Mesohippus
"middle horse"
Mesohippus lived during the Oligocene period, some 25 to 40 million years ago. It had longer legs than Eohippus and stood about two feet tall. It had also lost a toe and now stood predominantly on its middle toe, although the other two were also used. The face of Mesohippus began to lengthen and increased in size. It had a slight facial fossa, or depression in the skull. The eyes grew rounder and were set wider apart and farther back.
Its teeth also grew larger and contained a single gap behind the front teeth, which is where the bit now rests in the modern equine. In addition, it had another grinding tooth, with a total of six. Like Eohippus, Mesohippus was a browser who fed on
tender twigs and fruit. The cerebral hemisphere, or cranial cavity, was notably larger; its brain was like that of today's equine. However, Mesohippus had died out by the mid-Oligocene period.
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