Phylogeny and Relationships of Taeniodonta, an Enigmatic Order of Eutherian Mammals (Paleogene, North America)
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Phylogeny and Relationships of Taeniodonta, an Enigmatic Order of Eutherian Mammals (Paleogene, North America) Thesis Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Deborah Lynn Weinstein Graduate Program in Evolution, Ecology, and Organismal Biology The Ohio State University 2009 Thesis Committee: John Hunter, Advisor William Ausich John Wenzel Copyright by Deborah Lynn Weinstein 2009 Abstract The Taeniodonta is group of eutherian mammals from the Paleogene of North America, whose exact place in eutherian phylogeny is uncertain. Taeniodonts evolved rapidly in the Paleocene to achieve, in some forms, large body size, hypselodont (i.e., evergrowing) canine and postcanine teeth, and peculiar patterns of tooth wear. Eleven genera of taeniodonts occur in two main subclades, recognized at the level of families or subfamilies depending on author, the Conoryctidae and the Stylinodontidae. The conoryctids were smaller, probably insectivorous or omnivorous, and retained a larger number of primitive characters than did the stylinodontids. The stylinodontids were larger than the conoryctids, possessed massive canines, and exhibit a trend toward hypselodonty of the canines and molars. Prior to this study, there has not been a comprehensive phylogeny of all of the currently recognized genera of taeniodonts. In Chapter 1, I review the history of research on the systematics, evolution, and paleobiology of the taeniodonts, with emphasis on recent discoveries of transitional forms. I identify the major unresolved phylogenetic issues that concern taeniodonts that I explore in subsequent chapters including the internal relations among taeniodonts, ii monophyletic versus diphyletic origins, ancestry, and the status of the taeniodonts as either stem or crown eutherians. In Chapter 2, Internal Relations Among the Taeniodonts, I take up the relations of genera of taeniodonts to one another and overall biogeographic history. I performed cladistic analyses using NONA and Winclada to determine the evolutionary relations of the known genera of the Taeniodonta. Two clades are well supported, a clade consisting of the conoryctids exclusive of Onychodectes (i.e., Conoryctella, Conoryctes, and Huerfanodon) and a clade consisting of all the known stylinodontids (Wortmania, Schochia, Psittacotherium, Ectoganus, and Stylinodon). Stratocladistic analysis, which takes into account the temporal sequence of taxa in the fossil record, supports the results of phylogenetic analysis using morphological characters alone. Phylogenetic, stratigraphic, and geographic data contribute to reconstructing the biogeographical history of the taeniodonts. In these analyses, the Late Cretaceous taeniodont Schowalteria occupies the most basal position in taeniodont phylogeny, pre‐dating an inferred conoryctid–stylinodontid split in the early Paleocene. In Chapter 3, External Relations of the Taeniodonts, I investigate the higher‐level relations and ancestry of the taeniodonts as well as the monophyletic or diphyletic origins. I describe a newly discovered fossil lower jaw from the early Paleocene of North Dakota that I interpret to be the lower jaw of Alveugena, a taxon previously argued to be a transitional form between cimolestids and the taeniodonts. This discovery contributes new characters and facilitates study of the relations between taeniodonts iii and basal cimolestans. This study corroborates the hypothesis that Alveugena is the sister taxon of the taeniodonts. Contrary to earlier analyses, the Late Cretaceous– Paleocene Cimolestes is found to be the sister taxon of Alveugena+Taeniodonta rather than the Paleocene Procerberus, thought by some to be closer to the taeniodonts. Stratocladistics provided additional support for the conclusions of the analyses of morphology alone and implicate Cimolestes as a possible ancestor to Alveugena and the taeniodonts. Further cladistic analyses including taeniodonts, Late Cretaceous stem eutherians, and Paleogene representatives of crown eutherian clades determine the higher‐level relations of taeniodonts. This study shows that the taeniodonts lack the synapomorphies that link crown eutherians together. In the final chapter, Conclusions, I will discuss the overall aspects of the taeniodonts. I will also discuss the evolutionary rates of the canine and molar evolution in the group, as well as rediagnosing the clades. In conclusion, the taeniodonts are a monophyletic group of stem eutherian mammals whose closest known sister group is Alveugena, and most likely Cimolestes gave rise to the Alveugena and the taeniodonts. iv Acknowledgements I first thank Dr. John Hunter, for getting me started with