Plesippus

The Hagerman horse (Equus simplicidens), also called the Hagerman zebra or the American zebra, was a North American species of equid from the Pliocene epoch and the Pleistocene epoch. It was one of the oldest horses of the genus Equus. Discovered in 1928 in Hagerman, Idaho, it is believed to have been like the Grévy's zebra of East Africa. It is the state fossil of Idaho.