The invasion of the land by vertebrates is one of the great transitions in the history of life. Numerous fossils document the metamorphosis from aquatic, lobe-finned fishes to terrestrial tetrapods. Anatomical and phylogenetic studies have focused on changes in the limbs and cranium during this transition; in contrast, the mandible has received little attention. Furthermore, while comparative anatomy has been used to predict function and ecology in early tetrapods, these inferences have not been tested using biomechanical techniques. This project will address how specific changes in mandibular morphology (arrangement and relative size of bones, loss of the Meckelian ossification, changes in tooth distribution and size) are related to changes in jaw mechanics and function across the fish-tetrapod transition. We will also explore how release from some functional constraints (breathing, hydrodynamic streamlining) may have allowed feeding to exert stronger selective pressure on mandibular morphology. Mandibular anatomy and function in the living Esox (pike) and Sphenodon will serve as end members to a series of fossil taxa that span the transition, including Eusthenopteron, Acathostega, Ventastega and Crassigyrinus. This study will combine biomechanical techniques (finite element analysis, in vitro validation and material properties testing) with comparative anatomy and geometric morphometrics (including both morphologic and functional characters) to quantitatively test the link between form and function, including the degree to which the mandible is “optimized” for feeding. The incoming researcher has experience collecting in vivo feeding data, reconstructing fossils and finite element modeling. This will be integrated with experience conducting in vitro experiments, and modeling/engineering expertise at the University of Bristol; additionally, this project will utilize tetrapodomorph specimens and extensive knowledge of these animals at the University of Cambridge.