High Quality Content by WIKIPEDIA articles! Panarthropoda is a taxon combining the phyla Arthropoda, Tardigrada, and Onychophora. Dunn et al. in 2008 suggested that the tardigrades could be grouped along with the nematodes, leaving Onychophora as the sister group to the arthropods. Originally, they were considered to be closely related to the annelids, grouped together as the Articulata, but newer studies place them among a group called the Ecdysozoa.