A redescription of the clam shrimp, Orthestheria shupei (Stephenson, in Stephenson & Stenzel, 1952) comb. nov., from the Cenomanian (Cretaceous) of Texas

Abstract

Orthestheria shupei comb. nov. is a small clam shrimp from the Red Branch Member of the Woodbine Formation in Texas, USA, originally described as belonging to the living genus, Cyzicus. The redescription herein reveals its ornamentation pattern consisting of straight lirae formed perpendicular to the growthband, with rare shorter intercalating lirae. This is one of only two known records of clam shrimp from the Cretaceous of North America. The genus, Orthestheria, is also known from China and South America, and it is used in a biostratigraphic scheme in China. Orthestheria is very similar to another genus, Nemestheria, which is classified in a separate subfamily (Jilinestheriidae vs Fushunograptidae). The diagnoses for both are useless for telling the genera apart—both diagnoses exploit vague language that allow the admission of a broad array of taxa within a narrow stratigraphic range. Deciphering clam shrimp phylogeny will only progress with meaningful diagnoses that circumscribe monophyletic groups. Despite the higher level taxonomic problems, the age of the Woodbine Formation is broadly consistent with the age predicted from the Asian biostratigraphic scheme using Orthestheria.