The General Relationships of Giraffidae

Abstract

Giraffidae is a small family of ruminants with approximately 53 species, all of which are extinct except for four extant giraffe species and the okapi. The Giraffa species are morphologically very similar. During the Miocene (18–6 million years ago), various diverse species of Giraffidae were found in numerous faunas in Eurasia and in Africa. Giraffidae are united by a set of major characteristics, including: (1) large body size (the smallest were the size of an okapi), (2) long and large metacarpals and metatarsals (when compared to antelopes and deer), (3) ossicones attached to the frontal bones and (4) presence of bi‐lobed lower canines. The family appears about 18 million years ago with the earliest fossils sampled in the Siwaliks of Pakistan, in Libya’s Gebel Zelten and in Kenya’s Moruorot Hill. From ancestral species of Gelocidae (Oligocene taxa), adaptive radiation resulted in numerous families, including Giraffidae, Palaeomerycidae and Climacoceridae (early to Middle Miocene 18–10 Ma). The basal Giraffidae (18–16 Ma) possess laterally directed ossicones, long necks and large elongated metapodials. One way to subdivide the family is into genera possessing simple premolars or complex premolars. Four groups of higher Giraffidae emerge separately from these basal taxa. The first branch, as represented by Sivatherium, is characterized by the presence of frontal sinuses, four ossicones, short necks and short metapodials. The second branch, as represented by Samotherium, is characterized by the lack of frontal sinuses, and the presence of two long slender ossicones, medium metapodials and longer necks. The third branch, as represented by Bohlinia, is characterized by the lack of a frontal sinus, and the presence of two short robust ossicones, long metapodials and a long neck. The fourth branch, as represented by Giraffa, is characterized by the presence of a frontal sinus, two robust and short ossicones, long metapodials and a long neck. The establishment of these four groups allows us to properly identify and classify a plethora of fossils and aid in the future classification of ruminants.