An order of the Podocopa (Ostracoda) containing a single family, Cytherellidae, and two extinct superorders. Platycopids are small marine or brackish-water ostracods with an asymmetrical shell that is oblong, nearly rectangular, and laterally compressed; their six pairs of appendages are adapted for burrowing and filter feeding. Both fossil and living species have the inner lamella of each valve calcified only in the distal rim, if at all; if a narrow duplicature is developed, it is continuous with the outer lamella and does not form a vestibule (troughlike cavity) between the lamellae. Recent platycopids are distinct from all other ostracods: The larger valve is rabbeted to overlap the smaller around the free edge; the carapace lacks vertical lobation; none of the postoral appendages serve as legs; and the posterior end of the body is more clearly delimited and tapering than in other ostracods.