![]() ![]() All bivalves live in or very close to the water, and have lamellar gills for respiration (which are also used for feeding in many species).īivalves include clams, scallops, mussels, oysters, and their relatives. Unlike all other mollusks, bivalves lack a distinct head with all of its associated organs (tentacles, radula, etc.), and have a pair of shells (called valves), which enclose a laterally compressed soft body, and are usually connected by a hinge and a flexible ligament. In fact, the only major feature that all mollusks possess is a sheet of tissue covering the body called the mantle, which (in most) covers the viscera and gills, and secretes the shell. At first glance, bivalves do not appear to have much in common with these other groups besides having a shell made of calcium carbonate, which most possess. Bivalves are also of major economic importance to humans, as sources of food and other products, and as damaging invasive species.īivalves are members of the phylum Mollusca, which also includes cephalopods (squids, octopuses, nautiloids, and ammonoids), gastropods (snails, slugs, and nudibranchs), scaphopods (tusk shells), polyplacophorans (chitons), the extinct rostroconchs, and three “minor” groups, the monoplacophorans, Caudofoveata, and Solenogastres (the latter two are generally collectively called “aplacophorans”). They have a long and rich fossil record that illustrates their complex evolutionary history. They live today throughout the world’s oceans and fresh waters, where they are of major ecological importance as a food source for other organisms and for their water-filtering capabilities. Access here.īivalves (also known as “pelecypods” or, in older literature, “lamellibranchs”) are a very diverse and abundant group of mollusks. References and Further Reading Virtual Collection:Ī virtual collection of interactive 3D models of bivalve specimens is associated with this chapter. Bivalve Phylogeny and Classification – 2. Chapter contents:Ĭlass Bivalvia: Introduction and Morphology ← – 1. For comments on the text we thank Chris McRoberts. Acknowledgments:įor assistance with illustrations, we are grateful to Alexandra Allmon, Franz Anthony, James Crampton, Katy Estes-Smargiassi, Liz Harper, Jon Hendricks, Carole Hickman, Linda Ivany, Claudia Johnson, Carlie Pietsch, Elizabeth Petsios, Gary Rosenberg, Leslie Skibinski, Christi Sobel, Chelsea Steffes, Jennifer Tegan, Vicky Wang, and Alex Zimmerman. Image above: Examples of different types of modern and fossil bivalves. In: The Digital Encyclopedia of Ancient Life. This chapter was first publicly shared on Octoit was last updated on February 14, 2022. Mikkelsen (Integrative Research Center, Field Museum of Natural History, Chicago, Illinois). Allmon (Paleontological Research Institution, Ithaca, New York) and Paula M. ![]()
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