hillock-tooth"), the name of an Oligocene genus of North American primitive ruminants related to the camels, and typifying the family Oreodontidae. Typical oreodonts were long-tailed, four-toed, partially plantigrade ruminants with sharp-crowned crescentic molars, of which the upper ones carry four cusps, and the first lower premolar canine-like both in shape and function. In the type genus there are forty-four teeth, forming an uninterrupted series. The vertebral artery pierces the neck-vertebrae in the normal manner. The name Oreodon is preoccupied by Orodus, the designation of a genus of Palaeozoic fishes, and is likewise antedated by Merycoidodon, which is now used by some writers. See Tylopoda.