Bovidae
Bovidae is the biological family of cloven-hoofed, ruminant mammals that includes cattle, bison, buffalo, antelopes, and goat-antelopes such as sheep and goats. There are 143 extant species and 300 known extinct species of bovids, which are divided into either 11 major subfamilies, or two subfamilies with thirteen tribes. The earliest known bovid had evolved by 20 million years ago, in the early Miocene.
The bovids show great variation in size and colouration of their fur. With exceptions in some domesticated forms, all male bovids have two or more horns, and in many species, females possess horns too. The size and shape of the horns vary greatly, but the basic structure is always one or more pairs of simple, unbranched, bony protrusions of the skull covered in a permanent sheath of keratin, and often with a spiral, twisted, or fluted shape, Most bovids bear 30 to 32 teeth.
Most bovids are diurnal. Social activity and feeding usually peak during dawn and dusk. Bovids typically rest before dawn, during midday, and after dark. They have various methods of social organisation and social behaviour, which are classified into solitary and gregarious behaviour. Bovids use different forms of vocal, olfactory, and tangible communication. Most species alternately feed and ruminate throughout the day. While small bovids forage in dense and closed habitat, larger species feed on high-fiber vegetation in open grasslands. Most bovids are polygynous. Mature bovids mate at least once a year and smaller species may even mate twice. In some species, newborn or neonate bovids remain hidden for a week to two months, regularly nursed by their mothers; in other species, neonates are followers, accompanying their travelling mothers shortly after birth.
The greatest diversities of Bovidae occur in Africa. The maximum concentration of species is in the savannas of Eastern Africa. Other bovid species also occur in Europe, Asia, and North America. A number of bovid species are domesticated, including three whose use has spread worldwide, these being the cattle, sheep, and goats. Dairy products, such as milk, butter, and cheese, are manufactured largely from domestic cattle. Bovids are also raised for their leather, meat, and wool.
Naming and etymology
The name Bovidae was coined by the British zoologist John Edward Gray in 1821. It is composed of the prefix bov- and the suffix -idae.Taxonomy
The family Bovidae is placed in the order Artiodactyla, the even-toed ungulates. It includes 143 extant species, accounting for nearly 55% of ungulate diversity, and 300 known extinct species.Until the beginning of the 21st century it was understood that the family of musk deer was sister to Cervidae, the family of antlered deer. However, a 2003 phylogenetic study by Alexandre Hassanin and colleagues, based on mitochondrial and nuclear analyses, revealed that Moschidae and Bovidae form a clade which is sister to Cervidae. According to the study, Cervidae diverged from the Bovidae-Moschidae clade 27 to 28 million years ago. The following cladogram is based on the 2003 study.
Molecular studies have supported monophyly in the family Bovidae; it is a "natural group" containing an ancestral species and all of their descendants. The number of subfamilies in Bovidae is disputed, with suggestions of as many as ten and as few as two subfamilies. However, molecular, morphological and fossil evidence indicates the existence of eight distinct subfamilies: Aepycerotinae, Alcelaphinae, Antilopinae, Bovinae, Caprinae, Cephalophinae, Hippotraginae and Reduncinae. In addition, three extinct subfamilies are known: Hypsodontinae, Oiocerinae and the subfamily Tethytraginae, which contains Tethytragus.
In 1992, Alan W. Gentry of the Natural History Museum, London divided the eight major subfamilies of Bovidae into two major clades on the basis of their evolutionary history: the Boodontia, which comprised only the Bovinae, and the Aegodontia, which consisted of the rest of the subfamilies. Boodonts have somewhat primitive teeth, resembling those of oxen, whereas aegodonts have more advanced teeth like those of goats.
A controversy exists about the recognition of Peleinae and Pantholopinae, comprising the genera Pelea and Pantholops respectively, as subfamilies. In 2000, American biologist George Schaller and palaeontologist Elisabeth Vrba suggested the inclusion of Pelea in Reduncinae, though the grey rhebok, the sole species of Pelea, is highly different from kobs and reduncines in morphology. Pantholops, earlier classified in the Antilopinae, was later placed in its own subfamily, Pantholopinae. However, molecular and morphological analysis supports the inclusion of Pantholops in Caprinae.
Below is a cladogram based on Yang et al.'','' 2013 and Calamari, 2021:
Alternatively, all members of the Aegodontia can be classified within the subfamily Antilopinae, with the individual subfamilies being tribes in this treatment.
Evolutionary history
Early Miocene and before
In the early Miocene, bovids began diverging from the cervids and giraffids. The earliest bovids, whose presence in Africa and Eurasia in the latter part of early Miocene has been ascertained, were small animals, somewhat similar to modern gazelles, and probably lived in woodland environments. Eotragus, the earliest known bovid, weighed and was nearly the same in size as the Thomson's gazelle. Early in their evolutionary history, the bovids split into two main clades: Boodontia and Aegodontia. This early split between Boodontia and Aegodontia has been attributed to the continental divide between these land masses. When these continents were later rejoined, this barrier was removed, and both groups expanded into the territory of the other. The tribes Bovini and Tragelaphini diverged in the early Miocene. Bovids are known to have reached the Americas in the Pleistocene by crossing the Bering land bridge.The present genera of Alcelaphinae appeared in the Pliocene. The extinct Alcelaphine genus Paramularius, which was the same in size as the hartebeest, is believed to have come into being in the Pliocene, but became extinct in the middle Pleistocene. Several genera of Hippotraginae are known since the Pliocene and Pleistocene. This subfamily appears to have diverged from the Alcelaphinae in the latter part of early Miocene. The Bovinae are believed to have diverged from the rest of the Bovidae in the early Miocene. The Boselaphini became extinct in Africa in the early Pliocene; their latest fossils were excavated in Langebaanweg and Lothagam.
