A water animal like an oyster whose shell has two parts hinged together?
An animal with a shell composed of two parts hinged together would be a bivalve, such as a mussel, clam, or oyster. Bivalves have two symmetrical shell halves that are connected by a hinge ligament, allowing the shell to open and close for protection and feeding. Oysters are filter feeders that play important roles in aquatic ecosystems.