Thread:Ghelæ/@comment-32744161-20180526135800/@comment-47205-20180527160418

The presence of proboscides isn't a valid criterion: remember that you have argued against defining taxa (e.g. Foliazoa, Cirruosidae) on the grounds of whether they have a particular type of part without regards for the creature's overall appearance.

Lack of roundness and absence of neck are defining what features they don't have, not something that they share. That's only useful when the majority of creatures in the parent taxon have such a feature, and a small minority need to be differentiated from them.

That leaves the choice of integument, which as discussed before is insufficient to define a family.

On top of this, they also have many differences, including different numbers of legs, different numbers of arms, different numbers of wings, different numbers of eyes, and different types of primary mouthparts. In any other family this would be grounds for splitting.