what are mollusca
By Laura Klappenbach. Mollusks (Mollusca) are a group of invertebrates that includes squid, octopuses, cuttlefish, nudibranchs, snails, slugs, limpets, sea hares, mussels, clams, oysters, scallops, as well as many less well-known animals.Scientists estimate that there are more than 100,000 species of mollusks alive today.This makes them the second largest phylum of animals, having fewer species than only the arthropods. Mollusks have soft bodies that consist of three basic parts: a foot, a visceral mass and a mantle.ollusks are classified within the following taxonomic hierarchy: Animals Invertebrates. Mollusks are divided into the following taxonomic groups: 1  Caudofoveates and solanogastrates (Aplacophorans) - There are about 70 species of caudofoveates and 250 species of solanogastrates alive today.