Figure 1.

A simplified topology of the metazoan radiation, based on the phylogeny and molecular clock results from reference [1]. The coloured circles are the estimated ages of the origin of the crown group of each clade, based on molecular clock estimates. The uncertainties on the divergence times are not shown on this diagram for clarity. These match closely with estimates from the fossil record, except for crown demosponges and crown cnidarians, which occur in the Cryogenian. The duration of the major glaciations are indicated: S, Sturtian; M, Marinoan; G, Gaskiers. (Online version in colour.)