Hippuritoida

They are an extinct order of heterodont bivalve mollusks. They had two asymmetrical valves and normally one of them was fixed to the substrate (sessile organisms). They appear in the fossil record in the Upper Jurassic, their greatest diversification occurs during the Cretaceous and they become extinct in the mass extinction event of the Cretaceous-Paleogene boundary. During the Cretaceous they were mainly responsible for the formation of reefs in the Tethys Sea.
_________________________________________________________________________________
Son un orden extinto de moluscos bivalvos heterodontos. Tenían dos valvas asimétricas y normalmente una de ellas estaba fijada al sustrato (organismos sésiles). Aparecen en el registro fósil en el Jurásico Superior, su mayor diversificación se produce durante el Cretácico y se extinguen en el evento de extinción masiva del límite Cretácico-Paleógeno. Durante el Cretácico fueron los principales responsables de la formación de arrecifes en el mar de Tetis.