Pupilloidea

Pupilloidea is a taxonomic superfamily of minute to small terrestrial pulmonate gastropods within the clade Stylommatophora. The group comprises several families, with Pupillidae and Valloniidae being the most widely recognized; the precise composition of Pupilloidea has varied across taxonomic revisions, and some classifications additionally include other related families.

Description and ecology: Members of Pupilloidea are typically small to minute in size, often less than 5 mm in maximum dimension. Shells are diverse in shape, commonly high-spired or compact, with smooth to sculptured surfaces. They inhabit a range of terrestrial microhabitats, including leaf litter, soil, moss, under stones, and dead wood in temperate and boreal regions; some are found in more arid zones.

Taxonomy and evolution: Historically, Pupilloidea has been treated as a distinct superfamily within Stylommatophora. Its circumscription has shifted with molecular data; as a result, some families have been moved to other groups in recent revisions. Despite changes, Pupillidae (genera such as Pupilla) and Valloniidae (Vallonia) remain common representatives in field guides.

Ecology and life history: Most species are hermaphroditic, with direct development or short lifecycle; they lay eggs in moist soil or leaf litter. They play roles in decomposition and nutrient cycling and are indicators of habitat quality in some ecosystems.

Conservation: Because of small size and specialized habitats, Pupilloidea species can be sensitive to habitat loss, pollution, and climate change; many have restricted distributions and are poorly known, making assessment challenging.