Boxplot showing the distribution of the ratio between the maximum transverse width of the cranium across
the postorbitals and the width across the quadrate cotylus of the squamosals for 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 the two variables of this raio were measured, exemplified in a skull roof of Hypacrosaurus altispinus (CMN 8675). Grey horizontal lines
delimit character states.