Cladoceramus

Cladoceramus is an extinct genus of fossil marine pteriomorphian bivalves that superficially resembled the related winged pearly oysters of the extant genus "Pteria". They lived in the Santonian stage of the Late Cretaceous.
Biostratigraphic significance.
The first appearance of the species "Cladoceramus undulatoplicatus" marks the beginning of the Santonian stage.
Distribution.
Fossils of the genus have been found in: