Hipparion \Hip*pa"ri*on\, n. [NL., fr. Gr. ? a pony, dim. of ? a
horse.] (Paleon.)
An extinct genus of Tertiary mammals allied to the horse, but
three-toed, having on each foot a small lateral hoof on each
side of the main central one. It is believed to be one of the
ancestral genera of the Horse family.