Bovids are the largest of 10 extant families within Artiodactyla, consisting of more than 140 extant and 300 extinct species. Designation of subfamilies within Bovidae has been controversial and many experts disagree about whether Bovidae is monophyletic or not. While as many as 10 and as few as 5 subfamilies have been suggested, the intersection of molecular, morphological, and fossil evidence suggests 8 distinct subfamilies: Aepycerotinae (impalas), Alcelaphinae (bonteboks, hartebeest, wildebeest, and relatives), Antilopinae (antelopes, dik-diks, gazelles, and relatives), Bovinae (bison, buffalos, cattle, and relatives), Caprinae (chamois, goats, serows, sheep, and relatives), Cephalophinae (duikers), Hippotraginae (addax, oryxes, roan antelopes, sable antelopes, and relatives), and Reduncinae (reedbucks, waterbucks, and relatives). Wild bovids can be found throughout Africa, much of Europe, Asia, and North America and characteristically inhabit grasslands. Their dentition, unguligrade limb morphology, and gastrointestinal specialization likely evolved as a result of their grazing lifestyle. All bovids have four-chambered, ruminating stomachs and at least one pair of horns, which are generally present on both sexes.
Species in the subfamily Bovinae are native to Africa, North America, Eurasia, India, and southern Asia. Bovinae is generally considered to include 24 species from 8 different genera, including nilgai, four-horned antelope, wild cattle, bison, Asian buffalo, African buffalo, and kudu. Sexual dimorphism is highly prevalent in this subfamily, with the males of some species weighing nearly twice as much as their female counterparts. Bovines have played an important role in the cultural evolution of humans, as numerous species within this subfamily have been domesticated for subsistence purposes.
The subfamily Antilopinae includes antelopes, dik-diks, gazelles, and relatives. Small to medium-sized, cover-dependent antelope are found throughout a majority of Africa but occur in particularly high densities in east Africa. Dwarf antelope, steenboks, and dik-diks occur in a variety of different habitats but are also restricted to the continent of Africa. Finally, true gazelles include the genera Eudorcas, Gazella, Nanger, and Procapra, among others. In general, bovids within the subfamily Antilocapinae occur throughout much of Asia and Africa.
Bovids within the subfamily Reduncinae are primarily distributed throughout parts of Eurasia and Africa. Reduncinae is comprised of only three genera, including Redunca (reedbucks), Pelea (rhebok), and Kobus (waterbucks). Species in Reduncinae are medium to large-sized grazers that often have strong ties to water. They also have long hair, and all species exhibit sexual dimorphism, as horns are only present in males.
Bovids in the subfamily Hippotraginae consist primarily of large grazing antelopes with large horns. Hippotraginae species are restricted to Africa and middle-east Asia and are primarily grazers. Most species in this subfamily live in arid habitats and have an erect mane along the nape of the neck. Recent accounts include 8 species from 3 different genera.
Ancelaphinae, consisting of 10 species from 4 genera, includes bonteboks, hartebeest, wildebeest, and relatives. All of the species in this subfamily are nomadic grazers that are native to Africa. Most species are size-dimorphic, with males being 10 to 20% larger than females, and both males and females possess double-curved horns, also known as lyrate.
The subfamily Caprinae consists of goats, sheep, muskox, and relatives. This subfamily of bovids consists of 12 genera, however, the organization of Caprinae is complex and several classifications have been suggested. The International Union for Conservation of Nature (IUCN) currently has a Taxonomy Working Group within their Caprinae Specialist Group to help alleviate some of the outstanding issues within Caprina taxonomy. Caprinids are especially adapted to montane and alpine environments, which explains why this is the only subfamily that is more diverse in Eurasia than Africa. In general, both genders have horns, however, horn morphology in many species is sexually dimorphic.
The subfamily Aepycerotinae consists a single species, the imapala. Aepycerotinae is endemic to Africa and is thought to have diverged from other bovids during the early Miocene, around 20 million years ago. Impala are sexually dimorphic, as only males possess horns..
Cephalophinae consists of 18 species of duiker from 3 genera. Duikers are highly specialized and are resident to the tropical forests of Africa. All species are easily recognizable as they have the same basic body plan but differ significantly in size from one species to the next. Duikers are size-dimoprhic, however, unlike most bovids, females are slightly larger than males. Also unlike most other bovids, duikers are primarily frugivorous.