Revival of forgotten characters and modern imaging techniques help to produce a robust phylogeny of the Diplopoda (Arthropoda, Myriapoda)

•SR-μCT of a millipede head and its first segments was done.•Images revealed numerous potential phylogenetically useful morphological characters.•The first 3D reconstruction of millipede head and leg morphology was done.•A morphological data matrix based on literature characters was compiled.•A phylogeny of Diplopoda was reconstructed.

The external and internal anatomy of millipedes (Diplopoda) is poorly known compared to some of the other myriapod and arthropod groups. Due to both language barriers, which hindered the assessment of the character-rich older literature, and non-phylogenetic thinking, our knowledge of morphological characters useful for phylogenetic work diminished over the last decades. Here, a new character matrix with 64 characters, mainly derived from old literature data, is used to reconstruct a phylogeny of Diplopoda. As a tool to further our knowledge about the morphology of the different millipede orders, we show how micro-computer tomography (μCT) can be used to assess and illustrate specific parts of the Platydesmida. With the advent of μCT it is now possible to analyse many taxa and characters in a comparatively short time. A focus is put on potential phylogenetically useful characters. Our results support a Verhoeffian classification of the Diplopoda: Polyxenida + Chilognatha. Pentazonia are the sistergroup to the Helminthomorpha. Colobognatha form the sistergroup to Eugnatha, the latter split into monophyletic Juliformia and Polydesmida + Nematophora.