A morphological description of Baptemys wyomingensis and an analysis of its phylogenetic relationship within Kinosternoidea

Transcription

1 University of Iowa Iowa Research Online Theses and Dissertations Spring 2014 A morphological description of Baptemys wyomingensis and an analysis of its phylogenetic relationship within Kinosternoidea Georgia Ellen Knauss University of Iowa Copyright 2014 Georgia Ellen Knauss This thesis is available at Iowa Research Online: Recommended Citation Knauss, Georgia Ellen. "A morphological description of Baptemys wyomingensis and an analysis of its phylogenetic relationship within Kinosternoidea." MS (Master of Science) thesis, University of Iowa, Follow this and additional works at: Part of the Geology Commons

2 A MORPHOLOGICAL DESCRIPTION OF BAPTEMYS WYOMINGENSIS AND AN ANALYSIS OF ITS PHYLOGENETIC RELATIONSHIP WITHIN KINOSTERNOIDEA by Georgia Ellen Knauss A thesis submitted in partial fulfillment of the requirements for the Master of Science degree in Geoscience in the Graduate College of The University of Iowa May 2014 Thesis Supervisor: Associate Professor Christopher A. Brochu

3 Copyright by GEORGIA ELLEN KNAUSS 2014 All Rights Reserved

4 Graduate College The University of Iowa Iowa City, Iowa CERTIFICATE OF APPROVAL MASTER S THESIS This is to certify that the Master s thesis of Georgia Ellen Knauss has been approved by the Examining Committee for the thesis requirement for the Master of Science degree in Geoscience at the May 2014 graduation. Thesis Committee: Christopher A. Brochu, Thesis Supervisor Jonathan M. Adrain Walter G. Joyce

5 To my husband, Shane Hansen, and my mother, Mary Jane Knauss, who have both provided more support and love than anyone could want ii

6 ACKNOWLEDGMENTS I would like to thank my advisor, Chris Brochu, for sharing his knowledge and stellar teaching and description skills with me; my other committee members, especially Walter Joyce, for suggesting this topic and helping to develop the research plan; Jonathan Adrain for his feedback and suggestions during my research; and a number of The University of Iowa s (UI) Geoscience Department faculty, staff, and students (especially Chris Harms and Talia Karim) for constructive feedback, discussion, and assistance with administrative needs. Thanks to all those who assisted in providing information on and/or access to collections under their care, including E. Gaffney and C. Mehling (AMNH), N. Gilmore and T. Daeschler (ANSP), L. Ivy and R. Stucky (DMNS), G. Wilson (formerly DMNS), A. Resetar (FMNH), S. Shelton and D. Pagnac (SDSM), D. Brinkman (TMP), P. Holroyd and H. Hutchison (UCMP), K.de Queiroz (USNM), K. Trujillo and M. Clementz (University of Wyoming), W. Joyce (formerly YPM); and T. Adrain (UI) for helping to obtain loans. A special thanks to the land owners and land management agencies (including the BLM) that allowed fossils to be collected from their land and stored in public repositories for future paleontological research. Funding for this project was provided by the Doris O. and Samuel P. Welles Research Fund (UCMP) and The University of Iowa s Department of Geoscience Littlefield Fund. I want to thank Dean Pearson, Merle Clark, Nancy and Terry Schaffer, Don and Kathy Wilkening, and many others associated with the Pioneer Trails Regional Museum in Bowman, ND, for getting me started in the field and paleontology laboratory and being there for me over the years. Thanks to my family and friends, especially to Shane for taking care of everything, including making delicious deserts; to Avery for making me play Ashes ; to Corbin for snuggling and smiling; and to Mary Jane Knauss for being there to listen to me and travel with me regardless of my attitude. iii

7 ABSTRACT The clade Kinosternoidea consists of the extant mud and musk turtles (Kinosternidae) and the Central American river turtle Dermatemys mawii. Baptemys, an Eocene turtle taxon from North America, has historically been allied to D. mawii within Dermatemydidae, but this relationship has never been rigorously tested in a global analysis. Molecular data and multiple morphological characters support monophyly of Kinosternoidea, but kinosternids and D. mawii are vastly different in their morphology, and the relationships of Dermatemys are controversial. Dermatemys mawii is highly adapted to consuming aquatic vegetation and is thus much more similar in gestalt to some emydids than to kinosternids. Dermatemys mawii was historically placed among tortoises (Testudinoidea) by a number of traits pertaining to their fully ossified shell and the development of a secondary palate. Different placements of D. mawii indicate radically different historical biogeographic scenarios and sequences of character evolution. Few relevant morphological characters have been used in global analyses of turtle relationships, and several fossil taxa are known that could prove critical to resolving this debate. Baptemys wyomingensis is the best-sampled fossil dermatemydid. A detailed description of B. wyomingensis, along with a consideration of its phylogenetic relationships, indicates additional morphological support for a close relationship with Dermatemys and a placement for D. mawii and Baptemys within Kinosternoidea, as well as an unexpected close relationship with Hoplochelys and Agomphus to the exclusion of the Kinosternids. A review of the alpha taxonomy of Baptemys reveals that the relationships between the species, other than B. wyomingensis and B. garmanii remain unclear due to a lack of published descriptions and it appears likely that Baptemys may be paraphyletic in regard to D. mawii. iv

8 TABLE OF CONTENTS LIST OF TABLES... VII LIST OF FIGURES... VIII LIST OF ABBREVIATIONS... XIV INTRODUCTION...1 Background...3 Geology, Geography, and Environment...10 SYSTEMATIC PALEONTOLOGY...15 Baptemys wyomingensis Leidy Baptemys garmanii (Cope 1872)...19 Baptemys spp. (1)...21 Baptemys spp. (2)...21 Baptemys spp. (3)...21 MORPHOLOGY...23 Skull...23 Skull Form...24 Dermal Roofing Elements...36 Palatal Elements...42 Palatoquadrate Elements...46 Braincase Elements...49 Lower Jaws...56 Post Cranial Axial Skeleton...68 Vertebrae...68 Shell...77 Carapace Form...78 Carapace Bones...79 Carapace Scales...96 Plastron Form Plastron Bones Plastron Scutes Appendicular Skeleton Pectoral Girdle Fore limb Pelvic Girdle Hind limb PHYLOGENETIC ANALYSIS Phylogenetic Methods Results of the Phylogenetic Analysis DISCUSSION v

9 APPENDIX A DERMATEMYS MAWII PLATES APPENDIX B BAPTEMYS PLASTRON ILLUSTRATIONS APPENDIX C SUPPORTING DATA - PHYLOGENTIC ANALYSIS Materials Fossil Turtles Extant Turtles Characters Characters used in this study Characters omitted from this study Character Matrix WORKS CITED vi

10 LIST OF TABLES Table 1. Genera of the family Dermatemydidae, according to Hay vii

11 LIST OF FIGURES Figure 1. Geographic distribution of Baptemys within the Wasatchian (brown), Bridgerian (dark orange), Uintan (orange), and Duchesnean (yellow) North American Land Mammal Ages and current distribution of Dermatemys mawii (olive-green)....2 Figure 2. Relationships within the Testudines proposed by Williams (1950)....5 Figure 3. Generalized stratigraphic correlations of the geologic units (modified from Robinson et al. 2004) that have produced specimens of Baptemys Figure 4. Generalized geographic and stratigraphic ranges of Baptemys spp. (1) blue (Bourque et al. 2008), Baptemys garmanii green, Baptemys spp. (2) yellow (Lucas et al. 1989), Baptemys wyomingensis orange, Baptemys spp. (3) gray (Eaton et al. 1998) Figure 5. YPM 3754, Baptemys wyomingensis. Skull stereophotographs in dorsal and ventral views Figure 6. YPM 3754, Baptemys wyomingensis. Skull stereophotographs in posterior and anterior views Figure 7. YPM 3754, Baptemys wyomingensis. Skull sketches in dorsal (A), posterior (B), ventral (C) and anterior (D) views Figure 8. USNM 13437, Baptemys wyomingensis. Skull stereophotographs in dorsal, ventral, and anterior views Figure 9. USNM 13437, Baptemys wyomingensis. Skull sketches in dorsal (A), ventral (B), and anterior (C) views Figure 10. DMNH 511, Baptemys wyomingensis. Skull stereophotographs in dorsal and ventral views Figure 11. DMNH 511, Baptemys wyomingensis. Skull sketches in dorsal (A) and ventral (B) views Figure 12. AMNH 5967, Baptemys wyomingensis. Skull stereophotographs in dorsal, ventral, and anterior views Figure 13. AMNH 5967, Baptemys wyomingensis. Skull sketches in dorsal (A), ventral (B), and anterior (C) views Figure 14. Baptemys wyomingensis. Photographs of YPM 3754 (A), USNM (B), AMNH 5967 (C), and DMNH 511 (D) in lateral views Figure 15. Baptemys wyomingensis. Sketches of YPM 3754 (A), USNM (B), AMNH 5967 (C), and DMNH 511 (D) in lateral views Figure 16. USNM 13437, Baptemys wyomingensis. Prefrontal and frontal in dorsal (A) and ventral (B) views viii

12 Figure 17. USNM 13437, Baptemys wyomingensis. Sketches of the prefrontal and frontal in dorsal (A) and ventral (B) views Figure 18. DMNH 511, Baptemys wyomingensis, dorsal stereophotographs of the basisphenoid skull region Figure 19. DMNH 511, Baptemys wyomingensis, dorsal sketch of the basisphenoid skull region Figure 20. YPM 3754, Baptemys wyomingensis. Lower jaw sketches in dorsal (A), ventral (B), and posterior (C) views Figure 21. YPM 3754, Baptemys wyomingensis. Lower jaw stereophotographs in dorsal, ventral, and posterior views Figure 22. DMNH 511, Baptemys wyomingensis. Lower jaw stereophotographs in dorsal, ventral and posterior views Figure 23. DMNH 511, Baptemys wyomingensis. Lower jaw sketches in dorsal (A), ventral (B) and posterior (C) views Figure 24. YPM 3754, Baptemys wyomingensis. Lower jaw stereophotographs in right and left lateral views Figure 25. YPM 3754, Baptemys wyomingensis. Lower jaw in left (A) and right (B) medial views Figure 26. YPM 3754, Baptemys wyomingensis. Lower jaw in left lateral (A), left medial (B), right lateral (C) and right medial (D) views Figure 27. DMNH 511, Baptemys wyomingensis. Lower jaw photographs in left lateral (A), left medial (B), right lateral (C), and right medial (D) views Figure 28. DMNH 511, Baptemys wyomingensis. Lower jaw sketches in left lateral (A), left medial (B), right lateral (C), and right medial (D) views Figure 29. AMNH 5967, Baptemys wyomingensis. Lower jaw stereophotographs in dorsal, ventral, and left and right lateral views Figure 30. AMNH 5967, Baptemys wyomingensis. Lower jaw sketches in dorsal (A), ventral (B), left lateral (C) and right lateral (D) views Figure 31. USNM 13437, Baptemys wyomingensis. Cervical vertebrae two through five in left lateral, anterior, posterior, dorsal, ventral, and right lateral views Figure 32. USNM 13437, Baptemys wyomingensis. Cervical vertebrae six through eight in left lateral, anterior, posterior, dorsal, ventral, and right lateral views Figure 33. USNM 13437, Baptemys wyomingensis. Thoracic vertebra one in left lateral, anterior, posterior, dorsal, ventral, and right lateral views Figure 34. USNM 13437, Baptemys wyomingensis. Sacral and/or anterior caudal vertebrae (A-D) and two posterior caudal vertebrae (E-F) in left lateral, anterior, posterior, dorsal, ventral, and right lateral views ix

13 Figure 35. YPM 3754, Baptemys wyomingensis. Carapace in dorsal view Figure 36. YPM 3754, Baptemys wyomingensis. Carapace sketch in dorsal view Figure 37. USNM 13437, Baptemys wyomingensis. Carapace in dorsal view Figure 38. USNM 13437, Baptemys wyomingensis. Carapace sketch in dorsal view Figure 39. YPM 3754, Baptemys wyomingensis. Carapace right lateral view Figure 40. YPM 3754, Baptemys wyomingensis. Carapace right lateral sketch Figure 41. YPM 3754, Baptemys wyomingensis. Carapace left lateral view Figure 42. YPM 3754, Baptemys wyomingensis. Carapace left lateral sketch Figure 43. USNM 13437, Baptemys wyomingensis. Carapace right lateral view Figure 44. USNM 13437, Baptemys wyomingensis. Carapace right lateral sketch Figure 45. USNM 13437, Baptemys wyomingensis. Carapace left lateral view Figure 46. USNM 13437, Baptemys wyomingensis. Carapace left lateral sketch Figure 47. Baptemys wyomingensis. Visceral images of UCMP peripherals one through three and first costal (A) and UCMP carapace (B) Figure 48. Baptemys wyomingensis. Images of the suprapygal region of UCMP (A), ANSP (B), DMNH (C), and UCMP (D) Figure 49. YPM 3754, Baptemys wyomingensis. Plastron in ventral view Figure 50. YPM 3754, Baptemys wyomingensis. Plastron sketch in ventral view Figure 51. USNM 13437, Baptemys wyomingensis. Plastron in ventral view Figure 52. USNM 13437, Baptemys wyomingensis. Plastron sketch in ventral view Figure 53. USNM 13437, Baptemys wyomingensis. Left pectoral girdle in dorsal (A), ventral (B), posterior (C), and anterior (D) views Figure 54. USNM 13437, Baptemys wyomingensis. Left humerus in anterior (lateral) (A), dorsal (B), posterior (medial) (C), ventral (D), proximal (E), and distal (F) views Figure 55. YPM 3754, Baptemys wyomingensis. Right humerus (H) in lateral view, right ulna in medial view (U) and a cervical vertebra (V) in anterior view Figure 56. USMN 13437, Baptemys wyomingensis. Left ulna in anterior (A), dorsal (B), posterior (C), ventral (D), and proximal (E) views. Right ulna in anterior (F), dorsal (G), posterior (H), ventral (I), and proximal (J) views x

14 Figure 57. USNM (A-E), YPM 3754 (F-J), USNM (K), Baptemys wyomingensis. Right radius in anterior (A, F), dorsal (B, G), posterior (C, H), ventral (D, I), and proximal (E, J) views. Left radius in posterior (K) view Figure 58. USNM 13437, Baptemys wyomingensis. Right centrale in proximal (A), ventral (B), dorsal (C), distal (D) views Figure 59. USNM 13437, Baptemys wyomingensis. Left pelvic girdle in dorsal (A) and ventral (D) views. Right pelvic girdle in dorsal (B) and ventral (C) views Figure 60. USNM 13437, Baptemys wyomingensis. Pelvic girdle in left (A) and right (B) lateral views Figure 61. USNM 13437, Baptemys wyomingensis. Epipubis in dorsal (A) and ventral (B) views Figure 62. USNM 13437, Baptemys wyomingensis. Left femur in anterior (A), dorsal (B), posterior (C), ventral (D), proximal (E), and distal (F) views Figure 63. USNM 13437, Baptemys wyomingensis. Right tibia in anterior (A), dorsal (B), posterior (C), ventral (D), proximal (E), and distal (F) views. Left tibia in anterior (G), dorsal (H), posterior (I), ventral (J), and proximal (K) views Figure 64. USMN 13437, Baptemys wyomingensis. Right fibula in anterior (A), dorsal (B), posterior (C), ventral (D), proximal (E), and distal (F) views Figure 65. YPM 3754, Baptemys wyomingensis. Right calcaneum-astragalus in proximal (A), distal (B), dorsal (C), ventral (D), anterior (E), posterior (F) Figure 66. USMN 13437, Baptemys wyomingensis. metapodials Figure 67. USMN 13437, Baptemys wyomingensis. proximal phalanges in dorsal (A), ventral (B), and lateral (C) views Figure 68. USMN 13437, Baptemys wyomingensis, medial phalanges in dorsal (A), ventral (B), and lateral (C) views Figure 69. USMN 13437, Baptemys wyomingensis. phalanx in dorsal and ventral views Figure 70. The single most parsimonious tree resulting from the phylogenetic analysis of Kinosternoidea showing character states (synapomorphic black ovals, homoplastic white ovals) that change unambiguously. Bootstrap values are shown at each node and Bremer support is provided after the / if greater than Figure 71. The single most parsimonious tree resulting from the phylogenetic analysis of Kinosternoidea with ACCTRAN optimized character distribution showing character states that change unambiguously in black and those that change ambiguously in red xi

15 Figure 72. The single most parsimonious tree resulting from the phylogenetic analysis of Kinosternoidea with DELTRAN optimized character distribution showing character states that change unambiguously in black and those that change ambiguously in red Figure A1. USNM 66669, Dermatemys mawii. Skull in dorsal (A) ventral (B), anterior (C), posterior (D), and left lateral (E) views Figure A2. USNM 66669, Dermatemys mawii. Jaw in dorsal (A) ventral (B), right lateral (C), right medial (D), and posterior (E) views Figure A3. FMNH 98950, Dermatemys mawii. Cervical vertebrae two through five in left lateral, anterior, posterior, dorsal, ventral, and right lateral views Figure A4. FMNH 98950, Dermatemys mawii. Cervical vertebrae six and seven in left lateral, anterior, posterior, dorsal, ventral, and right lateral views Figure A5. USNM 66669, Dermatemys mawii, carapace in dorsal view Figure A6. USNM 66669, Dermatemys mawii, Carapace right lateral view Figure A7. USNM 66669, Dermatemys mawii, Carapace left lateral view Figure A8. USNM 66669, Dermatemys mawii. Plastron in ventral view Figure A9. FMNH 98950, Dermatemys mawii. Plastron in dorsal view Figure A10. FMNH 98950, Dermatemys mawii. Right pectoral girdle in ventral (A), dorsal (B), anterior (C), and posterior (D) views Figure A11. FMNH 98950, Dermatemys mawii. Forelimb. Left humerus in dorsal (A), posterior (B), ventral (C), anterior (D) proximal (E), and distal (F) views. Left ulna in anterior (G), dorsal (H), posterior (I) and ventral (J) views. Right radius in anterior (K), dorsal (L), posterior (M) and ventral (N) views Figure A12. FMNH 98950, Dermatemys mawii. Right centrale in proximal (A), ventral (B), dorsal (C), distal (D) views Figure A13. USNM 66669, Dermatemys mawii, Pelvic girdle in right lateral (A), left lateral (B), dorsal (C), and ventral (D) views Figure A14. FMNH 98950, Dermatemys mawii. Hindlimb. Left femur in anterior (A), dorsal (B), posterior (C), ventral (D), proximal (E), and distal (F) views. Left tibia in anterior (G), dorsal (H), posterior (I) and ventral (J) views. Left fibula in anterior (K), dorsal (L), posterior (M) and ventral (N) views Figure A15. FMNH 98950, Dermatemys mawii. Right calcaneum-astragalus in proximal (A), distal (B), dorsal (C) and ventral (D) Figure B1. Sketches of select Baptemys wyomingensis plastra ANSP (A), UCMP (B), UCMP (C), AMNH 5967 (D), UCMP (E), UCMP (F), UCMP (G), UCMP (H), DMNH 511 (I) in ventral view xii

16 Figure B2. Baptemys garmanii, Sketches of select plastra YPM PU (A), AMNH 6109 (B), AMNH 6110 (C), UCMP (D), UCMP (E), UCMP (F) in ventral view xiii

17 LIST OF ABBREVIATIONS Institutional Abbreviations: AMNH: American Museum of Natural History, New York City, New York ANSP: Academy of Natural Sciences, Philadelphia, Pennsylvania DMNS (DMNH): Denver Museum of Nature and Science (previously Denver Museum of Natural History), Denver, Colorado FMNH: Field Museum of Natural History, Chicago, Illinois SDSM: South Dakota School of Mines, Rapid City, South Dakota UCM: University of Colorado Museum, Boulder, Colorado UCMP: University of California Museum of Paleontology, Berkeley, California UMMP: University of Michigan Museum of Paleontology, Ann Arbor, Michigan USNM: United States National Museum, Washington, D.C. YPM: Yale Peabody Museum of Natural History, New Haven, Connecticut Anatomical Terms: AB acet acp am AN ani apo art abdominal acetabulum acromion process area articularis mandibularis anal apertura narium interna antrum postoticum articular xiv

18 ast astragalus AXL axial bictb bicipital tubercle bo bs c calc basioccipital basisphenoid costal calcaneum capit capitellum cc ccc ccp ccr canalis cavernosus canalis caroticus cerebralis canalis caroticus palatinum cavum cranii CER cervical cl cm co cor cp cpt cptf cavum labyrinthicum condylus mandibularis condylus occipitalis coracoid coronoid process crista pterygoideus caput femur cpth caput humerus cr cro commissural ridge coronoid crso crista supraoccipitalis den dentary denp dentary pocket dk dorsal keel xv

19 ectf ent epi ex ectepicondylar foramen entoplastron epiplastron exoccipital faccc foramen anterius canalis carotici cerebralis faccp foramen anterius canalis carotici palatinum faf fai fd FE fe fibc fossa acustico-facialis foramen alveolaris inferior foramen dentofaciale majus femoral fissura ethmoidalis fibular condyle fibep fibular epicondyle fic fim fio fio fjp fm fmk fn foramen intermandibularis caudalis foramen intermandibularis medius foramen intermandibularis oralis foramen interorbitale foramen jugulare posterius foramen magnum fossa Meckelii fossa nasalis fnab foramen nervi abducentis fnac foramen nervi acustici fnat fnf fnh fnt foramen nervi auriculotemporalis foramen nervi facialis foramina nervi hypoglossi foramen nervi trigemini xvi

20 fo fon fp fossa orbitalis foramen orbito-nasale foramen praepalatinum fpcci foramen posterius canalis carotici interni fpct fpp fpt fr fti fts gf foramen posterius chorda tympani foramen palatinum posterius fenestra postotica frontal fossa temporalis inferior fossa temporalis superior glenoid fossa GUL gular HUM humeral hyo hyoplastron hypo hypoplastron ica incisura columellae auris ilnch ilial notch IM inframarginal ING inguinal intbf intertubercular fossa intrf intertrochanteric fossa ju lar lp M mp jugal labial ridge lateral process of the humerus marginal medial process of the humerus mtishp metischial process xvii

21 mx mxt n nc nuc maxilla maxillary tooth neural neural canal nuchal olec olecranon op pa pal par pcl opisthotic parietal palatine processus articularis processus clinoideus pctp pectineal process of the pubis per pf peripheral prefrontal pipa processus inferior parietalis PL pm po plural premaxilla postorbital pozg postzygapophysis pp processus paroccipitalis ppte processus pterygoideus externus pr pra prootic prearticular przg prezygapophysis pt pto py pterygoid processus trochlearis oticum pygal xviii

22 qu qu rb scm sc scp sf so spy st sq sur svo tbo thlp tibc quadrate quadratojugal rostrum basisphenoid sulcus cartilaginis Meckelii sulcus cavernosus scapula sulcus olfactorius supraoccipital suprapygal sella turcica squamosal surangular sulcus vomeri tuberculum basioccipitale thelial process of the ilium tibial condyle trmj trochanter major trmn trochanter minor troc trpo V vk vo xi trochlea transverse process vertebral ventral keel vomer xiphiplastron xix

23 1 INTRODUCTION Baptemys wyomingensis Leidy 1870, a dermatemydid, is one of the largest (carapace length mm; plastral length mm) and most common turtles known from the middle Eocene, Bridgerian NALMA (North American Land Mammal Age), of North America and closely resembles the only extant member of the clade, Dermatemys mawii Gray 1847, a riverine turtle with a range limited to southern Mexico, Guatemala, and Belize (Figure 1). In addition to B. wyomingensis, all taxa along the stem of D. mawii are late Paleocene-Eocene fossil taxa currently classified as Baptemys. Representatives of Baptemys have been documented from Texas to North Dakota, within the central portion of the United States. The oldest published occurrence of Baptemys is from the late Clarkforkian or earliest Wasatchian NALMA of the Big Horn Basin, Wyoming, and the youngest representatives have been reported from the Duchesnean NALMA of Sevier Plateau, Utah (Figure 1). Baptemys wyomingensis is often used for fossil dermatemydid specimens regardless of appropriateness, because it is the type species known to be common in wellsampled Eocene deposits (i.e., Bridger Formation), and the alpha taxonomy of fossil dermatemydids has not been well described in the literature. Complete and comprehensive morphological descriptions are imperative for constructing and testing phylogenetic hypothesis, studying biostratigraphy, and environmental changes. Therefore, the information presented here is three fold: 1) to summarize the alpha taxonomy of Baptemys, 2) to present a detailed morphological description of the type species B. wyomingensis, with comparisons to D. mawii and other kinosternoids, and 3) to place B. wyomingensis in a phylogenetic context and review the relationships within Kinosternoidea.

