Early Eocene (Wasatchian)

Willwood Formation

Powell, WY, USA

52mm hoof. First we have had

Mammal, Coryphodontidae.

Coryphodon is a genus of early hoofed mammal that appeared during the Latest Paleocene in 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 that whole area 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.

An adult Coryphodon was about the size of a dairy cow, which was actually large enough to make it the largest land mammal of its time.  It would have looked somewhat like a hippo and apparently had a similar lifestyle.  Though it bore hooves, it is not related to any modern ungulates nor any other modern mammals.