Phylogenetic relationships of pachybolid and several other spirobolidan millipede species based on maximum likelihood analysis (ML) of a 660 bp COI gene fragment. Numbers at nodes indicate branch support based on bootstrapping (ML) / posterior probabilities (BI) / bootstrapping (NJ). Scale bar: 0.3 substitutions/site. # indicates branches with < 50% ML and NJ bootstrap support or < 0.95 posterior probability, - indicates non-supported branches. The coloured areas mark the Pseudospirobolellidae (minus Benoitolus) (purple), Trigoniulinae (red), and non-trigoniuline Pachybolidae (plus Benoitolus) (yellow).