Zoology 10th Edition by Stephen Miller,John Harley

Exercise 12

Phylogenetic relationships within the Ecdysozoa are controversial. Two major clades include the Panarthropoda and Cycloneuralia. Within the Cycloneuralia, the nematodes and nematomorphs are sister groups. The kinorhynchs and priapulids are also closely related. The relationship of the loriciferans to these phyla is less certain. Two traditional nematode classes do not reflect phylogeny of this phylum. Molecular evidence suggests that there are three major clades within the Nematoda.
What uncertainties exist in our understanding of phylogentic relationships within the Ecdysozoa, and what type of evidence is required in order to resolve these uncertainties?