24 Figure 1. Geographic distribution of Baptemys within the Wasatchian (brown), Bridgerian (dark orange), Uintan (orange), and Duchesnean (yellow) North American Land Mammal Ages and current distribution of Dermatemys mawii (olive-green). 2

25 3 Background Our understanding of the relationships within Testudines has changed significantly over the years due to the incorporation of explicitly defined morphological characters, specifically synapomorphies, into phylogenetic analysis and advancement in molecular data use in phylogenetic analyses. For instance, the classification by Williams (1950) (Figure 2) included the families Dermatemydidae, Testudinidae, and Chelydridae (Kinosterninae, Staurotypinae, Chelydridae) within the superfamily Testudinoidea. According to Meylan (1987), Williams (1950) used plesiomorphic or homoplastic characters to include Kinosternidae within Testudinoidea. Additional phylogenetic analyses, which included characters derived from the skull, cranial arteries, pelvic girdle, hind limb, and shell (Albrecht 1979; Gaffney 1975, 1979, 1984; Gaffney and Meylan 1988; McDowell 1961; Meylan 1987; Meylan and Gaffney 1989; Zug 1971) showed Williams (1950) reconstruction of Testudinoidea to be polyphyletic, and they instead supported the monophyletic clade Trionychoidea (Kinosternoidea + Trionychia). The monophyly of Trionychoidea has been questioned, and the primary morphological characters supporting the Trionychoidea clade are cranial characters that have since been shown not to be homologous (Jamniczky and Russell 2004, 2007). Only one unambiguous character, the palatine contribution to anterior extension of lateral braincase wall, unites the clade (Joyce 2007). In addition, two separate molecular analyses based on an intron from the RNA fingerprint protein 35 and mtdna (cytochrome b and 12s rdna) support a polyphyletic Trionychoidea (Fujita et al. 2004; Shaffer et al. 1997, respectively), with Trionychia (Trionychidae + Carettochelyidae) as sister to the remaining Cryptodira. More recent molecular studies (e.g., Krenz et al. 2005; Barley et al. 2010) have suggested that Chelydridae and Kinosternoidea are sister taxa. Interestingly, this relationship (although excluding D. mawii) was recognized in early morphological classifications (by Gray e.g., 1869, 1870). Baur (1893) coined the term Chelydroidea to unite chelydrids and kinosternoids, including D. mawii, based on the

26 4 following seven traits: no parietal/squamosal contact, foramen palatinum posterius present and located between the palatine and maxilla, one biconvex cervical, articular surface between the sixth and seventh cervicals not platycoelous, raised pedestal on the visceral surface of the nuchal for articulation with the eighth cervical vertebra absent, costiform process present, a complete series of inframarginals. Williams (1950), who also favored this phylogenetic arrangement, added an additional trait, a procoelous eighth cervical, to the list (Figure 2). This classification was previously abandoned due largely to the same cranial features with questionable homologies mentioned above that unite trionychoids with kinosternoids (Meylan and Gaffney 1989). In addition, if the detailed character matrix of Joyce (2007) is mapped on to the topology of Barley et al. (2010), many of the characters occur in basal chelonioids as well and thus must be considered symplesiomorphies. Of the previously recognized traits uniting Kinosternoidea and Chelydridae the only unambiguous synapomorphy is the presence of a true costiform processes (not homologous with the structure found in Trionychidae with the same name; see Joyce 2007 for a discussion). In addition, from a time and geographical standpoint, a close relationship between Kinosternoidea and Chelydridae is more parsimonious than the previously proposed Trionychoidea (Kinosternoidea + Trionychia). The earliest chelydrids or stem-chelydrids that have been reported are from the Campanian of Mexico (Brinkman and Rodriguez de la Rosa 2006, Brinkman 2005, Hutchison et al. 1998), and even older fossils from the Santonian of Canada (Brinkman 2003) and Turonian of Utah (Eaton, Cifelli, et al. 1999) have been noted; similarly, the earliest kinosternoids have been reported from the Campanian of Mexico and Utah (Brinkman and Rodriguez de la Rosa 2006; Hutchison et al. 1998). Since the earliest known specimens of both Kinosternoidea and Chelydridae are from the Campanian of Central America (Brinkman and Rodriguez de la Rosa 2006) and other more complete but advanced representatives are from the United States this is congruent with an origination for this clade in the Western Hemisphere whereas the

27 5 earliest stem-trionychids are from the Barremian, Middle Cretaceous, of Japan (Nakajima et al. 2009, Hirayama 2002). Figure 2. Relationships within the Testudines proposed by Williams (1950).

28 6 In addition, from a time and geographical standpoint, a close relationship between Kinosternoidea and Chelydridae is more parsimonious than the previously proposed Trionychoidea (Kinosternoidea + Trionychia). The earliest chelydrids or stem-chelydrids that have been reported are from the Campanian of Mexico (Brinkman and Rodriguez de la Rosa 2006, Brinkman 2005, Hutchison et al. 1998), and even older fossils from the Santonian of Canada (Brinkman 2003) and Turonian of Utah (Eaton, Cifelli, et al. 1999) have been noted; similarly, the earliest kinosternoids have been reported from the Campanian of Mexico and Utah (Brinkman and Rodriguez de la Rosa 2006; Hutchison et al. 1998). Since the earliest known specimens of both Kinosternoidea and Chelydridae are from the Campanian of Central America (Brinkman and Rodriguez de la Rosa 2006) and other more complete but advanced representatives are from the United States this is congruent with an origination for this clade in the Western Hemisphere whereas the earliest stem-trionychids are from the Barremian, Middle Cretaceous, of Japan (Nakajima et al. 2009, Hirayama 2002). In a review of basal chelydrids and kinosternoids additional characters supporting Chelydroidea were revealed. These characters are all plastral and include 1) reduced abdominal scales that do not contact one another along the midline (except in A. pectoralis), 2) plastron extremely reduced in size and greatly thickened along the midline and along the bridge, and 3) inframarginal series reduced in number to three, but complete across the bridge, thereby limiting contact between the other plastral scales and the marginals. Chelydroidea can thus be identified using these four (1-3 listed immediately above and the elongated costiform process mentioned earlier) unambiguous morphological synapomorphies. It is anticipated that additional detailed morphological descriptions; associated phylogenetic analysis of early chelydrids including Protochelydra zangerli Erickson 1973, Denverus middletoni Hutchison and Holroyd 2003, Tullochelys montana Hutchison 2013, and Emarginochelys cretacea Whetstone

29 7 1978; and future early chelydroid discoveries, will add additional support to Chelydroidea, but this is beyond the scope of this study. Gaffney and Meylan (1988) coined the term Kinosternoidae for the clade, which includes Dermatemydidae, Hoplochelys, and Kinosternidae. Although the close relationships of these taxa were acknowledged in earlier phylogenies (Gaffney 1979; 1984; Hutchison and Bramble 1981) the clade was not formally named at that time. In 2004, Joyce and colleagues modified the term to Kinosternoidea and, as currently conceived, this clade includes the extant mud and musk turtles (Kinosternidae) and the Central American river turtle D. mawii. Kinosternids are semi-aquatic and currently range from southeastern Canada to southern Brazil. Dermatemys mawii is riverine with a range restricted to southern Mexico, Belize, and Guatemala (Vogt et al. 2011). Like their modern day counterparts, kinosternoid fossils have been discovered only in the Americas, indicating that this clade has been restricted historically to the western hemisphere. Kinosternids and D. mawii are vastly different in their morphology. Dermatemys mawii is highly adapted to consuming aquatic vegetation and is thus much more similar in gestalt to emydids with equivalent diet preferences than to kinosternids. Yet, D. mawii possesses morphological characteristics (four inframarginals) that were long known to be primitive, thus seeming to support the phylogenetic distinctness of this taxon. Morphologic characters of the skull, vertebrae, and shell nevertheless support the sister group relationship of Kinosternidae and D. mawii. Molecular data (e.g., Fujita et al. 2004; Shaffer et al. 1997) give additional support to Kinosternoidea by placing D. mawii as the closest living relative of the extant kinosternids in global analyses. Interestingly, due to varying ideas regarding phylogeny and classification, the application of the name Dermatemydidae has changed vastly over time. Originally Dermatemydidae was defined by Hay (1908) as a class of turtles diagnosed by the presence of four inframarginals (including fossil genera from the late Cretaceous through the Oligocene and 3 Recent genera, Table 1), but to the exclusion of numerous turtles that

30 8 exhibit this trait as well, particularly Chelonioidea, Pleurodira, and Platysternon megacephalum. Later Dermatemydidae was referred to as a wastebasket taxon (Hutchison and Archibald 1986). Today Dermatemydidae is restricted to the smallest possible monophyletic group that includes D. mawii, but not any representative of any other typically recognized turtle family. According to our current understanding of turtle phylogeny, Dermatemydidae thus includes only the extinct Cenozoic taxon Baptemys wyomingensis and the extant Central American river turtle D. mawii (Gaffney and Meylan 1988; Joyce et al. 2004). The removal of the majority of the genera from Dermatemydidae has caused and continues to cause confusion in the literature because the biogeographic distribution, the geologic range (Hutchison 1982; Hutchison 1998; Hutchison and Archibald 1986), and morphological synapomorphies (Hutchison and Bramble 1981) of Dermatemydidae are now different. This distinction has not yet been realized or accepted by all, and some papers continue to refer to the Dermatemydidae in the old, non-monophyletic context (Vogt et al. 2011). In his description of B. wyomingensis Leidy (1870) noted the similarities between B. wyomingensis and D. mawii, including a similar shell size (45 cm long and 30 cm Table 1. Genera of the family Dermatemydidae, according to Hay Age Recent Genera Pleistocene None Pliocene Miocene Oligocene Eocene Cretaceous Dermatemys, Staurotypus, Claudius None None Xenochelys, Anosteira? Anosteira, Baptemys,?Pseudotrionyx, Kallistira, Notomorpha, Alamosemys, Hoplochelys Adocus, Homorophus, Zygoramma, Agomphus, Compsemys, Basilemys

31 9 wide) and shell shape as well as elongation of the vertebral plates and scutes. Leidy (1870) not only recognized the close relationship between B. wyomingensis and D. mawii, but also noted the similarities of both to extant kinosternids, including three characters observed in the type of B. wyomingensis related to plastron proportion and shape (interspaces of the carapace and plastron, plastron pedicle depth, and posterior end of the plastron) that are intermediate between those observed in D. mawii and the extant kinosternid Staurotypus. Species attributed to Baptemys range stratigraphically from the Wasatchian into the Duchesnean NALMAs (Eaton, Hutchison et al. 1999, Estes 1988, Hay 1908, Hutchison 1980, Hutchison 1998, Holroyd et al. 2001, Lucas et al. 1989, Zonneveld et al. 2000). These species, of which at least two remain unnamed, included Baptemys spp. from the earliest Wasatchian, B. garmanii (including B. tricarinata) from the mid-late Wasatchian, Baptemys spp. from the earliest Bridgerian, B. wyomingensis (including B. fluviatilis) from the Bridgerian and Uintan, and Baptemys spp. from the Duchesnean (see Systematic Paleontology for further discussion). Of the species currently placed within Baptemys, the type species B. wyomingensis is the most common within museum collections and published papers. This may be in part due to the result of incorrect assignment. Zonneveld and colleagues (2000) mentioned that species identification of Baptemys is problematic because of poorly understood systematics, an issue that has been noted for more than thirty years (Gaffney 1979, Hutchison 1980). Additional prior detailed morphological descriptions of Baptemys are limited to Hay s (1908) description of B. fluviatilis and B. tricarinata (which have been informally synonymized with B. wyomingensis and B. garmanii respectively) and his review of B. wyomingensis. Estes (1988) published a brief description and an image of a skull, which was identified as B. garmanii (recognized as B. tricarinata as that time) based on morphological characters of shell material found at the same locality. The first detailed description of D. mawii was published by Bienz (1895) based on a slightly non-typical

32 10 specimen of D. mawii. Since that time comparisons between D. mawii and other Testudines have resulted in detailed descriptions of specific morphological features. For example, Pritchard (1988) studied the neural scute count and morphology among living turtles, Zug (1971) studied the pelvic girdle and hind limb morphology, and Hutchison and Bramble (1981) studied plastral scute patterns. While no recent morphological studies have looked at variation within D. mawii, a recent phylogeographic analysis using molecular data discovered that the sequence divergence between lineages is high enough to represent species-level differences in other taxa (Gonzalez-Porter et al. 2011). Geology, Geography, and Environment The majority of known Baptemys specimens were collected in Wyoming from the Greater Green River, Wind River, and Big Horn Basins (Figure 1 and Figure 3). The high numbers of specimens available for study is, in part, a result of the long history of paleontological field expeditions that have concentrated on the well-known expansive badland exposures, fossil-rich horizons, and large swaths of pubic lands within these basins. The type specimens of B. wyomingensis and B. garmanii and a number of reference specimens (see Systematic Paleontology for a list) were collected during early expeditions that began in the late 1800s to these areas and were led or funded by eastern institutions such as AMNH, YPM, PU, and USNM. While there is a long history of fossil collecting in these areas, more recent detailed studies undertaken in these intermountain basins to document environmental changes and the impact of these changes to Paleogene fauna and flora (e.g., Aubry et al. 1998; Gingerich 1980, 2001; Gunnell 2001; and papers within) have greatly increased the fossil collections of numerous institutions (i.e., UCMP, DMNS, UMMP, University of Florida, UCM). Turtles thrived in North America during the Eocene (Hay 1908; Hutchison 1980, 1982; Hutchison and Archibald 1986); in part this has been hypothesized to be a result of increased warming, equable climates (Estes and Hutchison 1980; Hutchison 1982; Wing

33 11 et al. 1991, Wing and Greenwood 1993), and numerous intermountain basins (i.e., H2O trap) (Lillegraven and Ostresh 1988). Published and unpublished occurrences of Baptemys outside Wyoming are rare and often fragmentary. At this time, non-wyoming occurrences are limited to North Dakota (Williston Basin; B. garmanii Estes 1988), New Mexico (Sierra Blanca Basin; Baptemys spp. (2) Spencer et al. 1989), Utah (Sevier Plateau; Baptemys spp. (3) Eaton, Hutchison, et al. 1999), Colorado (Piceance Creek Basin; i.e., UCM 9659 Baptemys sp. and Sand Wash Basin; B. wyomingensis Stuckey et al and DMNH 511), and Texas (Gulf Coastal Plain; Baptemys sp. Westgate 1989). All geologic units producing Baptemys were deposited in fluvial and/or lacustrine settings and consist primarily of sandstone and mudstones. These include the Golden Valley Formation (Williston Basin); the Willwood Formation (Big Horn Basin); the Lysite and Lost Cabin Members of the Wind River Formation (Wind River Basin); the Luman Tongue and unnamed members of the Green River Formation, the Cathedral Bluffs Tongue, La Barge Member, and the Main Body of the Wasatch Formation, the Blacks Fork (also documented as Bridger B) and Twin Buttes (including Bridger C) Members of the Bridger Formation, and the Washakie Formation (Great Green River Basin); the Brian Head Formation (Sevier Plateau); the Cub Mountain Formation (Sierra Blanca Basin); and the Laredo Formation (Gulf Coastal Plain). Generalized stratigraphic correlations for these units are illustrated in Figure 3. To date, no occurrences have been documented within the Eocene deposits including the Green River, Uinta, and Duchene River Formations of the Uinta Basin, Utah, which is unexpected due to the high number of fossils that have been collected. While collecting and taphonomic biases may impact taxon presence and absence this seems unlikely in well-sampled intervals such as the Uinta Formation in the Uinta Basin, but is quite possible in other areas with Eocene exposures. The environmental settings of the geologic units noted above and the morphologic similarities with D. mawii indicate that B. wyomingensis likely preferred the same (or similar) environmental conditions that

34 Figure 3. Generalized stratigraphic correlations of the geologic units (modified from Robinson et al. 2004) that have produced specimens of Baptemys. NOTE: Each number refers to occurrences of Baptemys spp. (1) (oval), B. garmanii (square), Baptemys spp. (2) (hexagon), B. wyomingensis (circle), Baptemys spp. (3) (triangle), and Baptemys sp. (no shape) within the associated formation. Information for these placements is specimen and/or literature based (locality numbers provided in parentheses if available): 1 - Bourque et el. 2008; 2 - UCMP (V99713), also Holroyd et al. 2001, Hutchison 1980; 3 - USNM 4129, UCMP (V70249), UCMP (V78131), UCMP , , and (V74024), UCMP and UCMP (V78131), UCMP (V70252); 12

35 NOTE (Figure 3, continued): 4 - YPM PU (also in Estes 1988); 5 - UCMP (V88002), UCMP (V70270); 6 - UCMP (V77065); 7 - AMNH 6110; 8 - UCMP (V80129); 9 - UCMP AMNH 6109, UCMP (V76208), UCMP (V76209), UCMP (V84228), UCMP and (V73064); UCMP (V76208); 10 - Bridger A and Cathedral Bluffs members of the Bridger Formation mentioned in Lucas et al. 1989, 11 - Lucas et al. 1989, 12 - AMNH 5967, AMNH 6004, UCMP (V73135), UCMP (V73135), UCMP (V81114), UCMP (V83006), UCMP (V82287), UCMP (V82288), UCMP (V94097), UCMP (V94097), UCMP (V81241), UCMP (V81239), AMNH 5934, DMNH (DMNH 167); 13 - UCM (L93099), UCMP (V81104), UCMP (V77106), UCMP (V94091), USNM 13437; 14 - ANSP 10074, AMNH 1494, UCMP (V94106), UCMP (V94109), UCMP (V94109), USNM 13438, USNM 16711, USNM 16713, YPM 3754, DMNH (DMNH 1523), DMNH (DMNH 1474), DMNH (DMNH 1474), DMNH (DMNH 869), DMNH (DMNH 869), DMNH (DMNH 1514), DMNH (DMNH 1483), UCMP (V5629), AMNH 4913, UCMP ; 15 - DMNH 511 (DMNH 228), Stucky et al. 1996; 16 - Westgate 1989; 17 - UCM 9659 (UCM 83282); 18 - Eaton et al

36 14 D. mawii preferred. According to Vogt et al. (2011), D. mawii prefers deep rivers and their tributaries, oxbow lakes and lagoons containing cool (only occasionally exceeding 30 degrees C), deep (usually over m, occasionally over 6 m) water, and a soft substrate. Dermatemys mawii, unlike numerous other aquatic and semiaquatic turtles, does not need to leave the water to sun and can digest plants at a lower temperature than other taxa; however, sex appears from laboratory studies to be influenced by temperature (inculpation at > 28 degrees Celsius produces females and at degrees Celsius produces males) (Vogt et al. 2011). Thus the absence of Baptemys from the Uinta Basin as well as other late Eocene and post Eocene deposits in general in the central United States is likely due to environmental variables related to the development of a more arid environment, which include filling of the lacustrine basins mentioned above and a decrease in large rivers and streams (Hutchison 1992, Lillegraven and Ostresh 1988), as there is a general decline in aquatic turtles from the Eocene into the Oligocene.

37 15 SYSTEMATIC PALEONTOLOGY The alpha taxonomy of Baptemys was summarized based on a review of the literature as well as a physical review of specimens from AMNH, DMNH, USNM, YPM (including the PU collection), ANSP, UCMP, and UCM. The generalized stratigraphic placement for the formal and informal species summarized here is provided in Figure 3, and the geographic distribution is provided in Figure 4. The phylogenetic nomenclature of turtles codified by Joyce et al. (2004) was followed; therefore, all taxonomic names reflect clade names. TESTUDINES Batsch 1788 CRYPTODIRA Cope 1868 CHELYDROIDEA Baur 1893 KINOSTERNOIDEA Gaffney and Meylan 1988 DERMATEMYDIDAE Baur 1888b Baptemys Leidy 1870 Type Species: Baptemys wyomingensis Leidy 1870 Age Range: late Clarkforkian through Duchesnean Revised Diagnosis: Member of Chelydroidea based on the presence of a thickened cruciform plastron (lost in some species), reduction of inframarginal scales to three (increased in some species), and true costiform processes that cross the visceral surface of the first peripherals. Member of Kinosternoidea based on the absence of pectoral scales and presence of inguinal scales that overlap the hyo/hypoplastron sutures (lost in some species). Member of Pan-Dermatemys based on the presence of rectangular vertebral scales that are at least one and a half times longer than wide, a greatly thickened plastron, and the presence of three distinct keels (lost in some species). Member of Dermatemydidae based on medial contact of the abdominals and extension of axillary buttress across peripherals and onto the first costal.

38 16 Figure 4. Generalized geographic and stratigraphic ranges of Baptemys spp. (1) blue (Bourque et al. 2008), Baptemys garmanii green, Baptemys spp. (2) yellow (Lucas et al. 1989), Baptemys wyomingensis orange, Baptemys spp. (3) gray (Eaton et al. 1998). Note: The specimens supporting B. garmanii and B. wyomingensis are provided in Figure 3 and listed in the Systematic Paleontology section. The dark orange are B. wyomingensis and the light orange are occurrences (Colorado, UCM 9659 and Texas late Uintan, Westgate 1989) of cf. B. wyomingensis in counties without B. wyomingensis.

