This member of the herring family, Clupeidae, is recognized by its anal fin extending to its
tail, and its deep body. Diplomystus also possessed two rows of scures (bony plates) behind
its head, dorsally (on its back) and ventrally (on the belly), extending to its paired fins. It
lived from the Cretaceous Period through to the Early Tertiary Period, therefore surviving
the mass extinction of 65 million years ago. Its fossils have been found worldwide, in both
fresh water and marine habitats. It is especially abundant in the Green River Formation
rocks of Wyoming, USA (see Mioplosus, above), where it grew to lengths in excess of
60cm/24in. Diplomystus fed on surface-water fish, as indicated by specimens fossilized with
their prey still.in their mouths or guts.