The above-mentioned four types of skull appendages are generally regarded as severally characteristic of as many family groups, namely the Giraffidae, Cervidae, Antilocapridae and Bovidae.
In the Giraffidae, which include not only giraffes (Giraffa) but also the okapi (Ocapia) and a number of extinct species from the Lower Pliocene Tertiary deposits of southern Europe, Asia and North Africa, the appendages on the skull are of type No.
Whether the Giraffidae were originally an African or a Euro-Asiatic group there is not yet sufficient evidence to decide.
More light is required with regard to the past history of the giraffe-family (Giraffidae), which includes the African okapi and the extinct Indian Sivatherium, and is unknown in the New World.