The Oreodon's proper name is Merycoidodon Culbertsoni, but they are more commonly known as oreodon. The oreodon was a small mammal, similar to a goat or sheep. The large front teeth in the skull give it a pig-like appearance. These fossil oreodon pieces are approximately 25 million to 50 million years old and are found in the Brule Formation, South Dakota, USA. Fossils from these unusual mammals are quite rare, with few new specimens being found.