Caption:
Dorsal reconstruction of the primitive marine arthropod, Marrella splendens, from the Middle Cambrian Burgess Shale of British Columbia. By far the most abundant animal of the Burgess Shale fauna, these small, delicate "lace crabs" probably swarmed in groups just above the seafloor where they fed on zooplankton and organic debris. More than a third of fossils recovered from the Burgess Shale belong to this species. They range in size from 2.5 to 19 mm.