Nacellidae

Nacellidae is a family of marine gastropods within the order Patellogastropoda, commonly known as true limpets. The family includes several genera, with Nacella as the type genus; taxonomy can vary among sources, with some treating Nacellidae as a distinct family and others placing related groups within Patellidae or recognizing different subfamily arrangements.

Members of Nacellidae are small to medium-sized limpets with a simple, cap-shaped shell. The shell is typically conical, with a low to moderate height, and shows concentric growth lines. The apex is usually located near the anterior edge, and the mantle and surrounding tissues form a smooth outline. The foot is broad and muscular, enabling strong adhesion to rocky surfaces in the intertidal zone. They are herbivorous grazers, feeding primarily on microalgae and biofilm on rock surfaces.

Distribution and habitat: Nacellidae species inhabit marine coastal environments, with many occurring on rocky shores in the Southern Hemisphere, including parts of South America, Africa, Australia, and subantarctic regions. They occupy intertidal to shallow subtidal zones, often in areas with strong wave action or exposed rock.

Ecology and life history: Like other patellogastropods, nacellids are mobile grazers that help control algal coverings on rocky substrates. Reproductive strategies vary by species, but many limpets release eggs and sperm into the water column or brood young in some lineages; larvae are typically free-swimming before settling as juveniles.

Evolution and fossil record: The group possesses a fossil record dating back to the Mesozoic, reflecting a long lineage of marine grazing gastropods adapted to rocky shores.