MARTINDALE, Mark Q; University of Hawai’i: Ctenophores: missing links or missing the boat?

Evolutionary developmental biologists have bemoaned the fact that there do not appear to be any �intermediate� phyla to help understand major transitions in animal body form. Virtually all evidence points to the fact that existing animal phyla originated over 500 million years ago, leaving little traces of their origins. Recent molecular phylogenies suggest that cnidarians are the sister group to the traditionally defined Bilateria, leaving the ctenophores as the only extant group linking the sponges to the rest of the Eumetazoa. Salient morphological, developmental, and molecular features of ctenophores will be discussed with emphasis placed on their significance for understanding eumetazoan evolution.