Biomechanics and Functional Morphology

We have discovered many novel and unusual feeding mechanisms in vertebrates. From the spectacular jaw protrusion of the sling-jaw wrasse, to the way pharyngeal jaws work in the popular redfish, the way bird skulls can move kinetically to produce complex motions, the mechanics of the slicing bite of the barracuda, and deriving a computational model for one of the greatest fishy bite force ever (in the ancient fossil placoderms), we reveal the ways that evolution has shaped jaws and skulls to perform a wide range of intriguing feeding behaviors.

My primary approach to the biomechanics of feeding is to build and test models of musculoskeletal systems, including physical models and computer models. We test these models using high-speed videography and experimental physiology. Biomechanical models for fish skulls have great potential for testing hypotheses of mechanical design in a diversity of fishes, for revealing functional transformations during growth and development, and for examining patterns of evolution in key functionally relevant characters in a phylogenetic context.

Fish Feeding Mechanisms. The evolution of the jaws and feeding mechanisms of fishes has been accompanied by spectacular radiation into a diversity of forms, often associated with complex mechanical designs that enable cranial kinesis. Coral reef fishes in particular have evolved a wide array of skull configurations that may exhibit highly kinetic, fast mechanisms (specializing on evasive prey) or conversely may possess stout jaws with high mechanical advantage for enhancing force transmission (typical of predators on hard prey). We have developed several computational biomechanical models that enable the calculation of muscle mechanics, illustrate the force transfer through levers and linkages, predict kinematic motions, and compute the total bite force capacity and jaw protrusion speeds in a wide range of species. Data on jaw biomechanics are interpreted in the context of phylogenetic trees in order to yield a picture of the evolutionary history of feeding mechanisms in some of the most diverse fish families on global coral reefs. Family level phylogenies of major reef fish groups are highlighted, as well as a large Tree of Life for all fishes. Results of integrating phylogenetics and biomechanics show that coral reef fishes often have close relatives with highly different jaw mechanisms, a phenomenon that we interpret as local phylogenetic divergence. More broadly, across groups of species, this local divergence produces a global pattern of repeated convergence in skull form and function that may be a major trend of feeding evolution in diverse coral reef fishes.