The subgenus Asinus encompasses four species and several subspecies of equidae characterized by long ears, a lean, straight-backed build, a scant tail and reputed to have considerable toughness and endurance.
The common Donkey or "Ass" is the best-known representative of the Subgenus, with both domesticated and feral varieties, ranging in size from the small burro to the horse-sized "Mammoth Jack" and other breeds. There is not a formal cutoff between the terminology "donkey" and "ass," though smaller animals are usually called donkeys and larger animals are asses. Both can be used to create a mule, which is a hybrid animal produced by a cross of a donkey and a horse.
Wild asses, include a number of truly wild, never domesicated subspecies of Equus Asinus that live in Africa and Asia. The closest relative to Equus africanus is the Grevy's zebra.[citation needed] They have similiarties, including small herds, longer ears and the skull is more ass shape.[citation needed]
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