Boxplot showing the distribution of the angle between the rostral surface of the predentary and the frontal
skull in a sample of iguanodontoidean ornithopods. The inserted smaller graph shows the Bayesian information criterion (BIC)
for various numbers of clusters in which the data can be classified. The photograph shows how this angle (A) was measured, exemplified in
Prosaurolophus maximus (MOR 447-7-27-7-5). Grey horizontal lines delimit character states.