THE SYSTEMATIC POSITION OF THE SABER-TOOTHED AND HORNED GIANTS OF THE EOCENE: THE UINTATHERES (ORDER DINOCERATA) BURGER, Benjamin J., Utah State University Uintah Basin Campus, Vernal, UT, 84078 United States of America Abstract The Elephant in the Tree (effect of Afrotheria) Eobasileus cornutus The Accepted Phylogenetic Tree

A single most parsimonious tree was Ever since their discovery in the American West in 1871, the saber-toothed horned uintatheres, found using a traditional search I decided to rerun the analysis, but hold the algorithm in TNT the results show a Skull and reconstruction of Eobasileus cornutus based on Field living taxa belonging to Afrotheria as a true belonging to the order Dinocerata have defied placement on the mammalian tree. Previous close relationship of uintatheres Museum of Chicago Specimen P 12710 collected from the Uinta monophyletic group, and using branch and researchers have suggested a wide range of relationships to insectivores, rodents, condylarths, with the African Elephant Formation of Northeastern Utah. bound search algorithm I reanalyzed the Loxodonta africana. Such a character matrix. The resulting single tree is proboscideans, pantodonts, and South American xenungulates. relationship harks back to early less parsimonious, with a tree length of 28,836 notions of Cope (1872), that meaning that an additional 518 state changes uintatheres were an extinct member occurred. This is the most parsimonious tree Utilizing a large dataset of characters downloaded from Morphobank, the two best known of the proboscideans (Wheeler, that still retains living members of the 1960). However, recent molecular Afrotheria within a monophyletic grouping. Middle Eocene uintatheres species Uintatherium anceps and Eobasileus cornutus were added phylogenies strongly support the The consistency index is 0.189 and retention to a large character matrix of 4,541 morphological characters sampled across 86 other Afrotheria clade, which was not index is 0.434. Both trees show a close resolved using morphological relationship of Eobasileus and Uintatherium mammalian taxa. Parsimony analysis was performed using nearest-neighbor interchange in evidence, and members are widely with Carodnia, supporting a clade referred as Mesquite, as well as search algorithms using TNT to find the most parsimonious placement of distributed in the tree. The close the Uintatheriamorpha. In the second tree, relationship between uintatheres and Uintatheres were not found to be close to Dinocerata among other mammals. Uintatheres were found to be most closely related to the proboscideans is likely due to elephants, and instead placed within the xenungulate Carodnia vieirai (together as Uintatheriamorpha). homoplastic characters associated Laurasiatheria clade, which includes with large graviportal adaptions Euliptyphla (shrews and hedgehogs), Pholidota found in both elephants and (pangolins), Carnivora (cats and dogs), uintatheres. Using molecular Perissodactyla (horses and rhinos) and If the molecular supported Afrotheria clade is held together, Uintatheriamorpha is positioned support, the Afrotheria clade was Cetartiodactyla (cows, hippos, and whales). In within Laurasiatheria (Liptyphla, Pholidota, Carnivora, Perissodactyla and Cetartiodactyla) held as a true monophyletic particular uintatheres group within other grouping, and a new search mesoaxial-grade ungulates, including excluding Chiroptera. The most parsimonious tree using TNT search algorithms split the algorithm was performed on perissodactyls, phenacodont condylarths, and Afrotheria clade across Mammalia, and resulted in the placement of rodents, proboscideans, morphological characters. South American ungulates. Uintatheres share the following hyraxes and sirenians among a polyphyletic ungulate clade including uintatheres. In light of synapomorphies with other mesoaxial The South America Connection Uintatherium anceps ungulates: 1) presence of hooved distal molecular data for living mammals, uintatheres were found within a monophyletic ungulate phalanges, 2) weight bore principally by third clade and not closely related to Afrotheria. The early Paleocene North American metacarpal as central axis of the fore and hind The xenungulate Carodnia from the Paleocene of South America was found to be the foot, 3) loss of the centrale bone (with no Protungulatum donnae is considered the most primitive member of a monophyletic clade that Skull and reconstruction of Uintatherium anceps based on American nearest extinct relative of uintatheres. Carodnia lacks the characteristic horns and indication of fusion with scaphoid), 4) lack of a Museum of Natural History specimen 1694 from the Bridger includes Condylarthra, Meridiungulata, Dinocerata + Xenungulata, Perissodactyla, and long saber-like canines, but postcranial features in the limbs support this relationship. deep cotylar fossa on the astragulus. Formation of Southwestern Wyoming. Cetartiodactyla. Morphological similarities between proboscideans, sirenians and uintatheres This also suggests a biotic interaction between North and South America during the early Paleocene followed by isolation during the late Paleocene and Eocene. are likely convergent adaptations. A clade composed of Xenungulata and Dinocerata (Uintatheriamorpha) is supported by a number of synapomorphies, including Uintatheres group within other mesoaxial-grade ungulates, including perissodactyls, traits of the nasal bone, maxilla-frontal contact, zygomatic arch, and a number of phenacodont condylarths, and South American ungulates, suggesting an interchange characters of the posterior premolars, as well between North and South America during the early Paleocene, and isolation of Africa. as a number of postcranial features in the feet. This relationship has been supported by Uintatheres share the following synapomorphies with other mesoaxial ungulates: various authors (Wheeler, 1961; McKenna, 1980; Gingerich, 1985; Schoch and Lucas, 1) presence of hooved distal phalanges, 2) weight bore principally by third metacarpal as 1985; Lucas, 1993) as well as criticized (Rose, central axis of the fore and hind foot, 3) loss of the centrale bone (with no indication of fusion 2006). Fossil pantodonts, once thought close relatives to uintatheres (Osborn, 1898) have with scaphoid), 4) lack of a deep cotylar fossa on the astragulus. long been argued unrelated based on major differences in the dentition (Simpson, 1929). By including more early fossil ungulate The nearest living relatives of uintatheres are rhinos, horses and tapirs. mammals, such as pantodonts in future studies, the strength of a monophyletic Uintatheriamorpha clade can be further tested.

