Dinosaur Brains Flight-ready Long Before They Took to the Air: A Study

Dinosaurs evolved the brain power for flight long before they took to the air, new evidence presented in the journal Nature suggests.

Contrary to the cliche, a "bird brain" describes a relatively enlarged brain with the capacity required for flight. However, based on high-resolution X-ray computed tomographic (CT) scans, researchers found that at least a few non-avian dinosaurs had brains as large or larger than Archaeopteryx, one of the earliest known birds, indicating that some dinosaurs already suspected of flight capability would have had the neurological tools to do so.

"Archaeopteryx has always been set up as a uniquely transitional species between feathered dinosaurs and modern birds, a halfway point," lead author Amy Balanoff, a research associate at the American Museum of Natural History and a postdoctoral researcher at Stony Brook University, said in a press release. "But by studying the cranial volume of closely related dinosaurs, we learned that Archaeopteryx might not have been so special."

This hyperinflated brain, necessary for the superior vision and coordination required to fly, is just one more item to add to the list of features once considered exclusive to modern birds, such as feathers and the presence of wishbones, but that are now known to have first appeared in non-avian dinosaurs, according to the study's authors.

In all, the researchers peered inside the braincases of more than two dozen specimens, including modern birds, Archaeopteryx and closely related non-avian dinosaurs like tyrannosaurus. By stitching together the results, the scientists were able to create three-dimensional reconstructions of the skulls' interiors.

Among those things they calculated, was the total volume as well as the size of each of the brain's major anatomical regions.

"The story of brain size is more than its relationship to body size," said coauthor Gabriel Bever, an assistant professor of anatomy at the New York Institute of Technology. "If we also consider how the different regions of the brain changed relative to each other, we can gain insight into what factors drove brain evolution as well as what developmental mechanisms facilitated those changes."

In doing so, the researchers found that, in terms of volumetric measurements, Archaeopteryx is not in a unique transitional position between non-avian dinosaurs and modern birds after all. In fact, several other non-avian dinosaurs sampled, including bird-like oviraptorosaurs and troodontids, boasted even larger brains relative to body size than it did.

"If Archaeopteryx had a flight-ready brain, which is almost certainly the case given its morphology, then so did at least some other non-avian dinosaurs," Balanoff said.

Finally, the researchers examined the neurological structure important to flight in modern birds called the wulst, which is used in information processing and motor control. As a result, the team identified an indentation in the digital brain cast of Archaeopteryx they believe might be homologous to the wulst seen in living birds. Moreover, they report, this indentation is not found in non-avian dinosaurs with bigger brains than Archaeopteryx, presenting the research team with a new question to explore in the future.