''Eupetaurus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

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

in the family Sciuridae. 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 of 50 species of squirrels in the family Sciuridae. Despite their name, they are not in fact capable of full flight in the same way as birds or bats, but they ar ...

found in the highest rocky cliffs near the treeline 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 planet's highest peaks, including the very highest, Mount Everest. Over 100 ...

and

Tibetan Plateau The Tibetan Plateau (, also known as the Qinghai–Tibet Plateau or the Qing–Zang Plateau () or as the Himalayan Plateau in India, is a vast elevated plateau located at the intersection of Central, South and East Asia covering most of the Ti ...

. 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 river to which India, Bangladesh, Nepal and China are the riparian states." is ...

and

Yarlung Tsangpo The Yarlung Tsangpo, also called Yarlung Zangbo () is the upper stream of the Brahmaputra River located in the Tibet Autonomous Region, China. It is the longest river of Tibet and the fifth longest in China. The upper section is also called Dan ...

rivers, and are thought to have diverged in the

Neogene The Neogene ( ), informally Upper Tertiary or Late Tertiary, 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 Mya. ...

, between 4.5 to 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 on mammals, describing about 2,000 new species and subspecies for the first time. He was appoin ...

, the only species in the genus was thought to be the

western woolly flying squirrel The western woolly flying squirrel (''Eupetaurus cinereus'') is a species of very large flying squirrel in the genus ''Eupetaurus''. It is native to northern Pakistan and northwestern India. It was long considered the only species in the genus un ...

(''E. cinereus''), which is found in northern

Pakistan Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's List of countries and dependencies by population, fifth-most populous country, with a population of almost 24 ...

and northwestern

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

. However, an analysis of museum specimens found evidence of two more species in the eastern Himalayas, the

Tibetan woolly flying squirrel The Tibetan woolly flying squirrel (''Eupetaurus tibetensis'') is a species of very large flying squirrel in the genus ''Eupetaurus''. It is found in the south-central portion of the Tibetan Plateau, namely south-central Tibet, northern Sikkim, a ...

(''E. tibetensis'') and the

Yunnan woolly flying squirrel The Yunnan woolly flying squirrel (''Eupetaurus nivamons'') is a species of very large flying squirrel in the genus ''Eupetaurus''. It is found on the southeastern margin of the Himalayas, namely in northwestern Yunnan and potentially Myanmar. I ...

(''E. nivamons''). There are currently three known species in the genus: *

Western woolly flying squirrel The western woolly flying squirrel (''Eupetaurus cinereus'') is a species of very large flying squirrel in the genus ''Eupetaurus''. It is native to northern Pakistan and northwestern India. It was long considered the only species in the genus un ...

(''Eupetaurus cinereus'') *

(''Eupetaurus tibetensis'') *

(''Eupetaurus nivamons'')

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 is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

and lower jaw 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