Dietary differences in archosaur and lepidosaur reptiles revealed by dental microwear textural analysis

Reptiles are key components of modern ecosystems, yet for many species detailed characterisations of their diets are lacking. Data currently used in dietary reconstructions are limited either to the last few meals or to proxy records of average diet over temporal scales of months to years, providing only coarse indications of trophic level(s). Proxies that record information over weeks to months would allow more accurate reconstructions of reptile diets and better predictions of how ecosystems might respond to global change drivers. Here, we apply dental microwear textural analysis (DMTA) to dietary guilds encompassing both archosaurian and lepidosaurian reptiles, demonstrating its value as a tool for characterising diets over temporal scales of weeks to months. DMTA, involving analysis of the three-dimensional, sub-micrometre scale textures created on tooth surfaces by interactions with food, reveals that the teeth of reptiles with diets dominated by invertebrates, particularly invertebrates with hard exoskeletons (e.g. beetles and snails), exhibit rougher microwear textures than reptiles with vertebrate-dominated diets. Teeth of fish-feeding reptiles exhibit the smoothest textures of all guilds. These results demonstrate the efficacy of DMTA as a dietary proxy in taxa from across the phylogenetic range of extant reptiles. This method is applicable to extant taxa (living or museum specimens) and extinct reptiles, providing new insights into past, present and future ecosystems.