Heterodonta

The Heterodonta are a subclass of bivalve mollusks. They are characterized by a hinge that typically has both lateral and cardinal teeth, though these can be reduced or absent. Unlike some other bivalves, they generally lack nacreous shell layers, instead having shells composed of crossed-lamellar or prismatic layers.12

Heterodonta are primarily modern burrowers, often possessing a muscular foot adapted for digging and long siphons for drawing in water. This lifestyle is reflected in their feeding habits, as they are mostly suspension feeders, collecting food particles from the water. This subclass includes familiar bivalves such as cockles, clams, shipworms, and giant clams. They are found in marine, estuarine, and freshwater environments.32