What is "nannippus"

Nannippus is an extinct genus of horse endemic to North America during the Miocene through Pliocene, ~13.3—3.3 Ma, living approximately .

Nannippus lived as far south as Central Mexico (N. peninsulatus) to as far north as Canada (N. lenticularis), to California in the west, North Carolina (N. lenticularis) and Florida (N. peninsulatus) in the east.