Equus and Plesippus—One-toed Horses // Hippidion—Hippidion Horses // Nannippus—Gazelle-horses
Although horses had most of their evolutionary history in North American, occasionally sending emigrants to Eurasia and South America, North American diversity had decreased to several genera by the beginning of the Pleistocene: Equus, Plesippus (often placed as a subgenus of Equus), Nannippus, and possibly Hippidion. Equus lasted to the great megafaunal extinction at the end of the Pleistocene; Plesippus (or Equus [Plesippus]) was essentially Blancan to perhaps into the Irvingtonian; Nannippus apparently was extinct by 2.2 mya (Morgan and Lucas 2003).
Morgan and Lucas 2003.
Last Update: 30 Apr 2014