 The family underwent an explosion of diversity in the Jurassic, reaching an maximum of diversity in the Cretaceous, although most genera became extinct at the end of this period.Although they were abundant in the Mesozoic era, they are today represented by only one living genus, "Neotrigonia", which inhabits waters off the coast of southern Australia.Before the beginning of the 19th century, no trigoniid had been described that was more recent than the Cretaceous Period.