THE ROLE OF THE PREDENTARY BONE IN EUOPLOCEPHALUS TUTUS DURING MASTICATION USING BIOMECHANICAL MODELING

The evolution of highly-efficient plant processing cranial morphology in ornithischian dinosaurs has produced a diversity of robust jaw structures, including the novel predentary bone found in these organisms. It is thought that these adaptations were involved with and led to the success of ornithischians through effectively processing plant material and developing a diverse range of feeding habits. This diversity includes three proposed morphotypes for the predentary bone, with each morphology having its own potential specializations for feeding. Specifically, it has been previously proposed that the predentary provided a fixed point for medial rotation of the dentaries during occlusion. As an initial case study of the role of the predentary bone in mastication, we modeled the skull of Euoplocephalus tutus, an armored dinosaur, to test this hypothesis. We built a biomechanical model of the skull, dentaries, and predentary of Euoplocephalus in the multibody dynamics simulation software, Adams by MSC. In this model, we utilized previous reconstructions of the adductor musculature and followed a previous methodology used by our group that utilized six degrees of freedom, contact forces, and ligament forces to constrain motion. Forces representing the adductor musculature cover the area of hypothesized attachment and are used to close the jaw. Our simulations test how varying the timing and magnitude of muscle forces affect the kinematics of the jaw and the possible rotation of the dentaries about the predentary. One interesting result of our model is the independent movement allowed to each dentary by connection with the predentary bone. This would likely have been beneficial for processing plant material on either side of the jaw. However, the ability of Euoplocephalus to utilize this potential advantage would depend on the properties of the tissue connecting the dentary and predentary, which are yet to be constrained.