0.2 0.1 0 I ► J T 1 . A H 10 20 ■ L ate P erm ian 30 SO 50 60 Early Triassic SO versus CC 1 0.9 0.8 I 0.7 , 0.6 ' 0.5 , 0.4 0.3 ‘ 0.2 0.1 0, ▲ ▲ A Early T riassic 10 -A -A — 20 30 SO 40 50 60 Middle Triassic SO versus CC x > eee< X M iddle T riassic Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 59: Early Permian species in the zone of theoretical reticulation: a. Apachella mulensis (modified from Batten 1989). b. Baylea huecoensis (modified from Batten 1989). c. Discotomaria nodosa (modified from Batten 1958). d. Glabrocingulum lupis (modified from Batten 1989). e. Glyptotomaria marginata (modified from Batten 1958). f. Hypselentoma ornata (modified from Batten 1989). g. Lamellospira spinosa (modified from Batten 1989). h. Paragoniozona nodilirata (modified from Batten 1958). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. H 111 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 60: Early Permian species in the zone of theoretical reticulation (modified from Batten 1958): a. Phymatopleura brazoensis b. Tapinotomaria crassa c. Tapinotomaria mirabilis d. Tapinotomaria rugosa 112 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ^ s g g g r t i s t t . 113 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 61: Late Permian species in the zone of theoretical reticulation (modified from Batten 1989): a. Ambozone dictyonema b. Ananias appeli c. Ananias labrectus d. Ananias ootomaria e. Ananias permianus f. Apachella exaggerata g. Apachella franciscana h. Apachella huecoensis i. Apachella nodosa 114 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 62: Late Permian species in the zone of theoretical reticulation: a. Apachellapseudostrigillata (modified from Batten 1989). b. Callitomaria stanislavi (modified from Batten 1958). c. Eirlysia exquisita (modified from Batten 1958). d. Dichostasia complex (modified from Yochelson 1956). e. Eirlysia nodosa (modified from Batten 1958). f. Eirlysia reticulata (modified from Batten 1958). g. Euconospirapulchra (modified from Batten 1958). h. Euconospira varizona (modified from Batten 1958). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 63: Late Permian species in the zone of theoretical reticulation: a. Glabrocingulum alveozonum (modified from Batten 1989). b. Glabrocingulum coronatum (modified from Batten 1989). c. Glyptotomariapistra (modified from Batten 1958). d. Peruvispira delicata (modified from Batten 1989). e. Platyzona cancellata (modified from Batten 1989). f. Shwedagonia elegans (modified from Batten 1958). g. Spiroscalapulchra (modified from Batten 1958). h. Tapinotomaria coronata (modified from Batten 1958). i. Tapinotomaria costata (modified from Batten 1958). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. H 119 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 64: Late Permian species in the zone of theoretical reticulation: a. Tapinotomaria globosa (modified from Batten 1958). b. Tapinotomariapyramidalis (modified from Batten 1958). c. Worthenia alticarinata (modified from Batten 1989). d. Worthenia arizonensis (modified from Batten 1989). e. Worthenia corrugata (modified from Batten 1989). f. Worthenia speciosa (modified from Batten 1989). g. Worthenia tabulata (modified from Batten 1989). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 121 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 65: Early Triassic species in the zone of theoretical reticulation (modified from Batten and Stokes 1986): a. Chartonella pagina b. Kittliconcha sciaphostera 122 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A B 123 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 66: Middle Triassic species in the zone of theoretical reticulation: a. Eucycloscala binodosa (modified from Yin and Yochelson 1983b). b. Eucycloscala obliquicostata (modified from Yin and Yochelson 1983b). c. Eucycloscala spinulosa (modified from Yin and Yochelson 1983b). d. Euryalox subcancellata (modified from Yin and Yochelson 1983a). e. Fossariopsis sinense (modified from Yin and Yochelson 1983b). f. Glyptotomaria triassica (modified from Yin and Yochelson 1983a). g. Triassocirrus pichleri (modified from Yin and Yochelson 1983 c). