Mechanics of food breakdown in herbivorous animals and relation to dental morphology

The qualitative observation that forbivores in both Mammalia and Orthoptera tend to have high, pointed, simple cusps, in contrast to the low, ridged, complex molars of graminivores, imply convergence in evolution. Across such a vast evolutionary separation, this would demonstrate that natural selection indeed shapes masticatory surfaces, and that the morphological patterns observed must be biomechanically specialised for fracturing corresponding food items in both taxa despite vast differences in anatomy and scale. As the molars of mammals and the molar regions of grasshopper mandibles are non-homologous, traditional quantitative metrics of comparison are not applicable. This thesis investigates these apparent morphological similarities using Dental Topographic Analysis (DTA), a landmark-free toolkit for quantification of aspects of the occlusal surface.
The first study investigates the application of freeware tools to the preparation of masticatory surface files for use in DTA. It is demonstrated that these tools can produce comparable results to the established proprietary method, and an accessible workflow applicable to disparate morphologies is proposed.
The second study investigates the use of microCT scanning for the 3D imaging of grasshopper mandibles to obtain surfaces for use in DTA. Comparisons between microCT scans and other scanning technologies reveal that this method produces accurate representations of the occlusal surface.
The third study investigates morphology and location of a feature of the grasshopper occlusal surface, the median cusp, and determines that this feature should be excluded from DTA of the molar region when possible.
The fourth study conducts DTA on an inter- and intra-specific grasshopper sample, and finds that mandibular side, sex, and wear affect resultant topographic metrics, and should be held consistent in samples when possible. Species/diet also affects topographic metrics in this taxa.
The fifth study conducts DTA on a much more diverse sample of grasshoppers, and investigates dietary vs. phylogenetic signal. Both signals are present, and as DTA metrics can differentiate between dietary categories even when phylogenetic signal IV is present, comparisons are drawn between DTA metrics of grasshoppers and mammals.