Ossicones are horn-like (or antler-like) protuberances on the heads of giraffes, male okapis, and their extinct relatives, such as Sivatherium, and the climacoceratids, such as Climacoceras. Only giraffes and okapis have true ossicones (as opposed to horns or antlers). The base that a deer's antlers grow from is very similar to an ossicone.