Equidae
Equidae (sometimes known as the horse family) is the taxonomic family of horses and related animals, including the extant horses, donkeys, and zebras, and many other species known only from fossils. All extant species are in the genus "Equus". Equidae belongs to the order Perissodactyla, which includes the extant tapirs and rhinoceros, and several extinct families.
Wild horse
The horse family Equidae and the genus "Equus" evolved in North America, before the species moved into the Eastern Hemisphere. Studies using ancient DNA, as well as DNA of recent individuals, show the presence of two closely related horse species in North America, the wild horse and "Haringtonhippus francisci", the "New World stilt-legged horse"; the latter has been taxonomically assigned to various names.