Fig. 6
From: The ecological origins of snakes as revealed by skull evolution
Ontogenetic and heterochrony analyses. a Regression analysis of 2D shape (regression score) onto log-centroid size for lizard (black squares), scolecophidian (green circles), alethinophidian (red circles), and tuatara (outgroup, orange squares) ontogenies. Embryos are shown as open circles (for snakes) or squares (for lizards and outgroup). The top left inset shows the expected regression lines for an acceleration model of heterochrony. b Dorsal views of 3D-rendered skulls from scolecophidian (Typhlops and Lethobia), alethinophidian (Boaedon, Cylindrophis, and Hydrophis), and lizard (Kentropyx, Tarentola, and Pogona) stage 10 embryos, showing the ossification levels of the different skull bones; delayed ossification of the parietal bone (blue color) in all scolecophidians and lizards is highlighted
