MIOHIPPUS

genus of extinct primitive horses that originated in North America during the middle Oligocene epoch (36.3 to 23.7 million years ago). Miohippus evolved from the earlier and more primitive genus Mesohippus and showed a tendency toward increased size and a more advanced dentition. The limbs of Miohippus were better adapted for running, although three functional toes were still present on all feet. Miohippus persisted into the succeeding Miocene epoch side by side with its more horselike and advanced descendants.