39 17 Baptemys wyomingensis Leidy 1870 Synonymies: B. fluviatilis Hay 1908 Type specimen: ANSP Type locality:...in the vicinity of Fort Bridger, Wyoming (Leidy 1870, p. 4), Uinta County, Wyoming Type horizon: Bridger Formation Age: late early Bridgerian early Uintan Referred specimens based on the presence of diagnostic characters (locality number if available in parentheses): Bridger Formation, Uinta County, Wyoming: AMNH 1494, UCMP (V94106), UCMP (V94109), UCMP (V94109), USNM 13438, USNM 16711, USNM 16713, YPM 3754; Sweetwater County, Wyoming: DMNH (DMNH 1523), DMNH (DMNH 1474), DMNH (DMNH 1474), DMNH (DMNH 869), DMNH (DMNH 869), DMNH (DMNH 1514), DMNH (DMNH 1483); Sublette County, Wyoming: UCMP (V5629); Unknown County: AMNH 4913; UCMP ; Blacks Fork Member, Bridger Formation, Uinta County, Wyoming: AMNH 5967, AMNH 6004, UCMP (V73135), UCMP (V73135), UCMP (V81114), UCMP (V83006); Lincoln County, Wyoming: UCMP (V82287), UCMP (V82288); Sweetwater County, Wyoming: UCMP (V94097), UCMP (V94097), UCMP (V81241), UCMP (V81239); Bridger B, Bridger Formation, Uinta County, Wyoming: AMNH 5934; and Sweetwater County, Wyoming: DMNH (DMNH 167); Twin Buttes Member, Bridger Formation, Uinta County, Wyoming: UCM (L93099), UCMP (V81104), UCMP (V77106); Bridger C, Bridger Formation, Uinta County, Wyoming: UCMP (V94091), USNM 13437; Washakie Formation, Moffat County, Colorado: DMNH 511 (DMNH 228)

40 18 Referred specimens based on stratigraphic occurrence: Bridger Formation, Wyoming: AMNH 1078, AMNH 1103, AMNH 1105, USNM 4111, USNM 971; Uinta County, Wyoming: AMNH 1107, UCMP (V84226), UCMP (V94109), USNM 5000; Sweetwater County, Wyoming: DMNH (DMNH 1474); Blacks Fork Member, Bridger Formation, Uinta County, Wyoming: UCMP (V94066), UCMP (V81105), UCMP (V81106); Lincoln County, Wyoming: UCMP (V82287); Sweetwater County, Wyoming, UCMP (V94105); Bridger B, Bridger Formation, Sweetwater County, Wyoming: DMNH (DMNH 1737) Diagnosis: Lack true costal keels, may have dense crenulations on posterior region of carapace, often with one dominate crenulation that may appear to be a very reduced keel but unlike a true keel it often curves and is not straight; midline keel, developed along the posterior half of the carapace (extends further anterior in B. garmanii and is absent in D. mawii); and partially expanded xiphiplastron (pointed in B. garmanii and further expanded and notched in D. mawii) Comments: The type of Baptemys fluviatilis (AMNH 1494) was from an unknown Eocene locality and was originally described by Hay (1908) to differ from B. wyomingensis in having a posteriorly pointed plastron (also found in B. garmanii) and only two suprapygals (instead of three) of which the posterior one is approximately three times larger than in B. wyomingensis. However, the posteriorly pointed plastron was inferred from an impression of the visceral surface of xiphiplastron; no actual bone is preserved. Thus the plastron was likely not as pointed as originally believed. In addition, the posterior shell region in Baptemys is often poorly preserved and incomplete, with this region only preserved in a handful of specimens, and in each there appear to be no more than two suprapygals; therefore, the apparent difference in the number of suprapygals does not appear to be diagnostic. The remaining features of the carapace are consistent with B. wyomingensis including a prominent midline keel that extends from neural five back onto the pygal and lack of costal keels.

41 19 Due in part to the commonality of B. wyomingensis some specimens have been arbitrarily referred to it in the literature. For example, Zonneveld and colleagues (2000) referred both early Bridgerian and late Wasatchian specimens to B. wyomingensis in part because it is the type species and most common taxa and because at least some of the specimens have a rounded xiphiplastron. Wheeler (1955) referred turtle shell fragments from the Eocene-age (Bridgerian) Roslyn Formation of Washington to B. fluviatilis; however, no morphological characteristics were published. Baptemys garmanii (Cope 1872) Synonymized: Baptemys tricarinata (Hay 1908), Notomorpha garmanii (Cope 1872), Notomorpha gravis (Cope 1872) Type specimen: USNM 4129 Type locality: from a bluff, six miles north of the Bear River (Cope 1872, p. 477), Sweetwater County, Wyoming Type horizon: Wasatch Formation ( Wasatch beds ) Age range: Wasatchian (Later Graybullian-Lostcabinian) Referred specimens (Locality number given in parentheses if available): Willwood Formation, Park County, Wyoming: UCMP (V99713); Wind River Formation, Fremont County Wyoming: AMNH 6110; Lysite Member, Wind River Formation, Fremont County, Wyoming: UCMP (V80129); Lost Cabin Member, Wind River Formation, Fremont or Natrona County, Wyoming: AMNH 6109; Fremont County, Wyoming: UCMP (V76208), UCMP (V76209), UCMP (V84228); Natrona County Wyoming: UCMP and (V73064); UCMP (V76208); Golden Valley Formation, Stark County, North Dakota: YPM PU 17402; Main Body, Wasatch Formation, Sweetwater County, Wyoming: UCMP (V70249), UCMP (V78131), UCMP , , and (V74024), UCMP and UCMP (V78131), UCMP (V70252); La Barge

42 20 Member, Wasatch Formation, Sublette County, Wyoming: UCMP (V77065); Luman Tongue, Green River Formation, Sweetwater County, Wyoming: UCMP (V88002), UCMP (V70270) Diagnosis: Low rounded costal keels that span the majority of the shell; single uninterrupted medial costal keel extending from the pygal to the anterior portion of the shell (typically further than in B. wyomingensis); triangular xiphiplastron that form a V- shaped xiphiplastral lobe (as in Hoplochelys, unlike the broader xiphiplastral lobe present in B. wyomingensis) Comments: Following Lucas et al. (1989), Hutchison (1998), Holroyd et al. (2001) as well as the author s personal observations of the types and published figures, all material referred to previously as B. tricarinata (e.g., Hay 1908a) and Notomorpha garmanii (e.g., Cope 1872) was synonymized as B. garmanii. Cope (1884) synonymized N. garmanii and N. gravis shortly after naming them; however, the specimen of N. gravis was lost even before Hay completed his review in 1908, and the specimen used by Hay to maintain the genus Notomorpha was in fact the type of N. garmanii. Thus this species name is maintained. The type of B. tricarinata was found in the Wind River Formation at the mouth of Alkali Creek, Fremont County, Wyoming (Hay 1908, p. 275) and is indistinguishable from N. garmanii. Reference was made by Hay (1908) to narrow neurals and slightly wider vertebral scutes; however, neither of these traits was documented during this analysis. It is apparent that B. garmanii is typically smaller than B. wyomingensis in overall size. Estes (1988) identified a skull to species level based on morphological characters of shell material found in the same area and in his brief description noted that the skull is shorter and has a less elaborate triturating surface than in B. wyomingensis.

43 21 Baptemys spp. (1) Comments: This species has not been formally described; therefore a type specimen, locality, and horizon are not available. The specimens discussed and briefly described by Bourque et al. (2008) were from the earliest Wasatchian (zone Wa-0, ~55.7 Ma) of the Willwood Formation in southern Big Horn Basin (Washakie County, Wyoming). They also refer to a few potential isolated elements from the latest Paleocene (Clarkforkian). This species was noted to differ from the younger representatives of Baptemys in the following ways: smaller adult body-size; thicker-shell; smaller plastral lobes; reduced entoplastron with the gular-humeral sulcus on or just posterior to the entohyoplastral suture; a smooth carapace with three keels that run nearly the length of the shell (the medial keel does not extend to the pygal); relatively straight, thick, and shortened peripherals; and a depression on the visceral surface of the xiphiplastron just posterior to the hypo/xiphiplastral suture (Bourque et al. 2008). Baptemys spp. (2) Comments: Only briefly mentioned by Lucas et al. (1989), this species is suggested to be intermediate in morphology between B. garmanii and B. wyomingensis, with a potentially diagnostic rippled sculpturing (or crenulations) over the majority of the carapace. Noted as originating from early Bridgerian age deposits of Bridger A Member of the Bridger Formation and the Cathedral Bluffs Member of the Wasatch Formation in southwestern Wyoming, it may also be represented by specimens from the Cub Mountain Formation, New Mexico (Lucas et al. 1989). Baptemys spp. (3) Comments: This species, mentioned briefly by Eaton, Hutchison, et al. (1999), has not been formally described; therefore, a type specimen, locality, and horizon are not available. Specimens were collected on the Sevier Plateau of Garfield and Kane Counties, Utah, from the Brian Head Formation, which, based on the age range of underlying and

44 22 overlying rocks, is inferred in this area to be middle to late Eocene. In addition, the fossils, including turtles and mammals, support a Duchesnean age (middle Eocene). This species of Baptemys is diagnosed in part by a broader plastron than is B. wyomingensis, as well as formation of a xiphiplastral notch.

45 23 MORPHOLOGY The B. wyomingensis description is concentrated on two specimens of B. wyomingensis (YPM 3754 and USNM 13437). These were chosen because they are the most complete shells currently available with associated skulls and other postcranial elements. Numerous additional specimens were included in the referred specimens, and the resulting observations for some of these were included in the description as applicable to address variation and to provide information on elements not readily available in YPM 3754 and USNM Since the cranial material associated with these specimens of B. wyomingensis were incomplete and because these are complex elements with numerous important characters, two additional skulls and associated lower jaws from DMNH 511 and AMNH 5967 were included in the description. In addition to the description of B. wyomingensis, a detailed review of the osteology of D. mawii was conducted; therefore, high resolution images were taken of D. mawii specimens (USNM 66669, FMNH 98950) and these are provided in Appendix A for comparison. Additional specimens of D. mawii and other extant kinosternoids were referred to during the review of B. wyomingensis in order to locate additional characters between the taxa. Skull Although at present four partial skulls of B. wyomingensis with associated shells are known, the Yale Peabody Museum specimen (YPM 3754; Figure 5-Figure 7) forms the basis of this description, with contributions from USNM (Figure 8, Figure 9 and Figure 16), DMNH 511 (Figure 10 and Figure 11), and AMNH 5967 (Figure 12 and Figure 13). Additional cranial elements were reviewed for variation and other pertinent information, but they are not included in the details of this description. The skull of YPM 3754 (Figure 5-Figure 7) is largely complete, missing only the anterior dorsal, surface including the prefrontals, most of the frontals, and the dorsal portions of the maxillae and premaxillae. The USNM skull is partially

46 24 disarticulated and incomplete. Four identifiable pieces are preserved. One flat piece contains most of the prefrontals and anterior half of the frontals (Figure 16). Two pieces are the right and left articular processes of the quadrates. The fourth and largest piece is the posterior portion of the brain case, including the prootics, opisthotics, basisphenoid, and supraoccipital (Figure 8 and Figure 9). The DMNH 511 (Figure 10 and Figure 11) skull is rather complete but crushed. The prefrontals, premaxillae, vomer, ventral maxillae and articular processes of the quadrates are incomplete. In addition, the postorbital and temporal bars and the dorsal surfaces of the parietal and supraoccipital are plaster reconstructions. The medial-dorsal portions of the AMNH 5967 skull (Figure 12) are complete and well preserved. The right and left postorbital bars, all of the left and portions of the right temporal region, and the posterior end of the crista supraoccipitalis are absent. The ventral surface of AMNH 5967 (Figure 13) is quite fractured, and many of the preserved bone fragments are held together with matrix that obscures the true shape and location of these elements. Skull Form The skull of YPM 3754 is three-dimensional, with only the left postorbital bar crushed slightly. The sutures are indistinct and difficult to trace. In dorsal view, the skull is triangular, narrowing anteriorly starting from just behind the orbits. Deep upper temporal emarginations present on the posterolateral halves of the skull nearly reach the orbits, leaving only narrow postorbital bars. Lower temporal emarginations are also present, and they extend dorsally to approximately the lower third of the orbits. The narrow crista supraoccipitalis extends significantly posterior to the condylus occipitals. There is light sculpturing to the roof of the skull and a sulcus for the keratinous beak (YPM 3754). The DMNH 511 skull, although larger and dorsal-ventrally crushed, is similar in shape in dorsal view to YPM The non-crushed disarticulated elements of USNM are also of similar shape but are larger than the elements of YPM 3754.

47 25 The AMNH 5967 skull is three-dimensional, although the posteroventral elements are crushed, slightly disarticulated, and similar in shape and size to that of YPM The overall shape and size of the skull of B. wyomingensis closely resembles that of D. mawii; however variation does occur in bone orientation and contacts. Figure 5. YPM 3754, Baptemys wyomingensis. Skull stereophotographs in dorsal and ventral views.

48 Figure 6. YPM 3754, Baptemys wyomingensis. Skull stereophotographs in posterior and anterior views. 26

49 Figure 7. YPM 3754, Baptemys wyomingensis. Skull sketches in dorsal (A), posterior (B), ventral (C) and anterior (D) views. 27

50 Figure 8. USNM 13437, Baptemys wyomingensis. Skull stereophotographs in dorsal, ventral, and anterior views. 28

51 Figure 9. USNM 13437, Baptemys wyomingensis. Skull sketches in dorsal (A), ventral (B), and anterior (C) views. 29

52 Figure 10. DMNH 511, Baptemys wyomingensis. Skull stereophotographs in dorsal and ventral views. 30

53 Figure 11. DMNH 511, Baptemys wyomingensis. Skull sketches in dorsal (A) and ventral (B) views. 31

54 Figure 12. AMNH 5967, Baptemys wyomingensis. Skull stereophotographs in dorsal, ventral, and anterior views. 32

55 Figure 13. AMNH 5967, Baptemys wyomingensis. Skull sketches in dorsal (A), ventral (B), and anterior (C) views. 33

56 Figure 14. Baptemys wyomingensis. Photographs of YPM 3754 (A), USNM (B), AMNH 5967 (C), and DMNH 511 (D) in lateral views. 34

57 Figure 15. Baptemys wyomingensis. Sketches of YPM 3754 (A), USNM (B), AMNH 5967 (C), and DMNH 511 (D) in lateral views. 35

58 36 Dermal Roofing Elements Prefrontal The prefrontals, eroded from YPM 3754, are nearly completely in AMNH 5967 and partially preserved in USNM and DMNH 511. The prefrontals form the anterior margin of the skull and roof of the fossa nasalis. Nasals are absent. The anterior edges border the dorsal edge of the apertura narium externa. Due to the incompleteness of the anterior margin of all four skulls, the amount of the apertura narium externa that is covered dorsally cannot be determined. The prefrontals meet at the midline anteriorly. Posteriorly they contact the frontals along sutures that are angled posterolaterally from the midline; these sutures then turn laterally to contact the orbital margins. In all other Kinosternoidea the prefrontal usually contacts the postorbital posterolaterally due to less lateral expansion of the frontal; however, this contact may also be polymorphic, as viewed between specimens of D. mawii (USNM and FMNH 98950) and within a specimen of Kinosternon flavescens Agassiz 1857 (FMNH 6849). Anterolaterally, the prefrontals contact the dorsal process of the maxillae along a horizontal suture at the level of the dorsal margin of the fossa nasalis. Within the anterior orbit wall, the posteroventrally angled prefrontal-maxilla suture nearly reaches the floor of the orbit (Figure 14 and Figure 15), terminating along the lateral edge of the foramen orbitonasale. Based on fragmentary remains of the prefrontal in YPM 3754, which are sutured to the maxillary, palatine, and vomer, it is apparent that the ventral process of the prefrontal must have extended posteriorly between the fossa nasalis and the orbit to form the posterolateral walls of the fossa nasalis and the anteromedial floor of the orbit. Medially the ventral process contacts the vomer and forms the dorsal and medial rims of the foramen orbito-nasale. The most posterior extent of the ventral process contacts the palatine, as in all other Kinosternidae and most Cryptodira. It is interesting to note that this contact is not present in trionychoids. On the ventral surface of the skull roof (Figure

59 37 16), the prefrontals thicken laterally to form the anterolateral margin of the foramen interorbitale or the anterodorsal portion of the orbit wall. Small depressions are located on the prefrontal anterior and posterior to the ventral process. The anterior depression is located medial to the ventral process and is located on the posterodorsal roof of the fossa nasalis anterior to the fissura ethmoidalis. The posterior depression is located in the anterodorsal wall of the orbit, lateral to the fissura ethmoidalis and, at its deepest point, houses the small foramen supraorbitale (USNM 13437). The prefrontals of the other Kinosternoidea are quite similar to that of B. wyomingensis, except for their posterior contact, as mentioned above. Frontal The frontals are not complete in any of the skulls; therefore, it is difficult to determine their general shape. In dorsal view they are flat, and if they were complete, they would likely be subtriangular due to a large anteromedial process that extends between the prefrontals. They are longer than the prefrontals, contact each other on the midline, and roof the anterior half of the sulcus olfactorius. Posterior to the prefrontals, the frontals widen and form the medial margin of the orbit. This widening does not usually occur in other kinosternoids; as discussed above, during this study it was observed in a specimen of D. mawii (USNM 66669) and on the left side of a K. flavescens specimen (FMNH 6849). Individual variation in the frontal contribution to the dorsal orbital margin is not uncommon and was previously reported in other taxa (Chelonia mydas, Boulenger, 1890, p. 618; Emys orbicularis, Siebenrock, 1897, p. 276, in Gaffney 1979). In B. wyomingensis the frontals contact the postorbitals posterolaterally by short sutures (YPM 3754) and the parietals posteriorly by transverse sutures. On the ventral surface, anterior processes of the frontals (USNM 13437, AMNH 5967) extend forward under the prefrontals to roof the teardrop shaped fissura ethmoidalis. The processes are broken anteriorly in USNM 13437, but the sutures are

60 38 visible on the prefrontals. In AMNH 5967, the processes are complete, but the sutures are not clearly defined. Posterior to the fissura ethmoidalis the frontals thicken medially, forming parasagittal ridges. These ridges angle posterolaterally and form the anterolateral walls of the sulcus olfactorius and the mid-dorsal margin of the foramen interorbitale. Lateral to the foramen interorbitale, one-third of a triangular depression is present on the posteroventral edge of the frontal that extends posteriorly onto the parietal and laterally onto the postorbital. Figure 16. USNM 13437, Baptemys wyomingensis. Prefrontal and frontal in dorsal (A) and ventral (B) views. Figure 17. USNM 13437, Baptemys wyomingensis. Sketches of the prefrontal and frontal in dorsal (A) and ventral (B) views.

61 39 Parietal The dorsal portions of the parietals are long, posteriorly pointed, and triangular. They contact each other on the midline. Anteriorly, the parietal contacts the frontal by a transverse suture, and anterolaterally, it contacts the postorbital by a short suture on the medial edge of the postorbital bar. The ventral process of the parietal extends posteriorly within the fossa temporalis superior to contact the anterior edge of the supraoccipital along an overlapping suture and posterolaterally to contact the prootic medial to the processus trochlearis oticum. The parietal forms the anteromedial border of the temporal emargination and roofs the posterior half of the sulcus olfactorius and the anterior half of the cavum cranii. The parietal is similar in D. mawii, Staurotypus triporcatus Wiegmann 1828 and other Kinosternidae, and E. cretacea; however, in kinosternids including Kinosternon sonoriense Le Conte 1854, K. flavescens, and S. odoratus the posterolateral contact occurs more laterally allowing the parietal to contribute to the processus trochlearis oticum. The anterior portion of the ventral process of the parietal forms a parasagittal ridge that contributes to the posterolateral wall of the sulcus olfactorius and the posteromedial wall of the orbit. Anteriorly, this ridge contacts the parasagittal ridge of the frontal. Extending further ventrally, the processus inferior parietalis forms the lateral wall of the cavum cranii and the posterior edge of the foramen interorbitale. The processus inferior parietalis broadly, though not as broadly as in kinosternids; contacts the palatine anteriorly and posteriorly forms the anterodorsal border of the foramen nervi trigemini. Only in YPM 3754 are the bones surrounding the foramen nervi trigemini preserved in place and uncrushed; however, the sutures are not clearly defined. The processus inferior parietalis appears to send a narrow process along the anteroventral edges of the foramen nervi trigemini to contact the quadrate posteriorly and the epipterygoid ventrally. On the left side of the skull (YPM 3754), a second narrow process seems to extend over the prootic along the posterodorsal edge of the foramen nervi trigemini but does not reach the

62 40 quadrate. The presence of the posterodorsal processes in B. wyomingensis is contra to Meylan and Gaffney (1989, p. 9-10); however, their thoughts on the presence (p. 18) or absence (p.10) of an anteroventral process are unclear. As Meylan and Gaffney (1989), noted the anteroventral parietal process usually occurs in D. mawii and was viewed in both specimens observed during this study (FMNH and USNM 66669). The ventral parietal process on the posterodorsal margin of the foramen nervi trigemini was only observed on the right side of USNM Jugal The jugals are nearly complete in YPM 3754; however, the left is crushed and the right is incomplete ventrally. The jugal contacts the maxilla anteroventrally, the postorbital dorsally, and the quadratojugal posteriorly. The jugal forms the posterior border of the orbit and the anterodorsal edge of the cheek emargination, which reaches the level of the lower margin of the orbit and restricts contact between the quadratojugal and maxilla. In Kinosternids, less cheek emargination restricts the jugal from ventral exposure and allows for quadratojugal-maxilla contact. The ventral process of the jugal lies on the maxilla and rises slightly on the posterolateral wall of the orbit to form the posteroventral margin of the fossa orbitalis. In addition to contacting the maxilla, the ventral process reaches the pterygoid within the orbit just anterior to the processus pterygoideus externus and the palatine posterolateral to the foramen palatinum posterius. These contacts occur in all other Kinosternoidea as well as in trionychids, but in chelydrids only the pterygoid-jugal contact occurs ventrally. Quadratojugal In YPM 3754, the right quadratojugal is incomplete, and the left is slightly crushed. The quadratojugals are not preserved in the other three skulls. The quadratojugal contacts the jugal anteroventrally and the postorbital anterodorsally. Posteriorly, the quadratojugal contacts the quadrate ventrally, forming a C-shaped suture along the rim of

63 41 the cavum tympani, and the squamosal dorsally by a short suture above the cavum tympani. The quadratojugal forms the posterodorsal half of the cheek emargination, the anterolateral margin of the temporal emargination, and part of the lateral wall of the fossa temporalis superior. Unlike kinosternids, the quadratojugal does not extend anteroventrally to contact the maxilla in B. wyomingensis or in D. mawii. Squamosal The left squamosal of YPM 3754 is complete, whereas the right is missing the posteromedial portion. The squamosals are not preserved in the other three skulls. The cone-shaped squamosal extends back from a short suture with the quadratojugal to cover the posterodorsal end of the quadrate and form the posterior portion of the antrum postoticum, which is fully continuous with the cavum tympani. Although the medial sutures within the fossa temporalis superior are indistinct, the squamosal appears to also contact the opisthotic posteromedially. These relationships appear to be similar in D. mawii, and in most other kinosternoids; however, S. odoratus has a medially expanded squamosal that nearly covers the entire dorsal surface of the quadrate. Postorbital Only preserved in YPM 3754, the wide, distally expanded postorbitals form the entire postorbital bar, as in D. mawii. The precise suture angles are difficult to determine due to crushing (left side) and unclear sutures. The postorbital extends from the parietalfrontal suture to contact the jugal anteroventrally and the quadratojugal posteroventrally. It forms the posterior border of the orbit and the anterior margin of the temporal emargination between the parietal and quadratojugal. The ventral surface of the orbital bar has a low ridge along the posterolateral edge of the orbital fossa. Medial to the ridge is a triangular depression that points laterally and extends medially onto the parietal and frontal is similar in other kinosternoids and occurs in other turtles as well, although the size and orientation do vary.

