Curiously, our analysis also reveals that Gryposaurus and Corythosaurus skulls dissipated stress very differently from each other. Gryposaurus had the typical tetrapod stress distribution, but Corythosaurus differed in experiencing very little stress in the snout. [7/11]

Our analyses reveal biologically relevant differences in the arrangement of the jaw muscles in these animals, where Gryposaurus had proportionately larger jaw muscles than Corythosaurus, but those of Corythosaurus had better leverage and could impart a greater force. [5/11]

Here, we sought out to test whether there are differences in feeding mechanics between the hadrosaurine Gryposaurus, and the coexisting lambeosaurine Corythosaurus from the DPF using Finite Element Analysis. [4/11]

Our analysis came with some unexpected observations, most notably the presence of secondary ridges and rounded mammillations on the teeth of early diverging hadrosaurines like Brachylophosaurus and Maiasaura, features classically thought of as lambeosaurine. [10/14]

Next, we used multivariate statistics to evaluate how these characters delineate phylogenetic groups when used together. We found that they are accurate overall, suggesting that with modification they can be used reliably. [8/14]

The presence and shape of marginal denticles was the best of the 4 characters. Although individual variation is present, rounded denticles are almost exclusive to lambeosaurines and non-hadrosaurid iguanodontians, and wedge-shaped denticles are never seen in hadrosaurids. [7/14]

The presence of a single secondary ridge on the tooth is individually variable, with variation in their presence even on the tooth row of individual animals. The presence of a single ridge should be grouped with their absence. [6/14]

Tooth aspect ratio is a very poor character, and although broad phylogenetic trends are present, individual variation is huge and clear differences between clades are not present. This character should only be used if describing major differences in aspect ratio. [5/14]

Our results have big implications:
The number of tooth rows is almost entirely related to size, this character is only useful at separating hadrosaurids from non-hadrosaurid iguanodontians. Lambeosaurines and hadrosaurines do not differ allometrically. [4/14]

We identified 4 fundamental tooth characters used widely across hadrosaur phylogenies over the last 2 decades and collected data for dozens of specimens across Iguanodontia. These were 1) number of tooth rows 2) tooth aspect ratio 3) secondary ridges 4) marginal denticles. [3/14]