Hyaenodon Skull, Partial (BU 790)

Hyaenodon crucians

Middle Oligocene (Orellan)

Brule Formation

White River Badlands

Custer County, South Dakota USA

Three species of Hyaenodon were common carnivores of the Dakota Badlands during the Eocene and Oligocene epochs. The largest of the three was H. horridus, which reached the size and weight of a black bear. The mid-sized version was H. cruentus, which probably looked and acted similarly to a modern-day wolf. The smallest of the three was H. mustelinus, which was about the size of a modern raccoon. These animals are found in the Chadron and Brule formations, where, for reasons unknown, Hyaenodon skulls are fairly common, but post-cranial remains are rare.