Bombers and Bivalves: First North American Occurrence of the RudistDuraniasp. (Bivalvia: Radiolitidae) in the Upper Cretaceous (Cenomanian) Greenhorn Limestone of Southeastern Colorado

Abstract

A colonial monospecific cluster of rudist bivalves from the lowermost Bridge Creek Limestone Member, Greenhorn Limestone (Upper Cenomanian) are attributable to Durania cf. D. cornupastoris. This discovery marks only the eighth recorded pre-Coniacian occurrence of rudist bivalves in the Cretaceous Western Interior and the only Cenomanian record of rudist Durania in North America. Discovered in 2011, the specimen was unearthed by aerial bombing at a training facility utilized during World War II. The appearance of rudist bivalves at mid-latitudes coincident with marked change in marine sediments likely represents the onset of mid-Cretaceous global warming.