Trigoniidae

Trigoniidae is a taxonomic family of saltwater clams, marine bivalve mollusks in the superfamily Trigonioidea. There is only one living genus, Neotrigonia, but in the geological past this family was well represented, widespread and common. The shells of species in this family are morphologically unusual, with very elaborate hinge teeth, and the exterior of the shell is highly ornamented.

Neotrigonia is a genus of living saltwater clams, in the family Trigoniidae, which otherwise consists only of fossil genera. For a long time the entire family was thought to be long extinct, but a living species that is now placed in this genus was discovered in 1802. At that time it was assigned to the fossil genus Trigonia. Currently, according to the World Register of Marine Species, 8 extant species in this genus are recognized.

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