Morphology of shells of land mollusks (Pulmonata, Stylommatophora): the most common morphological groups, morphological subgroups.

Abstract

The work is based on the analysis of morphological features of the shell in 511 species of terrestrial mollusks from 50 families and 149 genera. Based on such morphological characteristics of the shell as its shape, size and surface sculpture, as well as the shape of the mouth and umbilicus, six main morphological groups of the shell were identified among terrestrial mollusks (Pulmonata, Stylommatophora). The largest number of subgroups are characterized by the groups of shells of discoid (6) and low conical (5) shapes.

For each of the identified groups, statistically significant combinations of features were established. It was found that the shape of the shell depends quite weakly on its size - each of the considered types of shell can include small, medium and large forms. Meanwhile, the shape of the umbilicus and mouth is quite strongly associated with the shape of the shell.

The most common species are those with a low conical shell. Among them, small species predominate, the shell of which has an oval mouth and is covered with a sculpture in the form of striations. In addition, species with a shell of a disc-shaped, low-cube-shaped, high-conical, cylindrical and spindle-shaped form are relatively common.

Shells of a low-conical form have the most plastic complex of features. This becomes possible due to the fact that the geometry of a low-conical shell can change both due to the degree of vertical transfer of the whorl and due to the degree of horizontal transfer of the whorl

The most conservative in terms of variation of morphological parameters are shells of spindle-shaped and cylindrical forms.