Jeffrey F. Mount, P. W. Signer; Early Cambrian innovation in shallow subtidal environments: Paleoenvironments of Early Cambrian shelly fossils. Geology ; 13 (10): 730–733. doi: https://doi.org/10.1130/0091-7613(1985)13<730:ECIISS>2.0.CO;2
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Contrary to onshore-offshore patterns described for several Phanerozoic clades, evolutionary innovations leading to the earliest shelly Metazoa did not originate in nearshore, stressed marine habitats. Paleoecological analyses of the Early Cambrian fauna and strata of the White-Inyo Mountains of California indicate that major shelly taxa and trace fossils appeared offshore from shallow-water, physically stressed environments and only later spread to nearshore habitats. Other lowermost Cambrian stratigraphic sections elsewhere in the world show similar patterns. The contrast in pattern of community evolution between the Early Cambrian and the remaining Phanerozoic suggests either temporally variable control on position of evolutionary innovation or a need for reexaminution of the data.