''Mustela aistoodonnivalis'', the missing-toothed pygmy weasel or Sichuan weasel, is a species of

weasel Weasels are mammals of the genus ''Mustela'' of the family Mustelidae. The genus ''Mustela'' includes the least weasels, polecats, stoats, ferrets and European mink. Members of this genus are small, active predators, with long and slender b ...

that inhabits mountains in the

Shaanxi Shaanxi (alternatively Shensi, see § Name) is a landlocked province of China. Officially part of Northwest China, it borders the province-level divisions of Shanxi (NE, E), Henan (E), Hubei (SE), Chongqing (S), Sichuan (SW), Gansu (W), N ...

and

Sichuan Sichuan (; zh, c=, labels=no, ; zh, p=Sìchuān; alternatively romanized as Szechuan or Szechwan; formerly also referred to as "West China" or "Western China" by Protestant missions) is a province in Southwest China occupying most of the ...

provinces of China.

Description

The external features of the missing toothed weasel are very similar to least weasels, but the tail is very long, exceeding one third of the length of body and head. The summer fur of the back, tail and head is dark brown, and there are no dark markings on face or head. Under the lip, chin and throat, the fur is white but the chest and belly are a pale yellow with some irregular and rusty-red spots. The backs of the front legs are brown, and the hind limbs are similarly brown but the inner lateral parts are white hairs with brown spots. The palms and soles have shorter hair. The second lower molar (M2) is absent unlike least weasels. The species is named for the second lower molar (M2) being absent unlike in the least weasel. Body length is . The tail of is about 40% as long as the body.

Taxonomy

Given that it closely resembles the least weasel, after its initial description some taxonomists synonymized these two species, believing the missing-toothed pygmy weasel to be a subspecies of least weasels with a longer tail and a missing tooth. However with a more thorough morphological examination of the skins and skulls, Groves concluded it was a separate species. A recent genetic and morphometric study has since proved that the missing-toothed pygmy weasel is indeed a separate species, more closely related to

stoat The stoat (''Mustela erminea''), also known as the Eurasian ermine, Beringian ermine and ermine, is a mustelid native to Eurasia and the northern portions of North America. Because of its wide circumpolar distribution, it is listed as Least Conc ...

s than it is to least weasel.

Distribution and habitat

Very few samples have ever been obtained of this species, all from the mountains of the Shaanxi and Sichuan provinces of China.

Ecology

The ecology of the missing-toothed pygmy weasel remains unstudied. The few individuals recorded have been found from 1,950–2,750 m a.s.l.

References

{{Taxonbar, from=Q104528100 Weasels Mammals of China Animals described in 1991