Figure 9 The frequency distribution of synontomorphies by apneumatic anatomical domain in the growth series of Tyrannosaurus rex. Growth stages are along the x-axis (corresponding to the numbered nodes of the ontogram in Fig. 2) and the y-axis corresponds to the number of synontomorphies. Changes to the skull frame are dominant over others and all are sustained throughout growth, aside from the dentition and cervical occiput. crv occ, cervical occiput; dntn, dentition; dtfo, dorsotemporal fossa; jnt srfc, joint surfaces; mscl scrs, muscle scars; nrvsc, neurovasculature; sbct srfc, subcutaneous surface; skl frm, skull frame. Full-size DOI: 10.7717/peerj.9192/fig-9