A new fossil mustelid from the Miocene of South Dakota, USA

Abstract.

A skull from the Barstovian of South Dakota has typical leptarctine characteristics, including robust zygomatic arches, double sagittal crests, grooves on the lingual side of the lower canines, and bony projections from the tympanic bullae. The robust mandibles and expanded masseteric fossa of this specimen indicate that it had large jaw muscles. Dental morphology and other characters lead us to agree with earlier suggestions that Hypsoparia is a valid genus. The morphology of Hypsoparia suggests that leptarctines were more herbivorous than most other Carnivora.