Mesozoic animals of North America

Exogyra is an extinct genus of marine oysters that belongs to the family Gryphaeidae (honeycomb oysters). These bivalves were cemented by the more cupped left valve. The right valve is flatter, and the beak is curved to one side. Exogyra lived on solid substrates in warm seas during the Jurassic and Cretaceous periods.

Pholadomya is a genus of saltwater clams, marine bivalve molluscs in the family Pholadomyidae.

thumb|right|225px|Diagram of Trigonia costata James Parkinson, showing main morphological features of the shell exterior;a) [[Anterior; p) Posterior; d) Dorsal; v) Ventral; F) Flank; A) Area; c) Costae; mc) Marginal CarinaTrigonia costata ranges from the Lower Jurassic (Toarcian) to Middle Jurassic (Callovian).]] thumb|350x350px|Trigonia sp. from the Jurassic of the Canjuers plateau, Var, France. Max Rouger Collection. Trigonia is an extinct genus of saltwater clams, fossil marine bivalve mollusk in the family Trigoniidae. The fossil range of the genus spans the Paleozoic, Mesozoic and Paleoce