Boxplot showing the distribution of the length/width ratio of the external bony naris of the premaxilla in a sample
of lambeosaurine hadrosaurids. 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 the two variables of the ratio were measured in a premaxilla of Corythosaurus
casuarius (ROM 1933).