Clam Shrimp

Clam shrimp are a group of branchiopod crustaceans possessing bivalved carapaces that resemble the shells of unrelated bivalve mollusks. Traditionally classified together in the order Conchostraca, that group later proved to be paraphyletic, since the water fleas of the order Diplostraca are nested within the clam shrimp lineage, meaning some water flea groups are more closely related to certain clam shrimp than either is to other clam shrimp they resemble. Clam shrimp are now divided into three orders, Cyclestherida, Laevicaudata and Spinicaudata, alongside the extinct family Leaiidae, with a fossil record reaching back to at least the Devonian period.