Morphology and ecology of the bradoriid arthropods Spinospitella and Nikolarites from the Cambrian (Series 2, Stage 4) of North Greenland (Laurentia)

Tuberculate fragments referred to Nikolarites spasskyi are compared with a complete carapace and other material of Spinospitella from Cambrian Series 2, Stage 4 in North Greenland. The descriptions expand earlier brief records from Laurentia of the two bradoriids, originally described from Siberia and Australia, respectively. The mutually exclusive occurrences of the two taxa indicate ecological control of their distribution in North Greenland. Robust fragments of Nikolarites spasskyi occur in reworked higher energy deposits of the Aftenstjernesø Formation, while thin-walled carapaces of Spinospitella characterise deeper water mudstones within the Buen and Aftenstjernesø formations