Phylum: Mollusca

Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda. The members are known as molluscs or mollusks (/ˈmɒləsk/). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estimated between 60,000 and 100,000 additional species, which a multitude of them died out in the Permian-Triassic mass extinction. Thus, classifying proportion of undescribed species is very high, as several taxa remain poorly studied. Members of this phylum include the cephalopodic squids, octopuses, cuttlefishes, nautiluses, with the extinct ammonites and belemnites; the bivalvic clams, oysters, scallops, mussels, and the extinct rudists; and the gastropodic snails, slugs, and abalone.