Postcranial anatomy of Viverravus (Mammalia, Carnivora) and implications for substrate use in basal Carnivora

ABSTRACT

A postcranial skeleton of the viverravid carnivoran, Viverravus acutus from the early Eocene of Wyoming, is described and compared to contemporary carnivorans (the viverravid Didymictis, and the miacids Miacis and Vulpavus), and to extant taxa belonging to the families Mustelidae, Procyonidae, Canidae, Viverridae, and Herpestidae. Based on humeral and femoral midshaft diameters, body mass for this animal is estimated to have been about 250 g, less than all but a few living species of Carnivora. Shoulder and hip morphology indicate a considerable range of motion and the structure of the humeroulnar joint suggests habitually flexed postures, characteristics typical of extant carnivorans that are excellent climbers. These similarities are also shared with miacids, supporting the hypothesis that basal members of the order Carnivora were well adapted for exploiting arboreal habitats. An astragalus tentatively attributed to the middle Eocene species Viverravus gracilis, however, is similar to that of Didymictis and suggests a greater emphasis on terrestrial locomotion than is found in miacids.