Hyaenodon: Nemesis of Burrowing Oreodonts

Dr. Kent A. Sundell
Tate Museum at Casper College, Casper, Wyoming

The genus Hyaenodon (order Creodonta) was a dominant predator of oreodonts (Merycoidodontidae) during the Oligocene within the White River Formation of North America. The taphonomy of predated oreodont skeletons in many recently prepared oreodont burrow fillings from Wyoming shows evidence of predator eating habits. The combined occlusional edge (more than 5 cm in Hyaenodon horridus) of the rear premolar and both molars produces characteristic shearing bite marks that sharply sever multiple grouped articulated bones like a cleaver. Many predated oreodont specimens with mid-shaft sheared off radius/ulna, tibia/fibula, all metatarsal, and all metacarpal bone groups have been observed. The most common taphonomic association in oreodont burrows are disarticulated upper skulls and multiple sheared (from body), but still articulated feet with toes. Presumably, Hyaenodon killed oreodonts in their burrows, ate all the meaty parts of the skeleton, including cracking and swallowing most large limb bones, leaving flesh poor skulls and feet behind ("leftovers"). The total length of the sheared edges, often exceeding 4 cm., is evidence that Hyaenodon is responsible for this type of bite mark. The dentitions of other common large Oligocene predators such as saber tooth cats (Hoplophoneus or Dinictis), dogs (Hesperocyon, Daphoenus, Mesocyon), and entelodonts (Archaeotherium) can not produce similar taphonomic associations. Additionally, the size variation between different species of Hyaenodon is similar to size variation between different species of Hyaenodon is similar in size variation within the oreodonts. Small hyaenodonts (Hyaenondon mustelinus) pursued small oreodonts (Miniochoerus gracilis) into small burrows.

Evidence

1. Shearing multiple grouped lower leg and foot bones.
2. Taphonomic association of meat deficient body parts "left over" after scavenging
3. Distinct associated canine bite marks
4. Proportional head and body size relationship is similar
5. Size variation between Oreodonts and Hyaenodonts is similar