Pupilla loessica

The shells of Pupilla loessica are about 3 mm high, thin, cylindrical-ovate and have a rounded conical apex.^[1] The approximately 5 strongly curved whorls gradually increase in height and are finely and irregularly ribbed.^[1] The short elliptical aperture has no denticles, no palatal callus and is only slightly broadened.^[1] The crest is at most indicated by a weak band.^[1]

The shells are usually a strong brown colour when fresh.^[1] The fine ribs evidence very low, fragile rims which are not always visible in recent shells.^[1] On weathered shells the fine ribs are still visible although less pronounced, as on the shells of the Pleistocene Pupilla loessica.^[1]

The width of the recent shells is 1.6-1.8 mm.^[1] The height of the shells of the recent shell is 2.5-3.3 mm.^[1]

The species differs from Pupilla muscorum by its smaller size, the strongly rounded and ribbed whorls and the lack of denticles and crest.^[1] The species is similar to Pupilla alpicola with similar intraspecific shell shape differences across time suggesting that similar niche shifts have led to similar transformations in parallel.^[4]

Pupilla loessica occur from woodland to dry steppe.^[3] The altitude ranges from 560 m a.s.l. to high altitude habitats around 3000 m a.s.l.^[1] This species prefer continental types of habitat with average annual temperatures markedly below 0 °C.^[1] The climate ranges from continental to sub-boreal climate.^[1] Although it is a frequent loess mollusc, it apparently lived in various glacial habitats.^[1]

Pupilla loessica is found in various different habitats in the Saylyugem Mountains.^[1] These habitats range from stony steppe via open woodland with Larix sibirica, shrubland, mesophilic meadows to humid high altitude meadows with Carex sp. and Dryas oxyodonta (alpine tundra).^[1]

For example in Saylyugem Mountains Pupilla loessica lives in 2200–2650 m a.s.l.^[1] The closest known meteorological station is the Kosh Agach Station: the average annual temperature recorded amounts to –6.7 °C (January –32 °C, July 13 °C) and the annual rainfall amounts to about 110–150 mm on average.^[1]

This species often accompanies the so-called Pupilla fauna and Columella fauna (according to Ložek 1964).^[5][1] In addition to Pupilla spp., species which like humidity, such as Columella columella or Vertigo genesii, are also often found together with Pupilla loessica.^[1] The corresponding accompanying fauna is also adapted to the cold habitats, including e.g. Columella columella, Vertigo genesii, Vallonia tenuilabris, etc.^[1] Such malacofauna in recent habitats (especially on the humid alpine meadows) correspond to those of the Pleistocene glacial habitats of the Central European region.^[1]

This article incorporates CC-BY-3.0 text from the reference^[1]