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. D # » * M'r t. . - jw ' i ¥ ,'i -V i 1 * . , / V Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 67: Middle Triassic species in the zone of theoretical reticulation (modified from Yin and Yochelson 1983a): a. Worthenia conica b. Worthenia tuberculifera c. Worthenia xui d. Zygites elegans Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A ) B 127 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. that the predator will injure itself and/or increases the effective body size of the shell, making it harder to crush (Vermeij 1977, Palmer 1979, Bertness and Cunningham 1981). Reticulation most likely defends against predation in that it in effect adds an extra layer of shell with minimal shell material. Signor and Brett (1984) suggested that durophagous predation had been a significant evolutionary forcing since the mid-Paleozoic. Thus, it could very well be that late Paleozoic gastropods had become quite specialized in a variety of areas including anti-predatory defense mechanisms. The vacancy of this morphospace during the Early Triassic is a product of the decline of predation as a driving force in morphological design. The post extinction “stressed” fauna is composed of forms that can be described as generalists and opportunists. Both of these terms imply broad environmental tolerance and a lesser degree of specialization. Indeed, the lack of this specialized form of ornamentation supports the suggestion of Fraiser and Bottjer (in review) that the microgastropods of the Early Triassic fauna are opportunists. Fraiser and Bottjer looked at global gastropod faunas from the Permian through Middle Triassic as well as the Recent and found that microgastropod dominated faunas are restricted to the Early Triassic. Not only are these Early Triassic gastropods rare in that they are small, but also in that the fauna is composed of large numbers of individuals and small taxonomic diversity. Fraiser and Bottjer found that 49% of the gastropods from the Sinbad Limestone consisted of Naticopsis utahensis and Omphaloptychia laevisphaera (Fraiser and Bottjer in review). O. laevisphaera has SO and CC values of zero, N. utahensis has an SO of zero and a CC of 0.88 (fig. 68). Batten 128 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure 68: Most abundant Early Triassic species (modified from Batten and Stokes 1986): a. Naticopsis utahensis b. Omphaloptychia laevisphaera Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 130 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. and Stokes referred to this ornament on N. utahensis as broad collabral cords, but they appear to be growth lines. For consistency, the author’s interpretation was used. The two Sinbad forms in the zone of theoretical reticulation are extremely rare. Out of 639 individuals, Fraiser and Bottjer found approximately ten Chartonella and zero Kittlichoncha individuals. Thus the individual abundance data further supports the SO- CC faunal data reported here since the overwhelming majority of individuals in the Sinbad Limestone exhibit simple collabral ornamentation or no ornamentation whatsoever (compare to figure 35). As discussed above for the modem test fauna, the Permo-Triassic gastropods studied here are absent from the area of