An alliance between hexapods and myriapods, the Atelocerata (¼Tracheata and Antennata), has a long history, and can accurately be described as the orthodox perspective on hexapod affinities. That said, theories compatible with the rival Tetraconata hypo- thesis date back at least to the neuroanatomical work of Holmgren and Hanstro¨ m (e.g., Hanstro ¨ m, 1926), emphasising characters of the optic lobes and midline neuropils of the brain shared by insects and crustaceans that have come back to the discussion in the past 15 years. I make this point to emphasise that Atelocerata cannot be claimed to be ‘‘the’’morphological solution to arthropod phylogeny. Indeed, some morphological cladistic analyses resolve Tetraconata in favour of Atelocerata (Giribet et al. 2005, fig. 1). That said, it is indisputable that Atelocerata does have a solid body of morphological support, reviewed by Klass and Kristensen (2001) and Bitsch and Bitsch (2004), including the limbless inter- calary segment, tentorial endoskeleton, postantennal organs, Mal- pighian tubules, and the single pretarsal (depressor) muscle. Ba¨cker et al. (2008) provide an additional argument from a restatement of classical ‘‘subcoxal theory’’, reconstructing concentric pleural sclerites around the leg base as an apomorphy in the myriapod/ hexapod groundpattern. Atelocerata is a ‘‘morphology-only’’hypothesis. No molecular data of any kind favour an alliance of myriapods and hexapods exclusive of crustaceans or chelicerates (apart from an alignment experiment conducted with a small fragment of 12S rRNA to debunk the placement of onychophorans within the Arthropoda; Wa¨ gele and Stanjek, 1995). This is a serious defect of the Atelocerata hypothesis. Because Tetraconata accommodates a large body of genetic information from diverse sources as well as numerous highly detailed features of the nervous system, it is depicted in favour of Atelocerata in Fig. 2.