Middle Cambrian trilobites from the Ekspedition Bræ Formation of North Greenland, with a reappraisal of the genusElrathina

Abstract

AbstractThe richly fossiliferous Ekspedition Bræ Formation of North Greenland yields a typical oligospecific fossil assemblage with well-preserved trilobites, helcionelloids, and lingulate brachiopods. The trilobites includeItagnostus subhastatusnew species,Itagnostussp. cf.I.gaspensis(Rasetti, 1948),Elrathina aphroditenew species,Elrathina athenanew species,Elrathina heranew species, andElrathia groenlandicanew species—a fossil assemblage typical of theBathyuriscus-ElrathinaZone as known from the Cordilleran regions of Laurentia. Excellent preservation allows a detailed assessment of the prosopon and elucidates aspects of the ontogenetic development ofElrathinaandElrathia. An evaluation ofElrathinaincludes a redescription of its type species,E.cordillerae(Rominger, 1887), based on the type material, and indicates that most specimens collected from the Burgess Shale and previously dealt with asE.cordilleraerepresent a new species.