Fig. 7: Body proportions and quadrupedality in dinosaurs.

Ancestral state reconstructions of A trunk volume, B forelimb length, C hind limb to forelimb length ratio and D neck to forelimb length ratio during the transitions to quadrupedality in Dinosauria. The patterns seen during the independent acquisition of quadrupedality in ornithischians and sauropods in the relative proportions of the torso and forelimb mirror the wider allometric patterns seen in quadrupeds and herbivores generally (Fig. 6, Hypothesis 6). Relatively short forelimbs in quadrupedal dinosaurs may relate to coupling of forelimb and neck lengths to maintain the ability to graze near ground level. This is indirectly supported by the narrow and uniform range of neck to forelimb length ratio observed across quadrupedal dinosaurs with very different overall body proportions (D). Circled numbers represent: 1 = Ornithischia; 2 = Ceratopsia; 3=Ornithopoda; 4 = Thyreophora; 5 = Sauropods; 6 = Neosauropoda; 7= Titanisauriformes; 8 = Theropoda; 9 = Eumaniraptora. WBCHV, whole-body convex hull volume. Source data are provided as a Source Data file. Animal images created with BioRender.com.