Pulmonata

Pulmonata is a historical grouping of air-breathing gastropods within the class Gastropoda. Members are characterized by a pallial lung derived from the mantle cavity, through which they breathe air via a small opening called the pneumostome. The group includes many terrestrial snails and slugs, as well as several freshwater snails. Most pulmonates lack an operculum, and their shells, when present, are often thin and single-handed or reduced in slugs.

In modern taxonomy, Pulmonata is not used as a formal, natural taxon. It was long treated as a subclass or order that included both land and freshwater lineages, notably the Stylommatophora (land snails and slugs) and Basommatophora (many freshwater snails). Contemporary classifications generally place these groups within larger clades of Heterobranchia and treat Pulmonata as an informal or historical name, with deeper relationships clarified by molecular data. As a result, the composition and rank of Pulmonata have undergone substantial revision.

Anatomy and life history are diverse. Most pulmonates are hermaphroditic and engage in internal fertilization, though some species show dioecy. They lay eggs or give birth to live young in certain taxa. Slugs and some shell-bearing snails show considerable variation in shell presence and reduction. Ecologically, pulmonates occupy a wide range of habitats, from forest floors and grasslands to human-altered environments, where many species are herbivores or detritivores. Some freshwater pulmonates are important grazers in lentic and lotic systems.

Pulmonata has played a role in studies of respiratory evolution, terrestrial adaptation, and molluscan diversity, but it is now largely treated as an historical concept rather than a formal, current taxonomic unit.