Neohipparion, a Three-Toed Horse

Abstract

No other lineage of mammals illustrates quite so clearly or so fully its growth or evolution in geologic time as that of the horse. In the history of the Equidae many forms antecedent to the living animal are now known, each marked by readily identifiable characters in the teeth, skull and skeleton. From Eohippus, the "dawn horse" of approximately 50 million years ago, to the equines of today, a score or more different kinds of genera and numerous species of extinct horses have been described. The changes that have produced the large and specialized animal of today from the diminutive and distinctly less specialized Eocene ancestor of long ago are demonstrated by an amazing array of fossil remains, found for the most part in the land-laid formations of the western United States.

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