Morphological disparity in theropod jaws: comparing discrete characters and geometric morphometrics

Disparity, the diversity of form and function of organisms, is frequently measured, and can be assessed from cladistic or phenetic characters, and from discrete characters or continuous characters such as landmarks, outlines, or ratios. But do these different methods of assessing disparity provide comparable results? Here we provide a large-scale test in which character sets are standardized for anatomical-functional comparability, and compare
three methods of capturing morphological disparity (discrete characters, morphometric outlines and geometric morphometric landmarks). We use coelurosaurian dinosaur mandibles as our case study. We find that all methods correlate significantly with each other and capture similar patterns of morphological variation. The correlation is strongest between the two morphometric methods, and weaker between the morphometric methods and the discrete characters. When expanding the scope of sampling for all three analyses to include all possible taxa results are consistent with a reduced standardized sample across all three measures. Our results from all methods confirm that Maniraptoriformes had the highest disparity of all coelurosaurians, and omnivores and herbivores had higher disparity than carnivores.