theoretical reticulation with CC values greater than zero and less than 0.30. This may suggest that 0.30 may pose a lower limit of what is biologically feasible for collabral cover. GENERIC TRENDS The results of the analysis of coiling morphospace for Worthenia, Glabrocingulum, Glyptotomaria, and Strobeus reveal similar patterns to that of the faunal analysis, namely that each epoch contains forms in a broad range of morphospace, although the datasets for Glyptotomaria and Strobeus, each consisting of two points, is not large enough to make any interpretations. The analysis of ornamentation space on Worthenia and Strobeus strongly support the interpretations drawn from the faunal trends. Indeed, these results indicate that the faunal trends are not solely a result of the presence of morphologically distinct higher taxa less common in the late Paleozoic, but rather are the result of selective forcings 131 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. operating on existing taxa. This is strongly evidenced by the fact that the primary occupant of the highly reticulated morphospace during the Later Permian was Worthenia. SOURCES OF ERROR Naturally, these interpretations are based on the data available. The impact of undescribed latest Permian and earliest Triassic faunas on these results is difficult to determine at this point. Elowever, it has been suggested that these faunas contain both “normal” non-stressed gastropod forms as well as morphologically complex “unusual” forms (Batten pers. comm. 2001) If this is the case, then the addition of these forms to the database would likely alter the faunal trends observed here. This may suggest that there could be significant geographical variations in Early Triassic gastropod faunas in terms of taxonomic and morphologic composition, implying that the trends observed from the Sinbad fauna are geographically restricted. However, the work of Fraiser and Bottjer (in review) has shown that the proliferation of microgastropods in the Early Triassic was a global phenomenon. Of course, this may not be the case for ornamentation space. On the other hand, gastropods from the Griesbachian of Oman, though slightly larger than the Sinbad forms, show many of the same morphological and taxonomic characteristics as those observed in the United States (pers. obs. from samples collected by Richard Twitchett, 2000) Along these lines, it is unfortunate that a Middle Triassic fauna from the United States was not included in this study, since this would help resolve questions of geographical variations. 132 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Chapter 6: Conclusions For the scope of this study, the Raup (1966) model has indeed proved adequate. The fact that there is a strong relationship in W-T space between W and T is a result of evolution, not because of an inherent covariation between W and T. The reason that we do not see forms with high T and high W values is that such a combination would result in a shell that is not ecologically practical for gastropods. Such shells would be largely uncoiled with no whorl embracement. These shells would provide little defense against predation and would be extremely difficult to balance. This is merely one example of how looking at unoccupied morphospace to see what forms have not been implemented can prove insightful to studies of evolution and functional morphology. Raup’s (1966) model combined with the SO-CC ornament morphospace suggested here can be used to model shell shape along with ornamentation. Although not all forms of ornamentation can be modeled using SO and CC, many forms of ornamentation can be confidently approximated, especially with additional parameters for the drawing