DENTICLE MORPHOMETRICS AND A POSSIBLY OMNIVOROUS FEEDING HABIT FOR THE THEROPOD DINOSAUR TROODON

Abstract

: As in many carnivorous vertebrates, the teeth of most theropod dinosaurs are characterized by serrations. Denticle size (or serration coarseness) and its inverse, serra- tion density, scale with relation to absolute tooth size along the same allometric curve for most groups of carnivorous vertebrates. One of the few fossil groups traditionally inter- preted as carnivorous that does not follow this same allometric scale is the theropod dino- saur family Troodontidae. Troodontids differ from all other theropods with the exception of therizinosauroids in that their serrations are particularly coarse; that is, their denticles are larger and correspondingly more widely spaced than expected for a plesiomorphic thero- pod of similar tooth size. Morphometric analysis of the teeth of herbivorous dinosaurs and lizards also show allometric scaling of serration coarseness, with plant-eaters generally having significantly larger denticles than meat-eaters for the same tooth size. The difference in the size of the denticles between herbivores and carnivores may be related to differences in the size and resistance of plant and muscle fibres. Troodon and therizinosauroid serra- tion coarseness plot along the herbivorous rather than the carnivorous curve. Although al- ternative explanations may exist, the denticle morphometrics of Troodon may be a reflection of the inclusion of a significant portion of plant matter in its diet compared to that of other theropods. The enlarged brain, grasping manus, and possible stereoscopic vision of the Troodontidae have traditionaly been interpreted as predatory adaptations. However, this same suite of characters is found in some herbivorous or omnivorous mammals; and, thus, may reflect a feeding habit in Troodon that involved the processing of a significant amount of plant matter.