<P> In the 1990s, molecular phylogenetic analyses of DNA sequences produced a coherent scheme showing arthropods as members of a superphylum labelled Ecdysozoa ("animals that moult"), which contained nematodes, priapulids and tardigrades but excluded annelids . This was backed up by studies of the anatomy and development of these animals, which showed that many of the features that supported the Articulata hypothesis showed significant differences between annelids and the earliest Panarthropods in their details, and some were hardly present at all in arthropods . This hypothesis groups annelids with molluscs and brachiopods in another superphylum, Lophotrochozoa . </P> <P> If the Ecdysozoa hypothesis is correct, then segmentation of arthropods and annelids either has evolved convergently or has been inherited from a much older ancestor and subsequently lost in several other lineages, such as the non-arthropod members of the Ecdysozoa . </P> <P> Arthropods belong to phylum Euarthropoda . The phylum is sometimes called Arthropoda, but strictly this term denotes a (putative - see Tactopoda) clade that also encompasses Phylum Onychophora . </P> <P> Euarthropoda is typically subdivided into five subphyla, of which one is extinct: </P>

What class of arthropods do crabs belong to
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