A comparison of the jaw mechanics in hadrosaurid and ceratopsid dinosaurs using finite element analysis.

Hadrosaurid and ceratopsid dentaries display traits that suggest divergent functions toward broadly similar diets of fibrous plants. Computed tomographic scans of dentaries of a lambeosaurine and a centrosaurine (Centrosaurus aptertus) were used to compare feeding function of these animals using finite element analysis (FEA). In the hadrosaur, mediolateral expansion of the dentary and elongation of the coronoid process of the surangular were optimally developed to withstand torsion associated with transverse-isognathous jaw occlusion. FEA results strongly suggest longitudinal rotation of the hadrosaurid mandible. Mediolaterally compressed mandibles and FEA stress for the ceratopsid are in compliance with purely isognathous jaw adduction, although palinal retraction during the powerstroke cannot be ruled out. The ceratopsid dentary is further reinforced by a longitudinal ridge on the lateral surface of that element. Surface texture indicating Sharpey's fibers within the ceratopsid coronoid process suggests greater bite force than in lambeosaurines. These findings corroborate previous interpretations and suggest complementary or alternative kinematics to maxillary pleurokinesis in hadrosaurs.