Ossicone

Ossicones are columnar or conical skin-covered bone structures on the heads of giraffes, male okapi, and some of their extinct relatives. Ossicones are distinguished from the superficially similar structures of horns and antlers by their unique development and a permanent covering of skin and fur.
Structure.
Giraffe ossicones consist of a highly vascularized and enervated bone core covered with vascularized and enervated skin. The base of an ossicone is attached to the skull with vascularized enervated connective tissue. Ossicones are formed at late pregnancy, but in early development they are not bony and not fused to the skull yet. Ossicones usually fuse to the skull at sexual maturity.
All male and female giraffes have a pair of parietal ossicones on the parietal bones of the skull. Males also usually have a single median ossicone on the frontal bone that is larger in northern animals and smaller in southern giraffes. Giraffes can also have small additional paired occipital ossicones on the occipital bones, paired orbital ossicones associated with eyes, and azygous ossicones.
In giraffes, male and female ossicones vary in structure and purpose (a manifestation of sexual dimorphism). Males typically have thicker ossicones that become bald on top due to frequent necking. In okapi, the male's ossicones are smaller in proportion to the head, and taper towards their tips, forming a sharper point than the comparatively blunt giraffe ossicone. Whereas female giraffes have reduced ossicones, female okapi lack ossicones entirely.
The morphology of ossicones in the extinct relatives of giraffes and okapi varies widely. Some species had two pairs of ossicones rather than one (e.g. "Giraffokeryx"), some had rugged textures (e.g. "Shansitherium"), and some had large, flattened ossicones (e.g. male "Prolibytherium").
Function.
Similar to species that possess horns or antlers, male giraffes use their ossicones as a weapon during combat where they use their heads as clubs with the ossicones concentrating the force of impact onto a small area. Ossicones also add weight to the animal's head, allowing it to deliver heavier blows. The nerve bundles and large blood supply in the ossicones led some researchers to speculate that the structures may also play a role in thermoregulation. Given the neurological composition of ossicones, and their importance to reproductive behavior, any research method affecting giraffe ossicones should be carefully reviewed for purpose and needs that are urgent enough to overcome the risk of pain and suffering to giraffes. Claims that ossicones are not ennervated, such as those made by Giraffe Conservation Foundation, should be considered inaccurate.
Examples.
Ossicones are only found in some members of the superfamily Giraffoidea, which includes the family Giraffidae (to which giraffes, okapi, and extinct relatives belong) and the entirely extinct family Climacoceratidae. It has been argued that the so-called ossicones known from fossils are actually horns; however, later research has revealed these structures to be consistent with the ossicones of giraffes and okapi. The following is a list of some ossicone-bearing genera: