The Cambrian Substrate Revolution

Abstract

The broad marine ecological settings prevalent during the late Neoproterozoic– early Phanerozoic (600–500 Ma) interval of early metazoan body plan origination strongly impacted the subsequent evolution and development of benthic metazoans. Recent work demonstrates that late Neoproterozoic seafloor sediment had well-developed microbial mats and poorly developed, vertically oriented bioturbation, thus producing fairly stable, relatively low water content substrates and a sharp water-sediment interface. Later in the Cambrian, seafloors with microbial mats became increasingly scarce in shallow-marine environments, largely due to the evolution of burrowing organisms with an increasing vertically oriented component to their bioturbation. The evolutionary and ecological effects of these substrate changes on benthic metazoans, referred to as the Cambrian substrate revolution, are presented here for two major animal phyla, the Echinodermata and the Mollusca.