Williamson's mouse-deer (Tragulus williamsoni) is a species of even-toed ungulate in the family Tragulidae. It is found in Thailand, and possibly in China. The species is named after the collector Walter James Franklin Williamson. 
Chevrotains, or mouse-deer, are small even-toed ungulates that make up the family Tragulidae, the only extant members of the infraorder Tragulina. The 10 extant species are placed in three genera, but several species also are known only from fossils. The extant species are found in forests in South and Southeast Asia, with a single species, the water chevrotain, in the rainforests of Central and West Africa. They are solitary or live in pairs, and feed almost exclusively on plant material. Chevrotains are the smallest hoofed mammals in the world. The Asian species weigh between 0.7 and 8.0 kg, while the African chevrotain is considerably larger at 7–16 kg (15–35 lb). With an average length of 45 cm (18 in) and an average height of 30 cm (12 in), the Java mouse-deer is the smallest extant (living) ungulate or hoofed mammal, as well as the smallest extant even-toed ungulate.
The Philippine mouse-deer, also known as the Balabac chevrotain or pilandok, is a small, nocturnal ruminant, which is endemic to Balabac and nearby smaller islands southwest of Palawan in the Philippines. The genus Tragulus means 'little goat' and the Philippine mouse-deer has been named so due to the horizontal pupils of the eyes. This position of the pupil allows for an increase in peripheral depth perception. It has traditionally been considered a subspecies of the greater mouse-deer. In 2004, though, T. nigricans was separated from T. napu as its own species due to differences in skull morphology. Contrary to its common name, the Philippine mouse-deer does not belong to the deer family Cervidae, but is a member of the chevrotain family.
The Java mouse-deer is a species of even-toed ungulate in the family Tragulidae. When it reaches maturity it is about the size of a rabbit, making it the smallest living ungulate. It is found in forests in Java and perhaps Bali, although sightings there have not been verified.
Tragulus is a genus of even-toed ungulates in the family Tragulidae that are known as mouse-deer. In Ancient Greek τράγος (tragos) means a male goat, while the Latin diminutive –ulus means 'tiny'. With a weight of 0.7–8.0 kg (1.5–17.6 lb) and a length of 40–75 cm (16–30 in), they are the smallest ungulates in the world, though the largest species of mouse-deer surpass some species of Neotragus antelopes in size. The mouse-deer are restricted to Southeast Asia from far southern China to the Philippines (Balabac) and Java.
The greater mouse-deer, greater Malay chevrotain, or napu is a species of even-toed ungulate in the family Tragulidae found in Sumatra, Borneo, and smaller Malaysian and Indonesian islands, and in southern Myanmar, southern Thailand, and peninsular Malaysia. Its natural habitat is subtropical or tropical, moist, lowland forest.
The Malayan weasel or Malay weasel is a weasel species native to the Malay Peninsula and the islands of Sumatra and Borneo. It is listed as Least Concern on the IUCN Red List.
The Indian spotted chevrotain is a species of even-toed ungulate in the family Tragulidae. It is native to India and possibly Nepal. It lives in rainforests and is nocturnal. It has a body length of 57.5 cm (22.6 in) with a 2.5 cm (0.98 in) long tail length and weighs around 3 kg (6.6 lb). This was earlier included under the name of Tragulus meminna, but studies on the systematics of the group have led to that name being restricted to the Sri Lankan spotted chevrotain.
Moschiola, the spotted chevrotains, are a genus of small even-toed ungulates in the family Tragulidae. They are found in forests in India, Sri Lanka and perhaps Nepal, and have pale-spotted or -striped upperparts unlike the other Asian members of the family, the mouse-deer of the genus Tragulus.
The lesser mouse-deer, lesser Malay chevrotain, or kanchil is a species of even-toed ungulate in the family Tragulidae.
The Vietnam mouse-deer, also known as the silver-backed chevrotain, is an even-toed ungulate in the family Tragulidae known only from Vietnam. It was first described in 1910 by British zoologist Oldfield Thomas, who procured four specimens from Nha Trang in Annam. Little is known about its distribution and ecology. After 1910, the Vietnam mouse-deer was reported next in 1990 near Dak Rong and Buon Luoi in the Gia Lai Province. With increasing hunting pressure, habitat loss due to deforestation and no more reports of the species in the wild, the mouse-deer was feared to have gone extinct. The IUCN listed the species as Data Deficient in 2008. In 2019, a study confirmed the presence of the Vietnam mouse-deer in dry low-lying forests of southern Vietnam with camera trap evidence. The mouse-deer is characterised by a rough coat with a strange double-tone coloration unseen in other chevrotains; the front part of the body is reddish brown and contrasts strongly with the greyish posterior. It has big reddish brown ears, white and dark reddish brown marks on the throat.
The Indian hog deer is a small deer native to the Indo-Gangetic Plain in Pakistan, northern India, Nepal, Bangladesh to mainland Southeast Asia. It also occurs in western Thailand, and is possibly extirpated from China, Myanmar, Laos, and Vietnam. Introduced populations exist in Australia, as well as the United States, and Sri Lanka.
Kloss's squirrel or Kloss squirrel is a species of rodent in the family Sciuridae. It is endemic to northern Sumatra in Indonesia. Population data is insufficient to assess its conservation status according to the IUCN. It is sometimes considered a subspecies of C. notatus.
Sir Walter James Franklin Williamson was a colonial British official who worked as a financial advisor to the Kingdom of Siam. He also took an interest in collecting stamps and studied the birds of the region, collecting specimens of natural history from Thailand. Several taxa have been described on the basis of his specimens and many commemorate him. He was for sometime editor of the Journal of the Natural History Society of Siam along with Malcolm Smith.