Abstract:

The transition from non-avian dinosaurs to birds is one of the most significant events in vertebrate evolution. The factors enabling the diversification of birds likely originated deep within the bird stem lineage. This presentation will highlight how investigating the evolution and ecology of non-avian dinosaurs provides crucial insights into the evolutionary processes shaping living bird diversity. Topics will include an overview of (1) the application of energetic models to predict body size distributions in non-avian dinosaurs and living amniotes, (2) the effects of ontogeny on a phylogenetic reassessment of basal theropod dinosaurs, and an in-depth (3) macroevolutionary analyses of reproductive scaling variation. Analyses of patterns of variation in reproductive traits reveal that across amniotes, species with larger relative brain sizes have larger individual offspring, fewer offspring, or both. Non-avian dinosaurs exhibit smaller, reptile-like egg sizes, and large eggs evolved only shortly before the origin of the bird crown group, associated with an evolutionary increase in relative brain mass. These findings provide insights into the evolutionary pressures shaping reproductive strategies and brain size across amniotes, underscoring the significance of these traits in the broader context of amniote diversification. In a continuation of my work exploring dinosaur ecology, I propose utilizing stable isotope geochemistry and geometric morphometrics to test for flocking behavior and dietary niche partitioning in basal theropods. This integrated approach will provide new insights into the evolutionary origins of key avian behaviors and ecological traits.