Evolution and systematics

The Bovidae are the largest family within the Artiodactyla (even-toed ungulates) and are comprised of six subfamilies, which include antelopes, cattle, duikers, gazelles, goats, and sheep. Their common characteristic is their unbranched, non-deciduous horns. The high frequency of convergent evolution within these animals suggests that this might not be a monophyletic group.

Based on tooth characteristics, some scientists suggest that the first Bovidae can be recognized from the late Oligocene. However, most agree that members of this family first appear in the fossil record during the Miocene, after which they rapidly diversified and became widely distributed. This rapid diversification during the Miocene, which resulted in all extant lineages being present by 16-17 million years ago, is supported by estimates based on molecular genetic evidence. Largely as a result of their rapid diversification, the phyloge-netic relationships within the Bovidae are perhaps some of the most difficult to elucidate of all ungulates.

The earliest fossil attributed to the Bovidae is Eotragus, found in 18-million-year-old Miocene deposits from Pakistan. It is recognized as a bovid by its horn cores, and it also possessed high-crowned cheek teeth typical of modern members of this family. Boselaphines first appear in the middle Miocene of Africa and Europe, perhaps earlier in Pakistan, and in the late Miocene in China. The boselaphines probably gave rise to the Bovini towards the late Miocene. Also in the late Miocene, Gazella, probably originating from an ancestor similar to the African Homoiodorcas, became widely distributed throughout Eurasia, and around this same epoch, modern antelopes first appeared in Africa. The first Caprinae probably evolved from Tethytragus found in Europe, with the first fossil sheep, Oioceros, occurring in the late Miocene. Leptobos and Parabos are the first cattle and are found in early Pliocene deposits from about five million years ago, when the ovibovines also are first known.

The family Bovidae is comprised of six subfamilies (An-tilopinae, Bovinae, Caprinae, Cephalophinae, Hippotraginae, and Neotraginae) with a total of 137 species in 46 genera (sometimes the subfamilies Aepycerotinae, Alcelaphinae, Peleinae, and Reduncinae are recognized). Not included in these totals are the short-horned water buffalo (Bubalus mephistopheles) from northeast China, which became extinct in the Shang Dynasty (1800-1200 B.C.), and the controversial "linh duong" (Pseudonovibos spiralis) from Vietnam and Cambodia. The validity of this latter animal is controversial because DNA evidence has suggested it is related to Antilopinae, to Bovinae, and to Caprinae, and one DNA analysis indicated

Topi (Damaliscus lunatus) usually live in herds of 15 to 20 animals. (Photo by David M. Maylen III. Reproduced by permission.)

that the horns of at least some specimens had been made from domestic cattle horn. Some authors recognize Capricornis as the genus to which serow belong; in this case, there would be 47 genera within the Bovidae.

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