Fig. 6: Evolution and scaling of torso and forelimb lengths in tetrapods.

Relative torso and forelimb size in quadrupedal striding and herbivorous taxa (Hypothesis 6). Results for the OUwie analysis for normalised torso volume in dietary categories, showing estimates of A macroevolutionary optimum (θ), B selection strength (ɑ) and C evolutionary rate (Hypothesis 3). In all three panels, each point corresponds to the parameter estimate for one of the sampled simulated evolutionary regimes. For all trophic regimes across tetrapods generally, the best fitting models for the torso were OU models, indicating some selection towards different torso volumes for taxa with different trophic ecologies. Consistent with Hypothesis 6, herbivores have higher long-term mean (θ) torso volume compared to other trophic ecologies. Insectivores had the lowest θ values, whereas piscivores show high uncertainty regarding the long-term mean. Carnivores are indistinguishable from omnivores, insectivores and piscivores in terms of θ. Allometric patterns support relatively large torso sizes and GA distances in D, E quadrupeds and G, H herbivores, supporting Hypothesis 6. However, contra to Hypothesis 6, these groups have relatively short forelimbs (F&I). WBCHV, whole-body convex hull volume. Source data are provided as a Source Data file.