Mollusca

Epic card · No. 14777

Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). 89,857 extant species of molluscs are recognized with estimates ranging over 251,000 species, making it the second-largest animal phylum after Arthropoda. The number of recognized fossil species is 57,219 with estimates between 60,000 and 100,000, and the proportion of undescribed extant species is very high. Many taxa remain poorly studied. Molluscs are the largest marine phylum, comprising about 23% of all the named marine organisms. They are highly diverse, not just in size and anatomical structure, but also in behavior and habitat, as numerous groups are freshwater and even terrestrial species. The phylum is typically divided into 7 or 8 taxonomic classes, of which two are entirely extinct. Cephalopod molluscs, such as squid, cuttlefish, and octopuses, are among the most neurologically advanced of all invertebrates—and either the giant squid or the colossal squid is the largest...

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