Fig 1.
Estimation of rates of cranial evolution on a time-calibrated phylogeny of Dinosauria using a variable-rates BM model of evolution.
(A) In the rostrum, ornithischians evolved faster than avian and non-avian theropods. (B) The cranial vault evolves fastest in non-avian dinosaurs with bony cranial ornaments. (C) Rates of evolution are generally conserved and low in the occipital region, with slightly elevated rates in Passeriformes and in pachycephalosaurs. Black triangle indicates the origin of Aves. See S2–S36 Figs for estimated rates for all cranial regions and phylogenetic hypotheses and detailed tip labels. Data and code archived at www.github.com/rnfelice/Dinosaur_Skulls. BM, Brownian Motion.
Fig 2.
Comparison of per-group evolutionary rate scalars.
Birds do not have the highest rates of evolution in any cranial region. For each group, mean rate scalar is the mean of the rate scalars in the post-burn-in posterior distribution under the variable-rates evolutionary model estimated using BayesTraits under the traditional Dinosaur phylogenetic hypothesis (Saurischia and Ornithischia as sister clades). Mean rates were scaled to the sum of the branch lengths in the corresponding subtree. Mean rate scalars were compared between groups using non-parametric t tests; significantly different distributions are indicated with ****p < 0.00005. These results are robust to subsampling of taxa (S1 Fig 37), Procrustes superimposition (S1 Fig 38) and alternative methods for comparing evolutionary rates (S39–S42 Figs). Data and code archived at www.github.com/rnfelice/Dinosaur_Skulls.
Fig 3.
Per-landmark evolutionary rates (under single-rate BM model) and Procrustes variance.
Landmarks and sliding semi-landmarks represented in the 9-module dataset (A, B) and 11-module dataset (C, D), illustrated on the skull of Erlikosaurus andrewsi (IGM 100/111). Landmarks are coloured according to evolutionary rate (A, C) and Procrustes variance (B, D), where a warmer colour indicates greater value. Data and code archived at www.github.com/rnfelice/Dinosaur_Skulls. BM, Brownian Motion; IGM, Paleontological Center, Mongolian Academy of Sciences.
Fig 4.
Phenotypic difference between each specimen for each landmark in the 11-module dataset and the mean skull shape.
For each specimen, the mean landmark configuration is plotted with points coloured relative to the Procrustes distance between the position of that point in the mean shape and in that specimen. Warmer colours denote landmarks having higher displacement from the mean, and cooler colours are more similar to the mean shape. Data and code archived at www.github.com/rnfelice/Dinosaur_Skulls.