Sometimes called a prehistoric 'ruminating hog,' the oreodont was a sheep-sized, cud-chewing plant-eater with a short face, tusk-like canine teeth, heavy body, long tail, short feet, and four-toed hooves. The now-extinct suborder Oreodonta was distantly related to pigs, hogs, camels, hippopotamuses, and the pig-like peccaries.
This stocky prehistoric mammal grazed amid the grasslands, prairies or savannas of North and Central America throughout much of the Cenozoic era. First appearing 48 million years ago (m.y.a.) during the warm Eocene epoch of the Paleogene period, the oreodonts dominated the American landscape 34 to 23 m.y.a. during the dry Oligocene epoch of the late Paleogene. But they mysteriously disappeared 4 m.y.a. during the colder Pliocene epoch of the late Neogene period, long before the arrival of humans in the New World.
Today, fossil jaws and teeth of the Oreodonta are commonly found amid the Oreodon beds of the White River badlands in South Dakota, Nebraska, and Wyoming. Many oreodont bones have also been reported at the John Day Fossil Beds National Monument in Oregon.