Edentulism, beaks, and biomechanical innovations in the evolution of theropod dinosaurs

Edentulism and beaks (rhamphothecae) are distinguishing features among extant birds and are traditionally regarded as a response to weight-saving demands for the evolution of flight. However, keratin-covered beaks paralleled by edentulism appeared in non-avian theropod dinosaurs and as early as the Early Cretaceous. Here, high-resolution, digital biomechanical models of the skull of the Cretaceous therizinosaur Erlikosaurus andrewsi are used to investigate the functional significance of these morphological specialisations and adaptations occurring in non-avian, maniraptoriform dinosaurs. Results of finite-element analyses provide evidence that keratinous beaks play an important role in enhancing cranial stability by mitigation stress and strain during feeding and represent an evolutionary innovation developed early in derived theropod dinosaurs.