Fossils of the Burgess Shale

Abstract

Until a decade or so ago, we contented ourselves with notions of a gradual progression of structural organization from few simple types in the Lower Cambrian to the abundance of organisms alive today. The reinterpretation of the Burgess Shale fossils initiated by Simon Conway Morris and Harry Whittington in 1985 changed all that. Representatives of every phylum except the Bryozoa are found from Lower or Middle Cambrian rocks. Organisms currently unassignable to any phylum also existed 530 mya, not as some isolated early evolutionary experiment, but as a world-wide metazoan radiation.

‘It may not be generally appreciated by biologists that first occurrence in the fossil record is not necessarily the same as time of origination.’ Fortey, Briggs and Wills, 1997, p. 430