procedure. This being said, it must be pointed out that Schindel (1990)was justified in saying that Raup’s (1966) model lacked biological detail. However, using Raup’s (1966) model as a base, modifications can be made to encompass other biological details, as was done here with the SO-CC ornament space and with Vermeij’s investigation of the angle of elevation of the coiling axis (Vermeij 1971). Although the resolution of the measurements made in this study is very coarse, more precise techniques can be used on physical specimens to study finer scale trends in morphospace occupancy. 133 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Erwin’s work (1990) suggests that the PT mass extinction was not selective on the basis of gross morphology. While this may be the case, the results of this study have significant paleoecological implications for the post extinction recovery. The ornamentation space results reported here support Erwin’s (1990) conclusion that the mass extinction set back the clock for the evolution of the gastropods. The Early Triassic was a time of vacant niches and those that were filled were occupied by generalist forms. As diversity returned to normal, specialization such as anti-predatory ornamentation became a competitive advantage once again. This gave rise to faunal compositions and morphologies that were reminiscent of pre-extinction times. 134 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. References Abbott, R.T., 1974. American Seashells, Second Edition. Van Nostrand Reinhold. Batten, R.L., 1958. Permian Gastropoda of the Southwestern United States: 2. Pleurotomariacea: Portlockiellidae, Phymatopleuridae, and Eotomariidae. Bulleitn of the American Museum of Natural Elistory v. 114, article 2 Batten, R.L., 1973. The Vicissitudes of the gastropods during the interval of Guadalupian-Ladinian time. In The Permian and Triassic Systems and Their Mutual Boundary, p. 596-607 Batten, R.L., 1989. Permian Gastropoda of the Southwestern United States. 7. Pleurotomariacea: Eotomariidae, Lophospiriidae, Gosseletinidae. American Museum Novitates no. 2958. Batten, R.L, and Stokes, W.M., 1986. Early Triassic Gastropods from the Sinbad Member of the Moenkopi Formation, San Rafael Swell, Utah. American Museum Novitates no. 2864 Bertness, M.D., and Cunningham, C., 1981. Crab shell-crushing predation and gastropod architectural defense. Journal of Experimental Biology and Ecology vol. 50, p. 213-230 Erwin, D.H., 1985. The Cerithiacea, Subulitacea, Pyramidellacea and Acteonacea of the Permian Basin, West Texas and New Mexico with a consideration of Permo- Triassic gastropod dynamics. Unpublished dissertation, University of California at Santa Barbara. Erwin, D.H., 1989. Regional paleoecology of Permian gastropod genera, Southwestern United States and the End-Permian mass extinction. Palaios vol. 4, p. 424-438 Erwin, D.H., 1990. Carboniferous-Triassic diversity patterns and the Permo-Triassic mass extinction. Paleobiology vol. 16 no. 2, p. 187-203 Erwin, D.H., 1993. The Great Paleozoic Crisis: life and death in the Permian. Columbia University Press. Fraiser, M.L., Bottjer, D.J., (in press). Jablonski, D., 1986. Background and mass extinctions: alternation of macroevolutionary regimes. Science vol. 231 p. 129-133 135 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Lincoln, R.J., Boxshall, G.A., Clark, P.F., 1982. A dictionary of ecology, evolution and systematics. Cambridge University Press McGhee, G.R. Jr., 1999. Theoretical Morphology: the concept and its applications. Columbia University Press. Palmer, A.R., 1979. Fish predation and the evolution of gastropod shell sculpture: experimental and geographic evidence. Evolution vol. 33, p. 697-713 Raup, D.M, 1962. Computer