Ossicones are horn

Horn (anatomy)

A horn is a pointed projection of the skin on the head of various animals, consisting of a covering of horn surrounding a core of living bone. True horns are found mainly among the ruminant artiodactyls, in the families Antilocapridae and Bovidae...

-like (or antler

Antler

Antlers are the usually large, branching bony appendages on the heads of most deer species.-Etymology:Antler originally meant the lowest tine, the "brow tine"...

-like) protuberances on the heads of giraffe

Giraffe

The giraffe is an African even-toed ungulate mammal, the tallest of all extant land-living animal species, and the largest ruminant...

s, male okapi

Okapi

The okapi , Okapia johnstoni, is a giraffid artiodactyl mammal native to the Ituri Rainforest, located in the northeast of the Democratic Republic of the Congo, in Central Africa...

s, and their extinct relatives, such as Sivatherium

Sivatherium

Sivatherium ' is an extinct genus of giraffid that ranged throughout Africa to Southern Asia . The African species, S...

, and the climacoceratids, such as Climacoceras

Climacoceras

Climacoceras was a genus of early Miocene artiodactyl ungulates of Africa and Europe. The members of Climacoceras were related to giraffes, as the genus was once placed within Giraffidae. Fossils of the two best known species of Climacoceras, C. africanus and C. gentryi have been both found in...

. Only giraffids

Giraffidae

The giraffids are ruminant artiodactyl mammals that share a common ancestor with deer and bovids. The biological family Giraffidae, once a diverse group spread throughout Eurasia and Africa, contains only two living members, the giraffe and the okapi. Both are confined to sub-saharan Africa: the...

 have true ossicones (as opposed to horns or antlers). The base that a deer's antlers grow from is very similar to ossicones.

Ossicones are similar to the horns of antelope

Antelope

Antelope is a term referring to many even-toed ungulate species indigenous to various regions in Africa and Eurasia. Antelopes comprise a miscellaneous group within the family Bovidae, encompassing those old-world species that are neither cattle, sheep, buffalo, bison, nor goats...

s and cattle

Cattle

Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...

, save that they are derived from ossified cartilage

Cartilage

Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...

, and that the ossicones remain covered in skin

Skin

-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...

 and fur

Fur

Fur is a synonym for hair, used more in reference to non-human animals, usually mammals; particularly those with extensives body hair coverage. The term is sometimes used to refer to the body hair of an animal as a complete coat, also known as the "pelage". Fur is also used to refer to animal...

, rather than horn. Antlers (such as on deer

Deer

Deer are the ruminant mammals forming the family Cervidae. Species in the Cervidae family include white-tailed deer, elk, moose, red deer, reindeer, fallow deer, roe deer and chital. Male deer of all species and female reindeer grow and shed new antlers each year...

) are derived from bone tissue: when mature, the skin and fur covering of the antlers, termed "velvet," is sloughed and scraped off to expose the bone of the antlers.