Compartmentalization is also the underlying advantage epithelia provide in triploblastic descendants of a diploblastic ancestor. |
The transition from diploblastic to triploblastic body plans hinges on the origin of mesoderm. |
A diploblastic condition of the organism preceded, as we have seen, the triploblastic. |
Hence ctenophores and cnidarians have traditionally been labelled diploblastic, along with sponges. |
The other diploblastic phylum, the Ctenophora, surprisingly, has not been reported to have septate junctions. |