give birth to only a single young. In other respects, however, they have primitive features, closer to nonruminants such as pigs. All species in the family lack antlers and horns, but both sexes have elongated canine teeth. These are especially prominent in males, where they project out on either side of the lower jaw, and are used in fights. Their legs are short and thin, which leave them lacking in agility, but also helps to maintain a smaller profile to aid in running through the dense foliage of their environments. Other pig-like features include the presence of four toes on each foot, the absence of facial scent glands, premolars with sharp crowns, and the form of their sexual behaviour and copulation. They are solitary or live in pairs. The young are weaned at three months of age, and reach sexual maturity between 5 and 10 months, depending on species. Parental care is relatively limited. Although they lack the types of scent glands found in most other ruminants, they do possess a chin gland for marking each other as mates or antagonists, and, in the case of the water chevrotain, anal and preputial glands for marking territory. Their territories are relatively small, on the order of , but neighbors generally ignore each other, rather than compete aggressively. Some of the species show a remarkable affinity with water, often remaining submerged for prolonged periods to evade predators or other unwelcome intrusions. This has also lent support to the idea that whales evolved from water-loving creatures that looked like small deer. Taxonomy Tragulidae's placement within Artiodactyla can be represented in the following cladogram: Traditionally, only four extant species were recognized in the family Tragulidae. In 2004, T. nigricans and T. versicolor were split from T. napu, and T. kanchil and T. williamsoni were split from T. javanicus. In 2005, M. indica and M. kathygre were split from M. meminna. With these changes, the 10 extant species are: Family Tragulidae Genus Hyemoschus Water chevrotain, Hyemoschus aquaticus Genus Moschiola Indian spotted chevrotain, Moschiola indica Sri Lankan spotted chevrotain, Moschiola meminna Yellow-striped chevrotain, Moschiola kathygre Genus Tragulus Java mouse-deer, Tragulus javanicus Lesser mouse-deer or kanchil, Tragulus kanchil Greater mouse-deer, Tragulus napu Philippine mouse-deer, Tragulus nigricans Vietnam mouse-deer, Tragulus versicolor Williamson's mouse-deer, Tragulus williamsoni Ancient chevrotains The Hypertragulidae were closely related to the Tragulidae. The six extinct chevrotain genera include: Genus Dorcatherium Dorcatherium minus from Pakistan Dorcatherium