| regnum = Animalia | phylum = Mollusca | classis = Bivalvia | subclassis = Heterodonta | ordo = Hippuritoida | subdivision_ranks = Families | subdivision = Antillocaprinidae Caprinidae Caprotinidae Diceratidae Dictyoptychidae Hippuritidae Ichthyosarcolitidae Plagioptychidae Polyconitidae Radiolitidae Requieniidae }} Rudists are a group of bizarrely shaped marine heterodont bivalves that arose during the Jurassic, and became so diverse during the Cretaceous that they were major reef-b… (More on Rudists)