Temporal range: Middle Eocene – Early Oligocene
Mesohippus (Greek: μεσο/meso meaning "middle" and ιππος/hippos meaning "horse") is an extinct genus of early horse. It lived some 30 to 40 million years ago from the Middle Eocene to the Early Oligocene. Like many fossil horses, Mesohippus was common in North America.
Mesohippus had longer legs than its predecessor Eohippus and stood about 60 cm (6 hands) tall. It had also lost a toe and stood predominantly on its middle toe, although the other two were also used. The face of Mesohippus was longer and larger than earlier equids. It had a slight facial fossa, or depression, in the skull. The eyes were rounder, and were set wider apart and farther back than in Hyracotherium.
Unlike earlier horses, its teeth were low crowned and contained a single gap behind the front teeth, where the bit now rests in the modern horse. In addition, it had another grinding tooth, making a total of six. Mesohippus was a browser that fed on tender twigs and fruit. The cerebral hemisphere, or cranial cavity, was notably larger than that of its predecessors; its brain was similar to that of modern horses.
- M. bairdi
- M. barbouri
- M. braquistylus
- M. equiceps
- M. hypostylus
- M. intermedius
- M. latidens
- M. longiceps
- M. metulophus
- M. montanensis
- M. obliquidens
- M. proteulophus
- M. westoni
- McKenna, M. C.; Bell, S. K. (1997). Classification of Mammals: Above the Species Level. Columbia University Press. p. 631. ISBN 978-0-231-11013-6.
- Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 255. ISBN 1-84028-152-9.
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