What is "concavodontinae"

Concavodontinae is an extinct subfamily of prehistoric bivalves in the family Praenuculidae. Concavodontinae species lived from the middle Ordovician, Caradoc epoch through the late Ordovician Ashgill epoch. Concavodontinae fossils are found in Europe and South America, and species are though to have been stationary attached to substrate in shallow infaunal marine water envoronments where they formed shells of an aragonite composition. The subfamily Concavodontinae was named by Teresa M. Sánchez in 1999.