Hornless rhinoceroses, with five fronttoes, ranging from the Oligocene to the Lower Pliocene in Europe, represent the genus Aceratherium, which may also occur in America, as it certainly does in India.
The breed is usually hornless.
The Theban goat, of the Sudan, which is hornless, displays the characteristic features of the last in an exaggerated degree, and in the form of the head and skull is very sheep-like.
From this it seems probable that Palaeotragus and Ocapia indicate the ancestral type of the giraffe-line; while it has been further suggested that the apparently hornless Helladotherium of the Female Okapi.