as aid in describing form in gastropod shells. Science vol.138, p. 150-152 Raup, D.M., 1966. Geometric Analysis of shell coiling: general problems. Journal of Paleontology v. 40 no. 5, p. 1178-1190. Raup, D.M., 1979. Size of the Permo-Triassic bottleneck and its evolutionary implications. Science vol. 206, p. 217-218 Raup, D.M., and Sepkoski, J.J., 1982. Mass extinctions in the marine fossil record. Science vol. 215, p. 1501-1503 Schindel, D.E., 1990. Unoccupied morphospace and the coiled geometry of gastropods: architectural constraint of geometric covariation? In: Causes of Evolution, R.A.Ross and W.D. Allmon, eds., University of Chicago Press, p.270-304 Signor, P.W., and Brett, C.E., 1984. The mid-Paleozoic precursor to the Mesozoic marine revolution. Paleobiology vol. 10, p. 229-245 Thompson, D’A, W., 1942. On Growth and Form, Cambridge University Press. Tracey, S., Todd, J.A., Erwin, D.H., 1993. Mollusca; Gastropoda, in The Fossil Record 2, Benton, M.J., editor. Chapman and Hall. Vermeij, G.J., 1971. Gastropod Evolution and Morphological Diversity in Relation to Shell Geometry. Journal of Zoology., London vol. 163, p. 15-23 Vermeij, G.J., 1977. The Mesozoic marine revolution; evidence from snails, predators and grazers. Paleobiology vol. 3 no. 3, p. 245-258. Williamson, P.G., 1981. Palaeontological documentation o f speciation in Cenozoic molluscs from Turkana Basin. Nature vol. 293, p. 437-43. Yin, Hong-fu and Yochelson, E.L., 1983a. Middle Triassic Gastrapoda from Qingyan, Guizhou province, China: 1-Pleurotomariacea and Murchisonianacea. Journal of Paleontology vol. 57 no. 1, p. 162-187 136 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Yin, Hong-fu and Yochelson, E.L., 1983b. Middle Triassic Gastrapoda from Qingyan, Guizhou province, China: 2-Trochacea and Neritacea. Journal of Paleontology vol. 57 no. 3, p. 515-538. Yin, Hong-fu and Yochelson, E.L., 1983c.Middle Triassic Gastrapoda from Qingyan, Guizhou province, China: 3-Euomphalacea and Loxonematacea. Journal of Paleontology vol. 57 no. 5, p. 1098-1127. Yochelson, E.L., 1956. Permian Gastropoda of the Southwestern United States 1. Euomphalacea, Trochonematacea, Pseudophoracea, Anomphalacea, Craspedostomatacea, and Platyceratacea. Bulletin of the American Museum of Natural History vol. 110, article 3, p. 173-276. Yochelson, E.L., 1960. Permian Gastropoda of the Southwestern United States 3. Bellerophontacea and Patellacea. Bulletin of the American Museum of Natural History vol. 119, article 4, p. 46-57. 137 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appendix 1: Early Permian Measurement Data Early Permian data was measured from Yochelson 1956, Batten 1958, Yochelson 1960, Erwin 1985 and Batten 1989. q o o r - O d O C O o o o o o o o so O T- « o > o <o o K5 E 0 1 A « O o o 8 c « E V c © c © ■ S © c © ■ S o o z z 8 o z 8 © T - C O T “ © h- i < D (D O S c c c c o o o o : z z z z © h - O O O W O O © < 0 © c e o o z £ 3 z * o c < 0 : % © © © c c c o o o z z z z -o c ©8©a>.g-g-g-g©® ■a*a c - o c c c c c c O O O O Q Q Q Q O O z z z z o o o o z z ® 0 © .£ c c a. o o C O Z Z ■ 5 'S 6 3 * 5 5 ■ s 6 E * 5 5 5 O « © © © . ^ o £ r . ( f l Z h h l 00 C M I © © « © .. E *S E 'S T t 88SSS ■ O T J T 3 T 3 C C C C < 0 C O (0 C O S 5 o o o .c Z Z Z h C M ■ * “ C M C M ^ « O f N t ® S © © © © 4 N 2 i n ^ ^ ^ ^ 5 2 o o a < 0 I 2 S 822 i ^ c m 0 0 0 9 O O O z z z o -c . z I- I !*g h zi : S 2 g 2 ______ .b O O O £ £ £ J C - I Z Z Z H I - H H © © 00 C O ^ o © ? s s d t * * * 1 c o o c n c o h - o ) - _ _ o o o o o a > C O C M in C M N O K) O <P C O o o 5 S S S 5 8 S © cq ^ T “ T “ t“ & 2 5 S S S 3 C O C M t- d co co a> co m co in ^ C M cd d w a> S h-inooocoinao^-cnoo CM©CO©©T-COh«COCM Cvi^NOJW ^cM CM ^^CO o o o o o o ‘ 5 o f f l « c © S 5 2 = O 3 2 ® i ® - o ^ St § -s 2 fi 3 O T > D ) E cl B W « 3 .2 c § : s £ il g li 1 If l-isil i o Q..O c * a o y h r © © © w ■ 2 x c 5 2 8 a m s © a. . 