Accordingly, Fig. 2 shows Myriapoda as monophyletic, and its internal relationships are as discussed by Shear and Edgecombe (2010) elsewhere in this issue.No convincing candidates for stem group Myriapoda have been found in any Cambrian Lagersta¨ tte, or indeed from any early Palaeozoic marine rocks (Edgecombe, 2004). The body fossil record of myriapods is unsampled until the mid Silurian (ingroup chilo- gnathan millipedes described by Wilson and Anderson, 2004 and Wilson, 2005), with crown group centipedes appearing at the end of the Silurian (Shear et al., 1998). This long ghost lineage appears to be partly filled by trace fossils. Diplichnites and Diplopodichus trackways from the late Middle or Upper Ordovician (Johnson et al., 1994) are consistent with a tracemaker having a millipede body- plan (Wilson, 2006). Using this to date the divergence of Diplopoda from Pauropoda sets a minimum age for Progoneata and Myriapoda as well. Early Cambrian records of the sister group, Tetraconata (Fig. 2), discussed below under Crustacea, emphasise an unsampled ghost lineage for Myriapoda of substantial duration.