Scenarios for Runx-WRPY evolution mapped onto alternative metazoan phylogenies. (A) Conventional phylogeny wherein the demosponge Amphimedon queenslandica (Amq) and the homoscleromorph sponge Oscarella carmela (Osc) are both classified as demosponges within the phylum Porifera. This scenario suggests that the WRPY motif was lost in the demosponge sub-lineage leading to Amq. (B) Alternative phylogeny wherein sponges are paraphyletic. In this tree homoscleromorphs are a sister group of eumetazoans within Epitheliozoa , which would imply that Runx gained the WRPY motif in the ancestors of the latter group following their divergence from demosponges, either prior to or after divergence from calcisponges.