Methods The Importance of Ungulate Feet Early Uintatheres from North America References and Acknowledgements The position of the central axis in the feet is an important character that divides the major groups of early ungulate mammals. Uintatheres exhibit a mesoaxial condition similar to phenacodont condylaths, South American ungulates, and perissodactyls. Earlier and smaller forms of uintatheres are known from the early Cope, E.D. 1872. Notice of proboscideans from the Eocene of southern Wyoming. American Philosophical To investigate the systematic relationship of uintatheres Society, Proceedings, 12:580. Eocene and late Paleocene of North America, but were not Gingerich, P.D. 1985. South American mammals in the Paleocene of North America; pp. 123-137 in F.G. Stehli Watch a video with other mammals both living and extinct I utilized the included in the analysis because they are known from less and S.D. Webbs (eds.), The Great American Biotic Interchange. Plenum Press, New York. Goloboff, P., Farris, J., & Nixon, K. 2008. TNT: a free program for phylogenetic analysis. Cladistics 24: 774- O’Leary et al. (2013) MorphoBank character matrix which complete skeletons. 786 presentation of this contains 4,541 morphological characters coded for 86 Lucas, S. 1993. Pantodonts, tillodonts, uintatheres, and pyrotheres are not ungulates; pp. 182-194 in F.S. Szalay, mammalian species. Mesoaxial M.J. Novacek, and M.C. McKenna (eds.), Mammal Phylogeny: Placentals. Springer-Verlag, New York. Maddison, W. P. and D.R. Maddison. 2015. Mesquite: a modular system for evolutionary analysis. Version 3.04 research on Feet http://mesquiteproject.org Marsh, O.C. 1884. Dinocerata, a monograph of an extinct order of gigantic mammals. United States Geological Using publications and fossil specimens housed at the Survey Monograph, 10:1-237. Field House Museum in Vernal, Utah, two of the most O’Leary, M. A., Bloch JI, Flynn, J.J., Gaudin, T.J., Giallombardo, A., Giannini, N.P., Goldber, S.L, Kraatz, Bathyopsis fissidens B.P., Luo, Z-X, Jin Meng, Xijun Ni, Novacek, M.J., Perini, F.A., Randall, Z.S., Rougier, G.W., Sargis, E.J., well known uintatheres were added to the character Silcox, M.T., Simmons, N.B., Spaulding, M. Velazco, P.M., Weksler, M., Wible, J.R. Cirranello, A.L. 2013. The Placental Mammal Ancestor and the Post–K-Pg Radiation of Placentals. Science 339:6120:662-667. matrix: Eobasileus cornutus known from the Uintan Data downloaded from http://www.morphobank.org/ Osborn, H.F. 1898. Evolution of the Amblypoda. Part I. Taligrada and Pantodonta. Bulletin of the American https://youtu.be/B6lmLo14Cc0

North American Land Mammal Age in the Uinta Hind Feet Formation of Utah and Washakie Formation of Wyoming Uintatherium Eohippus Museum of Natural History 10:169-218. Hippopotamus Metamynodon Rose, K.D. 1996. The beginning of the age of mammals. John Hopkins University Press, Baltimore p. 428. and Uintatherium anceps known from the Bridgerian Wheeler, W.H. 1960. The uintatheres and the Cope-Marsh war. Science, 131: 1171-1176. North American Land Mammal Age of the Bridger Paraxial Pachyaena Wheeler, W.H. 1961. Revision of the Uintatheres. Peabody Museum of Natural History Bulletin, 14. Schoch, R. and Lucas, S. 1985. The phylogeny and classification of the Dinocerata (Mammalia, Eutheria). Formation of Wyoming. The resulting character matrix Feet Bulletin of Geological Institutions, University of Uppsala 11:31-50. Simpson, G.G. 1929. A new Paleocene Uintathere and molar evolution in the Amblypoda. American Museum was analyzed with the computer program TNT to retrieve Novitates 387:1-9. the most parsimonious tree (Goloboff et al 2000). As well Turnbull, W.D. 2002. The mammalian faunas of the Washakie Formation, Eocene Age, of Southern Wyoming. Part IV. The Uintatheres. Fieldiana Geology 47:1-189. as using the computer program Mesquite (Maddison & Maddison, 2011) to analyze resulting trees and map Silhouettes used in cladogram downloaded from http://www.phylopic.org Morganucodon by morphological characters across various clades. Probathyopsis newbilli FunkMonk (Michael B. H.) Ornithorhynchus by Sarah Werning Eomaia by Nobu Tamura Macropus by Cathy Rattus by Maija Karala and Equus Mercedes Yrayzoz. Help support T. Michael Keesey’s FHPR 1151 Eobasileus cornutus from the Washakie Formation of Wyoming work at: https://www.patreon.com/tmkeesey

Fore Feet Fore Eohippus Metamynodon Special thanks to Steve Stroka, and Dale Gray at the Field House Museum in Vernal, Utah for Sus Pachyaena Uintatherium allowing me to work in their collections and play with their Uintatheres.