Neuroanatomical convergence between pterosaurs and non-avian paravians in the evolution of flight

The oldest known pterosaurs lived approximately 220 million years ago¹ and were already animals capable of powered flight,² an ability that later evolved independently among paravian dinosaurs, the group that includes living birds and their closest non-avian relatives.³ Flight is a complex locomotory mode that requires physiological adaptations⁴ and a dramatic transformation of the body plan, including changes in body proportions, specialized integument, and acquisition of novel neurosensory capabilities.⁵ Although pterosaurs and birds developed distinct skeletal and integumentary adaptations for flight, they are hypothesized to share neuroanatomical traits linked to aerial locomotion.^6,7,8,9 Here, we use geometric morphometrics and phylogenetically informed analyses to assess the origin and evolution of brain shape and size in pterosaurs, tracing the transformation from their non-volant closest relatives (lagerpetids), and compare their trajectory with that in the dinosaur-bird transition. Pterosaurs have globular brains with moderately enlarged hemispheres, more closely resembling non-avian paravians such as troodontids and Archaeopteryx lithographica than living birds. Whereas birds inherited their basic brain structure from their dinosaurian ancestors,^{10,11,12,13,14,15,16,17} pterosaurs share only the ventrolateralization of the optic lobe with their closest non-volant relatives, the lagerpetids. This suggests that, in contrast to the bird-line archosaurs, where exaptation may have played a central role in the stepwise assembly of the avian brain configuration, brain evolution in pterosaurs seems to have unfolded rapidly at the origin of flight.