Early Eocene (Wasatchian)

Willwood Formation

Powell, WY, USA

Large 48mm x 40mm upper molar

Mammal, Coryphodontidae.

Coryphodon was a herbivorous hoofed mammal about the size of a dairy cow, large enough to make it the largest land mammal of its time.  It would have looked more like a hippo and perhaps had a similar lifestyle.  Though it bore hooves, it is unrelated to any modern ungulates.

Coryphodon is known from Latest Paleocene of North America and spread into Europe and Asia in the Early Eocene.  It is best known from the Early Eocene of what is now the Rocky Mountain region of North America.  At the time the region was covered by subtropical forest extending up through Canada.  It died out during the Middle Eocene with the family surviving in Asia until the end of the epoch.