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.[1]