Orohippus

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Orohippus (Gr., "mountain horse") is an extinct ancestor of the modern horse that lived in the Eocene (about 50 million years ago). It is believed to have evolved from palaeotheres such as Hyracotherium, as the earliest evidence for Orohippus appears about 2 million years after the first appearance of Hyracotherium. The anatomical differences between the two are slight: they were the same size, but Orohippus had a slimmer body, a more elongated head, slimmer forelimbs and longer hind legs, all of which are characteristics of a good jumper. The upper premolars of Orohippus are more molariform (flat-surfaced) than in Hyracotherium, giving Orohippus more teeth for grinding, and the crests on the teeth are more pronounced, indicating that Orohippus probably fed on tougher plants.