Analysis of variance comparing the number of laminae and number of cell classes in the tectum of type 1 (“laminar brains”) and type 2 (“elaborate brains”) species, as classified by Butler and Hodos (ref. [1]).

Critical values for F statistics and associated significance levels are presented for conventional tabular values (harmonic interpolation [26])–which would be appropriate only if the traits did not present a significant phylogenetic signal (see table 2) –, as well as based on analyses of data simulated along the phylogeny shown in figure 1 under a bounded Ornstein-Uhlenbeck model of trait change. The parameters for the OU model can be found in Table S1. See text for more information.