Figure 1.

Phylogenetic relationships among major metazoan lineages. The topology of the tree is consistent with several recent molecular phylogenetic analyses [100-106]. Estimated divergence times for Cnidaria versus Bilateria, protostomes versus deuterostomes, and lophotrochozoans versus ecdysozoans are indicated in the white boxes [18]. The origin of the homeobox gene superclass must have predated the split between animals, plants, and fungi.