prosobranch

Prosobranchs, or Prosobranchia, are a traditional grouping within the class Gastropoda. The name derives from Greek pro- meaning before and branchia meaning gills, a reference to the typical anterior position of the gill and mantle cavity relative to the heart. The term is used as an informal, historical category rather than a single natural lineage.

Characteristics of prosobranchs are diverse, but they are predominantly marine snails, with a scattered representation in freshwater groups. A common feature is the gill (ctenidium) and mantle cavity located anterior to the heart. Many prosobranchs possess an operculum that can close the shell aperture. Shells exhibit wide variation in shape and sculpture, and feeding modes range from herbivory to predation and scavenging.

Taxonomic status is that prosobranchia is considered an informal, paraphyletic grouping in modern systematics. Many traditional members are now placed in more narrowly defined clades such as Vetigastropoda, Neritimorpha, and Caenogastropoda. Consequently, the term is less used in contemporary classifications, though it remains encountered in older literature and some teaching contexts.

Distribution and ecology: Prosobranchs are cosmopolitan, primarily occupying marine environments from intertidal zones to deep sea. Freshwater representatives exist but are less common, and terrestrial forms are rare in modern classifications. They occupy a broad range of habitats, including rocky shores, coral reefs, sandy bottoms, and seagrass beds.