"Molecular evidence shows that some limited number of Hox genes have existed in the Cnidaria since before the earliest true Bilatera, making these genes pre-Paleozoic."
Minimal ProtoHox cluster ... (Goog)
"Bilaterian animals have a Hox gene cluster essential for patterning the main body axis, and a ParaHox gene cluster." "Here we characterize the full Hox/ParaHox gene complements and genomic organization in two cnidarian species ..." "... the ProtoHox cluster might have consisted of only two anterior genes. Non-anterior genes could have appeared independently in the Hox and ParaHox clusters, possibly after the separation of bilaterians and cnidarians."
The cnidarian-bilaterian ancestor possessed at least 56 homeoboxes (Goog)
Full length article. "Phylogenetic analyses were performed on 130 homeodomains from the sequenced genome of the sea anemone Nematostella vectensis ..." "The homeodomain superclass underwent extensive radiations prior to the evolutionary split between Cnidaria and Bilateria."