Studying flight capability in dinosaur brains

Archaeopteryx, a dinosaur the size of a turkey, has often been viewed as the Kitty Hawk of bird flight. Around 150 million years ago, this early bird changed the way dinosaurs moved around in the world, from running, climbing, slithering, leaping or swimming to soaring through the air.

This celebrated species glided above the spike-backed Stegosaurus and the long-necked Brachiosaurus of the Jurassic period.

Feathers, hollow bones and a brain capable of processing information to make flight possible all came together, distinguishing Archaeopteryx from its land-limited cousins.

And yet, recent research suggests that while this creature may have been among the first to fly, it was likely not the first to have the brain power to make flight possible.

Led by Stony Brook University research instructor Amy Balanoff, a team of scientists used CT scanners to examine the brains of older dinosaurs that are considered the distant cousins of Archaeopteryx, modern birds and Archaeopteryx itself.

While the researchers weren’t able to look at the brains themselves, they were able to study the relative size of different areas by looking at the skulls. It is like examining the outline of a hard suitcase stuffed to capacity. By looking at different compartments, scientists could see what was there and how much space it filled. In the scientists’ case, they used CT scanners to determine the volume of different brain regions.

Archaeopteryx, it seems, wasn’t alone among its contemporaries and even, in some cases, its predecessors in having a bird-like brain capable of flight.

“This feature that we thought was more restricted in its nature now needs to be expanded to include more groups,” said Balanoff, who is also a research associate in paleontology at the American Museum of Natural History.

Creatures that have an enlarged or hyperinflated forebrain, which is important in providing superior vision and the coordination necessary for flight, include oviraptorosaurs and troodontids.

This study “establishes that the evolutionary origin of the relatively large brain of Archaeopteryx was not the result of nature selecting for flight capability,” explained Gabriel Bever, an assistant professor of anatomy at the New York Institute of Technology, a co-author on the study and Balanoff’s husband. “Large brains evolved prior to flight and were simply inherited by Archaeopteryx and other early birds.”

This, Bever, continued, is an important example of evolution taking existing structures and assembling them in a way that moves the group along its evolutionary trajectory.

The forebrain is what really expanded along bird lineage, Balanoff added. That part of the brain is larger among species with stronger cognition.

“A lot of characteristics that we’ve associated with flying birds are not unique to flying birds,” she said. “They show up much earlier with nonavian dinosaurs.”

Balanoff described the finding as further evidence of a random process, rather than being directional.

She said the result wasn’t surprising, given that other bird-like features, like feathers and hollow bones, were present before Archaeopteryx. One of the first-known dinosaurs capable of powered flight, Archaeopteryx was discovered only two years after Darwin predicted in “The Origin of Species” that there should be “transitional fossils,” Balanoff said.

The latest findings were published in the journal Nature in July of this year.

Balanoff joined SBU this summer and will be one of several teachers in a gross anatomy class for medical students this fall. “Paleontologists in general are often found in anatomy departments, teaching human gross anatomy,” she said.

Balanoff and Bever met when they were at the University of Texas, when Balanoff was working on her master’s degree and Bever was conducting research for his doctorate.

Balanoff didn’t grow up in Texas with a burning desire to uncover more information about dinosaurs or dinosaur brains.

“My father [Howard Balanoff, a professor at Texas State] is a political scientist. I was thinking more along the lines of politics,” she said.

As a freshman in college at the University of Texas, however, she took a course with Timothy Rowe — a collaborator on the Nature article — and switched her major to geology.

Going forward, Balanoff plans to focus on an area of the modern bird brain called the wulst, which may have a similarity to a structure in the brain in the Archaeopteryx.

“The scientific importance of the wulst to our understanding of neurological evolution,” predicted Bever, “will eventually far outweigh its importance as a systematic character supporting Archaeopteryx as an early bird.”