Monday 19 July 2010

Some Burgess Shale animals were coloured

Colour in Burgess Shale animals and the effect of light on evolution in the Cambrian

Andrew R. Parker.   Proc. R. Soc. Lond. B  7 June 1998   vol. 265  no. 1400  967-972. 


Diffraction gratings are reported from external surfaces of the hard, protective parts of Wiwaxia corrugata, Canadia spinosa and Marrella splendens from the Burgess Shale (Middle Cambrian (515 million years), British Columbia). As a consequence, these animals would have displayed iridescence in their natural environment: Cambrian animals have previously been accurately reconstructed in black and white only. A diversity of extant marine animals inhabiting a similar depth to the Burgess Shale fauna possess functional diffraction gratings. The Cambrian is a unique period in the history of animal life where predatory lifestyles and eyes capable of producing visual images were evolving rapidly. The discovery of colour in Cambrian animals prompts a new hypothesis on the initiation of the ‘Big Bang’ in animal evolution which occurred during the Cambrian: light was introduced into the behavioural systems of metazoan animals for the first time. This introduction, of what was to become generally the most powerful stimulus in metazoan behavioural systems, would have triggered turbulence in metazoan evolution.