64 42 Palatal Elements Premaxilla The premaxillae are not complete in any of the skulls. Anteriorly rounded ventral portions of premaxillae are present in YPM 3754 and contact each other medially. Premaxillae are also present in DMNH 511; however, the premaxillary sutures are not clear, and their anterior surfaces are broken. In ventral view, the premaxilla is a triangular element that contacts the maxilla laterally along a posteromedially-angled suture and contacts the vomer posteriorly. It forms the anterior-most portion of the labial ridge and triturating surface. There is a depression on the ventral surface of the premaxilla between the labial ridge and the premaxilla-vomer suture. The bone is exceptionally thin in this area and readily erodes, as is also found in D. mawii. The foramen praepalatinum is located on the premaxilla-vomer suture posterior to the depression and lateral to the midline as in D. mawii. There is some disagreement with the presence of the foramina praepalatinum in all Kinosternoidea, Meylan and Gaffney (1989) and Hutchison (1991) state that instead the foramen intermaxillaris is present in Staurotypus, Claudius and Xenochelys formosa Hay 1906 (PU 13686) as in trionychians. Joyce (2007), however, disagrees with the homology of this feature and refers to the foramen in staurotypines as the foramen praepalatinum, stating that the right and left foramen praepalatinum fuse to form one large opening. In addition, Meylan (1987,61) notes that the foramen intermaxillaris occurs in staurotypines as in Trionychidae and Carettochelys, except that it is only present in mature individuals. The S. triporcatus (AMNH ) skull examined during this study lacks the one large opening and instead has two small foramina praepalatinum. This is interpreted here to suggest two different processes occur to form a morphologically similar structure. Bone is lost in Staurotypines during ontogeny, whereas in Trionychidae and Carettochelys bone never forms in this region; therefore, following Joyce (2007) these structures are not interpreted to be homologous.

65 43 In dorsal view the premaxillae form the floor of the fossa nasalis, and a ridge extends posterodorsally along their medial contact. In D. mawii the premaxillae usually form the anteroventral rim of the apertura narium externa, except that in some specimens (USNM 66669) the maxillae meet on the anterodorsal surface of the premaxillae, thereby restricting the premaxillae from the apertura narium externa. This area is not preserved in any of the B. wyomingensis skulls. Maxilla The maxillae are incomplete in YPM 3754; only the ventral portions are preserved, with the left more complete than the right. Only the anterodorsal process of the left maxilla is preserved in AMNH The maxillae of DMNH 511 are also partially preserved; the preserved dorsal surfaces are crushed, and the triturating surfaces are disarticulated. Anteriorly a process of the maxilla extends dorsally to contact the prefrontal at the level of the dorsal margin of the orbit. This anterodorsal process forms the lateral border of the apertura narium externa and the lateral portions of the anteroventral wall of the fossa orbitalis. Within the posterior fossa orbitalis a ridge formed by the maxilla trends posteromedially to contact the ridge on the palatine. This ridge forms the lower rim of the foramen orbito-nasale. In B. wyomingensis the ridge is formed equally by the maxilla and palatine, whereas the ridge is formed almost entirely by the maxilla in D. mawii. Slightly posterolateral to this ridge lies the foramen supramaxillare; in D. mawii this foramen actually passes under the ridge, but in other Kinosternidae the foramen is located even further laterally than in B. wyomingensis. The dorsal surface of the maxilla s horizontal plate extends anteriorly from the foramen orbito-nasale to medially contact only the premaxilla. The extension is broader in D. mawii, allowing the maxilla to contact the ventral vomer process as well as the premaxilla, as is usual for turtles (Gaffney 1979, p. 92).

66 44 Posterior to the foramen orbito-nasale the dorsal surface of the maxilla contacts the palatine medially and terminates at a posterior contact with the jugal, anterior to the processus pterygoideus. The maxillary sutures surrounding the foramen palatinum posterius are nearly fused and difficult to interpret. The maxilla may extend in to the foramen palatinum posterius, forming the anterodorsal margin as in D. mawii. Relationships on the ventral surface of the maxilla are similar, except it appears that a strut extends posteromedially along the lateral edge of the foramen palatinum posterius to contact the pterygoid posteriorly (contra Meylan and Gaffney 1989, figure 6). The nomenclature of the palate follows Meylan and Gaffney (1989); however, this does not infer homology with equally named structures in other turtles. The ventral surface of the maxilla forms most of the triturating surface of the skull; this is in contrast to S. triporcatus and X. formosa, where the palatines and vomer contribute substantially to the triturating surface. In B. wyomingensis a high labial ridge and a low lingual ridge run the length of the maxilla and are lightly crenulated. The lingual ridge forms the posterolateral edge of the palate. A single short, lightly crenulated maxillary tooth of medium height separates these ridges. The maxillary tooth is restricted to the posterior two-thirds of the maxillae. Low troughs separate the labial and lingual ridges from the maxillary tooth. Posterior to the maxilla-premaxilla suture, the cusp-like commissural ridge extends anterolaterally at a right angle from the lingual ridge. A depression separates the commissural ridge from the maxillary tooth. Dermatemys mawii is the only other Kinosternoidea to posses these distinctive palate structures. In D. mawii a shallow trough separates the maxillary tooth into one strong medial ridge and a less defined shorter lateral ridge. Additionally, the commissural ridges are wider in D. mawii, extending from the labial walls to the expanded anterolateral edges of the maxillae, nearly meeting at the midline. Emarginochelys cretacea has a low, non-crenulated, S- shaped maxillary tooth located on the posterior half of the maxilla, perpendicular to the

67 45 labial and lingual ridges, whereas in B. wyomingensis and D. mawii the tooth parallels these ridges. Vomer The vomer, preserved in YPM 3754 and AMNH 5967, is a long and narrow element that extends posteriorly between the palatines to contact the pterygoids. The ventral ridge of the vomer extends nearly the entire length of the bone. The ridge, extremely poorly developed posteriorly, is developed into a ventral process anteriorly. The anteroventral vomer process contacts only the premaxilla anteriorly, whereas in D. mawii the anteroventral vomer process also contacts the maxilla. In both taxa the anteroventral vomer process forms the medial border of apertura narium interna, which is oval shaped in B. wyomingensis but flatter and more circular in D. mawii. Posterior to the ventral process, the paired dorsal processes of the vomer reach anteriorly to contact the prefrontals (AMNH 5967). These processes form the lateral walls of the U-shaped sulcus vomeri, which opens into the foramen interorbitale posteriorly, the fossa nasalis anteriorly and the teardrop-shaped fissura ethmoidalis dorsally. The sulcus vomeri of D. mawii is narrower and more V-shaped, extending upward into a circular fissura ethmoidalis. Palatine In YPM 3754 the rectangular palatines are nearly complete; however, each foramen orbito-nasale may have been posteriorly enlarged due to breakage of the palatines. The flat palatine roofs some of the apertura narium interna and contacts the vomer medially by a parasagittal suture and the pterygoid posteriorly by a posteroconvex suture. The posterolateral process articulates with the maxilla and forms the medial and anterior sides of the foramen palatinum posterius. The foramen palatinum posterius is located lateral to the posterior trituration surface of the maxilla. This foramen lies on the palatine-maxilla suture and extends posteriorly to the palatine-maxilla-pterygoid suture.

68 46 On the dorsal surface of the palatine, a small process extends dorsally to contact the epipterygoid and the descending processus inferior parietalis. This palatine process forms the anteroventral corner of the lateral cavum cranii wall and is similar or slightly smaller in D. mawii. In other kinosternids the process is longer. For example, in staurotypines the process nearly reaches the cavum cranii roof, while it is of medium height in kinosternines, only reaching midway up the cavum cranii wall. The process is thought to occur in all Trionychoidea, but not in other turtle clades (Meylan and Gaffney 1989). Lateral to the cavum cranii and posterior to the foramen interorbitale, the palatine extends dorsolaterally to contact the pterygoid and the jugal. The dorsal surface of the palatinepterygoid suture lies in a long, narrow trough on the processus pterygoideus externus. From observations in modern kinosternoids, an anterolateral process of the epipterygoid extends into the trough covering the palatine-pterygoid suture. Palatoquadrate Elements Quadrate In YPM 3754 the left quadrate is complete and the right quadrate is missing the posterolateral and anterolateral edges. Within the fossa temporalis superior the quadrate forms the lateral half of the trochlearis oticum and contacts the prootic medially and the opisthotic posteromedially, as in D. mawii. The right side of AMNH 5967 and both sides of DMNH 511 support these contacts but are incomplete and crushed. The quadrate contribution to the trochlearis oticum is reduced in kinosternines, forming only the lateral third. In addition, the medial edge of the trochlearis is more defined in kinosternids than in B. wyomingensis or D. mawii. In lateral view, the quadrate contacts the quadratojugal anterolaterally and the squamosal posterolaterally. The quadrate forms a large circular (left) to oval (right) cavum tympani. The true shape was between circular and oval. The incisura columellae auris, a circular fissure on the posterior edge of the cavum tympani, opens posteroventrally as in all Kinosternoidea with preserved skulls. The incisura

69 47 columellae auris is slightly larger in D. mawii than in B. wyomingensis, perhaps due to compression. In dermatemydids the opening is larger and more circular than in other Kinosternoidea, whereas it is completely closed in Trionychia. The antrum postoticum extends backward from the cavum tympani; the anterior portion is formed by the quadrate. Ventral to the cavum tympani, the processus articularis of the quadrate forms the condylus mandibularis, which is bean shaped with convexolateral and concavomedial articular surfaces that contact the area articularis mandibularis of the lower jaw. Anteromedially, the ventral process of the quadrate contacts the prootic below the processus trochlearis oticum, the parietal posteroventral to the foramen nervi trigemini, the epipterygoid ventral to the foramen nervi trigemini via the processus epipterygoideus, and the pterygoid dorsomedial to the condylus mandibularis. Epipterygoid The triangular epipterygoids are only visible in YPM 3745, and the sutures are indistinct. The epipterygoid contacts the parietal dorsally, the pterygoid ventrally, the quadrate posteriorly, and the palatine anteriorly. Based on comparisons with modern kinosternoids, the epipterygoid may have had an anterolateral process, incomplete in YPM 3754, that would have extended anteriorly, covering the palatine-pterygoid on the ventral surface of the processus pterygoideus externus. The epipterygoid forms the ventromedial wall of the cavum tympani. Pterygoid The long, anteriorly winged pterygoids are complete in YPM 3754 and nearly complete in DMNH 511 and AMNH Anteriorly they contact each other on the midline, but they are separated posteromedially by the basisphenoid and basioccipital along posterolaterally trending sutures. On the ventral surface, the pterygoid contacts the maxilla anterolaterally and the palatines and vomer anteromedially, but on the dorsal

70 48 surface the pterygoid contacts the jugal, and contact with the maxilla is restricted by the palatine-jugal contact. A low ridge separates the quadrate process of the pterygoid from the medial pterygoid plate. This ridge originates near the rear of the processus pterygoideus externus and runs posteriorly, medial to the fossa temporalis inferior, and then angles posterolaterally, passing anterior to the foramen posterius canalis caroticus interni and ending near the pterygoid-quadrate suture. A shallow depression, presumably the articulation site of the pterygoideus jaw musculature, is present on the pterygoid surface between the ridge and the posteromedial border of the fossa temporalis inferior. In D. mawii this ridge does not extend as far anteriorly, and the depression is slightly more expanded posteriorly, as is similar in kinosternines. The lack of anterior extension is similar in staurotypines and E. cretacea; however, the ridge and depression extend posteriorly with very little arcing, and instead of terminating medial to the process articulars of the quadrate, they terminate just anterior to the foramen posterius canalis carotici interni. Posteriorly the pterygoid reaches the tuberculum basioccipitale. The foramen posterius canalis carotici interni of B. wyomingensis is completely contained within the pterygoid medial to the processus articularis of the quadrate as in Trionychia. In all other Kinosternoidea with known skulls, the foramen is not enclosed within the pterygoid but instead is open posteriorly. Anterolaterally the processus pterygoideus externus extends dorsally into the fossa temporalis inferior to contact the posterior edge of the maxilla and the anteromedial process of the jugal and palatine. This process is moderate in size, extends ventrally relative to the main part of the pterygoid, and has a slight dorsal curve. The processus pterygoideus externus is similar in D. mawii but is reduced or absent in other kinosternoids. For example, Claudius angustatus Cope 1865 has no processus pterygoideus externus, where as K. flavescens, K. sonoriense, and S. odoratus have reduced processes that do not extend as far ventrally relative to the main pterygoid and do not curve dorsally at their lateral extent. The processus pterygoideus externus is also

71 49 present in S. salvini but it is not as prominent as in B. wyomingensis due to the expansion of the titrating surface that incorporates the pterygoid. Posterior to the process pterygoideus externus, the crista pterygoideus (a ridge on the dorsal surface of the pterygoid) contacts the epipterygoid and processus inferior parietalis of the parietal within the medial edge of the fossa temporalis inferior, ventral to the foramen nervi trigemini, thereby forming the ventrolateral cavum cranii wall. The skull from DMNH 511 was originally disarticulated, and the glue that was used to hold it together deteriorated, exposing a portion of the dorsal surface of the pterygoids, basisphenoid, and basioccipital (Figure 18 and Figure 19). It appears that the rostrum basisphenoidale covers nearly the entire dorsal surface of the pterygoid. If this is an accurate representation, it is an unusual extension of a process that in most other turtles is contained almost entirely to the anterior extension of the basisphenoid. Lateral to the rostrum basisphenoidale, the pterygoid is visible in the sulcus cavernosus. The right sulcus is more clearly defined. In D. mawii the sulcus cavernosus is wider and less clearly defined due to a shorter rostrum basisphenoidale (see Gaffney 1979; figure 58). Braincase Elements Supraoccipital The supraoccipital is a triangular bone that narrows posteriorly to form the crista supraoccipitalis (YPM 3754, USNM 13437, AMNH 5967). The crista supraoccipitalis, complete only on USNM 13437, is slightly longer than the main part of the supraoccipital. It extends almost straight back, but posteriorly the flange is bent or crushed to the right. The supraoccipital is covered by the parietals anteriorly and contacts the prootics anterolaterally, the opisthotics laterally, and the exoccipitals posterolaterally. The supraoccipital forms the dorsal border of the oval foramen magnum and the posterodorsal roof of the cavum cranii. Within the cavum cranii the ventral surface of the supraoccipital has a posteriorly pointed triangular depression, whereas posteriorly low

72 50 ridges are present on the crista supraoccipital. The supraoccipital roofs the cava labyrinthicum and forms the recessus labyrinthicus supraoccipitalis that contain the canales semicircularis anterior and posterior. These features are quite similar in D. mawii and other kinosternoids, with only slight variation in the relative height and posterior pointedness of the crista supraoccipital. Exoccipital Sutures are difficult to see in YPM 3754, but both exoccipitals are complete. The exoccipitals are missing in USNM 13437; however, the sutures with the supraoccipital and opisthotic are preserved. The exoccipital is located ventral and lateral to the supraoccipital. Anteriorly and laterally it contacts the opisthotic, and ventrally it contacts the basioccipital to participate to the condylus occipitalis. The exoccipital is complete and forms the lateral margin of the foramen magnum, which has a greater height than width. The surface of the exoccipital along the lateral margin of the foramen magnum is smooth in B. wyomingensis (YPM 3754), whereas in D. mawii and other kinosternoids there is a low ridge extending dorsomedial to ventral lateral. From the rim of the foramen magnum, the exoccipital splits and forms a lateral and a medial process. The medial process forms the floor of the foramen magnum, and contacts the medial process of the other exoccipital on the condylus occipitalis. Both the lateral and medial processes form the sides of the foramen jugulare posterius. In YPM 3754 and DMNH 511, the foramen is open ventrolaterally, which may not be natural but instead may be attributed to preservation or preparation. The foramen is closed in D. mawii but open in K. flavescens, K. sonoriense, and S. odoratus. From the condylus occipitals the medial process continues ventrolaterally to contact the basioccipital. Slightly concave, the medial process contains two small foramina nervi hypoglossi on the medial border of the foramen jugulare posterius. In the disarticulated DMNH 511, a portion of the internal surface of the exoccipital is exposed. Although the sutures are difficult to determine, it appears similar

73 51 to D. mawii; however, there appear to be three foramen nervi hypoglossi in DMNH 511 instead of the two reported from D. mawii (Gaffney 1979; figure 58). Basioccipital The mushroom shaped basioccipital is preserved in YPM 3754 and DMNH 511. It contacts the basisphenoid anteromedially by an anteroconvex suture and the pterygoids anterolaterally and laterally. The basioccipital is depressed medially. Posterior to this depression the basioccipital narrows posteriorly forming the ventral third of the condylus occipitalis and contacting the exoccipitals, which form the dorsal two-thirds. Lateral and slightly anterior to the condylus occipitalis two pairs of elongate tuberculae basioccipitale extend posteriorly from the main basioccipital. The ventrolateral pair are more robust and extend further posteriorly over a more dorsomedial pair. Dermatemys mawii has only one large anterior set of tuberculae basioccipitale; however, the size and number of sets of this structure varies among other kinosternids; for example, S. salvini has two sets of nearly equal length. The ventral surface of the basioccipital was observed in DMNH 511. Internally it is relatively smooth, with the posterior medial surfacing raised slightly dorsally. The sutures between the basioccipital and exoccipitals appear to be partially fused and are difficult to interpret. Prootic The rectangular (triangular when covered by the parietal) prootics are complete in YPM 3754, nearly complete in USNM and DMNH 511, and partially complete in AMNH The prootic forms the medial half of the processus trochlearis oticum, while the quadrate forms the lateral half. This is very similar in D. mawii, Kinosternon, and C. angustatus, whereas in S. odoratus the prootic exposure is very narrow due to medial expansion of the squamosal that nearly covers the entire dorsal surface of the quadrate and the lateral edge of the prootic and lateral expansion of the parietal. In

74 52 addition to a lateral contact with the quadrate, the prootic of B. wyomingensis contacts the parietal medially, the opisthotic posterolaterally, and the supraoccipital posteromedially. Anteroventrally, the prootic continues to contact the quadrate and the parietal. It forms the dorsal edge of the foramen nervi trigemini (YPM 3754 right side) but may be covered in part by a ventral parietal process (YPM 3754 left side, USNM 13437). The posteromedial end of the prootic forms the anterior cavum labyrinthicum wall (USNM 13437) or recessus labyrinthicus prooticus where the canalis semicircularis anterior and canalis semicircularis horizontalis are housed. Anterior and ventral to the cavum labyrinthicum, the prootic forms the dorsal edge of the foramen cavernosum and roofs the canalis cavernosus. Anterior to the recessus labyrinthicum prooticus on the lateral cavum cranii wall is the shallow fossa acustico-facialis that contains three foramina. The anterior foramen nervi facialis opens into the canalis cavernosus anterolaterally and the posterior paired foramina nervi acustici open posteriorly into the recessus labyrinthicum prooticus. Opisthotic The opisthotics are complete in YPM 3745 and nearly complete in USNM and DMNH 511; however, the sutures are not clear in all specimens. The opisthotic contacts the supraoccipital medially, the prootic anteriorly, the quadrate laterally, the squamosal posterolaterally, and the exoccipital posteromedially. There is no foramen stapedio-temporale as in D. mawii; however, all other kinosternoids have a small foramen stapedio-temporale. A small posteriorly pointing process, or bump, protrudes on the posterolateral edge of the processus paroccipitalis of the opisthotic. In posterior view, the opisthotic forms the dorsal edge of the fenestra postotica, which opens medially into the foramen jugulare posterius. The lack of a bar between these openings is attributed to preservation or preparation, not to true osteological relationships. Anterior to the foramen and fenestra, a strut, the processus interfenestralis of the opisthotic, extends ventrally and widens posteroventrally to contact the pterygoid. This process contains the canalis nervi

75 53 glossopharyngei (YPM 3754, left side) and separates the cavum acustico-jugulare into two parts; the posterior is the recessus scalae tympani. In USNM the cavum labyrinthicum and associated structures are visible. The opisthotic forms the posterior cavum labyrinthicum wall, and the recessus labyrinthicus opisthoticus, which houses the canalis semicircularis horizontalis and canalis semicircularis posterior, is also exposed. Basisphenoid The basisphenoid is complete in DMNH 511 and YPM 3754 and partially complete in USNM It is centered at the midline and narrows anteriorly, extending between the posterior half of the pterygoids. Posteriorly the basisphenoid articulates with the basioccipital. The basisphenoid forms a portion of the cavum cranii floor. The incomplete USNM skull displays internal features of the basisphenoid; however, the dorsum sella and processus clinoideus are eroded, thus unclear, and neither the rostrum basisphenoidale nor the sella turcica was preserved. In the partially disarticulated DMNH 511 (Figure 18 and Figure 19), these structures are preserved. The rostrum basisphenoidale are long, extending anteriorly over the pterygoids nearly to the pterygoid-palatine contact. In D. mawii the rostrum basisphenoidale are much shorter and truncate anteriorly near the anterior point of the basisphenoid. In both B. wyomingensis specimens, the foramina anterius canalis carotici cerebralis lie close together near their end, just posterior to the sella turcica, whereas in D. mawii the foramina anterius canalis carotici cerebralis lie a bit further apart anterior to the sella turcica. In DMNH 511 the canalis caroticus palatinum and foramen anterius canalis carotici palatinum are partially preserved on the left dorsal surface, and appear to be larger than the canalis caroticus cerebralis. A small portion of the canalis caroticus palatinum may also be observed in the incomplete basisphenoid of USNM Posterior to the sella turcica in USNM the posterior foramina nervi abducentis are visible in the cavum cranii; they do not occur in DMNH 511.

76 Figure 18. DMNH 511, Baptemys wyomingensis, dorsal stereophotographs of the basisphenoid skull region. 54

77 Figure 19. DMNH 511, Baptemys wyomingensis, dorsal sketch of the basisphenoid skull region. 55

78 56 Lower Jaws The lower jaws of YPM 3754 and DMNS 511 are nearly complete, fully articulated, and uncrushed, except for the dorsal-ventrally crushed processus coronoideus and area articularis mandibularis (Figure 20-Figure 28). The posterior ends of the lower jaws and the anterior portion of the left dentary are missing from AMNH 5967 (Figure 29-Figure 30), and only small portions of the right and left dentaries are preserved in USNM The jaw is a broad U-shaped element with dentary pockets (sensu Meylan and Gaffney 1989) just anterior to the coronoid processes. The coronoid process and midline tooth of the labial ridge are raised substantially above the level of the jaw. The area behind the coronoid process is short, forming only one-fourth of the jaw. Figure 20. YPM 3754, Baptemys wyomingensis. Lower jaw sketches in dorsal (A), ventral (B), and posterior (C) views.

