Climatic controls on dinosaur evolution, diversity and biogeography

Dinosaurs were dominant members of terrestrial ecosystems throughout the Mesozoic, yet only recently are studies beginning to illuminate the key role of global climate variation in controlling dinosaur biodiversity, global distribution, and macroevolution. Our work uses statistical, biogeographic, and phylogenetic comparative approaches with comprehensive fossil occurrence data and paleoclimate data from general circulation models to quantitatively examine key hypotheses connecting patterns of dinosaur diversity and evolution with climatic conditions. We examined the impact of climate change in driving early dinosaur evolution across the end-Triassic mass extinction (ETME). Our results demonstrate that the geographic distribution of early sauropodomorphs was constrained by climate and following the ETME, the expansion of climate zones facilitated the geographic expansion of sauropodomorphs and other dinosaurs. Evolutionary model-fitting analyses provide evidence for an important evolutionary shift from cooler to warmer climatic niches during the origin of Sauropoda. This same approach is also revealing the relationship between climatic conditions and dinosaur diversity in the Jurassic to Cretaceous, with implications for our understanding of the origins of sauropod gigantism and the evolution of herbivory. Our results suggest that primary productivity was a key climatic factor in driving sauropod evolution and promoting the evolution of larger body sizes, supporting the hypothesis that gigantism was facilitated by the increasing availability of high quality vegetation. Analyses of dinosaur paleoclimatic niche space show evidence of niche partitioning between herbivorous theropods and ‘traditional’ herbivorous dinosaurs (e.g. sauropods), indicating that climatic changes may have influenced evolutionary innovations related to dinosaur diet. Further work examining the relationship between dinosaur diversity and changes in vegetation using state-of-the-art vegetation models will illuminate the key role played by environmental change in controlling dinosaur diversity and evolution throughout the Mesozoic.