Rudists

Rudists Temporal range: Late Jurassic–Late Cretaceous PreꞒ Ꞓ O S D C P T J K Pg N
Rudist bivalves from the Cretaceous of the Oman Mountains, United Arab Emirates; scale bar is 10 mm
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Infraclass:	Heteroconchia
Subterclass:	Euheterodonta
Superorder:	Imparidentia
Order:	†Hippuritida
Families
See text

Rudists are a group of extinct box-, tube- or ring-shaped marine heterodont bivalves belonging to the order Hippuritida that arose during the Late Jurassic and became so diverse during the Cretaceous that they were major reef-building organisms in the Tethys Ocean, until their complete extinction at the close of the Cretaceous.