World’s smallest freshwater snail? A new genus and species of subterranean snail (Gastropoda, Cochliopidae) with extremely tiny shell from Los Chorros, Coahuila, northern Mexico

Abstract

This paper describes a new genus and species of stygobitic gastropod from a small groundwater-fed spring in Los Chorros, Coahuila, northern Mexico. Microphreatus saltillensis gen. et sp. nov. is described based on shell morphology, because so far, no living individuals could be obtained. Conchologically, the new genus can be well distinguished from all other subterranean genera by a unique combination of characteristic proto- and teleoconch features.

We also reassigned into the new genus Balconorbis coronae (Hershler, 1987), a subterranean snail from Southwestern Texas, so that the new genus consists of two species. One of the most striking features of the new snail is its extremely small shell (about 0.73 mm shell width, 0.36 mm shell height) making the species probably the world’s smallest known freshwater gastropod. Microphreatus saltillensis gen. et sp. nov. is restricted in its distribution to a small water source in a touristic recreation area.

This limited distribution and increased anthropogenic impacts make conservation efforts urgently necessary.