Investigating the biomechanics of a lizard skull using advanced computer modelling techniques with experimental validation

Lizard skulls vary greatly in shape and construction, and radical changes in skull form during evolution have made this an intriguing subject of research. The mechanics of feeding have surely been affected by this change in skull form, but whether this change in feeding is the driving force behind the change in skull shape is the underlying question being addressed throughout this project. Here the skull of 'Uromastyx hardwickii', an akinetic herbivorous lizard has been analysed using advanced computer modelling techniques. This study aimed to perform a multibody dynamics analysis (MDA) on a biting lizard skull so that bite forces, joint forces, ligament forces and muscle forces could be accurately predicted. Then, using this MDA load data stresses and strains within the skull were assessed using finite element analysis (FEA). These FE analyses were used to assess biting performance and to test hypotheses that consider biomechanical optimization of bone as the main reason behind the modification of skull shape during its evolution. Sutures were modelled and their effect on skull strains was assessed through a series of investigative studies. Finally, representative basal skull forms were examined to highlight potential implications of specific skull variations. To assist in validation of the computational modelling experimental strain gauging was conducted. The MDA provided detailed information on cranial biomechanics and associated cranial forces in this animal. It is believed that this technique will play a pivotal role in the analysis of skulls in the future and this study has demonstrated its definite potential. Cranial kinesis was seen to be mechanically significant in reducing joint reaction forces acting upon the skull, and specific groups of sutures (i.e. the frontal-parietal suture) in the Uromastyx skull played a substantial role in relieving strain compared to the other sutures, raising the questions about the original role of mesokinesis in squamate evolution