how is the former classified?
It is currently thought to be a member of the group Hymenocarina.
Canadaspis
 It is currently thought to be a member of the group Hymenocarina, which are interpreted as mandibulate stem-crustaceans.
crustacea and hexapoda have what features in common It is now well accepted that the crustacean group is paraphyletic, and comprises all animals in the clade Pancrustacea other than hexapods. what is the first group that you are talking about? It forms a large, diverse arthropod taxon which includes such animals as crabs, lobsters, crayfish, shrimps, prawns, krill, woodlice, and barnacles. can you describe their body? It is composed of segments, which are grouped into three regions: the "cephalon" or head, the "pereon" or thorax, and the "pleon" or abdomen. and where do they generally live? Majority live in either marine or freshwater environments. have their fossils been found? Yes, they have a rich and extensive fossil record. can you name any organism of this taxon whose fossil has been discovered? Yes, "Canadaspis" and "Perspicaris".
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Canadaspis [SEP] Classification of "Canadaspis"
Three alternatives exist for "Canadaspis"'s classification. They concern its relationship to the crustacea; it was originally thought that it falls within that clade, but this no longer appears to be the case. The alternatives are that it is a stem group crustacean, but others believe it is more basal still, falling in the base of the Euarthropoda. It is currently thought to be a member of the group Hymenocarina, which are interpreted as mandibulate stem-crustaceans.