Zoology 9th Edition by Stephen Miller

Exercise 1

Two hypotheses explain relationships among the aschelminthes. The older hypothesis contends that the phyla are related based on the presence of a pseudocoelom, cuticle, muscular pharynx, and adhesive glands. The more recent hypothesis states that they are probably polyphyletic. Ecdysozoans and lophotrochozoans are distinguished by the fact that the former molt their cuticle and the latter do not molt.
What strongly suggests that each of the seven phyla covered in this chapter had an independent evolution?