The certain fossil record of animals begins around 540 million years ago, close to the base of the Cambrian Period.
A series of extraordinary discoveries starting over 100 years ago with Walcott’s discovery of the Burgess Shale has
accelerated in the last thirty years or so with the description of exceptionally-preserved Cambrian fossils from around the
world. Such deposits of “Burgess Shale Type” have been recently complemented by other types of exceptional preservation.
Together with a remarkable growth in knowledge about the environments that these early animals lived in, these discoveries
have long exerted a fascination and strong influence on views on the origins of animals, and indeed, the nature of
evolution itself. Attention is now shifting to the period of time just before animals become common, at the base of the
Cambrian and in the preceding Ediacaran Period. Remarkable though the Burgess Shale deposits have been, a substantial
gap still exists in our knowledge of the earliest animals. Nevertheless, the fossils from this most remarkable period of evolutionary
history continue to exert a strong influence on many aspects of animal evolution, not least recent theories about
Keywords: Cambrian explosion, Ediacara, Animal evolution, Developmental evolution.
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