8 2 .2 o -S .E s-s © © £ 3 * 0 i f 1 1 o * r c ■ £ ■ = . * 3 o © - S I I I 1 1 1 6 3 * r a S “ c o © = : ra E aI l f 3 C m C I if! ® .E - i E I l i s s & s i . c o © w a2 2 2 § n g g 8 - g ! § § § § i i l l i g - § i 2 2 i i o g - | _ nm fflm 5‘4L.2.2.S! — — 2 S ? 5 CDCC g g g g a 2 o n n ^ ' X3- Qi:i c § .§ .§ . c o a a) id a) to to a > a > a) a > .£ 2 .£ .£ .£ 3 .£ o o 3 3 □ £ 2 2 2 — <<<<mmmmmOOOOOOOUQOQOQOQUJlijLiJOC9<9(i>(9 138 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Genus Species Spire Index Metorthonema distortus 3.53 Metorthonema sinistralis 3.27 Neiisonia laticincta 1.23 Omphalotrochus alleni Omphalotrochus cochisensis 0.891 Omphalotrochus hessensis 0.769 Omphalotrochus spinosus Omphalotrochus wolfcampensis 0.856 Orthonema columna 2.67 Orthonema illineatus 2.48 Orthonema paxillex 4.06 Orthonema pupa 2.2 Orthonema striatonodosum 3.28 Orthonema telescopium 3.24 Orthonema trlclngulata Paragoniozona nodilirata Phymatopleura brazoensis Platyzona pagoda 2.08 Platyzona rotunda 1.19 Sallya bicincta Shansiella conica 1.28 Shansiella tabulata 1.12 Sinuitina keytei Soleniscus diminutus 2.31 Soleniscus variablilis 1.96 Streptacis inflata 6.04 Streptacis pierd 3.38 Tapinotomaria crassa 1.12 Tapinotomaria duplicostata Tapinotomaria mirabllis Tapinotomaria rugosa 1.296 Tapinotomaria submirabilis Warthia crassus Warthia angustior Warthia waageni heta T W Spiral Omamen 3.7 15.5 1.07 Threads 5 11.4 1.14 None 31 1.66 2 Threads and Cords None 45 1 1.77 None 44 1.04 1.75 None None None 4 14.3 1.08 Threads 19 2.9 1.39 Thread 3.5 16.35 1.12 Threas 5 11.4 1.12 Threads 8.5 6.69 1.24 Cord 8.5 6.69 1.2 Threads 5.5 10.39 1.1 Threads Threads and Cords 37 1.33 1.75 Threads and Cords 19 2.9 1.67 Threads and Cords 32.5 1.57 2.09 Cords Lirae 26 2.05 1.44 Threads 32 1.6 1.45 Threads and Cords 12 4.7 1.35 None 28 1.88 1.43 None 2 28.6 1.03 None 8 7.12 1.27 None 35 1.43 1.65 Threads and Cords 36 1.38 1.26 Threads and Cords 20 2.75 2.02 Cords 35.5 1.4 1.44 Threads and Cords 24 2.25 1.9 Threads and Cords None None None #SO Collabral Ornament CC 3 None 0 0 None 0 Cords 0 None 0 0 None 0 0 None 0 0 Spines 0 None 0 2 None 0 1 None 0 3 None 0 4 None 0 1 Nodes 2 None 0 3 None 0 16 Cords and Nodes 0.65 22 Cords and Nodes 0.442 18 None 0 15 None 0 12 Cords 26 None 0 15 None 0 0 None 0 0 None 0 0 None 0 0 None 0 13 Cords and Nodes 0.84 16 None 0 5 Cords and Spines 0.657 13 Cords and Nodes 0.961 9 Cords and Spines 0 None 0 0 None 0 0 None 0 Appendix 2: Late Permian Measurement Data Late Permian data was measured from Yochelson 1956, Batten 1958, Yochelson 1960, Erwin 1985 and Batten 1989. C O o IA o C O o * o O ) o X ) g g ■Sf S S t i f f 2 2 e 2 8 2 2 8 E 8 8 0 0 ^ - 0 O O I O O O ' * - t - C M C M C M ■ o C C C D (0 < 0 EE 33 a > m C M C O C M o C M C M C O C M E E E 33 3 ■ o -a T 3 c c c C O C D < 0 C O < 0 < 0 ■ O - D T J ■ o T J •D O O O O f O O . C O Z O Z F Z Z F S co m C D pd C O C M C O C M C M C O C O o S in 0 5 C O G O C O C O s . O) in O C O C O C O h * G O C O N . in in o i l t i p i i i i i i s i i i l i 05 a 1 1 1 W =0 C D iS c .y C l Q . C O Q . 'Q. Q . q 2 2 C C L Q . tilSfif1 r t s L-<5. O Q. <0 » C O 3 c = = = Q - ® ® g -5 -S S. S. S.