“D” is for Dissacus
Dissacus is a member of the Family Mesonychidae, a group of carnivorous hoofed mammals.
Until recently, paleontologists thought that modern whales found their ancestry in the mesonychids due to the similar shape of their teeth. More recently collected fossils now place whales closer to hippos and other cloven-hoofed mammals.
Dissacus is not known from The Breaks, but is known from other localities of similar age in western North America.
Part of the Blogging from A to Z challenge.