Fig. 1: Brain and body size across 4679 animal species.

a The eight major animal classes (those listed above, excluding crocodilians owing to their small sample size) are shown in the central phylogeny with clades collapsed to triangles sized proportionally to the number of species. Each clade is expanded to show finer phylogenetic structure, with bars at the tips proportional to body size (pale) and brain size (dark). b The predicted relationships estimated in our global curve model across all 4679 species with the median prediction superimposed upon a random sample (n = 100) of the posterior. The median prediction from our global slope model is shown for comparison with a dashed line. c The posterior distribution of estimated curvature (quadratic parameters) for each of the eight non-crocodilian classes (n = 4676) compared to the global (grand mean) curvature outlined with a black dashed line. All groups substantially overlap the grand mean and are thus not significantly different from a global curve estimated across all species. Silhouettes are not proportional to size and are shown for illustrative purposes only. The major animal clades are indicated by the coloured silhouettes; the colour scheme is used throughout the manuscript to facilitate quick comparisons between results.