 These patterns – a few common species and many rare ones ; the dominance of arthropods and sponges ; and the percentage frequencies of different life @-@ styles – seem to apply to all of the Burgess Shale . However the identity of the dominant species differs between sites . For example , Marrella splendens is often credited as the commonest animal in the Burgess Shale , because of its abundance among the specimens collected by Walcott , but is only the third @-@ most abundant organism in the Greater Phyllopod Bed , and very rare at other localities . 