79 Figure 21. YPM 3754, Baptemys wyomingensis. Lower jaw stereophotographs in dorsal, ventral, and posterior views. 57

80 Figure 22. DMNH 511, Baptemys wyomingensis. Lower jaw stereophotographs in dorsal, ventral and posterior views. 58

81 Figure 23. DMNH 511, Baptemys wyomingensis. Lower jaw sketches in dorsal (A), ventral (B) and posterior (C) views. 59

82 60 Figure 24. YPM 3754, Baptemys wyomingensis. Lower jaw stereophotographs in right and left lateral views. Figure 25. YPM 3754, Baptemys wyomingensis. Lower jaw in left (A) and right (B) medial views.

83 61 Figure 26. YPM 3754, Baptemys wyomingensis. Lower jaw in left lateral (A), left medial (B), right lateral (C) and right medial (D) views. Dentary The long dentaries are fused at the midline and form the anterior U-shaped margin of the lower jaws. Posteriorly the dentary reaches the level of processus coronoideus. In lateral view, the dentary contacts the surangular posteriorly by an undulating suture. In medial view the dentary contacts the coronoid posterodorsally, the angular posteroventrally, and the prearticular posteriorly. The dentary pocket (sensu Meylan and Gaffney 1989), which forms a triturating surface with the maxillary tooth of the upper jaw, is located on the posterior two-thirds of the dorsal surface of the dentary. An anterolaterally directed ridge forms the anterior margin of the pocket. This ridge interacts with the maxilla during trituration by contacting the trough behind the commissural ridge. The ridge terminates laterally in a cusp on the labial ridge that extends dorsally nearly as high as the symphyseal cusp. Posteriorly the pocket terminates at the processus coronoideus. The labial and lingual ridges of the dentary are only lightly crenulated. The

84 62 titrating surface is similar but more advanced in D. mawii, with the addition of a ridge extending down the middle of the dentary pocket, parallel to the labial and lingual ridges. In D. mawii all three ridges are highly crenulated and occasionally form small cusps. On the titrating surface of D. mawii, anteromedial to the dentary pocket and posterolateral to the symphysis, is the triangular symphyseal pocket, which is not developed in B. wyomingensis. In addition to the dermatemydids, Adocus sp. and possibly E. cretacea have more complex titrating surfaces that include dentary pockets, while other kinosternoids have less developed titrating surfaces consisting of a relatively flat surface between low labial and lingual ridges. This surface can be of a moderate width (K. flavescens, K. sonoriense, C. angustatus) or may be more expanded (S. triporcatus, S. odoratus). A ridge runs parallel to and below the labial ridge on the lateral surface of the dentary in B. wyomingensis. The ridge marks the ventral extent of contact between the lateral surface of the dentary and the medial surface of the labial ridge of the maxilla; it is more pronounced in D. mawii and S. triporcatus. The large circular foramen dentofaciale majus lies posterior to the lateral ridge and ventral to the posterior limits of the titrating surface in the anterior portion of a depression that is likely the attachment area for the Musculus adductor mandibulae externus pars superficialis. Within Kinosternoidea this depression is variable; it is well defined in D. mawii and S. triporcatus, as in B. wyomingensis, but it may be less defined (K sonoriense, FMNH 45813), and the foramen may lie outside of the depression (S. odoratus, FMNH 22069). The sulcus cartilaginis Meckelii opens on the medial side of the dentary and extends anteriorly from the posterior end of the dentaries across the dentary symphysis. The sulcus is broad in YPM 3754 and narrows anteriorly; in DMNH 511 the dentary curves around, further narrowing the sulcus. Although the area is partially crushed in YPM 3754, it appears that near the posterior end of the sulcus cartilaginis Meckelii, the opening for the canalis alveolaris inferior, the foramen alveolare inferius, is preserved.

85 63 Figure 27. DMNH 511, Baptemys wyomingensis. Lower jaw photographs in left lateral (A), left medial (B), right lateral (C), and right medial (D) views. Figure 28. DMNH 511, Baptemys wyomingensis. Lower jaw sketches in left lateral (A), left medial (B), right lateral (C), and right medial (D) views.

86 Figure 29. AMNH 5967, Baptemys wyomingensis. Lower jaw stereophotographs in dorsal, ventral, and left and right lateral views. 64

87 65 Figure 30. AMNH 5967, Baptemys wyomingensis. Lower jaw sketches in dorsal (A), ventral (B), left lateral (C) and right lateral (D) views. Coronoid The coronoid is much smaller than the dentary and forms only the dorsal and dorsomedial surfaces of the processus coronoideus. It does not appear to contribute to the titrating surface in B. wyomingensis or D. mawii, as occurs in S. triporcatus and possibly other Kinosternoidea; however, the sutures are poorly defined and difficult to interpret in a number of specimens observed during this study. The processus coronoideus in B. wyomingensis is extended dorsally over twice as far as the symphyseal cusp of the dentary, where as in D. mawii the processus is only slightly higher than the symphyseal cusp. In medial view the coronoid extends anteroventrally between the dentary (anterior) and prearticular (posteromedially) to contact the posterodorsal edge of the foramen intermandibularis medius. There is much less medial exposure of the coronoid in D. mawii, as it is covered ventrally by the dentary and prearticular and does not extend

88 66 anteroventrally to the foramen intermandibularis medius. Laterally, in B. wyomingensis the coronoid is nearly covered by the dentary and surangular; only the dorsal edge is visible. The posterior edge of the coronoid forms the anterior margin of the large, ovalshaped dorsal opening of the fossa Meckelii. Prearticular The prearticular forms the posteromedial surface of the jaw and the medial wall of the fossa Meckelii. Anteriorly the prearticular terminates at the anterior opening of the fossa Meckelii (foramen intermandibularis medius). The prearticular contacts the coronoid dorsally, the angular ventrally, and the articular posteriorly along the medial rim of the articular surface. A posterior process extends dorsally to form the medial edge of the dorsal opening of the fossa Meckelii. The pinhole-sized foramen intermandibularis caudalis, found in YPM 3754 (left side) and possibly in DMNH 511, is formed dorsally by the prearticular and ventrally by the angular. In addition, a second pinhole-sized opening, possibly the foramen intermandibularis oralis, lies slightly anterior on the angular-prearticular suture of YPM 3754 (left side). However, only one foramen is present along this suture in S. odoratus, K. flavescens, K. sonoriense, and D. mawii, and in at least the latter it is believed to be the foramen intermandibularis caudalis (Meylan and Gaffney 1989) Angular The angular is a long element that forms the posteromedially side of the jaw below and posterior to the foramen intermandibularis medius. Dorsally the angular contacts the prearticular, and anteriorly it contacts the dentary. Posteriorly it narrows and wraps around the posteroventral surface of the jaw to contact the posterolateral process of articular below the area articularis mandibularis and the surangular. As mentioned above (see Prearticular ) the pinhole-sized foramen intermandibularis caudalis is located midway along the angular-prearticular suture ventral to the dorsal opening of the fossa

89 67 Meckelii, and the foramen intermandibularis oralis is located slightly posteriorly along the same suture. Surangular The surangular is a tall bone that forms part of the coronoid process, the posterolateral surface of the jaw, and one-third of the area articularis mandibularis. It contacts the articular posteromedially and extends anteriorly under the dentary to contact the angular ventrally. Contacting the coronoid anterodorsally, the surangular extends back to form the lateral side of the dorsal opening of the fossa Meckelii and the lateral articulation of the area articularis mandibularis. The contribution of the surangular to the area articularis mandibularis is variable within kinosternoids; often it forms only oneforth or less of the articular surface. On the center of the lateral surface of the surangular, the large foramen nervi auriculotemporalis is located just anterior to the area articularis mandibularis. In DMNH 511 (right side) there appears to be an additional foramen in the surangular located on the dorsal surface, posterolateral to the fossa Meckelii opening, anterior to the area articulars mandibularis. This extra foramen (currently unnamed) does occur in Kinosternids including S. triporcatus, K. sonoriense, K. flavescens, C. angustatus, and S. odoratus. Articular The articular is a semicircular element that is located posterior to the dorsal opening of the fossa Meckelii. It forms the medial two-thirds of the area articularis mandibularis, which faces posterodorsally to articulate with the condylus mandibularis. The articular contacts the prearticular medially, the surangular laterally, on the area articularis surface, and the angular ventrally. It appears that the foramen posterius chorda tympani is located just ventral to the medial half of the area articularis mandibularis in B. wyomingensis. This foramen does not appear to be present in D. mawii; however, a small foramen was also visible in K. flavescens, K. sonoriense, and S. odoratus

90 68 Post Cranial Axial Skeleton Vertebrae Cervical Vertebrae Cervical vertebrae two through eight from USNM (Figure 31 and Figure 32) are preserved but disarticulated. The cervical formula is (2((3))4))5))6}}7}}8), which is similar to most Kinosternids but differs from D. mawii, where the second cervical instead of the third is biconvex. Williams (1950) studied variation within living Testudines and noted that the location of the anterior biconvex cervical may vary. For example, as noted above the third cervical is typically biconvex in Kinosternids, but biconvex fourth and second cervicals are known. Cervical variation appears to be common within many species of Testudines; therefore, it must be noted here that it is possible that the vertebrae from USNM may not represent the normal vertebral formula for B. wyomingensis. The second cervical of USNM is nearly complete, lacking only the prezygapophyses and the articular surface of the left postzygapophysis. The centrum is opisthocoelous and constricted medially, like an hourglass. The general shape of the second cervical from B. wyomingensis is similar to D. mawii, except that the centrum of D. mawii is procoelous. The anterior articular surface of the B. wyomingensis centrum is only slightly anteroconvex, appearing nearly flat. The transverse processes are directed slightly ventrally and end just anterior to the centrum. In other kinosternoids (e.g., S. triporcatus) these processes are more developed and may extend much further laterally, in some cases even further than the postzygapophyses. The left postzygapophysis is broken, but the right is complete and faces ventrally to slightly laterally. Although not complete, the broken edges of the second cervical indicate that both a ventral and dorsal keel were present. Posterior and lateral to the ventral keel, posteroventral processes extend below the articular surface of the centrum and are nearly fused medially.

91 69 Also nearly complete, the third cervical of USNM is missing only the prezygapophyses, the left transverse process, and the articular surface of the left postzygapophysis. Anteriorly, the biconvex centrum is wide and flat, and medially it is constricted similarly to cervical two. The right transverse process is longer than in cervical two but not directed as strong ventrally. The convex anterior centrum articulation in B. wyomingensis makes these processes appear more defined than in D. mawii, where the articulation is concave. These processes are not directed as laterally as in S. triporcatus. The low ventral keel is nearly complete and grades posteriorly into the centrum. Two short, round posteroventral processes extend posterolaterally from the ventral keel, ending below and slightly anterior to the posterior articular surface of the centrum. These processes may be more (e.g., S. triporcatus) or less developed (e.g., C. serpentina) in other taxa and when present appear to provide space for the ventral keel during vertebral articulation. A very low dorsal keel runs the length of the midline. Cervical four of USNM is broken into two pieces. One consists of the anterior half of the centrum, the prezygapophyses, and all but the posterior end of the postzygapophyses, and the second is the posterior half of the centrum. As in all kinosternoids with known vertebral formulas except D. mawii, the fourth cervical of B. wyomingensis is the first procoelous cervical vertebrae. The centrum is wide anteriorly with transverse processes that are more continuous with the anterior articular surface than in either cervical two or three. The centrum is constricted medially. The ventral keel is incomplete but was intermediate in height. Posterior to the ventral keel, two posteroventral processes terminate just below and slightly anterior to the posterior centrum articulation. The dorsal keel is low and extends between the lateral keels of the postzygapophyses. The preservation condition of the fifth cervical is similar to that of the fourth cervical, with the posterior half of the centrum broken off. The procoelous fifth cervical is wider than the fourth, with even broader transverse processes that are nearly

92 70 continuous with the anterior centrum articulation. As in D. mawii, these transverse processes are directed anteriorly unlike in S. triporcatus, where they are directed laterally. The articular surfaces of the prezygapophyses angle more steeply posteriorly than in the fourth cervical. Due to the incomplete ventral and dorsal surfaces, keel size and presence cannot be documented. The ventral portion of cervical six is nearly complete except for the left posterior articular process of the centrum. If complete the centrum would be procoelous. Dorsally the prezygapophyses are articulated to the centrum and face posteromedially. The postzygapophyses are broken off. A single, isolated postzygapophysis of the correct size and shape is associated with USNM and is attributed to cervical six, as no other cervical is missing its posterodorsal quarter. The centrum of cervical six is approximately equal in width to cervical five and is also constricted medially. The posterior end is doubly convex. A ventral keel is present, but there is no evidence of a dorsal keel. Overall vertebral shape is similar to that of D. mawii. The massive seventh cervical is complete except for the right prezygapophysis. The anterior double concave surface is wider than the posterior double convex surface. The ventral keel extends along the anterior three-fourths of the centrum and separates into two keels posterolaterally, forming a triangular depression beneath the centrum s posterior articular surface. The prezygapophyses, less massive than the postzygapophyses, are similar in size to the prezygapophyses of cervicals four through six. Large dorsal keels on the postzygapophyses contribute to the dorsal extension of the seventh cervical and they also produce a pronounced triangular depression between them. Two pieces of the eighth cervical are preserved. The centrum lacks the left half of the anterior double concave articular surface. The postzygapophyseal section is missing the right articular surface. Centrum eight is much shorter than centra two through seven, but it is nearly equal in length to the eighth postzygapophyses. As in D. mawii and most other Testudines, the base of only a single ventral keel is present on the posterior half of

93 71 the centrum in B. wyomingensis. Kinosternids and C. insculpta have a paired ventral keel. The postzygapophyses are similar in shape but larger and more dorsally curved than those of cervical seven. Thoracic Vertebrae The thoracic vertebrae are difficult to observe because they are an internal shell feature. Only two thoracic (dorsal) vertebrae were identified from USNM (Figure 33), as the visceral surface of the shell was covered with plaster during reconstruction and stabilization. One of these is the nearly complete first dorsal, and the other is incomplete; therefore, its location within the vertebral series is unknown. YPM 3745 has not been fully prepared, so no internal features are visible. Due to lack of preservation or preparation, no additional thoracic vertebrae were observed on other specimens of Baptemys. The first dorsal of USNM is missing the posterior articular surface of the centrum and the articular surface of the right prezygapophysis. The centrum is flatter than those of the cervical centra. The anterior articular surface is concave. Lateral to the anterior articular surface and ventral to the prezygapophyses are square, articular surfaces for the first thoracic (dorsal) ribs. From the shape of the articular surface, it appears that the ribs would extend posterolaterally as in D. mawii. In S. triporcatus and C. angustatus the first thoracic ribs are directed more horizontally. Although not completely preserved in USNM 13437, the posterior end of the first thoracic vertebrae appears to be similar to that of D. mawii in being only slightly expanded where it contacts the second thoracic ribs. In staurotypines the contact between the second thoracic rib and first thoracic vertebrae is more expanded, resulting in a nearly square vertebral centrum. On the dorsal surface of B. wyomingensis (USNM 13437) is a wide process that once articulated with the shell.

94 Figure 31. USNM 13437, Baptemys wyomingensis. Cervical vertebrae two through five in left lateral, anterior, posterior, dorsal, ventral, and right lateral views. 72

95 Figure 32. USNM 13437, Baptemys wyomingensis. Cervical vertebrae six through eight in left lateral, anterior, posterior, dorsal, ventral, and right lateral views. 73

96 74 Approximately half of a centrum comprises the other USNM dorsal vertebra. The preserved end is inferred to be anterior due to its laterally expanded nature. Posteriorly from the wide anterior end, the ventral surface narrows rapidly. On the dorsal surface the areas that articulate with the neural bones are visible, but not complete. Figure 33. USNM 13437, Baptemys wyomingensis. Thoracic vertebra one in left lateral, anterior, posterior, dorsal, ventral, and right lateral views.

97 75 Sacral and Caudal Vertebrae What remains of the sacral and caudal vertebrae of USNM (Figure 34) is not articulated, and it is impossible to determine the precise number that would have been present. No other specimens of B. wyomingensis with articulated vertebrae were observed during this study. Two isolated centra, two isolated neural arches, and two articulated vertebra from USNM are present. The centra are short and pinched into a keel ventrally. Sutural surfaces are positioned laterally to the centrum s anterior articular surface. The articular surfaces differ in size and shape between vertebrae. One centrum (Figure 34, A) has a wide, almost flat anterior surface and a tall key-hole shaped posteriorly convex surface. Another centrum (Figure 34, C) has a concave anterior fossa that is narrower than the lateral sides and a posterior surface that is flat and triangular. The two neural arches are similar in shape and have large rib articular surfaces placed ventrolaterally, which indicates that these are sacral or anterior caudal vertebrae. The larger (Figure 34, B) of the two caudals has a lower dorsal keel, and prezygapophyses with dorsomedially facing articular surfaces, and it is missing the postzygapophyses. The smaller neural arch (Figure 34, D) is missing the prezygapophyses, but the laterally facing postzygapophyseal articular surfaces are preserved. As noted above, in addition to the sacral or anterior caudal vertebrae, two posterior caudal vertebrae (Figure 34, E-F) were preserved. One of the posterior caudal vertebrae (Figure 30, E) consists of a partially complete centrum that is broken anteroventrally, with only the left transverse process preserved. The centrum is much more convex posteriorly than in the sacral/anterior caudal (Figure 30, A and C) or other posterior caudal (Figure 30, F) centra. The other posterior caudal vertebra (Figure 30, F) is nearly complete, with only the left prezygapophysis and the postzygapophyses missing or incomplete. The centrum is anteriorly flat to slightly convex posteriorly. It is expected that all caudal vertebrae would be procoelous (contra Joyce 2007, p. 47) if preserved. No

98 76 opisthocoelous caudal vertebrae were observed during this study. In addition to those described here, a procoelous caudal vertebra is preserved from AMNH 5934 (Hay 1908, p. 274). Extant kinosternoids including D. mawii, kinosternines, and staurotypines have entirely procoelous caudal vertebrae. Figure 34. USNM 13437, Baptemys wyomingensis. Sacral and/or anterior caudal vertebrae (A-D) and two posterior caudal vertebrae (E-F) in left lateral, anterior, posterior, dorsal, ventral, and right lateral views.

99 77 Shell A Yale Peabody Museum shell (YPM 3754) and a United States National Museum shell (USNM 13437) are the primary sources of the following description, and if differences exist, they are noted (Figure 35-Figure 52). When no specimen number is given, the two shells are alike in that feature. Additional specimens are referred to describe elements or surfaces that are lacking or not visible on YPM 3754 or USNM In general form and size the shell of B. wyomingensis is nearly identical to D. mawii (Appendix A, Figure A.5); however, there is some variation, which is discussed as applicable in the following sections. The shell of YPM 3754 is nearly complete. The carapace (Figure 35, Figure 36, Figure 39-Figure 42) lacks the distal end of the right fifth costal, the proximal two-thirds of the right sixth and seventh costals, a small triangle of the anteroproximal edge of the right eighth costal, most of the right seventh peripheral, and the distal edges of the peripherals posterior to the middle of number nine on the right and posterior to the middle of the tenth on the left. The plastron (Figure 49 and Figure 50) is entirely complete. The shell of USNM is also nearly complete and is larger than YPM The carapace (Figure 37, Figure 38, Figure 43-Figure 46) is missing the proximal twothirds of the left tenth peripheral and the posteroproximal corner of the left ninth peripheral. Plaster-filled gaps between a number of the bones indicate the shell was previously disarticulated and reconstructed. The plastron (Figure 51 and Figure 52) is complete except for the anterior point of the entoplastron, the posterolateral corner of the left hypoplastron, the posterolateral bulge of the right xiphiplastron, and the anterolateral corner of the left xiphiplastron.

100 78 Carapace Form A nuchal, eight neurals, eight paired costals, eleven paired peripherals, one to two suprapygals, and a single pygal form the carapace. The carapace sulci indicate that one cervical scale, five vertebral scales, four paired pleural scales, and twelve paired marginal scales were present. The carapace of YPM 3754 (Figure 35, Figure 36, Figure 39-Figure 42) is crushed dorsoventrally, resulting in disarticulation and cracking of the bones (CL of ~ 44 cm). The first two neurals and costals are pushed slightly ventral to the nuchal and following neurals and costals. The neurals posterior to neural five and the left costals posterior to costal four are raised above the rest of the shell and are closer to their true position. Additionally the left shell edge between peripherals three and eight is pushed ventrally. This distortion affects observations of overall carapace shape and the shape and measurements of individual bones. Since sediment fills YPM 3754, internal surfaces are not visible. United States National Museum (Figure 37, Figure 38, Figure 43-Figure 46) does not appear crushed and is larger than YPM Some of the increased shell length and width measurements may be attributed to the plaster fill between bones. During reconstruction, the carapace and plastron were connected with a light gray plaster-like material. This material also covers the visceral surfaces of both sides of the shell, making identification of internal structures impossible. The crushed carapace of YPM 3754 forms a low to moderate dome in cross section, while the oval carapace of USNM 3754 has a higher dome. The carapaces are longer than wide The fine shell surface sculpting becomes coarse posteriorly, especially proximal to the midline keel. Prominent midline keels are visible on the posterior ends of both shells. The medial keel on YPM 3754 begins on the anterior fourth of neural six and extends posteriorly to the middle of the pygal. On USNM 3754 the medial keel begins on

101 79 the anterior fourth of neural five and becomes more prominent than the one on YPM 3754 as it extends posteriorly to the back edge of the pygal. Lateral to the medial keels, the costals are rugose and pitted. Both specimens have left and right costal ridges that are less prominent than the medial keel but slightly more prominent than the remaining rugosities. These are not considered to be true keels, as they are irregularly formed. The left main rugosity of YPM 3754 lies 40 mm from the medial keel and extends posteriorly from the pleural sulcus on costal six to the pleuraovertebral sulcus on costal eight. A similarly shaped rugosity would probably also have been present on the right costals if they were preserved. The costal rugosities of USNM are more prominent. These trend posterolaterally from costal six, 50 mm from the midline, to the proximal edge of the eleventh peripherals, 71 mm from the midline. These prominent costal rugosities were observed on a number of but not all B. wyomingensis specimens (e.g., AMNH 5967, DMNS 40960, DMNS 511, UCMP , UCMP , USNM 16711, USNM 16713). Carapace Bones Nuchal The nuchal bone is wider than long. The posteroconvex anterior edge forms the front of the shell. The posterodistally angled lateral sides contact the first peripherals. Posterolaterally the nuchal bone contacts the first costals along posteromedially-angled sutures that terminate at an anteroconvex suture with neural one. The visceral surface of the nuchal was not visible in either YPM or USNM. Additional specimens reviewed reveal that while the nuchal spines consistently extends onto the first peripherals as it usually does in D. mawii, the extent is quite variable from just past the anterior margin (see examples in Figure 47) to all the way across, ending at the posterior margin.

