Encyclopedia of Astrobiology, Ricardo Amils, José Cernicharo Quintanilla, Henderson James Cleaves, pp. 229, Springer, 2011, ISBN 978-3-642-11271-3, ... The Cambrian explosion was a major evolutionary radiation of organisms, notably multicellular animals (metazoans), that occurred during the Cambrian period (542–588 Ma). Pre-Cambrian fossils reveal a mainly microbial biota, with complex, large-bodied organisms only becoming conspicuous during the latest Proterozoic Eon (the Ediacaran biota) ...
