Equidae, more commonly referred to as the horse family, consists of 22 species; most are extinct. The number of living species currently stands at 7, all belonging to the genus Equus. The genus is divided into the non-caballoid and caballoid groups. Donkeys and zebras belong to the former, horses to the latter. The Equidae family evolved about 54 million years ago during the early Eocene. Africa hosts 4 of the extant species of Equidae; a fifth species, also native to Africa, the quagga zebra, fell into extinction in 1883.
