Studies are trickling out on the fauna of early Cambrian, as you certainly know (Gould, 1989) fossil sediments in shale deposits (such as the Burgess Shale in British Columbia and the Maotianshan Shale in China) are the evidence that in early cambrian a lot of animal phyla (that is body plans) evolved and extinguished themselves, we’re now left with about fourty phyla, four among the arthropods, but the shale fossils are the evidence of tens of unfortunate or unfit ones.
With suggestive names such as Hallucigenia (above, that baffled scholars for decades) or the fierce predator Anomalocaris those guys were eating each other and creating the first real predatory food chain.
The example of the Maotianshan Shale indicates that the burst of anatomical innovations (new body plans) that characterizes the early Cambrian also was accompanied by the rapid development of new feeding strategies and by an unprecedented expansion of ecological interactions (prey-predator relationships).
