What Kind of Animals Are in the Mollusk Family?

The mollusk family is one of the most diverse groups of animals in the world. The University of California Museum of Paleontology says scientists estimate that 50,000 to 200,000 species belong to the mollusk family. Organisms such as octopuses, snails, clams, squid, oysters, scallops and chitons all belong to the mollusk family. The characteristic that all of these organisms have in common is that they have soft bodies with a head and a foot region. The soft bodies usually are covered by a hard exoskeleton.

  1. Bivalvia

    • Bivalvia is the first group of animals in the mollusk family. It includes organisms like clams, scallops and mussels. Bivalve organisms are known for their halved shells and ability to burrow into the sand of the ocean floor. Bivalves have been used for jewelry, decoration, food and money throughout history, according to the U.C. Museum of Paleontology. There are about 10,000 different species of bivalve organisms.

    Gastropoda

    • Gastropoda is the largest group within the mollusk family, including about 80 percent of living mollusks, according to the U.C. Museum of Paleontology. Experts think there could be as many as 150,000 living species of gastropods, residing in every habitat on Earth. Organisms like slugs, snails, limpets and sea hares all belong to the gastropod group.

    Cephalopoda

    • The Cephalopoda group includes organisms such as octopuses, squids, ammonites and nautilus, according to the U.S. Museum of Paleontology. Cephalopods are the largest and most intelligent organisms within the mollusk family. This is due mainly to their ancient evolutionary history that scientists say dates back more than 500 million years. There are about 17,000 living species within the cephalopod family.

    Scaphopoda

    • The Scaphopoda group is commonly referred to as "tusk shells" because of the appearance of their shells, according to the U.C. Museum of Paleontology. Scaphopods don't have eyes and spend their adult lives buried beneath sand or mud. The majority of their body stays beneath the ground except for a small opening that's used to suck in food. Adult scaphopods can live at depths as low as 15,500 feet. About 750 to 1,200 living species of scaphopods exist.

    Aplacophora

    • Organisms within the Aplacophora group are unique because they look like worms and do not have shells, according to the U.C. Museum of Paleontology. Only 320 living species of alpacophorans exist in the world. These organisms secrete tiny calcareous spicules, which give them an extremely shiny appearance.

    Polyplacophora

    • Polyplacophora organisms are commonly referred to as chitons and are characterized by having eight valves on their shells, according to the U.C. Museum of Paleontology. Most live in rocky intertidal zones or the shallow zone just below the low-tide level. However, a few of these organisms live in water as deep as 23,000 feet.