Fossil brain scans show pterosaurs evolved flight in a flash

Details of the investigation, which relied on advanced imaging methods to examine the internal brain cavities of pterosaur fossils and received partial support from the National Science Foundation, appeared Nov. 26 in Current Biology.

According to Matteo Fabbri, Ph.D., assistant professor of functional anatomy and evolution at the Johns Hopkins University School of Medicine, the results strengthen the idea that the enlarged brains seen in birds and likely in their ancestors were not responsible for allowing pterosaurs to take to the air.

"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," Fabbri says.

Giant Fliers With Surprising Brain Structure

Fabbri describes pterosaurs as powerful airborne predators of the dinosaur era, capable of reaching 500 pounds in some species and stretching up to 30 feet across the wings. Pterosaurs are recognized as the earliest of the three major vertebrate lineages (in addition to birds and bats) that eventually achieved powered flight on their own.

To investigate how pterosaurs gained this ability and whether their path differed from that of birds and bats, the team examined the reptile's evolutionary history. They looked closely at shifts in the shape and size of the brain over time and focused on the optic lobe, the region involved in vision that has been linked to flight capabilities.

CT Scans Reveal Clues From Early Relatives

Using CT imaging and specialized software that allowed them to digitally model fossilized nervous system structures, the researchers concentrated on the closest known relative of the pterosaur. This animal, the flightless and tree-climbing lagerpetid, was first identified by scientists in 2016 and lived during the Triassic period between 242 and 212 million years ago. In 2020, another team confirmed the lagerpetid's close evolutionary connection to pterosaurs.

"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," says corresponding author Mario Bronzati, a researcher at University of Tübingen, Germany.

Fabbri notes that pterosaurs also had enlarged optic lobes. Outside of this trait, however, he explains that their brain shape and size differed considerably from those of the lagerpetid.

"The few similarities suggest that flying pterosaurs, which appeared very soon after the lagerpetid, likely acquired flight in a burst at their origin," Fabbri says. "Essentially, pterosaur brains quickly transformed acquiring all they needed to take flight from the beginning."

Comparing Pterosaur and Bird Flight

In contrast, modern birds are thought to have evolved flight through a more gradual process. They appear to have inherited several key traits, including expansion of the cerebrum, cerebellum and optic lobes, from earlier relatives before further adapting these regions for flight, Fabbri says. Support for this gradual model comes from 2024 research from the laboratory of Amy Balanoff, Ph.D., assistant professor of functional anatomy and evolution at Johns Hopkins Medicine, which highlights the importance of cerebellum expansion in the origins of bird flight. The cerebellum is located at the back of the brain and helps regulate muscle coordination and other functions.

"Any information that can fill in the gaps of what we don't know about dinosaur and bird brains is important in understanding flight and neurosensory evolution within pterosaur and bird lineages," Balanoff says.

Insights From Fossilized Brains Across Species

The team also examined brain cavities from crococdylians (crocodile ancestors) and early, extinct birds, comparing these structures with those of pterosaurs.

Their analysis showed that pterosaurs had moderately enlarged brain hemispheres, a feature comparable to other dinosaur groups. These include two-legged, bird-like troodontids that lived between the Late Jurassic and Late Cretaceous periods from 163 to 66 million years ago, as well as Archaeopteryx lithographica, the oldest-known bird that lived between 150.8 and 125.45 million years ago. These prehistoric species differ strongly from modern birds, which have significantly larger brain cavities.

Looking Ahead to Future Research

Fabbri says that future progress will depend on understanding how the brain's internal structure, not just its size and shape, enabled pterosaurs to achieve flight. He explains that this will be essential for uncovering the broader biological principles that govern the evolution of flight.

Funding support for this research was provided by the Alexander von Humboldt Foundation, Brazilian Federal Government, The Paleontological Society, Agencia Nacional de Promoción Científica y Técnica, Conselho Nacional de Desenvolvimento Científico e Tecnológico, the European Union NextGeneration EU/PRTR, the National Science Foundation ( NSF DEB 1754596, NSF IOB-0517257, IOS-1050154, IOS-1456503), and the Swedish Research Council

In addition to Fabbri and Bronzati, other scientists who contributed to this research are Akinobu Watanabe from New York Institute of Technology, Roger Benson from the American Museum of Natural History, Rodrigo Müller from Federal University of Santa Maria, Brazil, Lawrence Witmer from the University of Ohio, Martín Ezcurra and M. Belén von Baczko from Bernardino Rivadavia Museum of Natural Science, Felipe Montefeltro from São Paulo State University; Bhart-Anjan Bhullar from Yale University; Julia Desojo from Universidad Nacional de La Plata, Argentina; Fabien Knoll from Museo Nacional de Ciencias Naturales, Spain; Max Langer from Universidade de São Paulo, Brazil; Stephan Lautenschlager from University of Birmingham; Michelle Stocker and Sterling Nesbitt from from Virginia Tech; Alan Turner from Stony Brook University; and Ingmar Werneburg from Eberhard Karls University of Tübingen.