All appendages of most primitive arthropods are assumed to
be similar with serial repetition of similar segments, resembling
the bodies of extinct trilobites and of recently discovered remiped
crustaceans. Affinities of crustaceans with the Chelicerata (A-20)
are uncertain. Crustaceans may have an evolutionary origin
independent from insects, centipedes, millipedes, and other terrestrial
arthropods.