However, in 2005 Katja Seipel and Volker Schmid suggested that cnidarians and ctenophores are simplified descendants of triploblastic animals, since ctenophores and the medusa stage of some cnidarians have striated muscle, which in bilaterians arises from the mesoderm.
22.
The earliest widely accepted animal fossils are the rather modern-looking cnidarians ( the group that includes jellyfish, sea anemones and " triploblastic bilaterian animal, in other words, an animal significantly more complex than the cnidarians.
23.
Many were flat and had a " quilted " appearance, and seemed so strange that there was a proposal to classify them as a separate triploblastic bilaterian animal, in other words, an animal significantly more complex than the cnidarians.
