''Eupetaurus'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...

in the family

Sciuridae Squirrels are members of the family Sciuridae (), a family that includes small or medium-sized rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrel ...

. Members of this genus are known as woolly flying squirrels. They are large to very large

flying squirrels Flying squirrels (scientifically known as Pteromyini or Petauristini) are a tribe (biology), tribe of 50 species of squirrels in the family (biology), family Squirrel, Sciuridae. Despite their name, they are not in fact capable of full flight i ...

found in the highest rocky cliffs near the

treeline The tree line is the edge of a habitat at which trees are capable of growing and beyond which they are not. It is found at high elevations and high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions (usually low ...

of the

Himalayas The Himalayas, or Himalaya ( ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the Earth's highest peaks, including the highest, Mount Everest. More than list of h ...

and

Tibetan Plateau The Tibetan Plateau, also known as the Qinghai–Tibet Plateau or Qingzang Plateau, is a vast elevated plateau located at the intersection of Central Asia, Central, South Asia, South, and East Asia. Geographically, it is located to the north of H ...

. Due to the inaccessibility of their montane habitat, they are difficult to study.

Taxonomy

Flying squirrels in the central and eastern Himalayas have been separated from those in the western Himalayas by the

Ganges The Ganges ( ; in India: Ganga, ; in Bangladesh: Padma, ). "The Ganges Basin, known in India as the Ganga and in Bangladesh as the Padma, is an international which goes through India, Bangladesh, Nepal and China." is a trans-boundary rive ...

and

Yarlung Tsangpo The Yarlung Tsangpo, also called Yarlung Zangbo () and Yalu Zangbu River () is a river that flows through the Tibet Autonomous Region of China and Arunachal Pradesh of India. It is the longest river of Tibet and the fifth longest in China. The u ...

rivers, and are thought to have diverged in the

Neogene The Neogene ( ,) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period million years ago. It is the second period of th ...

, between 4.5 and 10.2 million years ago.

Species

For more than a century since its description by

Oldfield Thomas Michael Rogers Oldfield Thomas (21 February 1858 – 16 June 1929) was a British zoologist. Career Thomas worked at the Natural History Museum, London, Natural History Museum on mammals, describing about 2,000 new species and subspecies for ...

, the only species in the genus was thought to be the western woolly flying squirrel (''E. cinereus''), which is found in northern

Pakistan Pakistan, officially the Islamic Republic of Pakistan, is a country in South Asia. It is the List of countries and dependencies by population, fifth-most populous country, with a population of over 241.5 million, having the Islam by country# ...

and northwestern

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

. However, an analysis of museum specimens found evidence of two more species in the eastern Himalayas, the Tibetan woolly flying squirrel (''E. tibetensis'') and the Yunnan woolly flying squirrel (''E. nivamons''). There are currently three known species in the genus: * Western woolly flying squirrel (''Eupetaurus cinereus'') * Yunnan woolly flying squirrel (''Eupetaurus nivamons'') * Tibetan woolly flying squirrel (''Eupetaurus tibetensis'')

Description

The cheek teeth are unique as they are both flat-crowned and high crowned (hypsodont), setting ''Eupetaurus'' apart from other squirrels and suggesting that they feed on very abrasive plant material, including pine needles.Zahler and Khan, 2003 The western woolly flying squirrel has a grizzled-grey pelage with pronounced frosting, in contrast to the more saturated brown coloration of the two other species, and has more robust cusps and cheek teeth.

Relationships

The woolly flying squirrels are unique among the flying squirrels because of their large size and unique dentition. This led a few early researchers to go so far as to create a distinct family. Some of their arguments were based on poorly drawn and labeled diagrams of the

cranium The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

and

lower jaw In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

of ''E. cinereus''. Zahler and Woods (1997) suggest instead that ''Eupetaurus'' is closely related to another genus of large flying squirrels, ''

Petaurista ''Petaurista'' is a genus of rodent in the family Sciuridae. They are large to very large flying squirrels found in forests and other wooded habitats in southern and eastern Asia. Like other flying squirrels, they are mostly nocturnal and able ...

''. A 2021 study suggested that ''Eupetaurus'' is the

sister genus In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

to a clade consisting of '' Aeromys'' and '' Biswamayopterus''.

References

{{Taxonbar, from=Q10759605 Eupetaurus Taxa named by Oldfield Thomas Rodent genera