® r o r a a v < D c <<<C O O Q C D C D C SC SC D QOQOQLiJLUillliJliiUiliiUJUJ 140 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Genus Species Spire Index Euphemites exquisitus Euphemites imperator Euphemites luxuriosus Euphemites sparciliratus Glabrodngulum alveozonum 0.983 Glabrocingulum carisbadensis 0.951 Glabrodngulum coronatum 0.768 Glyptotomaria pistra 0.631 Gosseletlna permlana 0.958 Hesperiella permian us 1.29 Hesperiella wordensis 1.34 Labridens shupei 1.53 Lacunospira alta 1.11 Lacunospira altsia 1.12 Lacunospira lirata 0.904 Lamellospira dncta 0.917 Lamellospira conica 1.01 Manzanospira manzanicum 1.26 Manzanospira wordensis 1.15 Omphalotrochus obtusispira 0.743 Pemvispira delicata 1.38 Platyceras bowsheri Platyzona anguispira 1.92 Platyzona cancellata 1.59 Sallya llnsa Sallya striata 0.702 Shwedagonia elegans 0.899 Splroscala pulchra 1.42 Strobeus girtyina 1.47 Tapinotomaria coronata 1.25 Tapinotomaria costata 1.03 Tapinotomaria globosa 0.967 Tapinotomaria pyramidalis 0.976 Warthia fissus Warthia saundersi Warthia welleri Worthenia alticarinata 1.27 Worthenia arizonensis 1.22 Theta T W Spiral Ornament Lirae Lirae Liras Liras 41 1.15 1.85 Threads and Cords Threads and Cords 41 1.15 2.02 Threads and Cords 35 1.43 1.52 Threads and Cords 44 1.04 2.48 Threads and Cords 21 2.61 1.56 Threads 23 2.36 1.73 19 2.9 1.44 None 44 1.04 2.3 Cords 24 2.25 1.73 Threads 23 2.36 1.34 Threads 22 2.48 1.47 Cords 27 1.96 1.8 Threads and Cords 35 1.43 1.56 Threads and Cords 33.5 1.51 1.46 None 22.9 2.37 1.58 Threads and Cords 16 3.49 1.51 Threads and Cords 20 2.75 1.6 Threads and Cords 40 1.19 1.82 Lirae 38 1.28 1.49 None 44 1.03 1.51 Threads and Cords 30 1.73 1.37 Threads and Cords 35 1.43 1.73 Threads 32 1.6 1.56 Threads and Cords 40 1.19 1.5 Threads and Cords 31 1.66 1.59 Threads and Cords 33 1.54 1.69 Threads and Cords None None None 29.9 1.74 1.55 Threads and Cords 42 2.69 1.84 Threads and Cords #SO Collabral Ornament CC 24 18 24 6 55 Cords and nodss 0.729 30 Nodss 0.601 15 Cords and Nodss 0.54 23 Cords 0.3 Cords 0.45 0 None 0 2 None 0 10 10 None 0 10 None 0 17 None 0 0 None 0 2 Cords 0.84 20 None 0 28 Cords 0.65 20 Cords 0 Ribs 0.571 20 Cords 0.459 4 Cords 0.8 11 None 0 16 Cords and Nodes 0.336 22 Cords and Nodes 0.84 14 Cords and Nodes 0.408 35 Cords and Nodes 0.48 0 None 0 0 None 0 0 None 0 19 Cords 0.625 16 Cords 0.61 Reproduced w ith permission o f th e copyright owner. Further reproduction prohibited without permission. Genus Species Spire Index Worthenia bialveozona 1.39 Worthenia bicarinata 0.88 Worthenia corrugata 0.987 Worthenia crenulata 1.12 Worthenia kingi 0.952 Worthenia latialveozona 1.66 Worthenia multilineata 1.24 Worthenia pilula 0.82 Worthenia planalveozona 1.11 Worthenia speciosa 1 Worthenia tabulata 1.13 to Theta T W Spiral Ornament #SO Collabral Ornament c c 20 2.75 1.35 Threads and Cords 17 None 0 39 1.23 1.78 Threads and Cords Reinforced GL's 41 1.15 2.23 Threads and Cords 27 Cords 0.45 45 1 1.82 Threads and Cords 15 None 0 38 1.28 1.72 Threads and Cords 16 None 0 16 3.49 1.37 Threads and Cords 24 None 0 36 1.38 1.75 Threads and Cords 20 None 0 55 0.7 2.66 Threads and Cords 10 None 0 38 1.28 1.13 None 0 35.5 1.4 1.86 Threads and Cords 26 Cords 0.6 Threads and Cords 30 Cords 0.4 Appendix 3: Early Triassic Measurement Data Early Triassic data was measured from Batten and Stokes 1986. o ° o © E « E o 2 A 5 o © § O z <0 0 5 0 0 7 O 00 C O in o (0 C M C M 00 C O M- o C O C O C O o o o o o © • g o U - n O - n - n ^ © © © © © © © © ^ ^ c E e e E c E E E c c e e e c c e E c O Q O O O O Q Q O O O O O O O O O Q O Z O Z Z O Z O O O Z Z Z Z Z Z Z Z O O OOOQOO«-C00>OO rtor^^-co^-oooinooo i " | - i l l I 3 3 3 E t 3 T3 TJ C C C U © (0 © __ < 0 < 0 < 0 IB T3 T3 ■© f g H g tniE T 2 3 W (0 EE 33 ■ O x » c e © © C M < l^> V W (0^00 « w © w w ■ D ■g ■o ■o■g C O E © c © C © c i © c © c © c 1 © c © c © c 1 © c E s i © C © c o o o o £ o o o £ o o o £ o o £ £ o o O z z z 1 - z z z H Z Z Z H z O H H z Z 00 G O 00 in C O O) in r * « » C O r * » in h- o > C O C O C O h*. p C O h- C O cq C O p <0 "M ; C M o i T ” ■ * ” ▼ - o > C O C O O) r-» C O C O in C O m C O C O O) C M C O d M; p h- r * » C M C O r«- C O C M C O C M C M C O o h- in in C O in in in 3: in o in C O 0 > C M in in C M C O 4 < p “ C M C O C M a (0 in h- in N. C M C M 00 C M C M O) 1 .64 m a C O ^ ^ ^ C O O) 00 C O - ^ p C M O) o P p T “ 00 00 d o O) 00 d N; O J T“ 0 0 3 « o p £ 3 S-i ™ „ m I « 1 s|!l«§i ■ £ C T I 5>2 .1 3 i9<D£o9Ea<0in = j © © £ J8 © w a. < £ *5 9 in S « c o .