Giraffidae

The Giraffidae are a family of ruminant artiodactyl mammals that share a common ancestor with cervids and bovids. This family, once a diverse group spread throughout Eurasia and Africa, presently comprises only two extant genera, the giraffe (one or more species of Giraffa, depending on taxonomic interpretation) and the okapi (the only known species of Okapia). Both are confined to sub-Saharan Africa: the giraffe to the open savannas, and the okapi to the dense rainforest of the Congo. The two genera look very different on first sight, but share a number of common features, including a long, dark-coloured tongue, lobed canine teeth, and horns covered in skin, called ossicones. Molecular studies present the Giraffidae as a sister group to the Cervidae, Moschidae, and Bovidae. The giraffids evolved from a group of even-toed ungulates in the early Miocene almost 25 million years ago. They formed part of a relatively late mammal diversification that also produced cattle, antelopes, and deer following a climate change that transformed subtropical woodlands into open savannah grasslands. The giraffids diversified into many now extinct forms that inhabited large parts of Eurasia and eventually spread into Africa, where the only still extant forms persist. The most primitive forms had short necks and were about the size of a modern red deer, somewhat similar to the modern okapi. The two main groups of extinct giraffids are: one group with robust limb bones, the Sivatheriinae, represented by Sivatherium during the Plio-Pleistocene, and another with long, slender limb bones classified in different subfamilies; either Giraffinae and Palaeotraginae or just Giraffinae (with the two tribes, Giraffini and Palaeotragini). While Giraffa and Palaeotragus can be easily attributed to the latter group, the placement of Okapia and Mitilanotherium remains disputed. Their closest fossil relatives include the deer-like palaeomerycids and the climacocerids, many genera of the latter having once been identified as giraffes themselves. Fossil records indicate that many other giraffids thrived between the Miocene epoch (around 20 million years ago) and the recent past. One major group of extinct giraffids, the sivatheres, had enormous, branching ossicones, and would have looked more like massive deer than giraffes. FAMILY GIRAFFIDAE The giraffe stands 5–6 m (16–20 ft) tall, with males taller than females. The giraffe and the okapi have characteristic long necks and long legs. Ossicones are present on males and females in the giraffe, but only on males in the okapi.