 The Artiopoda have subsequently been considered to consist of two clades; one reusing Trilobitomorpha to encompass trilobites, nektaspids, concilitergans and xandarellids, and the other called Vicissicaudata encompassing aglaspidids, xenopods and cheloniellids.This topology is not recovered in some studies.The broader relationships of the artiopods (and lamellipedians) currently remain unclear, and the possibility that they are a paraphyletic assemblage giving rise to the crown-group euarthropods cannot be excluded.