evodevojournal.biomedcentral.com/articles/10....
Antero-posterior patterning in the brittle star Amphipholis squamata and the evolution of echinoderm body plans - EvoDevoAlthough the adult pentaradial body plan of echinoderms evolved from a bilateral ancestor, identifying axial homologies between the morphologically divergent echinoderms and their bilaterian relatives...evodevojournal.biomedcentral.com