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Miohippus
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Illustration of Miohippus, an extinct prehistoric horse, showing a small, deer-sized animal with a spotted brown coat and a scale bar for size reference. An inset details the bones of its forefoot, highlighting its three toes. A reconstructed skeleton of Miohippus intermedius. This diagram traces the evolution of the horse from the small, multi-toed Hyracotherium (dawn horse) of the Eocene epoch to the modern single-toed Equus, showing changes in size, limb structure, and forefoot bones, with illustrations of key ancestral species to scale.
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Miohippus
Miohippus The ancestral horse Miohippus, in an artist's conception. Existing toe bones of the forefoot are numbered outward from the centre of the body.

Miohippus

fossil mammal genus
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History
A reconstructed skeleton of Miohippus intermedius.
A reconstructed skeleton of Miohippus intermedius.

Miohippus, genus of extinct horses that originated in North America during the Late Eocene Epoch (37.2–33.9 million years ago). Miohippus evolved from the earlier genus Mesohippus; however, the former was larger and had a more-derived dentition than the latter. The number of toes in Miohippus was reduced to three, which enabled it to run considerably faster than its five-toed ancestors. Miohippus persisted into the Miocene Epoch (23–5.3 million years ago) side by side with its more horselike one-toed relatives.

This article was most recently revised and updated by John P. Rafferty.