Cladoceramus is an extinct genus of fossil marine pteriomorphian bivalves that superficially resembled the related winged pearly oysters of the extant genus Pteria.

Adult shells of Cladoceramus are small to very large size (more than 1 metre [3 ft 3 in] in length).

[1] Many species with fine, discrete, juvenile ornamentation on umbo, consisting of closely and evenly to subevenly spaced raised concentric growth lines without rugae.

Posterior auricle well-defined, triangular, separated from disc by auricular sulcus; a post-umbonal sulcus occurs in some species, as do very small anterior auricles ("ears").

[1] The first appearance of the species Cladoceramus undulatoplicatus marks the beginning of the Santonian stage.