Small carbonaceous fossils from the Early Cambrian of North Greenland.
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The major Cambrian Burgess Shale-type Lagerstätten provide crucial glimpses into flourishing communities of soft-bodied Metazoans from early on in the establishment of Animal-dominated ecosystems. As instances of exceptional preservation, Burgess Shale-type Lagerstätten are rare, and seem to be temporally restricted to the Cambrian. Nevertheless, Cambrian Burgess Shale-type Lagerstätten can exhibit substantial between-site variations in taxonomic composition and diversity, even at a relatively local scale. Although the overall ecological structure and diversity dynamics of Burgess Shale-type biotas appear to have been broadly conserved, community-level differences have been detected among sites surrounding the Burgess Shale, such as the Greater Phyllopod Bed, the Tulip Beds, and the more recently discovered assemblages from Marble Canyon and the ‘thin’ Stephen Formation. Lagerstätten sites from South China also show comparable faunal differentiation at various scales beyond a relatively stable underlying structure. Spatial variations in community composition and diversity are well-known from modern marine Invertebrate faunas and have been evidenced to some extent in the (mostly skeletal) fossil record, as far back as the late Ediacaran. A similar faunal partitioning may account for the emerging disparity of Cambrian Lagerstätten. Sampling Metazoan diversity across environmental variables (e.g. depth, substrate), however, has been hampered by the relatively narrow spatial extent of Burgess Shale-type deposits. Although the known outcrop area of the Burgess Shale and Chengjiang deposits has been continuously expanded, comparatively little is known of the spatial variation in faunas surrounding another major Cambrian Lagerstätte; the Sirius Passet biota from North Greenland.