Early Metazoan Evolution: Reconciling Paleontology and Molecular Biology

SYNOPSIS.Molecular "clocks" are now widely accepted as pointing to a protracted, but cryptic, history of pre-Ediacaran metazoan evolution.The inhabitants of this interval (ca.1300-600 Myr ago) are usually envisaged as equivalent to either planktotrophic larvae or the meiofauna.Reassessment of the evidence, however, suggests that this pre-Ediacaran history was neither deep nor was represented by analogues of microscopic living metazoans.The origination of this Kingdom may have been no earlier than ca.650 Myr, and the earliest forms emerged from the Metazoa-Fungi-Mycetozoa stem-group.Accordingly the time-frame and search image need to be reset with this hypothesis in mind.