Fig. 1

The ten-module model identified from the 16 cranial regions. a Network graph of the results from phylogenetically-corrected EMMLi analysis, showing the 16 cranial regions defined in this study, colour-coded by the ten identified modules. Regions were grouped into modules when the between-region trait correlation (represented by line thickness) was within 0.2 of the lowest internal trait correlation (represented by circle size). The resulting ten modules are visualised on Siphonops annulatus in (b) ventral, (c) dorsal and (d) lateral views. The ten modules comprise the following grouping of regions (see Additional file 1: Figure S1, for region definitions): Fr (light pink): frontal (Fr); Pa (black): parietal (Pa); NPM(d) (green): nasopremaxilla (dorsal) (NPM(d)); Max (orange): maxillopalatine (lateral surface (Max(l)), interdental plate (Max(i)), palatine shelf (Max(p))); Occ (light purple): os basale (occipital region (Occ) and occipital condyle (Co)); Qu-Sq (red): quadrate (lateral surface (Qu) and jaw joint articular surface (JJ)) and squamosal (Sq); BS-Vo (purple): ventral surface of os basale (BS) and vomer (Vo); NPM(p) (gold): palatal surface of nasopremaxilla; Pt (light blue): pterygoid (Pt); St (yellow): stapes (St)