DIETARY ECOLOGY OF EARLY AMNIOTES AND THEIR RELATIVES AS EXPLORED THROUGH 3D SURFACE MODELING

The late Carboniferous and early Permian played host to a major transition in the ecology of terrestrial vertebrates. This period saw the diversification of the first reptiles and synapsids, including some of the first known terrestrial vertebrate herbivores and hypercarnivores. Along with such dietary shifts, significant changes in global climate and plant community structure also occurred. The causes and character of this diversification in the dietary ecology remain poorly understood, having been explored primarily via low-resolution, global studies of diversity, or through granular ecological assessments of individual taxa. In this study, we aimed to characterize dietary diversity at an intermediate scale. To do so, we determined the breadth of diets present in four different tetrapod assemblages from the late Carboniferous and early Permian of Atlantic Canada. These localities spanned from the Arnsbergian (late Mississippian) to the Artinskian (early Permian) and witnessed the entirety of the floral turnover associated with the Late Carboniferous Aridification Event. To determine diet, we microCT imaged tetrapod jaw fragments from each locality, extracting surface models of each tooth. These surface models were then analyzed using Orientation Patch Count rotated (OPCr) analysis via the R package molaR. OPCr determines the number of uniquely oriented patches on the surface of each tooth, a number strongly correlated with the degree of plant material in the animal’s diet. While OPCr has been used previously to reconstruct the diets of fossil mammals and reptiles, our study features the oldest material to be analyzed using this method. We then compared our OPCr results to a pre-existing, modern saurian dataset to confirm dietary interpretations. Preliminary results of this analysis from late Pennsylvanian amniotes show patch counts roughly equivalent to those of modern insectivorous and piscivorous reptiles, in-line with the consensus understanding of tetrapod ecology from that time. By applying this standardized method (OPCr) at a regional scale, we were able to more accurately quantify the changes in tetrapod dietary diversity than previous studies.