Eoarctos vorax a basal arctoid from North Dakota
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ID: 000375761
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An exquisitely preserved skeleton (USNM 637259) of a basal ursoid is the basis of a monograph in Journal of Vertebrate Paleontology Memoir. The following is an abstract: An exquisitely preserved male skeleton of an early arctoid, Eoarctos vorax new genus and species, provides a unique window into the origin and early divergence of Carnivora. Recovered from the Fitterer Ranch locality in the early Oligocene (Orellan to Whitneyan North American Land Mammal ages) Brule Formation of southwestern North Dakota (~32 Ma), the new arctoid offers an opportunity to evaluate the fundamental relationships of the caniform (dog-like) carnivorans. Eoarctos vorax possesses a suite of plesiomorphic characters inherited from its miacid ancestors, making it an ideal model for ancestral arctoids. We present a comprehensive treatment of E. vorax, combining traditional description with photographic documentation, modern microCT, laser scans, and photogrammetry.Showing its plesiomorphic morphology, Eoarctos vorax is scansorial in locomotion, somewhat like a modern raccoon, retaining the ability to climb trees and lacking cursorial adaptations present in the early canid Hesperocyon. However, E. vorax shows clear signs of durophagous cranio-dental adaptations, presumably for an obligatory diet of mollusks, and frequent damage to shell-crushing premolars, plus associated dental infections.We review several other key North American early arctoids and present total-evidence (nuclear DNA and discrete morphological characters) Bayesian and parsimony analyses of Caniformia phylogeny, including extinct stem taxa plus a living member of all modern families. We recognize an endemic North American ursoid clade, family Subparictidae, which includes Eoarctos vorax as its most derived member. We demonstrate the importance of North America as an early cradle of evolution for caniform carnivorans, including early precursors of Canidae, Amphicyonidae, Ursidae, and Pinnipedia.