Evolutionary Innovations of the Feeding Apparatus in Herbivorous Dinosaurs

Although most studies in feeding biology of non-avian dinosaurs have investigated feeding function and ecology in carnivorous dinosaurs, the complex diversity of feeding in herbivorous dinosaurs has recently been explored in much greater detail. Herbivorous non-avian dinosaurs, composed of nearly all sauropodomorphs and ornithischians as well as a few theropod groups (i.e., ornithomimosaurs, therizinosaurs, and oviraptorosaurs), show a wide range of craniomandibular feeding mechanisms, each with unique adaptations for processing various forms of plant-life. Here, I will review over a century of feeding studies in herbivorous dinosaurs, with particular focus on more recent advancements in our knowledge of their feeding evolution and ecology. These studies have primarily focused on the many components influencing the functional morphology of the head and neck of these animals, including: dental morphology, with studies in dental microwear and macrowear, overall morphological analysis of the skull and cervical vertebrae, reconstruction of cranial musculature and other soft tissues of the head, and biomechanics of the skull, with comparative analyses of mechanical advantage of the jaw system and 3D computer modeling in the form of finite element analyses and multibody dynamics analyses with the use of laser scans and CTs of dinosaur skulls. All these studies are instrumental in our understanding of the evolution and diversity of bite forces as well as feeding mechanisms that range from orthal to palinal feeding motions as well as bilateral hemi-mandibular long-axis rotation (especially in a variety of ornithischians). The similarities and differences between herbivorous dinosaurs and the herbivores of today (especially mammalian megaherbivores) show a great deal about how evolutionary opportunities and constraints have made a significant impact on the diverse nature of herbivory and its importance in ecosystems around the world.