Resolving Pterosaur Dietary Ecology using Tooth Microwear and Biomechanics
thesisposted on 14.11.2019, 11:23 by Jordan Bestwick
Pterosaurs are an extinct group of Mesozoic flying reptiles that lived between 210 and 66 million years ago and whose diets are poorly constrained. A range of diets have been proposed, including piscivory, insectivory and carnivory, but it is unclear if these hypotheses hold up to scientific scrutiny. Quantitative analysis of the three-dimensional sub-micron scale surface textures on their teeth – dental microwear textural analysis (DMTA) – offers a novel, robust approach for hypothesis testing as microwear formation is determined by the material properties of consumed foods. This thesis presents the first quantitative reconstructions of pterosaur dietary ecology and evolution by: (i) synthesising pterosaur dietary hypotheses and corresponding supporting evidence; (ii) DMTA of the non-occlusal tooth surfaces of extant reptiles and bats with known diets; (iii) using these data as modern frameworks to test dietary hypotheses from seventeen pterosaur genera using DMTA; and; (iv) exploring intraspecific microwear textures, and the influence of endogenous non-dietary variables (tooth position, relative bite force and tooth shape), along the tooth rows of extant reptiles. Qualitative lines of evidence support 87.3% of dietary hypotheses, with comparative anatomy the most common (62.1% of total). DMTA of extant reptiles and bats reveals dietary signals; taxa with invertebrate-dominated diets exhibit the roughest textures and taxa with vertebrate-dominated diets exhibit the smoothest textures. Pterosaur microwear differences analysed in the context of modern reptiles and bats reveal a range of diets, including carnivores, piscivores, invertebrate consumers and generalists. This verifies dietary hypotheses for some pterosaurs, provides better constraints for others and provides novel evidence of diet for others. The ancestral pterosaur diet is revealed to have been invertebrate-dominated and later pterosaurs shifted towards piscivory and carnivory. This thesis provides robust evidence of pterosaur dietary ecology and highlights the power and applicability of DMTA for reconstructing the diets of extant and extinct reptiles.