this project and being there through all of it, and for helpful discussions on thesis matters. I would also like to thank my intrepid committee members, John Wenzel for his help with the cladistics found within and Bill Ausich for help with the past and with my future. I would also like to thank Judy Galkin for her tireless efforts as I searched the American Museum of Natural History collections and Michael Brett‐Surman for his help at the National Museum of Natural History. I thank David Fox and especially Jonathan Marcot for help using their program StrataPhy. Finally, I would like to thank the Ohio State University Department of Evolution, Ecology, and Organismal Biology and a University Fellowship and Teaching Associateship that have supported my work. v Vita June 2003………………..………………………………….Revere High School 2007…………………………………………………………….B.A. Biology & Evolutionary Biology, Case Western Reserve University 2007–2008…………………………………………………..University Fellowship, Ohio State University 2008–2009…………………………………………………..Graduate Teaching Associate, Department of Evolution, Ecology and Organismal Biology, Ohio State University Publications Croft, D.A and D. Weinstein. 2008. The first application of the mesowear method to endemic South American ungulates (Notoungulata). Palaeogeography, Palaeoclimatology, Palaeoecology 269: 103–114. Fields of Study Major Field: Evolution, Ecology, and Organismal Biology vi Table of Contents Abstract………………………………………………………………………………………………………………………….ii Acknowledgements………………………………………………………………………………………………………..v Vita………………………………………………………………………………………………………………………………..vi Table of Contents………………………………………………………………………………………………………….vii List of Tables………………………………………………………………………………………………………………..viii List of Figures…………………………………………………………………………………………………………………ix Chapter 1: Taeniodont Overview and the History of Their Classification…………………………1 Chapter 2: Internal Structure of Taeniodont Phylogeny……………..…………………….………….20 Chapter 3: Taeniodonta's Placement in the Phylogeny of Eutherian Mammals ……………32 Chapter 4: Conclusions…………………………………………………………………………………………………45 References……………………………………………………………………………………………………………………54 Appendix A: Description of the lower jaw of Alveugena……………………………………………….59 Appendix B: Characters and Matrices…………………………………………………………………………..66 vii List of Tables Table 1. Literature used to code characters for the genera and species in the study..….21 Table 2. List of biogeographic placement of taeniodont specimens..……………………………27 viii List of Figures Figure 1. Schoch's (1986) reconstruction of Onychodectes……………….…………………………….1 Figure 2. Schoch's (1986) reconstruction of Stylinodon…………………………………………………..1 Figure 3. Skulls of Conoryctes (1) and Psittacotherium (2) from Matthew (1937)……………2 Figure 4. Stylinodon right manus from Matthew (1937)….……………………………………………..3 Figure 5. Known chronostratigraphic distribution of the taeniodonts.………...…………………5 Figure 6. Plot of known Taeniodonta localities…..…………………………………………………………..6 Figure 7. Schoch’s (1986) phylogeny of taeniodont genera with families also shown.....10 Figure 8. Lucas and Williamson’s (1993) phylogeny………………………………………………………12 Figure 9. Eberle’s (1999) most parsimonious phylogeny……………………………………………….15 Figure 10. Internal structure tree from cladistic analysis.....………………………………………….23 Figure 11. Internal structure trees from stratocladistic analysis…..……………………………….25 Figure 12. General movements of the taeniodonts based on biogeographical data..……28 Figure 13. Biographically optimized internal tree from cladistic analysis.……………………..30 Figure 14. Cimolestid relations of tree from cladistic analysis………………….…………………..33 Figure 15. External relations tree from cladistic analysis……………………..………..………..……35 Figure 16. External relations tree from stratocladistic analysis…….….……………………………40 Figure 17. External relations among stem Eutheria from cladistic analysis…………………..42 ix Figure 18. External relations among crown Eutheria from cladistic analysis…………………43 Figure 19. Known taeniodont stratigraphic distributions with phylogeny.…………………….46 Figure 20. Patterns of character divergence in canines and first molars.………………………49 Figure 21. Alveugena lower jaw in buccal, lingual, and occlusal view……………………………61 x Chapter 1: Taeniodont Overview and the History of Their Classification Interest in the origin of placental mammals has led to the discovery of many mammalian taxa. Although several of these groups do not lead to extant mammals, they are part of the overall biotic environment in which extant placental mammals originated. One of the most interesting of these groups is the Taeniodonta, which has been viewed variously in the Linnean hierarchy as either an order (Rose, 2006; Schoch, 1986) or a suborder (McKenna and Bell, 1997) of eutherian mammals. In this study, Taeniodonta will be viewed as an order, which