Boxplot showing the distribution of the ratio between the height of the neural spine and that of the centrum
of the tallest posterior dorsal or sacral vertebrae (in adults) 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 dorsal vertebra of Bactrosaurus johnsoni (AMNH 6553).
Grey horizontal lines delimit character states.