Evolution and systematics

The subfamily Hippotraginae, the grazing antelopes, includes 24 species in 11 genera. Fossil bovids first appear in early Miocene deposits; the earliest African material being from Libya about 20 million years ago. Analysis of mitochondrial DNA suggests there was a rapid radiation of the family in that period, perhaps in association with the emergence of savanna habitat in Africa, and that all living lineages had arisen by 16-17 million years ago (mya).

The subfamily classification used recognizes three tribes. The Reduncini includes nine species in three genera: Redunca (reedbucks) comprises the southern reedbuck (R. arundinum), bohor reedbuck (R. redunca), and mountain reedbuck (R. ful-vorufula). Kobus contains the waterbuck (K. ettipsiprymnus), the lechwe (K leche) and Nile lechwe (K. megaceros), the kob (K. kob), and the puku (K vardonii). The gray rhebok (Pelea capre-olus) is also included, although its classification is controver sial and it is sometimes placed in its own subfamily (Peleinae), or even with the dwarf antelopes (Antilopinae; Neotragini) or goats (Caprinae).

The Alcelaphini, with eight species in five genera, includes the black wildebeest (Connochaetes gnou), the blue wildebeest (C. taurinus), the sassabies, and the hartebeests. The sassabies comprise three species: Hunter's hartebeest (D. hunter), the blesbok and bontebok (D. pygargus), and the topi (D. lunatus), while the hartebeests include the hartebeest (Alcelaphus buse-laphus) and Lichtenstein's hartebeest (A. lichtensteini). The impala (Aepyceros melampus) is sometimes placed in the Antilopinae, or in its own subfamily (Aepycerotinae), but it is now thought to be an early offshoot of the Alcelaphini.

The horse-like antelopes (Hippotragini) have seven species in three genera. Hippotragus contains the extinct bluebuck (H. leucophaeus), the roan (H. equinus), and the sable (H. niger), plus three oryx species, the scimitar-horned oryx

Wildebeest (Commachaetes taurinus) mating, Ngorongoro Crater, Tanzania. (Photo by Animals Animals ©A. & M. Shah. Reproduced by permission.)

(Oryx dammah), the Arabian oryx (O. leucoryx), and the gems-bok (O. gazella). The addax (Addax nasomaculatus) is also included.

Some authorities elevate these tribes to subfamily status (Reduncinae, Alcelaphinae, and Hippotraginae).

Alcelaphines appeared first in the fossil record about five mya and appear to be almost wholly African in their evolution. Early Pleistocene remains of Pelea are known, while Hippotra-gus species and the southern reedbuck first appear in the middle and upper Pleistocene. Earlier Redunca species appeared in the late Pliocene or lower Pleistocene, at which time the first Kobus fossils are recorded. Fossil Aepycerotine over three million years old are known from East Africa.

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