Pseudoperna

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Pseudoperna is an extinct genus of very small oysters that lived in the Cretaceous period. They often formed tight groups and attached themselves to the shells of larger animals, such as Inoceramus. Fossils are usually found as calcite valve shells, sometimes preserved attached to the shells they lived on, like Mytiloides. Two species are known: Pseudoperna rugosa and Pseudoperna lapillicola. The genus was named by Logan in 1899 and belongs to the oyster family Ostreidae.