102 Figure 35. YPM 3754, Baptemys wyomingensis. Carapace in dorsal view. 80

103 Figure 36. YPM 3754, Baptemys wyomingensis. Carapace sketch in dorsal view. 81

104 Figure 37. USNM 13437, Baptemys wyomingensis. Carapace in dorsal view. 82

105 Figure 38. USNM 13437, Baptemys wyomingensis. Carapace sketch in dorsal view. 83

106 84 Figure 39. YPM 3754, Baptemys wyomingensis. Carapace right lateral view. Figure 40. YPM 3754, Baptemys wyomingensis. Carapace right lateral sketch.

107 85 Figure 41. YPM 3754, Baptemys wyomingensis. Carapace left lateral view. Figure 42. YPM 3754, Baptemys wyomingensis. Carapace left lateral sketch.

108 86 Figure 43. USNM 13437, Baptemys wyomingensis. Carapace right lateral view. Figure 44. USNM 13437, Baptemys wyomingensis. Carapace right lateral sketch.

109 87 Figure 45. USNM 13437, Baptemys wyomingensis. Carapace left lateral view. Figure 46. USNM 13437, Baptemys wyomingensis. Carapace left lateral sketch.

110 Figure 47. Baptemys wyomingensis. Visceral images of UCMP peripherals one through three and first costal (A) and UCMP carapace (B). 88

111 89 Costals A complete series of neural bones restrict all eight costal pairs from meeting at the midline. The first costals are trapezoidal elements. Costals two through six are horizontal rectangles except for the posteroproximal processes that contact the neurals and the small distal processes that reach the peripheral sutures. The first costals contact the main body nuchal anteroproximally along posteroproximally trending sutures, the first through third peripherals distally along posterodistally trending sutures, neural one laterally along vertical sutures, neural two posteroproximally along posterodistally trending sutures, and the second costals along horizontal to slightly posteroconvex sutures. The second costals contact neural two medially along posteroproximally angled sutures and neural three posteromedially along posterolaterally angled sutures. From the neurals the second costals extend laterally, horizontally contacting the first costals anteriorly and the third costals posteriorly, to terminate distally at the third and fourth peripherals. The third costals contact the fourth, fifth, and sixth peripherals distally; the second costals anteriorly; the fourth costals posteriorly; neural three proximally; and neural four posteroproximally. The fourth costals contact the sixth and seventh peripherals distally, the third costals anteriorly, the fifth costals posteriorly, neural four proximally along a posteroproximally trending suture, and neural five posteroproximally. The fifth costals contact the seventh and eighth peripherals distally, the fourth costals anteriorly, the sixth costals posteriorly, neural five proximally along a posteroproximal suture, and neural six posteroproximally. The sixth costals contact the eighth and ninth peripherals distally, the fifth costals anteriorly, the seventh costals posteriorly, neural six proximally along a posteroproximal suture, and neural seven posteroproximally. While the patterns described above for costal-peripheral contacts are the most common, variation does occur. For example, the suture between the third and fourth costals may be

112 90 in line with the suture between the fifth and sixth peripherals, thereby excluding contact between the third costals and the sixth peripherals. Posterior to the sixth costals in YPM 3754 and the seventh costal in USNM 13437, the neural and suprapygal sutures are not distinct due to fusion of sutures between bones. In both specimens the seventh costals contact the ninth and tenth peripherals distally, the sixth costals anteriorly, the eighth costals posteriorly, and neural seven proximally along a posteroproximally trending suture. In USNM the seventh costals also contact the eighth neural posteroproximally. Due to indistinct sutures it is impossible to tell if this occurs in YPM The eighth costals in both specimens contact the tenth and eleventh peripherals distally, the seventh costals anteriorly, neural eight and possibly suprapygal one proximally, and suprapygal two posteriorly. Although the sutures are not readily visible due to their fusion, the eighth costal in YPM 3754 may also contact neural seven anteroproximally. This contact is restricted in USNM by neural eight and the seventh costals. A review of additional specimens revealed that while variation in the medial contacts of the seven and eighth costals may occur, accurate detailed observations are often problematic due to fusion of sutures or because of crushing that is in some cases further complicated by reconstruction. In some specimens the anterolateral-posteromedially angled portion of the medial (neural) contact of the seventh costal is slightly interrupted and differs from other costals-neural sutures in its shape due to a potentially divided or medially constricted seventh neural (e.g., UCMP , ANSP 10074; see Figure 48). The medial contact of costal eight may be similarly interrupted as it contacts the eighth neural along an anterolateralposteromedially direct suture that angles posterolaterally along the lateral edge of the anterior suprapygal and may or may not be slightly convex (e.g., ANSP 10074, and DMNH48164 vs. UCMP ; see Figure 48). From observations of partially disarticulated carapaces, the visceral surfaces of the first costals receive thoracic ribs one and two (Figure 47). The first ribs lie anterior

113 91 and slightly ventral to the second ribs and extend proximally to meet the first thoracic vertebra. The second ribs extend ventroproximally from the proximal edge of the first costals to contact thoracic vertebrae one and two. The dorsoventrally flattened, round distal ends of the second ribs fit into the notch on the third peripherals. Anterior to the second thoracic rib-peripheral contact, the axillary buttresses contact the ventrodistal margins of the first costals (Figure 47). Often the axillary buttress itself is not preserved; however, a small notch along the anterior costal edge marks the location of the axillary buttress. Viscerally costals two through eight are nearly smooth except for the proximal edge, where the ribs extend ventroproximally to articulate with the thoracic vertebrae. The rib necks are triangular-shaped where the rib heads are broken off. Peripherals The eleven-paired peripherals are tightly sutured to the costals. Except for the proximally narrow first pair, the peripherals are rectangle elements. The first peripherals contact the nuchal along posterodistally-angled sutures, the first costals proximally, and the second peripherals posteriorly. Peripherals two through eleven contact each other, along approximately straight sutures and the peripheral anterior and posterior to them except for the eleventh peripherals, which posteriorly contact the lateral edges of the pygal. Proximally the peripherals contact only the costals except for the eleventh peripherals, which contact the suprapygal. The second peripherals contact the first costals. The third peripherals contact the first costals and the anterodistal edge of the second costal. The fourth peripherals mostly contact the posterodistal edges of the second costal but also extend to the anterodistal edge of the third costals. The fifth peripherals contact only the third costals proximally on both sides of YPM 3754 and on the right side of USMN 13437; however, the relationship is unclear on the left side of USMN The sixth peripherals contact the fourth costals and the posterior corner of the third costals. The seventh peripherals contact a small portion of the fourth costals and half of

114 92 the fifth costals. Anteroproximally the eighth peripherals contact the fifth costals and posteroproximally the sixth costal. The anteroproximal half of the ninth peripherals contact the sixth costals and the posteroproximal half of the seventh costals. The tenth peripherals contact the seventh and eight costals. Besides contacting the suprapygal, the eleventh peripherals also contact costal eight anteroproximally. Peripherals four through seven or eight suture to the plastron and contribute to the plastral bridge. The second and third peripherals, while not contributing to the surficial ossified portion of the bridge, do articulate with the elongated axillary buttresses. While the articulation with the second peripheral is partially visible in USNM (left side, Figure 37) a number of disarticulated shells display the contacts of the axillary buttresses in much greater detail (e.g., Figure 47). The fourth peripherals form the distal sides of the axillary notches and contact the hyoplastra. The fifth peripherals also contact the hyoplastra. The contacts of the sixth through eighth peripherals differ on USNM and YPM On YPM 3754 and on the right side of USNM 13437, the sixth peripherals anteroproximally contact the hyoplastra and posteroproximally contact the hypoplastra. The sixth peripherals on the left side of USNM only contact the hypoplastra. On both plastra the seventh peripherals contact the hypoplastra. On YPM 3754, all of the proximal edge contacts the hypoplastra whereas on USNM only the anteroproximal corner contacts the hypoplastra. The anteroproximal edges of the eighth peripherals on YPM 3754 contact the hypoplastron and form the distal edges of the inguinal notches. This contact is absent on USNM 13437, as the eighth peripherals are excluded from the plastral bridge. A review of additional specimens showed that variation of the surficial contacts of the posterior plastral bridge as well as the amount of extension of the hypoplastral buttress are not unusual. See the Hypoplastron section for further discussion

115 93 Neurals A complete series of eight neurals form a continuous row, restricting contact of the costals on the midline. Neural one is an anterior-posteriorly elongate quadrilateral element. Convex anterior and posterior ends contact the nuchal and second neural respectively. Neural one is narrower posteriorly and widest near the middle due to convex lateral sides that contact the first costals. Neurals two through six are hexagonal or coffin-shaped elements that narrow posteriorly toward the midline. The wide anterior end of neural two medially contacts neural one along a posteroconvex suture and anterolaterally contacts the first costals along a posterolaterally-angled suture. The posteromedially-angled sides contact the second costals and terminate at a posteroconvex suture with neural three. The third neural is similar to neural two, except the posterior end in YPM 3754 is horizontally instead of posteroconvexally sutured to the following neural (neural four). The anterolateral sides of neural three contact the second costals, and the posteromedially-angled sides contact the third costals. Neural four contacts costal three anterolaterally and costal four laterally, and the slightly posteroconvex back end of neural four contacts neural five. The wide anterior end of neural five laterally contacts the fourth costals. The long edges of neural five contact the fifth costals, and the horizontal posterior edge contacts neural six (not visible in YPM 3754). Neural six contacts the fifth costals anterolaterally, the six costals laterally, and neural seven posteriorly along a horizontal suture. Neural seven also appears to be coffin-shaped, however it is difficult to identify sutures on the posterior end of YPM If the interpretations of the sutures on YPM 3754 are correct, neural seven contacts the seventh costals anterolaterally, neural eight posteriorly along a horizontal suture and possibly the eighth costals posterolaterally. Neural seven of USNM is six sided and shorter than neurals one through six and does not contact the eight costals. What appears to be a vertebral sulcus crosses neural seven in YPM In both specimens, neural eight contacts the eighth costals laterally. While five sides of neural eight are visible in USNM 13437, the location of the posterior

116 94 suture is unclear. Neural eight in USNM contacts the seventh costals anterolaterally; these relationships are unclear in YPM This region of the shell as discussed above is often problematic; however, it was visible in select fully prepared or disarticulated specimens. The shape of neural seven and neural eight are variable between individuals (see Figure 48 for select examples). Neural seven may be elongated and at times divided or expanded posteriorly (e.g., UCMP , ANSP 10074), while in other individuals it is short (e.g., UCMP ), similar to USNM described above. Neural eight was observed to be both round and very short (e.g., UCMP , AMNH 1494) as well as broad and hexagonal (e.g., ANSP 10074, UCMP ). Suprapygals The sutures are unclear on the posterodorsal surface of USNM and YPM 3754, and the visceral surfaces are not available for study; therefore, it is difficult to distinguish the number of suprapygals. The suprapygal-pygal suture is horizontal medially and then angles posterodistally on both sides, allowing the suprapygal to contact peripheral eleven posterolaterally. The suprapygal narrows anteriorly while laterally contacting the eighth costals. The distance it extends anteriorly cannot be observed on either specimen. Anterior to the suprapygal-pygal suture on YPM 3754 is a horizontal line where bone appears to have grown on bone. From observations of disarticulated and prepared specimens, two suprapygal are typical. The anterior suprapygal is four sided and is wider than the neurals, but it is similar in length (Figure 48). It contacts neural eight anteriorly along a horizontal suture, the eighth costals laterally along slightly convex slightly anteromedial-posterolaterally orientated sutures, and the posterior suprapygal along a horizontal suture. Nearly twice as long and three times as wide as the anterior suprapygal, the posterior suprapygal is trapezoidal and contacts the eighth costals laterally and, as mentioned above, the pygal and eleventh peripherals posteriorly.

117 Figure 48. Baptemys wyomingensis. Images of the suprapygal region of UCMP (A), ANSP (B), DMNH (C), and UCMP (D). 95

118 96 Pygal The rectangular pygal contacts the posterior suprapygal anteriorly and the eleventh peripherals laterally. The anterior edge is not completely horizontal, as the distal edges angle posteriorly. The horizontal posterior edge, often broken, is complete in USNM 13437, and there is a small notch on the midline. Of the specimens observed, the majority have a notch, although this size and shape is variable. Only a few specimens that lacked the notch were observed. The one B. garmanii pygal observed with an associated shell has a small notch. Carapace Scales Cervical The cervical scale is an elongate four-sided element that widens posteriorly and is restricted to the nuchal bone. The sides, which contact the first marginals along posterodistally-angled sulci, terminate at a horizontal sulcus with vertebral one. Vertebrals The shield -shaped (four-sided) first vertebral scale narrows posteriorly to contact vertebral two horizontally. The anterior margin contacts the cervical horizontally, and laterally it meets the first and second marginals at a posterolateral angle. Along posteromedially trending sulci the lateral sides contact the first pleurals. Vertebral scale one covers the posterior half of the nuchal, the anteroproximal corner of the first peripherals, the anteroproximal corner of the first costals and the anterior three-fifths of neural one. Vertebral scales two through five are narrower than vertebral one. The second through fourth vertebral scales are elongate four-sided elements with slightly rounded corners and small, laterally pointed processes that extend distally to reach the pleural sulci. Vertebral scale two contacts the first and second pleurals. It covers the posterior two-fifths of neural one, all of neural two, the front three-fifths of neural three, the

119 97 posteroproximal edges of the first costals, the proximal edge of the second costals, and the anteroproximal edges of the third costals. Posterior to vertebral two, vertebral three contacts the second and third pleurals laterally. Vertebral scale three covers the posterior two-fifths of neural three, all of neural four, the anterior three-fourths of neural five, the posteroproximal corners of the third costals, the proximal edge of the four costals, and the anteroproximal corners of the fifth costals. Sutures and sulci are not clear on the back of YPM There may be an extra groove or sulcus across neural seven, indicating that either there was an extra scale present or there was a kink under one of the scales. Vertebral scale four covers the posterior fourth of neural five, all of neural six, and the anterior half of neural seven (YPM 3754) or all of neural seven and some of neural eight (USNM 13437, possibly YPM 3754). This scale contacts the third and fourth pleurals laterally. Posterior to vertebral four, vertebral five contacts the fourth pleurals anterolaterally and the eleventh and twelfth marginals posteriorly. The fifth vertebral is an inverted shield -shaped element that covers at least one suprapygal, some (USNM 13437) or possibly all of neural eight (YPM 3754), the posterior half of the eighth costals, the anterior edge of the pygal, and nearly all of the proximal side of the eleventh peripherals except for the most anterior corner. Pleurals The first pleural scales are four sided. The distal sides curve laterally and have small processes that extend out to meet the second-third, third-fourth, and fourth-fifth marginal sulci. The anteroproximal edges contact vertebral one along posteroproximally trending sulci, and the proximal edges contact vertebral two vertically. The distal edges anteriorly contact marginals two and three along posterodistally angled sulci and laterally contact marginals four and five vertically. The posterior edges horizontally contact the second pleurals. Anteriorly, the first pleurals cover the posterior two-thirds of the first

120 98 costals and the anterior half of the second costals. Distally the first pleurals overlap onto the posteroproximal corners of the first peripherals, the proximal edges of the second and third peripherals, and the anterior edges of the fourth peripherals. The second and third pleurals are horizontally orientated rectangles, with small distal processes that extend to meet the marginal sulci. The second pleurals contact marginals five, six, and seven distally; vertebral two proximally; and the third pleurals posteriorly. The second pleurals cover nearly all of the third costals except for the proximal edges. They overlap the posterior edge of costal two, the posteroproximal corner of the fourth peripheral, the proximal edges of the fifth and sixth peripherals, and the anterior edge of the fourth costals. Extending posteriorly from the second pleurals, the third pleurals cover the posterior edges of the fourth costals, all of the fifth costals except the proximal edge, the anterior edges of the sixth costals, and the proximal edges of peripherals seven and eight. The third pleurals contact vertebral three anteroproximally and vertebral four posteroproximally. Laterally they contact the posteroproximal edges of the seventh marginals, the proximal edges of the eighth marginals, and the anteroproximal edges of the ninth marginals. Distally the slightly rounded fourth pleurals contact the posteroproximal edges of the ninth marginals, the proximal edges of the tenth, and the anteroproximal edges of the eleventh. They contact vertebral four proximally and vertebral five posteroproximally. The fourth pleurals cover the posterior edges of the sixth costals, most of the seventh costals aside from the proximal edges, and the anterior edges of the eighth costals. Distally they extend onto the proximal edges of the ninth and tenth peripherals and the anteroproximal corner of the eleventh. Marginals On the dorsal shell surface the twelve-paired rectangular marginal scales are restricted to the nuchal and peripherals. The first marginals cover the anterolateral edges

121 99 of the nuchal and the anterodistal corners of the first peripherals. The second marginals cover the posterior half of the first peripherals and the anterior half of the second peripherals. This trend of the marginals covering the peripheral sutures continues posteriorly along the shell. One exception occurs with the twelfth marginals, where they cover the posteroproximal corners of the eleventh peripherals and extend onto the lateral sides of the pygal. The first marginals contact the cervical scale anteriorly, the second marginal scales posteriorly, and vertebral one proximally. The second marginals proximally contact vertebral one and the first pleurals and posteriorly the third marginals. Marginals three through eleven contact the marginals anterior and posterior to them, as well as pleurals along their proximal edge. Marginals three and four only contact pleural one. The fifth marginals contact both the first and second pleurals. The sixth marginals contact only the second pleurals, while the seventh marginals contact the second and third pleurals. The eighth marginals contact only the third pleurals, and the ninth marginals contact the third and fourth pleurals. The tenth marginals contact only the fourth pleurals, while the eleventh contacts the fourth pleurals and the fourth vertebral. The twelfth marginals contact vertebral four anteriorly and the eleventh marginals laterally. Additional contacts occur ventrally, where marginals four through eight cover portions of the plastral bridge. The fourth marginals contact the axillary scutes on the third and fourth peripherals. The scute contacts differ between and within specimens of B. wyomingensis due the inconsistent number of inframarginal scutes. For example the scale contacts posterior to the fourth marginals differ between YPM 3754 and USNM The variation occurs because on USNM fewer peripherals contribute to the plastral bridge, and the left side has three inframarginal scutes instead of four, as on the right and on both sides of YPM On YPM 3754, the fifth marginals contact the axillary scutes and the second inframarginals on the lateral edges of the hyoplastra. The sixth marginals contact the

122 100 posterodistal processes of the second inframarginals and the distal edge of the third inframarginals on the hyoplastra and hypoplastra. The seventh marginals contact the posterodistal edge of the third inframarginals, the lateral edge of the inguinal on the hypoplastron anteriorly, and peripheral seven posteriorly. The sulci are not clear, but the eighth marginals may contact the inguinal scales. On the left side of USNM 13437, marginal five contacts the inguinal and the second inframarginal on peripheral four and the hyoplastron. Marginal six contacts the second inframarginal on the hyoplastron and hypoplastron and the axial on the hypoplastron and peripheral six. Marginal seven contacts the inguinal scute on peripherals six, and marginals seven and eight may contact (sulci are not clear) the inguinals on the seventh peripherals. The right side of USNM has one additional inframarginal. The fifth, seventh, and eighth marginal contacts are the same. The sixth marginals, however, contact the posterior edge of inframarginal two, the distal edge of inframarginal three, and the anterodistal edge of the inguinal. Plastron Form The finely sculptured plastron is broad, well ossified, and akinetic. Four paired bones and one unpaired bone form the tightly sutured plastron. The anterior and posterior lobes and the bridge each form a third of the plastral length. The anterior lobe is rounded with a slight notch at the midline, which is more pronounced in YPM 3754 (Figure 49- Figure 50). The rounded posterior lobe lacks a xiphiplastral notch. The plastra of YPM 3754 and USNM (Figure 51-Figure 52) appear quite similar at first glance; however, the plastron of YPM 3754 is broader or more expanded than USNM and requires an additional peripheral for the larger bridge.

123 101 Plastron Bones Epiplastra The four-sided epiplastra are the anterior bones of the plastron and meet at the midline along a vertical suture. Proximally, the epiplastra contact the hyoplastra and entoplastron along sutures that angle posterolaterally from the midline. A small notch occurs on the lateral margins of the epiplastra at the gular-humeral scute sulci. Entoplastron The wide, diamond -shaped entoplastron is centered at the plastral midline. The anterior and posterior halves are tightly sutured to the epiplastra and hyoplastra respectively. Posteriorly the ento-hyoplastral sutures angle anterolaterally from the midline. A review of other specimens shows that the shape of the entoplastron is commonly variable from having rounded anterior and posterior limits, as in YPM 3754, to being slightly pointed anteriorly and/or posteriorly, as in USNM Hyoplastron The anterolateral processes of the hyoplastra extend anteriorly to meet the epiplastra and entoplastron. Posterior to the entoplastron, the hyoplastra widen into horizontal rectangles that meet at the midline. The lateral hyoplastral edges of USNM and YPM 3754 contact the fourth and fifth peripheral bones. In YPM 3754, the hyoplastra also contact the anterior halves of the sixth peripherals. The posterior edges of the hyoplastra contact the hypoplastra horizontally. The right and left hyo-hypoplastral sutures are not continuous across the midline; in both YPM 3754 and USNM 13437, the left sutures lie anterior to the right. The lateral edges of the hyoplastra form the anteroproximal half of the bridge, and the axillary notches are positioned posterior to the entoplastron.