© © ™ ® = J = .1 .1 "i £ © « , - S S 2 2 S 5 5 « 2 » » © _ »£ n . Q. 2 > ~ ^ £ w n a. a. u .u © © E ? & S U S S t t f br&K ' i ' i i l i . s i i J i g f i | | | | | l . 8 8 8« « J | l # f & 8 « 8 1 5 2 8 8 8 3 S £ E 8 e £ i I I I g O < m o 0 0 0 U 0 2 2 z z z o o c l q . S > 5 5 i C n Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Appendix 4: Middle Triassic Measurement Data Middle Triassic data was measured from Yin and Yochelson 1983a, Yin and Yochelson 1983b and Yin and Yochelson 1983c. M o t o r ( o n o o o m N C M q G O O) (D h- d ^ o d d d < o o o o d ■n o o o oo o o C O <o N * o d o co co in in m o co m co oo <o m co ^ in m o d o o d S3? a . 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Further reproduction prohibited without permission. Genus Species Spire Index Theta T W Spiral Ornament #SO Collabral Ornament CC Visdlia paudvoluta Lirae 6 None 0 Worthenia conica 1.41 32 1.6 1.74 Threads 10 Tubercles 0.96 Worthenia ecki 1.38 36 1.38 1.73 Threads and lirae 18 None 0 Worthenia esinensis 1.45 26 2.05 1.39 Threads and lirae 5 None 0 Worthenia extensus 1.36 39.5 1.21 1.7 Threads Threads Worthenia gigas 1.25 Lirae 8 None 0 Worthenia hausmanni 1 Lirae Tubercles Worthenia ligylirae 1.13 28 1.88 1.77 Lirae 13 Threads Worthenia nuda 1.1 39.5 1.21 1.77 Threads 25 None 0 Worthenia tuberculifera 1.4 27 1.96 1.47 Lirae 21 Tubercles 0.92 Worthenia xul 1.16 33.4 1.52 1.67 Lirae 7 Tubercles 0.574 Worthenia zardini 1.58 Lirae 22 Zygites elegans 0.686 Threads 20 Threads 0.872 Zygopleura arctecosta 10.9 5.19 1.44 None 0 Ribs 0.6 Zygopleura walmstedti 13 4.33 1.48 None 0 Ribs 4 ^
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University of Southern California Dissertations and Theses
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Asset Metadata
Creator
Marenco, Pedro Jose
(author)
Core Title
Morphologic trends in Permo-Triassic gastropods: A theoretical morphology approach
Degree
Master of Science
Degree Program
Geology
Publisher
University of Southern California
(original),
University of Southern California. Libraries
(digital)
Tag
OAI-PMH Harvest,paleontology
Language
English
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Digitized by ProQuest
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Permanent Link (DOI)
https://doi.org/10.25549/usctheses-c16-299209
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UC11342328
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1414849.pdf (filename),usctheses-c16-299209 (legacy record id)
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1414849.pdf
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299209
Document Type
Thesis
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Marenco, Pedro Jose
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texts
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University of Southern California
(contributing entity),
University of Southern California Dissertations and Theses
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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 au...
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University of Southern California Digital Library
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USC Digital Library, University of Southern California, University Park Campus, Los Angeles, California 90089, USA
Tags
paleontology