Arthropods and onychophorans share segmental leg musculature (versus distinct musculation of each leg in tardigrades; Schmidt-Rhaesa and Kulessa, 2007), have nephridia or nephridial derivatives that arise from the walls of coelomic cavities (Mayer, 2006a), and onychophorans have arthropod-type hemocyanin (Kusche et al., 2002)