Final answer:
Discovering that Nematoida is the sister-group to Panarthropoda would clarify ancestral traits for Ecdysozoans, suggesting an intermediate body cavity type between pseudocoelom and coelomate, and confirm the importance of molting through ecdysis in ancestral forms.
Step-by-step explanation:
If we discovered that Nematoida was the sister-group of Panarthropoda, this relationship could help resolve the characteristics of the ancient ancestor of the Ecdysozoa by providing insights based on shared traits between the two groups. Since both groups would have likely inherited characteristics from their most recent common ancestor, shared features such as a cuticle, molting through ecdysis, and potentially a similar body plan could indicate what evolutionary traits were present in the ancient ecdysozoan ancestor. For example, if Nematoida (roundworms with a pseudocoel body cavity) and Panarthropoda (arthropods with a coelomate body and jointed appendages) are sister-groups, it would suggest that the common ancestor might have had similar features, such as a body cavity type that is intermediate between a pseudocoelom and a coelom, as well as a propensity for molting. Understanding this relationship might also shed light on the nervous and digestive system organization, since these two groups exhibit a range of complexities in these systems.