Evolution and systematics

The Bovinae is comprised of 24 extant species in three tribes: Boselaphini, Bovini, and Tragelaphini. Genetic evidence supports the idea that the Bovinae is a monophyletic group and a sister group to the subfamily Antilopinae. The tribe Bovini is also monophyletic and a sister group to the Boselaphini. The Boselaphini, today represented by only two living species, the nilgai (Boselaphus tragocamelus) and the chousingha (Tetracerus quadricornis), both of India, are probably the most primitive of the Bovinae and closest to the ancestors of this subfamily. The Bovini tribe includes yak (Bos grunniens), the various species of wild cattle (Bos), the European and American bisons (Bison), Asian (water) buffaloes and anoas (Bubalus), African buffalo (Syncerus caffer), and probably the saola (Pseudoryx nghetinhensis). The yak is sometimes placed into the genus Poephagus, while Bison have been suggested to belong to Bos, as has yak. Yaks appear from behavioral and genetic evidence to be intermediate between cattle and bison. The modern members of the tribe Tragelaphini are all African species, which have probably been separated from other Bovinae for 15 million years. Fossils attributed to nyala (Tragelaphus angasii) have been found in 6.5-million-year-old deposits. The mountain nyala (Tragelaphus buxtoni) is believed to be the precursor of kudu (Tragelaphus strepsiceros and T. imberbis). Other tragelaphines include the bongo (Tragelaphus eurycerus), bushbuck (T. scriptus), sitatunga (T. spekii), and elands (Taurotragus).

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