Suidae is the biological family to which pigs belong. In addition to numerous fossil species, up to sixteen extant species are currently recognized, including the domestic pig Sus scrofa domesticus or Sus domesticus. The extant species are classified into between four and eight genera. In addition to numerous species of wild pig, these include the babirusa Babyrousa babyrussa and the warthog Phacochoerus aethiopicus. All suids are native to the Old World, ranging from Asia and its islands, to Europe, and Africa.
The earliest fossil suids date from the Oligocene epoch of Asia, and their descendants reached Europe during the Miocene. Several fossil species are known, and show adaptations to a wide range of different diets, from strict herbivory to possible carrion-eating (in Tetraconodon).
Suids belong to the order Artiodactyla, and are generally regarded as the living members of that order most similar to the ancestral form. Unlike most other members of the order, they have four toes on each foot, although they walk only on the middle two digits, with the others staying clear of the ground. They also have a simple stomach, rather than the more complex, ruminant, stomach found in most other Artiodactyl families.
They are small to medium animals, varying in size from 58 to 66 cm (23 to 26 in) in length, and 6 to 9 kg (13 to 20 lb) in weight in the case of the Pygmy Hog, to 130–210 cm (4–7 ft) and 130–275 kg (300–600 lb) in the Giant Forest Hog. They have large heads and short necks, with relatively small eyes and prominent ears. Their heads have a distinctive snout, ending in a disc-shaped nose. Suids typically have a bristly coat, and a short tail ending in a tassle. The males possess a corkscrew-shaped penis, which fits into a similarly shaped groove in the female's cervix.
Suids have a well developed sense of hearing, and are vocal animals, communicating with a series of grunts, squeals, and similar sounds. They also have an acute sense of smell. Many species are omnivorous, eating grass, leaves, roots, insects, worms, and even frogs or mice. Other species are more selective and purely herbivorous.
Their teeth reflect their diet, and suids retain the upper incisors, which are lost in most other Artiodactyls. The canine teeth are enlarged to form prominent tusks, used for rooting in moist earth or undergrowth, and in fighting. They have only a short diastema. The number of teeth varies between species, but the general dental formula is:
Behaviour and reproduction
Despite their apparently 'primitive' anatomy, suids are intelligent and adaptable animals. Adult females (sows) and their young travel in a group (sounder; see List of animal names), whilst adult males (boars) are either solitary, or travel in small bachelor groups. Males generally are not territorial, and come into conflict only during the mating season.
Litter size varies between one and twelve, depending on the species. The mother prepares a grass nest or similar den, which the young leave after about ten days. Suids are weaned at around three months, and become sexually mature at 18 months. In practice, however, male suids are unlikely to gain access to sows in the wild until they have reached their full physical size, at around four years of age. In all species, the male is significantly larger than the female, and possesses more prominent tusks.
- Subfamily †Cainochoerinae
- Subfamily †Hyotheriinae
- Subfamily †Listriodontinae
- Subfamily Suinae
- Tribe Babyrousini
- Tribe †Hippohyini
- Tribe Potamochoerini
- Genus †Celebochoerus (Pliocene to Pleistocene)
- Genus Hylochoerus (Pleistocene to Recent)
- Genus †Kolpochoerus (Miocene to Pleistocene) (Jr synonyms Ectopotamochoerus, Mesochoerus, Omochoerus, Promesochoerus)
- Genus Potamochoerus (Miocene to Recent)
- Genus †Propotamochoerus (Miocene to Pliocene)
- Tribe Suini
- Genus †Eumaiochoerus (Miocene)
- Genus †Hippopotamodon (Miocene to Pleistocene) (Jr synonym Limnostonyx)
- Genus †Korynochoerus (Miocene to Pliocene)
- Genus †Microstonyx (Miocene)
- Genus Sus (Miocene to Recent)
- Species Sus ahoenobarbus Palawan Bearded Pig
- Species Sus barbatus Bearded Pig
- Species Sus bucculentus Vietnamese Warty Pig
- Species Sus cebifrons Visayan Warty Pig
- Species Sus celebensis Celebes Warty Pig
- Species Sus heureni Flores Warty Pig
- Species Sus oliveri Mindoro Warty Pig
- Species Sus philippensis Philippine Warty Pig
- Species Sus scrofa (also called S. domesticus) Domestic pig, wild boar
- Species Sus verrucosus Javan Warty Pig
- Tribe Phacochoerini
- Tribe incertae sedis 
- Subfamily †Tetraconodontine
- Subfamily incertae sedis
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