124 Figure 49. YPM 3754, Baptemys wyomingensis. Plastron in ventral view. 102

125 Figure 50. YPM 3754, Baptemys wyomingensis. Plastron sketch in ventral view. 103

126 Figure 51. USNM 13437, Baptemys wyomingensis. Plastron in ventral view. 104

127 Figure 52. USNM 13437, Baptemys wyomingensis. Plastron sketch in ventral view. 105

128 106 Observations of other specimens (Figure 47) show that the axillary buttress extends anteriorly, as in D. mawii, to insert a foot -ike process on the distal margin of the first costal, the posteroproximal margin of the second peripheral, and the anteroproximal margin of the third peripheral. Hypoplastron Anteriorly the hypoplastra are rectangular, narrowing posteriorly to form the anterior portion of the posterior plastral lobe. The hypoplastra meet each other along their entire length at the midline. Laterally the hypoplastra form the posteroproximal portions of the plastral bridges. In USNM 13437, the hypoplastra suture to only the sixth and seventh peripherals; however, in YPM 3754, they contact the posteroproximal edge of the sixth, the proximal edge of the seventh, and the anteroproximal edge of the eighth. If the hyo-hypoplastral suture occurs posterior to the fifth-sixth peripheral suture, the surficial contacts of the hypoplastron may extend onto peripheral eight, and the buttress may reach the ninth peripheral (visible in UCMP and UCMP ). Based on a review of specimens, this does not appear to be directly related to the size of the shell. Unfortunately, only a few specimens of B. wyomingensis preserve this portion of the shell. Posteriorly the hypo-xiphiplastral sutures, which angle slightly posterolaterally from the midline, are Z-shaped near the lateral margin (YPM 3754). The inguinal notch is located anterior to the hypo-xiphiplastral suture. Xiphiplastron The distally rounded xiphiplastra form approximately two-thirds of the posterior plastral lobe and meet each other at the midline. A small indentation occurs along the lateral margins of the xiphiplastra at the femoral-anal scute sulci. Posterior to the indentations, the xiphiplastra bulge outward in B. wyomingensis. Additional plastral sketches are provided in Appendix B to illustrate the variation in the xiphiplastron within

129 107 B. wyomingensis and between B. wyomingensis and the pointed or V-shaped plastral lobe found in B. garmanii. Plastron Scutes This study will use the plastral terminology and primary homology statements from Hutchison and Bramble (1981). Each scute pair meets at the midline, occasionally forming sinuous sulci as on the hyoplastron and hypoplastra of YPM 3754 and on the hypoplastra of USNM All of the sulci between scutes are convex posteriorly except for the humeral-abdominal, which is nearly horizontal. Gulars (set 1) As the most anterior scute set, the triangular gulars cover most of the epiplastra and extend across the anterior half (YPM 3754) to most (USNM 13437) of the entoplastron. As mentioned above, the gular-humeral sulci are convex posteriorly; however, toward the lateral margin the sulcus makes one anteroconvex dome. Medial to the dome the gulars may extend (USNM 13437) or may not extend (YPM 3754) onto the hyoplastra. Extension onto the hyoplastra occurs if the sulci cross the ento-hyoplastral suture posterior to the entoplastral lateral points. Humerals (set 3) Anterolaterally the pentagonal humerals extend briefly onto the epiplastra within the anteriorly convex dome of the gular-humeral sulci on YPM 3754 but are not visible on USNM Anteromedially the humerals cover the back of the entoplastron. The humerals also cover most but not all of the hyoplastra, restricting the humeral-abdominal sulci to the hyoplastra. Posterolaterally the humerals contact the first two inframarginals. Abdominals (set 5) The abdominals are rectangular, with the exception of the small posterolateral processes that reach the inguinal notch rims and hinder contact between the femoral and

130 108 the inguinal scutes. These processes are absent in D. mawii, where the abdominals are excluded from contacting the inguinal notch. The abdominals extend anteriorly onto the posterior edge of the hyoplastra and posteriorly cover the anterior end of the hypoplastra, thereby restricting the abdomino-femoral sulci to the hypoplastra. Laterally the abdominals contact the posterior three inframarginals on YPM 3754 and USNM (right side), but they contact only the posterior two on the left side of USNM Femorals (set 6) The vertically orientated rectangular femoral scutes cover the hypoplastra posteriorly, extend across the hypo-xiphiplastral sutures, and continue onto the anterior edges of the xiphiplastra. The lateral edges of the femoral scutes contact the sides of the posterior lobe. The femoro-anal sulci are restricted to the xiphiplastra. Anals (set 7) The triangular anals are restricted to the posterior end of the xiphiplastra and contact the posterior and posterolateral edges of the plastron. Inframarginals The number and shape of the inframarginals vary between shells. The right bridge of USNM and both sides of YPM 3754 have four inframarginals, while the left bridge of USNM has three. The proximodistally elongated anterior inframarginals (axillary scutes) contact the fourth and fifth marginals. They cover the anterodistal edges of the hyoplastra, including half of the axial notches and the anteroproximal corner of the fourth peripherals. The second inframarginals on YPM 3754 and the right side of USNM are restricted entirely to the hyoplastron. They contact the humeral and abdominal scales proximally and the fifth and sixth marginals distally. On the left bridge of USNM 13437, the second inframarginal is much longer, nearly equal in length to the second plus the

131 109 third inframarginals of the right side. It covers the hyo-hypoplastral suture and contacts the humeral and abdominal scales proximally and the fifth and sixth marginals distally. The third inframarginals on YPM 3654 and on the right side of USNM cover the hyo-hypoplastral sutures and contact the abdominal scutes proximally and the sixth marginals distally. The posterior inframarginals (inguinals) contact the seventh and eighth marginals distally and the abdominals proximally. They cover the posterodistal arm of the hypoplastra, including half of the inguinal notches, and they reach laterally to cover the sixth and seventh peripheral edges of USNM and the seventh and eighth peripheral edges of YPM Appendicular Skeleton Pectoral Girdle The left scapula and coracoid are preserved in USNM (Figure 53). The bones of the pectoral girdle are disarticulated and incomplete, making it difficult or impossible to describe all spatial relationships. No articulated (scapula + coracoid) pectoral girdles from B. wyomingensis were observed during this study. In addition, only four other scapulae and one coracoid were observed. Scapula The left scapula from USNM is complete, but the scapula is broken into two pieces dorsal to the glenoid fossa. The scapula s lateral surface forms the anterodorsal two-thirds of the bean-shaped glenoid fossa. The long, circular scapula is nearly twice the length of the acromion process and extends dorsally from the glenoid fossa at an approximately 90-degree angle and angles medially near the dorsal end. The scapula shape and angle is similar to that in other kinosternoids. The angle between the scapula and acromion is variable among other taxa; for example it is, smaller at

132 110 approximately 70 degrees in most trionychids (Meylan 1987 and author s personal observations). The anteromedially angled acromion process is oval in cross section and lies in a ventral plane. On the dorsal surface of the acromion process, a prominent unnamed process extends posteromedially toward a similar but less pronounced process on the Figure 53. USNM 13437, Baptemys wyomingensis. Left pectoral girdle in dorsal (A), ventral (B), posterior (C), and anterior (D) views.

133 111 coracoid. Below the unnamed process, a shallow groove is formed on the ventral surface of the acromion process. The unnamed process is also found in D. mawii and all extant kinosternoids, and likely in B. garmanii, although no scapula-shell associations were observed in this study, DMNH (Locality DMNH 3783, Lost Cabin Member, Wind River Formation, Fremont County, Wyoming) consists of an isolated left acromion process and small portion of the coracoid and scapula, which has the unnamed process. The space between the process on the acromion and the process on the coracoid is variable between taxa. In B. wyomingensis, D. mawii, and the inferred B. garmanii specimen, these processes are separated, whereas in kinosternines and staurotypines, they are fused together, forming a small pocket ventromedial to the acromion processes. In kinosternines and staurotypines the medial process of the acromion is longer, extending further anterior than the coracoid process. Similar processes are not known from any other Testudines. As in other kinosternoids, the medial end of the acromion process in B. wyomingensis is slightly expanded. Coracoid The proximal end of the left coracoid is missing from USNM The lateral end of the coracoid is round and articulates with the scapula to form the posteroventral third of the glenoid fossa. Medial to the glenoid, the round coracoid neck narrows and then flattens dorsoventrally. A prominent process on the dorsal surface of the coracoid extends anterolaterally. The coracoid process is located directly posterior to the process on the acromion process of the scapula but is thinner and not as prominent. A low ridge runs along the anterior margin of the ventral surface. On a more complete right coracoid preserved from UCMP 45477, from the medial process the coracoid becomes dorsalventrally flattened, the posterior edge is straight and the anterior surface is slightly expanded. The coracoid of D. mawii is less expanded and straighter than that of B.

134 112 wyomingensis, while those of extant staurotypines and kinosternines are more expanded and curve slightly anteriorly medially. Fore limb The left humerus, ulna, radius, and one carpal are preserved from USNM The disarticulated bones of the fore limb in USNM make it difficult or impossible to determine contacts and distal bone identifications. Phalanges are also preserved and are discussed in a separate section, as the fore and hind limb elements were not differentiated from each other. The YPM specimen (3754) preserved the right humerus, ulna, and radius. The humerus and ulna remain encased in matrix with only one side visible. Humerus The left humerus of USMN (Figure 54) is complete, but the distal end is crushed dorsal-ventrally. In dorsal view, the caput humerus is slightly oval and angles faintly posteroventrally. The caput shape does vary between specimens, as it is slightly elongated and more ovate and less circular in some (e.g., USNM , USNM ) than in USNM 13437, but it is still not as ovate or as posteroventrally orientated as in D. mawii. Anterior to the caput humerus is a small lateral shoulder, that grades into the ventrally directed lateral process. The medial process is more pronounced and is directed medially as well as ventrally. An articular surface is located medial to the caput along the dorsal surface of the medial process. Ventral to the caput humerus is the intertubercular fossa, which is partially bounded ventrally by a low ridge that connects the distal edges of the lateral and medial processes. The dorsally arched subcylindrical humeral shaft is concave medially and nearly straight laterally. Slightly distal to the caput is a small circular fossa on the dorsal surface of the humeral shaft. The ventral surface of the expanded distal humeral end has two condyles. The anterior, capitellum, is convex and circular, whereas the posterior, trochlea, is flat and broad. The capitellum is more

135 113 prominent than the trochlea in B. wyomingensis and other kinosternoids, while in other taxa the processes appear nearly identical (i.e., Adocus) or the trochlea is more prominent (i.e., C. serpentina). Figure 54. USNM 13437, Baptemys wyomingensis. Left humerus in anterior (lateral) (A), dorsal (B), posterior (medial) (C), ventral (D), proximal (E), and distal (F) views. A completely formed ectepicondylar foramen is present on the dorsolateral and ventrolateral surfaces anterior to the capitellum in B. wyomingensis. The ectepicondylar foramen is not completely formed in all taxa, leaving the ectepicondylar canal open

136 114 laterally. However, this feature is not stable, as it is both open and closed in kinosternines (Sternotherus and Kinosternon) and D. mawii. Meylan (1987) mentioned that the status of the canal varies with ontogeny in certain clades (chelydrids), which may be the case with the kinosternines and/or D. mawii. The canal was believed by Meylan (1987) and by Hutchison (1991) to always be open in staurotypines, yet the canal in the S. triporcatus (AMNH ) viewed in this study was completely closed. Figure 55. YPM 3754, Baptemys wyomingensis. Right humerus (H) in lateral view, right ulna in medial view (U) and a cervical vertebra (V) in anterior view.

137 115 A triangular fossa extends proximally from the capitellum and trochlea to the narrow section of the humeral shaft. The humerus of D. mawii is nearly identical to that of B. wyomingensis, except that with a less massive humeral shaft, it appears slightly more delicate. In addition, the overall shape of the humerus of B. wyomingensis is very similar to other kinosternoids; however some variation does occur. For instance, the medial process of C. angustatus is proportionately higher than it is in other taxa, and the intertubercular fossa is proportionately narrower in kinosternines and staurotypines than in dermatemydid. Ulna The right ulna of YPM 3754 (Figure 55) is complete but incased partially in matrix, while the left and right ulnae of USMN (Figure 56) are partially preserved. As in D. mawii the ulna is approximately two-thirds the length of the humerus, whereas in kinosternids these two elements are slightly closer to equal lengths, and in other testudines they are nearly equal in length. The left ulna of USMN is complete except for the distal articular surface, while only a portion of the right s proximal end is preserved. The dorsal side of the left USMN ulna extends proximally further than in D. mawii and other kinosternoids forming a prominent incipient olecranon, which contributes to the triangular articular surface. Upon review of other B. wyomingensis ulnae (UCMP , USNM 16713), some of the olecranon expansion in USMN appears to be a result of elongation due to crushing. A low bicipital tubercle extends along the radial (anterior) side of the ulna from the distal edge of the proximal articular surface to the middle of the shaft. Distal to the process, the ulna narrows between the concave medial and lateral sides. The distal end of the ulna is expanded and flattened and has a shallow depression on the radial half of the ventral surface. Due to the incomplete and unprepared nature of the USNM and YPM 3754 ulnae respectively, the total amount of expansion and the precise shape of the distal articular surfaces were further

138 116 studied in AMNH The distal ulna end is similar to that of other kinosternoids and cryptodires, with the posterior side extending further distally than the medial side, and a distinct ridge separating the two articular surfaces that contact the ulnare and intermedium. Figure 56. USMN 13437, Baptemys wyomingensis. Left ulna in anterior (A), dorsal (B), posterior (C), ventral (D), and proximal (E) views. Right ulna in anterior (F), dorsal (G), posterior (H), ventral (I), and proximal (J) views.

139 117 Radius Only the proximal halves of the right radii are preserved in USNM (Figure 57, A-E) and YPM 3754 (Figure 57, F-J), and they appear similar to other kinosternoid radii. The proximal radial surface, which articulates with the capitellum of the humerus, is oval-shaped with a depression or inset on the nearly flat medial side that contacts the ulna. The dorsal edge of the radius extends proximally over the articular surface. There are low processes on the dorsomedial and ventromedial edge of the radius distal to the articular surface. There is a small shallow fossa between the ridges on the radial s medial Figure 57. USNM (A-E), YPM 3754 (F-J), USNM (K), Baptemys wyomingensis. Right radius in anterior (A, F), dorsal (B, G), posterior (C, H), ventral (D, I), and proximal (E, J) views. Left radius in posterior (K) view.

140 118 surface. A second USNM specimen (16713) contains a complete left radius (Figure 57, K). The distal end of the radius extends further anterodistally, and it is approximately twice as wide as the proximal end, unlike the nearly equal ends of the radius in D. mawii. Carpals One carpal, the right fused centrale, is preserved from USNM (Figure 58). Wide and short, it flattens laterally and is tightly fused with no visible sutures. The proximal surface is convex, the distal surface is flat to slightly concave, the dorsal surface is convex with a depression medial of the midline, and the ventral surface is slightly concave and has two shallower depressions medial and lateral to the one on the dorsal surface. The centrale of B. wyomingensis is similar to that of D. mawii and other kinosternoids. Few other podials, carpals or tarsals, were observed during this study. However, another USNM specimen (16713) does have associated podials here believed to represent tarsals based on the presence of an astragalus-calcaneum, a fifth metatarsal, and a complete tibia. Figure 58. USNM 13437, Baptemys wyomingensis. Right centrale in proximal (A), ventral (B), dorsal (C), distal (D) views.

141 119 Pelvic Girdle The ilia, pubes, ischia, and epipubis are partially preserved in USNM (Figure 59, Figure 60, and Figure 61). Specific bone shapes and articular surfaces cannot be described from USNM because the bones of the pelvic girdle are disarticulated and incomplete, as were the majority of the observed pelvic girdle elements in other specimens. Three other specimens (AMNH 5934, UCMP 45477, UCMP ) are referred to in the following description, as they contain partially articulated pelvic girdles. Ilium The left and right ilia from USNM are nearly complete and are missing only some of their articular surfaces. Anteriorly the ilium is triangular in cross section. The ventral portion of the anterior articular surface is oval and forms the dorsal third of the acetabulum. Posterior to the iliopubic suture, the ilial notch is present on the ventromedial edge of the acetabulum. The ilial notch is found only in kinosternoids. Often it has been noted (Joyce 2007, Meylan and Gaffney 1989) that D. mawii is unique among the kinosternoids in lacking the ilial notch; however, specimens of D. mawii (i.e., USNM 66669) observed during this study have this notch. A second feature of the ilium, which is diagnostic of kinosternoids, is the thelial process. Even though it was not previously recognized as present in D. mawii by all authors (i.e., Joyce 2007, Meylan and Gaffney 1989), it was confirmed to be present on D. mawii specimens observed during this study. In addition, although select other taxa including Lissemys, carettochelyids, E. cretacea, and Adocus (Meylan and Gaffney 1989; Shaffer et al 1997 as well as personal observations) have thelial processes on the dorsal surface of their ilia, these processes may not be homologous structures as Joyce (2007) pointed out the iliotibialis muscle originates on this thelial process in both kinosternids and D. mawii but does not in Trionychidae (Zug 1971). Distal to the acetabulum and anterior to the prominent thelial process, the anterior one-third of the ilium is dorsoventrally flattened. The thelial process

142 120 slopes gradually posteriorly and contacts the dorsomedial ridge of the ilia, which extends posteriorly from the iliopubic suture. The posterior two-thirds of the ilium between the thelial process and the distal end is expanded ventrally, flattens lateromedially, and angles posteromedially. The ventral surface of the ilium arches dorsally. The posteromedial surface is concave below the dorsal edge. Figure 59. USNM 13437, Baptemys wyomingensis. Left pelvic girdle in dorsal (A) and ventral (D) views. Right pelvic girdle in dorsal (B) and ventral (C) views.

143 Figure 60. USNM 13437, Baptemys wyomingensis. Pelvic girdle in left (A) and right (B) lateral views. 121

144 122 Pubis The left pubis of USNM is nearly complete, but it is missing the anteromedial process and the medial edge. The right pubis of USNM is less complete; it is missing the medial edge, anteromedial process, and the acetabulum region. The posterolateral surface of the process forms the anteroventral third of the acetabulum, contacting the ischium posteromedially and the ilium posteriorly. Anterior to the acetabulum, the pubis thins, expands, and arches dorsally. The lateral side of the pubis curves inward and has a long, rectangular pectineal process that extends anterolaterally past the lateral extent of the acetabulum. A bulge is present along the middle of the anterior edge of the pectineal process. Medial to the pectineal process, the anterior pubic edge is concave and extends anteriorly, forming the lateral edge of a medial process. The anterior portion of this medial process is complete in UCMP The anterior edge slopes posteromedially to the pubic symphysis, and together the pubes form a V-shaped suture with the epipubis. While the posterior portion of the medial process is not complete in any specimen observed in this study, the portions that are preserved indicate that even if complete the pubis symphysis would not contact the ischiadic symphysis without additional cartilage (which may fully ossify in some individuals); therefore, the thyroid fenestra (puboishiadic foramen) would be undivided as in D. mawii. Epipubis An epipubis is preserved in USNM Posteriorly it comes to a point where it would articulate with the pubes; this contact can be observed in UCMP , where the pubes and epipubis are articulated. The anterior shape of the epipubis is variable between specimens; for example, it may be broad as in USNM and UCMP 45477, or it may be pointed as in UCMP This variation is consistent with variation observed in D. mawii (i.e., pointed USNM 66669; broadened FMNH 98950) during this study.

145 123 Figure 61. USNM 13437, Baptemys wyomingensis. Epipubis in dorsal (A) and ventral (B) views. Ischium The right and left ischia from USNM are incomplete medially. If complete, the ischia would contact at the midline. The lateral articular surface of the ischium forms the posteroventral third of the acetabulum. From the acetabulum, the ischium extends medially and the dorsal surface angles posteriorly, and if it were complete, it would form the metischial process. The dorsal side is nearly flat but rises slightly medially, whereas the ventral surface is concave medial to the acetabulum and then thickens medially. This medial thickening can be extreme; and may include an ossified hypogastroid (e.g., UCMP 45477). This is comparable to that found in some specimens of D. mawii (FMNH 98950). The anterior ischial edge is flat, whereas the posterior edge is concave. On the left ischium, the lateral edge of the metischial process extends posteriorly further than the acetabulum. Hind limb The left femur, right and left tibias, and the right fibula are preserved from USNM The bones of the hind limb are disarticulated in USNM 13437, making it difficult

146 124 or impossible to determine contacts and bone identifications. In addition to those elements preserved from USNM 13437, the fused right astragalus-calcaneum is preserved from YPM Femur The left femur of USNM is preserved; however, the proximal end is crushed anteroposteriorly, and the distal end is crushed dorsoventrally (Figure 62). The caput femur is round, points slightly medially (anteriorly), and extends at a slightly greater than 90 degree angle from the neck. The anterior trochanter minor and the posterior trochanter major are directed ventrally from the caput femur. Between the trochanters and ventral to the caput femur lies a well-defined, U-shaped intertrochanteric fossa. The ventral fossa boundary is not distinct, as there is no ridge connecting the distal ends of the trochanters as occurs in other taxa including D. mawii, instead the fossa shallows ventrally. Below the caput femur, the dorsally arched, S-shaped femoral shaft is round in cross-section and then flattens and expands distally. Two condyles are developed on the distoventral surface and together form a U-shaped articular surface. The posterior fibular condyle is prominent and has a sharp lateral edge. Posteroproximal to the fibular condyle along the posterior surface of the femoral shaft is the low, short ridge of the fibular epicondyle, which is better preserved in UCMP and UCMP It is present in other kinosternoids and was observed to be quite conspicuous in some specimens of D. mawii (FMNH 98950). The less prominent anterior tibial condyle is round and convex. A shallow groove separates the rounded surface of the anterior condyle from the sloping surface of the fibular condyle. Proximal to the condyles on the ventral femoral surface is a depression.

147 125 Figure 62. USNM 13437, Baptemys wyomingensis. Left femur in anterior (A), dorsal (B), posterior (C), ventral (D), proximal (E), and distal (F) views. Tibia The right tibia and all but the distal end of the left tibia of USNM are preserved (Figure 63). Proximally the tibia is triangular in cross-section, and the articular surface is directed slightly ventrally. The proximal articular surface is concave anteriorly but is wider and flat posteriorly. A low ridge separates the two areas. Below the medial (anterior) articular surface, the tibia expands anteriorly, and there is a small process. Distal to this expansion the tibia narrows, and on the dorsal surface a low ridge angles

148 126 distomedially between the expanded proximal and distal ends. A second ridge is located on the lateral edge of the tibia halfway between the dorsal ridge and the distal end. A groove runs along the ventromedial surface of the process. The tibial shaft is concave medially and nearly straight laterally. The distal end is less expanded and thinner than the proximal. The distal articular surface is saddle-shaped, with the pointed anterior end extending further distally. Figure 63. USNM 13437, Baptemys wyomingensis. Right tibia in anterior (A), dorsal (B), posterior (C), ventral (D), proximal (E), and distal (F) views. Left tibia in anterior (G), dorsal (H), posterior (I), ventral (J), and proximal (K) views.

149 127 Fibula The right fibula of USNM is preserved and complete (Figure 64). It is slightly longer and much narrower than the tibia. The proximal articular surface is slightly convex and slopes ventrally. The fibular shaft is round and narrow. A low, pitted process lies on the proximal third of the medial (anterior) side of the fibula. The distal articular surface is a flat to slightly convex oval and slopes ventroposteriorly. On the distoventral surface, a low ridge extends proximally to the narrow portion of the fibular shaft. Figure 64. USMN 13437, Baptemys wyomingensis. Right fibula in anterior (A), dorsal (B), posterior (C), ventral (D), proximal (E), and distal (F) views.

150 128 Tarsals One tarsal, the right fused calcaneum+astragalus (fibulare+intermedium), is preserved from YPM 3754 (Figure 65). Two long articular surfaces are present proximally. Additionally, a process, the calcaneum, extends posteroventrally and is separated from the astragalus by a visible suture. The lateral or fibular articular surface of the tarsal is concave and angles laterally from the midline, while the medial or tibial articular surface is convex and angles medially from the midline. Dorsally the tarsal is incomplete or not cleaned properly. On the lower lateral side is an articular surface that wraps onto the distal end. The ventral side of the astragalus is concave with a rounded pulley process on the anterior side that extends onto the distal surface. The sides and center of the distal surface extend further distally with depressions between them. Figure 65. YPM 3754, Baptemys wyomingensis. Right calcaneum-astragalus in proximal (A), distal (B), dorsal (C), ventral (D), anterior (E), posterior (F).

151 129 Metapodials and Phalanges Seven metapodials, fifteen phalanges, and nine phalanx are preserved from USNM All elements are disarticulated; therefore, positional relationships between them cannot be described. One digit is preserved from YPM 3754 within a small (4 cm long) rectangle of sandstone. This digit contains one metapodial, two phalanges, and one phalanx. Figure 66. USMN 13437, Baptemys wyomingensis. metapodials.

