Fig. 5 in New psittacosaurid highlights skull enlargement in horned dinosaurs

Fig. 5. Regression of skull dimensions (cm) against body mass (log kg) in dinosaurian herbivores. Seven ceratopsians are plotted (1–7); frilled species (3–7) are plotted with, and without, the frill. A. Regression of skull length as a function of body mass shows that ceratopsians broadly overlap a comparable regression for other dinosaurian herbivores at body mass less than 100 kg. Larger−bodied ceratopsians (4–7;>1,000 kg), in contrast, have skulls approaching or exceeding a length of 1 m and plot outside the 95% confidence interval for other dinosaurian herbivores (lower curve). The largest ornithopods have comparable skull lengths to large−bodied ceratopsians. B. Regression of skull/trunk length as a function of body mass shows that ceratopsians have proportionately larger skulls even at moderate body masses between 10 and 100 kg broadly overlap a similar regression for other dinosaurian herbivores at body mass less than 100 kg. Larger−bodied ceratopsians (4–7;>1,000 kg), plot outside the 95% confidence interval for other dinosaurian herbivores including hadrosaurids (lower curve).