Abstract
The origin of pterosaurs, the first vertebrates to achieve powered flight, is poorly understood, owing to the temporal and morphological gaps that separate them from their closest non-flying relatives, the lagerpetids. Although both groups coexisted during the Late Triassic, their limited sympatry is currently unexplained, indicating that ecological partitioning, potentially linked to palaeoclimate, influenced their early evolution. Here we analysed pterosauromorph (pterosaur + lagerpetid) palaeobiogeography using phylogeny-based probabilistic methods and integrating fossil occurrences with palaeoclimate data. Our results reveal distinct climatic preferences and dispersal histories: lagerpetids tolerated a broader range of conditions, including arid belts, enabling a widespread distribution from the Middle to early Late Triassic. Conversely, pterosaurs preferred wetter environments, resulting in a patchier geographical distribution that expanded only as humidity increased in the Late Triassic, probably following the Carnian Pluvial Event. This major environmental disturbance, potentially driven by changes in CO(2)-related thermal constraints and/or palaeogeography, appears to have had a key role in shaping early pterosauromorph evolution by promoting spatial segregation and distinct climatic niche occupation.