What is "megatrigoniidae"

' Megatrigoniidae ' is an extinct family of fossil saltwater clams, marine bivalve mollusks in the subclass Paleoheterodonta. This family of bivalves is known in the fossil record from the Jurassic period, Tithonian age, to the Cretaceous period, Maastrichtian age. Species in this family were facultatively mobile infaunal suspension feeders.