Analyses of mitochondrial ribosomal RNA sequences suggest
that velvet worms are highly modified chelicerates or are related
to chelicerates, crustaceans, and insects. This interpretation contradicts
the other current major hypotheses of onychophoran
evolutionary affiliations based on morphological, behavioral,
and physiological evidence. On the basis of the present data of
reproductive features, biogeography, and phylogeny, onychophorans
may be placed between the polychaete annelids and the
arthropods or as ancestors to their larvae.