Hypohippus equinus

Hypohippus
Hypohippus osborni skeleton
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Perissodactyla
Family:	Equidae
Subfamily:	†Anchitheriinae
Genus:	Hypohippus

Hypohippus ("Low horse") is an extinct genus of three-toed horse, which lived 17–11 million years ago. It was the size of a pony, and fossils of it have been found in Nebraska, Colorado, and Montana.

...
Wikipedia