Early Jurassic origin of avian endothermy and thermophysiological diversity in Dinosauria

A fundamental question in dinosaur evolution is how they adapted to substantial long-term shifts in Earth System during the Mesozoic and when they developed environmentally independent, avian-style acclimatization due to the evolution of an endothermic physiology. Combining fossil occurrences with macroevolutionary and paleoclimatic models, we unveil distinct evolutionary pathways in the main dinosaur lineages: ornithischians and theropods diversified across broader climatic landscapes, trending toward cooler niches. An Early Jurassic shift to colder climates in Theropoda suggests an early adoption of endothermic thermophysiology. Conversely, sauropodomorphs exhibited prolonged climatic conservatism associated with higher thermal conditions. Paleo-biome mapping emphasizes temperature, rather than plant productivity, as the primary driver of this pattern, suggesting poikilothermic physiology with a stronger dependence on higher temperatures in sauropods since the Early Jurassic. ### Competing Interest Statement The authors have declared no competing interest.