Pliohippus arose in the middle Miocene, around 15 million years ago.

The long and slim limbs of Pliohippus reveal a quick-footed steppe animal.

[2] Until recently, because of its many anatomical similarities, Pliohippus was believed to be the ancestor of the present-day horse and its relatives in Equus.

[3] Pliohippus stood approximately 1.25 metres, similar to the modern horse.

Also like the modern horse, Pliohippus was a grazer that fed on steppe grasses of the North American plains it inhabited.