Pupilla bigranata is a species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of minute air-breathing land snail

Land snail

A land snail is any of the many species of snail that live on land, as opposed to those that live in salt water and fresh water. Land snails are terrestrial gastropod mollusks that have shells, It is not always an easy matter to say which species are terrestrial, because some are more or less...

, a terrestrial

Terrestrial animal

Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...

 pulmonate gastropod mollusk or micromollusk

Micromollusk

A micromollusk is a descriptive term for a shelled mollusk which is extremely small, even at full adult size. The word is usually, but not exclusively, applied to marine mollusks, although in addition, numerous species of land snails and freshwater mollusks also reach adult size at very small...

 in the family Pupillidae

Pupillidae

Pupillidae is a family of mostly minute, air-breathing, land snails, terrestrial pulmonate gastropod mollusks or micromollusks in the clade Stylommatophora....

.

Description

The shell

Gastropod shell

The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...

 of Pupilla bigranata is smaller than Pupilla muscorum

Pupilla muscorum

Pupilla muscorum is a species of minute air-breathing land snail, a terrestrial pulmonate gastropod mollusk or micromollusk in the family Pupillidae.- Taxonomy :A variety Pupilla muscorum var...

, whorls

Whorl (mollusc)

A whorl is a single, complete 360° revolution or turn in the spiral growth of a mollusc shell. A spiral configuration of the shell is found in of numerous gastropods, but it is also found in shelled cephalopods including Nautilus, Spirula and the large extinct subclass of cephalopods known as the...

 are slightly more rounded, cervical callus is strong, palatal tooth are more strongly developed and parietal tooth is also prominent.

The height of the shell is 2.5-3.5 mm. The width of the shell is 1.5 mm and shell diameter does not vary much.

Distribution

Distribution of Pupilla bigranata include Central Europe and Western Europe.

• Very scattered in Switzerland, only 3 of 20 formerly known populations seem to have survived. Critically endangered in Switzerland.
• endangered in Germany. Extinct in Bavaria
  Bavaria
  Bavaria, formally the Free State of Bavaria is a state of Germany, located in the southeast of Germany. With an area of , it is the largest state by area, forming almost 20% of the total land area of Germany...
  
  ; critically endangered in Rheinland-Pfalz
• rare in Austria.

Ecology

Pupilla alpicola occur in dry and warm grassy slopes on calcareous substrate. In Switzerland in up to 2000 m altitude.