Functional morphology of the oviraptorosaurian cranium

Oviraptorosaurians were a group of theropod dinosaurs that reached high diversity in the Late Cretaceous (100.5-66 million years ago). Later diverging members evolved a distinctive cranium which was extensively pneumatised, short and tall, and ended in a robust, toothless beak. Their skull has been previously interpreted as adapted for a powerful bite as part of a herbivorous or omnivorous diet. This thesis focusses on testing whether these interpretations of oviraptorosaurian cranial function are accurate. Digital 3D models were created of four key oviraptorosaurian species - early diverging oviraptorosaurian Incisivosaurus gauthieri, and later diverging oviraptorid oviraptorosaurians Citipati osmolskae, Conchoraptor gracilis, and Khaan mckennai. Finite element analysis using scaled loads demonstrates oviraptorosaurian cranial shape was stronger (lower stresses) and more efficient (lower total strain energy) compared with other herbivorous theropod crania (Erlikosaurus and Ornithomimus) and performed similarly well or better compared with large carnivore Allosaurus. Digital volumetric reconstructions of jaw adductor musculature quantify elevated bite forces in oviraptorosaurians compared with other herbivorous theropods (349-499 N in Citipati down in order of cranial size to 53-83 N in Incisivosaurus). Maximum angles of oviraptorosaurian jaw gape were estimated as similar to but more limited than reported estimates for herbivorous theropod Erlikosaurus and greatly more limited than carnivorous theropods. When approaches were combined to model muscle driven biting, oviraptorosaurians display greater cranial stress than other theropods indicating that the increased relative force of their jaw adductor musculature outweighs the effect of a comparatively strengthened cranial morphology. Oviraptorid crania may function closer to structural safety limits while feeding due to the influence of other functional or developmental pressures acting on their cranial shape. Nevertheless, it appears Oviraptoridae were adapted for powerful bites as part of a predominately but not necessarily exclusively herbivorous diet, distinct from other herbivorous theropods, while cranial function varied among oviraptorids with different species favouring different positions of biting.