Figure 1.

(A) Simplified metazoan phylogeny, emphasizing the position of cnidaria as a sister group to bilaterians as well as the cnidarian phylogeny highlighting the relationships between the major groups. CBA (cnidarian-bilaterian ancestor). Data based on [89,90]. (B) Adult Nematostella polyp. (*) mouth, (ten) tentacles, (pha) pharynx, (mes) mesenteries (phy) physa. Figure modified from [91,92]. (C) Schematic cross section of a complete/adult mesenteries at the gonadal section (adapted from [83,93]). (p-ecto) pharyngeal ectoderm, (ecto) ectoderm, (rM) retractor muscle, (pM) parietal muscle, (cM) circular muscle.