The Gastropoda form a class within the phylum Mollusca. Known informally as gastropods, they are sometimes referred to as univalves, although the term is misleading since the shell does not truly function as a valve, unlike the paired shells of pelecypods (Bivalvia) which in a way do. Gastropods are more commonly known as snails and slugs.
The Gastropoda is the most diversified class within the Mollusca with some 60,000 to 80,000 living species contained within 409 recent families and another 202 families known only as Fossils. Among animals they are second only to insects in its number of known species.
