Fig. 2: Ancestral character estimations for neuroanatomical traits.

Ancestral character estimations (ACEs) based on the Brownian Motion (BM) model of trait evolution are provided for absolute (a, b, d) and relative (c, e) volumes, alongside node-wise 95% confidence intervals (colored bars on tree nodes). ACEs for cerebellar (a), cerebral (b), and relative cerebellar-to-cerebral (c) volumes were calculated from, and mapped to, the full 34-species tree, whereas ansiform (d) and relative ansiform-to-cerebellar volumes (e) were calculated from, and mapped to, the 13-species tree. Note that the ratios in (c, e) serve merely to illustrate how ratios may result from the allometries described in Fig. 3a, c. Gradient colors on the tree represent log₁₀-transformed brain area volumes (in mm³) (a, b, d), and volumetric fractions (in percentages) (c, e), respectively. The ancestral node was estimated at 73 million years to present. N = 34 species in (a–c) and N = 13 in (d, e).