152 Figure 67. USMN 13437, Baptemys wyomingensis. proximal phalanges in dorsal (A), ventral (B), and lateral (C) views. 130

153 131 Figure 68. USMN 13437, Baptemys wyomingensis, medial phalanges in dorsal (A), ventral (B), and lateral (C) views. Figure 69. USMN 13437, Baptemys wyomingensis. phalanx in dorsal and ventral views.

154 132 PHYLOGENETIC ANALYSIS Phylogenetic Methods In order to complete a phylogenetic review of Kinosternoidea and to further understand the relationship between members of Dermatemydidae, Kinosternidae, and taxa presumed to lie on the stem of Kinosternidae or Kinosternoidea, a morphological data set was constructed in McClade 4.08a (2005), which combines characters used in prior phylogenetic analyses (Hutchison 1991; Hutchison and Bramble 1981; Joyce, 2007; Meylan and Gaffney 1989) with newly developed characters. Additional characters were reviewed from analyses that concentrate primarily on determining the phylogenetic relationships within Kinosternidae (Iverson 1991) and Trionychia (Meylan 1987); however, the majority of these characters either overlapped with characters provided in the analyses listed above, required extensive measurements of numerous specimens of each taxa and were often not reproducible, were developed in reference to terminal taxa not used in this analysis, or required soft tissue and were therefore excluded. Following recent advances in molecular phylogenetics (Near et al. 2005; Parham et al. 2006; Barley et al. 2010) and a review of the morphological characters (i.e., true costiform process; reduced abdominal scales that do not contact one another along the midline; plastron extremely reduced in size and greatly thickened along the midline and along the bridge; and inframarginal series reduced in number to three but complete across the bridge, thereby limiting contact between the other plastral scales and the marginals) that support the clade Chelydroidea (Chelydridae + Kinosternoidea), the extant chelydrids Chelydra serpentina Linnaeus 1758 and Macrochelys temminckii Troost in Harlan 1835 are scored as the outgroup taxa (see Background for additional information). In addition to five extant kinosternoids, seven fossil kinosternoid terminals were scored. Hoplochelys saliens, Hoplochelys paludosa, Hoplochelys bicarinata, Hoplochelys

155 133 elongate, and Hoplochelys laqueata (e.g., Gilmore 1919) are synonymized with Hoplochelys crassa Cope 1888; following Hutchison and Weems (1998), Agomphus tardus, Agomphus masculinus, and Agomphus turgidus (e.g., Hay 1908a) are synonymized with Agomphus pectoralis Cope 1868; following Lucas et al. (1989), Hutchison (1998), and this study all material previously referred to as Baptemys garmanii and Baptemys tricarinata (e.g., Hay 1908) was scored as a single terminal, Baptemys garmanii; and following Lucas et al. (1989) and this study Baptemys fluviatilis (e.g., Hay 1908) was synonymized with Baptemys wyomingensis (Leidy 1870). Emarginochelys cretacea previously considered a kinosternid by some (Meylan and Gaffney 1989), was excluded from this analysis of Kinosternoidea because it possesses the chelydrid rib-like costiform process (i.e., spans two peripherals to insert in peripheral three), which is unique among turtles and recognized as a distinguishing characteristic for chelydrids. The final matrix consists of 12 terminal taxa and 46 morphological characters that code features of the carapace (18 characters), plastron (15 characters), skull (7 characters), and non-shell postcrania (6 characters). Missing data were scored? and not-applicable data were scored -. Lists of the anatomical sources and characters and the character matrix are provided in Appendix C. Eleven characters (3, 9, 16, 19, 20, 21, 22, 33, 39, 44, 45) form morphoclines and were run as ordered. The remaining characters were run unordered, and all characters were given equal weight. The skeletal data matrix was analyzed under parsimony using PAUP* (version 4.0b10, Swofford 2002). The branch and bound search algorithm was used, and minimum branch lengths were set to collapse. Support for each node was measured by calculating bootstrap (Felsenstein 1985) values with 10,000 bootstrap replicates and 100 random sequence addition replicates. Bremer support values for the most parsimonious tree were calculated using TreeRot.v2 (1999).

156 134 Results of the Phylogenetic Analysis The phylogenetic analysis resulted in a single, fully resolved tree (Figure 70) with a tree length of 97 steps, consistency index (CI) of 0.701, retention index (RI) of 0.790, and rescaled consistency index (RC) of Character state optimization of unambiguous state changes (those present at the same node under both the assumptions of ACCTRAN and DELTRAN optimization) are displayed on Figure 70, while Figure 71 and Figure 72 display all characters under ACCTRAN and DELTRAN respectively with ambiguous character states shown in red. Bootstrap values of 70% or greater were regarded as strong support and bootstrap values of less than 70% as weak support (Hillis and Bull 1993). Six clades have bootstrap values greater than 70%, and four clades have Bremer support values (Bremer 1994) greater than 1 (see Figure 70). The Kinosternoidea clade, which is composed of all ingroup taxa, is supported by six unambiguous characters: costiform process tapered and spanning peripheral I to insert into peripheral II (character 3, state 1; further modified in both the linages lead to D. mawii and K. flavescens), neural V contacts costals IV and V anteriorly (character 14, state 1; reversed in X. formosa and S. carinatus and variable in C. serpentina), overlap of the inguinal scale with the hyo/hypoplastral suture (character 25, state 2; modified in some taxa as inframarginal scale set increases), loss of pectoral scales (character 27, state 1), foramen stapedio-temporale reduced (character 39, state 1; entirely lost in some taxa state 2), and presence of medial pectoral processes on the scapula and coracoid (character 46, state 1). Four characters provide additional support is given to this clade under ACCTRAN optimization. Of particular note is presence of an iliac notch (character 45, state 2; modified to only slightly developed, state 1, in D. mawii), which is not scorable for fossil taxa other than B. wyomingensis, and therefore under DELTRAN two acquisitions are equally parsimonious (once for B. wyomingensis and once for kinosternids). The other three characters supporting this node under ACCTRAN optimization are either quite homoplastic and missing from nearly all fossil taxa

157 135 (character 7, state 1 and character 42, state 1) or appear better suited under DELTRAN optimization (character 17, see discussion under following node). The clade composed of H. crassa, A. pectoralis, B. garmanii, B. wyomingensis, and D. mawii (non-kinosternids) is supported by two unambiguous characters: the presence of an elongate hypoplastral buttress that terminates on peripheral VIII (character 21, state 2) and the anterior contact of neural III with costals II and III (character 12, state 1; which also occurs in one of the outgroup taxa, M. temminckii). One ambiguous character, vertebrals II-IV more or less rectangular in adults (character 17, state 1), also supports this clade under DELTRAN optimization. It may support a larger clade given additional taxa not currently known; however, the kinosternids (clade composed of all other ingroup taxa) are united by state 2 of this character (i.e., vertebrals II-IV distinctly hexagonal). Under ACCTRAN optimization three additional characters support this node: frontal contribution to the orbit (character 34, state 1), presence of lingual ridges (character 36, state 1), loss of foramen stapedio-temporale (character 39, state 2). In previous analyses, these characters have been used to unite B. wyomingensis and D. mawii to the exclusion of other kinosternoids, and since these characters are not scorable for fossil taxa other than B. wyomingensis, under DELTRAN optimization the original hypothesis is still supported. One additional character supports this node under ACCTRAN optimization and it relates to the anterior elongation of the hyoplastral buttress (character 20). Under DELTRAN optimization the anterior elongation occurred separately within H. crassa (terminates on peripherals, state 1) and the B. garmanii, B. wyomingensis, D. mawii clade (terminates on costal I, state 2); in part this ambiguity is due to the detailed scoring of this character, which accounts for extent of elongation (anterior peripherals vs. anterior peripherals and costal I) instead of only presence/absence. Continuing to the next node along the branch leading to D. mawii, A. pectoralis, B. garmanii, B. wyomingensis, and D. mawii are united primarily by two unambiguous

158 136 characters: the medial contact of the abdominals (character 28, state 2; which is slightly modified in D. mawii state 3) and the lack of abdominal contribution to the axillary notch (character 29, state 1) as well as, the reduction of the costiform processes (character 3, state 2; completely lost in A. crassa, state 3 and also occurs in S. carinatus and K. flavescens, state 2), whereas B. garmanii, B. wyomingensis, and D. mawii are united, as mentioned above, by the increased extension of the hyoplastral buttress to contact costal I in addition to the anterior peripherals (character 20, state 2). Support for a B. wyomingensis and D. mawii clade is supported unambiguously by the expansion of the posterior plastral lobe (ordered character 19, state 1, further modified in D. mawii, state 2). Under ACCTRAN additional support from this node comes from four plastral characters that are variable in B. wyomingensis: the extension of the inguinal buttress (character 21, state 3 and character 23, state 2), increased inframarginals (from three to four, character 24), and overlap of a medial inframarginal with the hyo/hypoplastral suture (character 25). As mentioned above, under DELTRAN additional support from non-shell characters (character 36, state 1; character 39, state 2; and character 42, state 1) is given to this node; however, these are not scorable for fossil taxa along the phylogenetic stem leading to B. wyomingensis and D. mawii. It is unknown if these are synapomorphies for a larger clade. The remainder of the traits previously noted as shared between B. wyomingensis and D. mawii proved to be non-discrete (i.e., a moderately deep inferior temporal emargination; McDowell 1961), not reproducible (i.e., trochlear process of crista temporalis concealed from lateral view by the temporal arch; McDowell 1961), or plesiomorphic (i.e., costal III typically spanning peripheral 5; Hutchison and Bramble 1981). The clade containing all Kinosternidae is supported by 13 unambiguous characters primarily related to reduction and/or loss of carapace and plastral elements [characters 8, 9 also occurs independently in D. mawii, 10, 16, 21 (state 0), 24 (state 2), 28 (state 0); all state 1 unless otherwise noted] as well as development of musk duct

159 137 grooves (character 15, state 2 modified in some, state 1), distinctly hexagonal vertebrals II-IV (character 17, state 2), humeral/femoral sulcus overlies the hypoplastron (character 33, state 1 modified in K. flavescens, state 2), maxilla and quadratojugal contact each other (character 35, state 1), presence of an enlarged nose scale (character 37, state 1), and double ventral processes of cervical vertebra VIII (character 41, state 1; also occurs independently in M. temminckii). As mentioned above, under DELTRAN optimization the presence of the iliac notch (character 45, state 2) may unite this group, but is also found in B. wyomingensis and to a lesser extent in D. mawii. Since the internal relationships within this well-supported clade are not the main interest of this analysis, a detailed review of the character states of each internal node within Kinosternidae is not provided. All characters optimizations are illustrated on Figure 70-Figure 72.

160 Figure 70. The single most parsimonious tree resulting from the phylogenetic analysis of Kinosternoidea showing character states (synapomorphic black ovals, homoplastic white ovals) that change unambiguously. Bootstrap values are shown at each node and Bremer support is provided after the / if greater than

161 Figure 71. The single most parsimonious tree resulting from the phylogenetic analysis of Kinosternoidea with ACCTRAN optimized character distribution showing character states that change unambiguously in black and those that change ambiguously in red. 139

162 Figure 72. The single most parsimonious tree resulting from the phylogenetic analysis of Kinosternoidea with DELTRAN optimized character distribution showing character states that change unambiguously in black and those that change ambiguously in red. 140

163 141 DISCUSSION The phylogenetic analysis revealed a number of interesting relationships within Kinosternoidea. Hoplochelys was previously interpreted to be a stem-kinosternid (Hutchison and Bramble 1981, Hutchison 1991, Joyce 2007), and Agomphus was previously interpreted as a stem-kinosternoid (Hutchison and Bramble 1981); however, in this analysis they both are stem-dermatemydids. This relationship drastically shortens the previously implied ghost range from 25 Ma to 5 Ma for the D. mawii lineage. The oldest stem-kinosternid has been reported from the Campanian (Brinkman and de la Rosa 2006), but prior to this analysis the oldest stem-dermatemydid was previously thought to be from the Tiffanian (Hutchison 1998). These unexpected relationships are partially present due to outgroup selection (and thereby inferred character polarization). For example, reduction (i.e., loss of medial contact) of abdominal scales (character 28, state 1) united Hoplochelys with Kinosternidae in prior analyses (e.g., Hutchison and Bramble 1981, Meylan and Gaffney 1989), but in this analysis this character state is inferred to be ancestral. Agomphus pectoralis, B. garmanii, B. wyomingensis, and D. mawii are therefore united based on the redevelopment of a medial abdominal scale contact (state 2, previously thought to be the ancestral condition). Thus determining additional support (or lack of support) for the monophyly of Chelydroidea (sister-group relationship of Kinosternoidea and Chelydridae) is important to the relationships within Kinosternoidea. It is anticipated that additional detailed morphological descriptions and associated phylogenetic analysis of early chelydrids and kinosternoids will add additional support to Chelydroidea. The clade composed of H. crassa, A. pectoralis, B. garmanii, B. wyomingensis, and D. mawii currently has poor support (Figure 70-Figure 72). This lack of support may be in part due to missing data, as none of the fossil taxa, other than B. wyomingensis, within this clade were scorable for cranial or non-shell postcranial characters. The addition of taxon descriptions and new specimens may provide additional support for

164 142 these relationships. As with fossil chelydrids, fossil kinosternoids are exceptionally rare and primarily consist of isolated and/or fragmentary shell elements; skulls and non-shell postcrania are practically non-existent. At this time only B. wyomingensis has a shell and skull in association that are currently available for study. However, it should be noted that there is a complete (or nearly complete) juvenile specimen of Baptemys from the Fossil Butte Member of the Green River Formation, which appears from photographs to be B. garmanii (Grande 2013). Two isolated kinosternoid skulls were referred to X. formosa (Williams 1952) and B. garmanii (Estes 1988) respectively; however, no associated shell elements were preserved. This could be problematic considering the rarity of fossil kinosternoids, since Williams (1952) points out that within Chelydroidea, the expected shell morphology versus skull morphology is not always as anticipated. Unfortunately, this lack of cranial elements greatly impacts the number of missing dermatemydid states in phylogenetic analyses, and an effort should be made to review the one skull referred to B. garmanii (Estes 1988) and score characters if possible for inclusion in a phylogenetic analysis. An interesting aspect of the sistergroup relationship between A. pectoralis and the B. garmanii, B. wyomingensis, and D. mawii clade to the exclusion of the kinosternids and H. crassa, is that A. pectoralis alone of all fossil Kinosternoids is only known from deposits in the eastern portion of the United States, whereas all other taxa are known from the interior of North America. This, along with its unusual suite of morphological characters raises some questions about its placement within Kinosternoidea, and, as shown above (Figure 70), this clade is not well supported. Baptemys garmanii had not been included in a phylogenetic analysis until now, and its inclusion demonstrates a paraphyletic relationship of Baptemys with respect to Dermatemys. The paraphyletic relationship may be magnified by the quality of the B. garmanii specimens available for study (as noted above), which are primarily limited to partially disarticulate, incomplete, and slightly crushed shells. Yet this paraphyletic

165 143 nature of Baptemys is not entirely surprising, as the characters that distinguish the individual species, which primarily include size (increases through time), ornamentation of the carapace (keels), and expansion of the plastral lobes and bridge, appear to form morphoclines that become continuous, as additional specimens are included. While some of the morphological differences between B. garmanii and B. wyomingensis shells are easily viewed (i.e., shape of xiphiplastron and entoplastron) others are not as easily described (or quantified), and this becomes more complicated as additional specimens, especially intermediate taxa, are added. Only a sampling of traditional morphometrics and general qualitative descriptions of different portions of the shell were used in this study; it is apparent that geometric morphometrics could be used on this taxa to further understand the shape variation that is currently qualitatively described. Although there are few complete shells of Baptemys, it is believed that individual elements could be analyzed (e.g., xiphiplastra, entoplastron, and individual neurals). These results can be used to look at the evolution of the shell and potentially to explore both speciation and environmental impacts. For example, D. mawii individuals that mature in slow moving water reach maturity at larger sizes than individuals in fast-moving water (Vogt et al. 2011), and recent molecular work on extant D. mawii from different river basins note that there may be species-level variation. Unfortunately, at this time there remain two to three unnamed taxa that are likely referable to Baptemys (see Systematic Paleontology section for details). A few specimens of a potentially separate species (Baptemys spp. 2) from B. wyomingensis were reviewed; however, the most complete specimen is currently under study at UCMP, and readily diagnosable characters were not observed from a review of other less complete specimens during this study. As outlined above in the Phylogenetic Analysis section, support for a B. wyomingensis and D. mawii clade comes from characters of or likely related to the extension of the inguinal buttress (characters 21, 23-25). Interestingly, all of these characters are variable within B. wyomingensis. This as stated implies support for

166 144 the division of B. wyomingensis, with a current range from the Bridgerian through early Uintan, into separate species. Yet these characters do not vary consistently (i.e., increased inframarginals do not always require an extensions of the inguinal buttress and vice versa) and can, as in the case of the number and overlap of inframarginals, vary within a specimen; therefore, it seems likely that there is some individual variation within B. wyomingensis. Species level analyses require large sample sizes in order to assess individual variations and proper species diagnoses. Variation within turtle shells is common and has been briefly explored in kinosternids (Hutchison 1991) as well as other turtle taxa (e.g., Gopherus, Auffenberg 1976; neurals multiple clades, Pritchard 1988). Additional specimens from this time period, including those housed at UCMP and UMMP, need to be studied further. Specimens of the oldest Baptemys occurrence (latest Clarkforkian-earliest Wasatchian) and youngest Baptemys occurrence (Duchesnean) were not available for this study because these taxa are currently under study by others. From the brief descriptions provided, it appears that they can be diagnosed on quantitative characters (i.e., medial keel not extending onto the pygal and xiphiplastral notch, respectively) as well as qualitative characters (i.e., narrower and broader xiphiplastron, respectively). Once these taxa have been fully described the taxonomy of Baptemys and the Dermatemydidae as a whole can be further explored. At this time, with the material currently available for study, Baptemys appears as a paraphyletic group with respect to D. mawii. It is possible that although B. garmanii, B. wyomingensis, and D. mawii are based on morphologically diagnosable characters, they represent an anagenetic event instead of a cladogenetic event. In that case, B. garmanii, representing the ancestral morphology, could have given rise to B. wyomingensis and then to D. mawii. Further understanding of the alpha taxonomy of Baptemys is important for the study of dermatemydid evolution both during the Eocene and in more recent times. Current assignment to species impacts presence/absence and first/last occurrences data at

167 145 the species level. It is likely that some of these specimens originally attributed to B. wyomingensis (e.g., in Gunnell and Bartels 2001, Zonneveld et al. 2000) from the Wasatch, Green River, and lower Bridger Formations are either B. garmanii or an undescribed species. In addition, it appears that an ecological shift occurred within the clade between the earlier bottom-walking representatives, where shell morphology closely resembles that of Staurotypus and other chelydroids and specimens that are generally found in fine-grained deposits to later representatives that have much more developed shells and, at least in the case of B. wyomingensis, are often found in coursegrained deposits (i.e., sandstones) representing lager fluvial systems. In conclusion, this description and comparative material will be useful for future taxonomic and systematic work with the Kinosternoidea, Chelydridae, and Cryptodira in general. This detailed description of B. wyomingensis, along with a consideration of its phylogenetic relationships, indicates additional morphological support for a close relationship with D. mawii and a placement for D. mawii and Baptemys within Kinosternoidea as well as an unexpected close relationship with Hoplochelys and Agomphus, to the exclusion of the Kinosternids. This decreases the ghost range for the D. mawii lineage, since it was previously understood that all taxa along the stem of D. mawii were late Paleocene Eocene (Clarkforkian Duchesnean) fossil taxa that have been documented from central portion of the United States and are currently classified as Baptemys. In addition, the discovery of a new character (character 46, medial pectoral process) added support to the Kinosternoidea clade as a whole. While a review of the alpha taxonomy of Baptemys, reveals that the relationships between the species, other than B. wyomingensis and B. garmanii remain unclear to date due to a lack of published descriptions, it appears likely that Baptemys may be paraphyletic in regard to D. mawii. Adding taxa or elements may form a monophyletic Baptemys clade; however, characters for the unnamed species suggest that the youngest taxa is closer to D. mawii than B. wyomingensis, and the oldest may prove to be closer to Hoplochelys than to B.

168 146 wyomingensis. Additionally, the comprehensive morphological description and review of alpha taxonomy will help in the future identification of Baptemys specimens and allow for additional exploration into the evolution of the clade.

169 147 APPENDIX A DERMATEMYS MAWII PLATES Figure A1. USNM 66669, Dermatemys mawii. Skull in dorsal (A) ventral (B), anterior (C), posterior (D), and left lateral (E) views.

170 Figure A2. USNM 66669, Dermatemys mawii. Jaw in dorsal (A) ventral (B), right lateral (C), right medial (D), and posterior (E) views. 148

171 Figure A3. FMNH 98950, Dermatemys mawii. Cervical vertebrae two through five in left lateral, anterior, posterior, dorsal, ventral, and right lateral views. 149

172 Figure A4. FMNH 98950, Dermatemys mawii. Cervical vertebrae six and seven in left lateral, anterior, posterior, dorsal, ventral, and right lateral views. 150

173 Figure A5. USNM 66669, Dermatemys mawii, carapace in dorsal view. 151

174 152 Figure A6. USNM 66669, Dermatemys mawii, Carapace right lateral view. Figure A7. USNM 66669, Dermatemys mawii, Carapace left lateral view.

175 Figure A8. USNM 66669, Dermatemys mawii. Plastron in ventral view. 153

176 Figure A9. FMNH 98950, Dermatemys mawii. Plastron in dorsal view. 154

177 Figure A10. FMNH 98950, Dermatemys mawii. Right pectoral girdle in ventral (A), dorsal (B), anterior (C), and posterior (D) views. 155

178 156 Figure A11. FMNH 98950, Dermatemys mawii. Forelimb. Left humerus in dorsal (A), posterior (B), ventral (C), anterior (D) proximal (E), and distal (F) views. Left ulna in anterior (G), dorsal (H), posterior (I) and ventral (J) views. Right radius in anterior (K), dorsal (L), posterior (M) and ventral (N) views. Figure A12. FMNH 98950, Dermatemys mawii. Right centrale in proximal (A), ventral (B), dorsal (C), distal (D) views.

179 Figure A13. USNM 66669, Dermatemys mawii, Pelvic girdle in right lateral (A), left lateral (B), dorsal (C), and ventral (D) views. 157

180 Figure A14. FMNH 98950, Dermatemys mawii. Hindlimb. Left femur in anterior (A), dorsal (B), posterior (C), ventral (D), proximal (E), and distal (F) views. Left tibia in anterior (G), dorsal (H), posterior (I) and ventral (J) views. Left fibula in anterior (K), dorsal (L), posterior (M) and ventral (N) views. 158

181 Figure A15. FMNH 98950, Dermatemys mawii. Right calcaneum-astragalus in proximal (A), distal (B), dorsal (C) and ventral (D). 159