EARLY CAMBRIAN OSTRACODE LARVAE WITH A UNIVALVED CARAPACE

Phosphatized univalves, recovered from the Lower Cambrian (approximate ly 530 million years old) Qiongzhusi Formation in southern China, are recognized as early instars belonging to bradoriid ostracodes whose la ter instars are bivalved. The univalved form is the primitive larval c haracter for shell-secreting crustaceans, although most post-Cambrian ostracodes bypassed this developmental phase. The univalved-bivalved t ransition during early ontogeny represents an important evolutionary e vent in ostracodes, with implications for crustacean classification, a nd implies that the ostracode ancestor achieved this bivalved capacity before the appearance of mineralized skeletons during the ''Cambrian explosion. ''