A new study suggests that ancient pterosaurs developed the ability to fly at the very beginning of their evolutionary history, around 220 million years ago, despite having relatively small brains similar to non-flying dinosaurs. This rapid evolution contrasts with the gradual process seen in birds. Researchers used CT scans to analyze brain cavities in fossils and their relatives.
Scientists led by Matteo Fabbri, an assistant professor of functional anatomy and evolution at Johns Hopkins University School of Medicine, have uncovered evidence that pterosaurs—giant flying reptiles of the dinosaur era—achieved powered flight explosively early in their lineage. Published on November 26 in Current Biology, the research utilized advanced CT imaging to reconstruct brain structures from pterosaur fossils and their closest relatives.
Pterosaurs, known as powerful airborne predators that could weigh up to 500 pounds and span 30 feet with their wings, represent the first major vertebrate group to evolve powered flight, predating birds and bats. The team focused on the lagerpetid, a flightless, tree-climbing reptile from the Triassic period (242 to 212 million years ago), identified in 2016 and confirmed as a pterosaur relative in 2020. This ancestor already exhibited an enlarged optic lobe, a feature tied to enhanced vision that likely aided the transition to flight.
"The lagerpetid's brain already showed features linked to improved vision, including an enlarged optic lobe, an adaptation that may have later helped their pterosaur relatives take to the skies," said corresponding author Mario Bronzati from the University of Tübingen, Germany.
Pterosaurs themselves possessed enlarged optic lobes but otherwise had brain shapes and sizes distinct from lagerpetids, indicating a sudden burst of adaptations at their origin. Fabbri noted, "Our study shows that pterosaurs evolved flight early on in their existence and that they did so with a smaller brain similar to true non-flying dinosaurs."
In comparison, birds evolved flight more gradually, with expansions in the cerebrum, cerebellum, and optic lobes inherited from earlier relatives. Recent work by Amy Balanoff at Johns Hopkins highlights the cerebellum's role in coordinating bird flight. The study also compared pterosaur brains to those of crocodylian ancestors, troodontids (163 to 66 million years ago), and Archaeopteryx (150.8 to 125.45 million years ago), finding moderately enlarged hemispheres akin to other dinosaurs, unlike the larger brains of modern birds.
Future research will explore internal brain structures to better understand the biological drivers of flight evolution across lineages.