Grandfather" to the modern horse, Pliohippus appears to be the source of the latest radiation in the horse family. It is believed to have given rise to Hippidion and Onohippidion, genera that thrived for a time in South American, and to Dinohippus which in turn led toEquus. Fossils of Pliohippus are found at many late Miocene localities in Colorado, the Great Plains of the US (Nebraska and the Dakotas) and Canada. Species in this genus lived from 12-6 million years ago.