Valloniidae

Valloniidae is a family of small air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Pupilloidea, within the clade Stylommatophora. The type genus is Vallonia.

Members are minute to small snails, typically less than 5 mm in maximum dimension. Shells are generally discoidal to planispiral with a low spire; surface may be smooth or only weakly ribbed, and color ranges from white to pale brown. The aperture is round and the umbilicus is variably developed, depending on genus.

Habitat and ecology: Valloniids occur in leaf litter, moss, decaying wood, and moist soil, from shaded woods to damp meadows. They are detritivores, feeding on microalgae, biofilm, and decomposing organic matter. Reproduction is sexual with hermaphroditic individuals common; most species lay eggs and exhibit direct development rather than free-living larval stages.

Distribution and diversity: The family has a worldwide distribution, with greatest species richness in temperate zones. It includes numerous described species and several fossil genera, reflecting a long evolutionary history.

Taxonomy: Classification within Pupilloidea has undergone revisions as new data emerge. The family name Valloniidae is anchored by the type genus Vallonia, and molecular studies have helped clarify relationships among valloniid genera.