Middle Miocene
The middle Miocene marked the spread of the bovids into China and the Indian subcontinent. According to Vrba, the radiation of the subfamily Alcelaphinae began in the latter part of middle Miocene. The Caprinae tribes probably diverged in the early middle Miocene. The Caprini emerged in the middle Miocene, and seem to have been replaced by other bovids and cervids in Eurasia. The earliest fossils of the antilopines are from the middle Miocene, though studies show the existence of the subfamily from the early Miocene. Speciation occurred in the tribe Antilopini during the middle or upper Miocene, mainly in Eurasia. Tribe Neotragini seems to have appeared in Africa by the end of Miocene, and had become widespread by the Pliocene.Late Miocene
By the late Miocene, around 10 Mya, the bovids rapidly diversified, leading to the creation of 70 new genera. This late Miocene radiation was partly because many bovids became adapted to more open, grassland habitats. The Aepycerotinae first appeared in the late Miocene, and no significant difference in the sizes of the primitive and modern impala has been noted. Fossils of ovibovines, a tribe of Caprinae, in Africa date back to the late Miocene. The earliest Hippotragine fossils date back to the late Miocene, and were excavated from sites such as Lothagam and Awash Valley. The first African fossils of Reduncinae date back to 6-7 Mya. Reduncinae and Peleinae probably diverged in the mid-Miocene.Plio-Pleistocene
African bovids continued becoming more adapted to mixed feeding, indicated by dental mesowear evidence, as their palaeoenvironment opened up.Characteristics
All bovids have the similar basic form - a snout with a blunt tip, one or more pairs of horns immediately after the oval or pointed ears, a distinct neck and limbs, and a tail varying in length and bushiness among the species. Most bovids exhibit sexual dimorphism, with males usually larger as well as heavier than females. Sexual dimorphism is more prominent in medium- to large-sized bovids. All bovids have four toes on each foot – they walk on the central two, while the outer two are much smaller and rarely touch the ground.The bovids show great variation in size: the gaur can weigh more than, and stand high at the shoulder. The royal antelope, in sharp contrast, is only tall and weighs at most. The klipspringer, another small antelope, stands at the shoulder and weighs just.
Differences occur in pelage colouration, ranging from a pale white to black. However, only the intermediate shades, such as brown and reddish brown, are commonly observed. In several species, females and juveniles exhibit a light-coloured coat, while those of males darken with age. As in the wildebeest, the coat may be marked with prominent or faint stripes. In some species such as the addax, the coat colour can vary by the season. Scent glands and sebaceous glands are often present.
Some species, such as the gemsbok, sable antelope, and Grant's gazelle, are camouflaged with strongly disruptive facial markings that conceal the highly recognisable eye. Many species, such as gazelles, may be made to look flat through countershading, hence blending into the background. The outlines of many bovids are broken up with bold disruptive colouration, the strongly contrasting patterns helping to delay recognition by predators. However, all the Hippotraginae have pale bodies and faces with conspicuous markings. The zoologist Tim Caro describes this as difficult to explain, but given that the species are diurnal, he suggests that the markings may function in communication. Strongly contrasting leg colouration is common only in the Bovidae, where for example Bos, Ovis, bontebok and gemsbok have white stockings. Again, communication is the likely function.
Excepting some domesticated forms, all male bovids have horns, and in many species, females too possess horns. The size and shape of the horns vary greatly, but the basic structure is a pair of simple bony protrusions without branches, often having a spiral, twisted, or fluted form, each covered in a permanent sheath of keratin. Although horns occur in a single pair on almost all bovid species, there are exceptions such as the four-horned antelope and the Jacob sheep. The unique horn structure is the only unambiguous morphological feature of bovids that distinguishes them from other pecorans. A high correlation exists between horn morphology and fighting behaviour of the individual. For instance, long horns are intended for wrestling and fencing, whereas curved horns are used in ramming. Males with horns directed inwards are monogamous and solitary, while those with horns directed outwards tend to be polygynous. These results were independent of body size.
Male horn development has been linked to sexual selection, Horns are small spikes in the monogamous duikers and other small antelopes, whereas in the polygynous, they are large and elaborately formed. Thus, to some extent, horns depict the degree of competition among males in a species. However, the presence of horns in females is likely due to natural selection. The horns of females are usually smaller than those of males, and are sometimes of a different shape. The horns of female bovids are believed to have evolved for defence against predators or to express territoriality, as non-territorial females, which are able to use crypsis for predator defence, often do not have horns. Females possess horns only in half of the bovid genera, and females in these genera are heavier than those in the rest. Females use horns mainly for stabbing.