An Archaic Ungulate of middle Paleocene age from Southeast Montana

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The Ohio State University

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A sample of five associated mammalian teeth collected from the Williston Basin in the Fort Union Formation of southeast Montana demonstrate the occurrence of an archaic ungulate at the School Well Locality, a site of known early middle Paleocene age. Study of interproximal wear facets on the teeth demonstrate that the teeth were adjacent to one another in life and belonged to the same side of the lower dentition of a single individual. Relative extent of wear on the specimens suggests that the animal was a young adult with a tooth eruption sequence typical for a placental mammal. Using character states scored on the specimens and a previously published character-by-taxon data matrix (Zack et al., 2005, and Williamson and Weil, 2011) a provisional assessment of the phylogenetic affinities of the School Well archaic ungulate was made. The matrix was analyzed using TNT (Tree analysis using New Technology), a phylogenetic data analysis program. The analysis produced a consensus tree of the 11 shortest trees, placing the unknown sample within the family-level clade Hyopsodontidae, and further within a subclade containing members of the subfamily Mioclaeninae. Further assessment of the identity and status of the School Well archaic ungulate as a possible new species will focus on comparisons within this subgroup.



Archaic Ungulate, Paleontology, Middle Paleocene, Promioclaenus