Platyceramus was a genus of Cretaceous bivalve molluscs belonging to the extinct inoceramid lineage.

Individuals of this species typically reached 1 m (3 ft 3 in) or more in axial length, but some exceptional specimens 3 m (9 ft 10 in) long have been found,[1] making it the largest known bivalve.

Its huge but very thin shell often provided shelter for schools of small fish, some of which became trapped and fossilised themselves.

The outer shell often provided habitat for its own juveniles,[2] also for oysters such as the epizoic oyster Pseudoperna congesta,[2] and barnacles.

This article about a prehistoric bivalve is a stub.