Mollusca is a phylum of protostomic invertebrate animals, commonly known as molluscs or mollusks. There are about 76,000 recognized extant species, making it the second largest animal phylum after Arthropoda. The number of fossil species is estimated to be between 60,000 and 100,000, with many groups yet to be studied.
Molluscs are the largest marine phylum, comprising around 23% of all named marine organisms. They display significant diversity in size, anatomy, behavior, and habitat, with some species found in freshwater and terrestrial environments. The phylum is typically divided into seven or eight classes, of which two are extinct.
Cephalopods, like squid and octopuses, are some of the most advanced invertebrates, while gastropods, including snails and slugs, are the most diverse class, making up 80% of all classified molluscan species.
