Biochronology and biogeography of Paradaphoenus (Carnivora: Amphicyonidae) within the Great Plains Region of North America

The amphicyonid, or “bear-dog,” Paradaphoenus was a small-bodied, hypercarnivorous carnivoran that lived in North America during the Oligocene. Specimens of Paradaphoenus are rare, in part owing to the common inaccurate referral of specimens to the abundant canid Hesperocyon, which was similar in size and morphology. Four new specimens of Paradaphoenus are noted from North Dakota and South Dakota that expand the geographic range of this taxon within the Great Plains region of North America and expand our knowledge of its anatomy. A single specimen from either a transitional Orellan/Whitneyan or early Whitneyan fauna in the Little Badlands area of North Dakota is referred to Paradaphoenus minimus. That taxon is elsewhere restricted to Orellan faunae, making that specimen the youngest occurrence of P. minimus yet recognized. The remaining specimens are from two early Whitneyan faunas, the Cedar Pass local fauna in South Dakota and a new locality within the Little Badlands area of North Dakota, and are referred to Paradaphoenus tooheyi. These discoveries highlight the difficulties of elucidating the biostratigraphic and biogeographic distributions of relatively rare taxa within the White River Chronofauna given the propensity for many specimen identifications to be biased in favor of more abundant, well-known taxa.