Feathered Dinosaurs Developed Larger Brains Before Actually Taking Flight
August 1, 2013

Bigger Bird Brains Developed Before Dinosaurs Could Fly

[ Watch the Video: CT Scan of Albatross Brain ]

redOrbit Staff & Wire Reports - Your Universe Online

Feathered dinosaurs actually developed the larger brains needed for flight before actually taking to the skies, according to a new study published Wednesday in the journal Nature.

In the study, lead author Amy Balanoff, a research associate at the American Museum of Natural History and a postdoctoral researcher at Stony Brook University, and her colleagues, used CT scans to analyze the skulls of feathered but flightless dinosaurs.

They discovered "the reptiles' brains were much more like that of Archaeopteryx, which is thought to be the first bird and lived 150 million years ago, than had been previously thought," explained Richard Gray, Science Correspondent with The Telegraph. "It means these other flightless dinosaurs may have already taken key evolutionary leaps towards becoming modern birds by developing 'flight ready brains.'"

The brains of birds can be distinguished from other creatures due to "hyperinflation," meaning they are enlarged in comparison to the size of their bodies, the researchers said. This phenomenon is most obvious in the forebrain, which is vital for providing the enhanced vision and coordination required for flight.

However, researchers have been finding more and more evidence feathers, wishbones and other features once considered to be unique to modern birds actually first appeared in non-avian dinosaurs. Now, thanks to Balanoff's team, scientists can now add the hyperinflated brain to that list.

Using CT scanners located at the Museum, Stony Brook University, University of Texas and Ohio University, the study authors were able to craft 3D reconstructions of more than two dozen specimens, including modern birds, the Archaeopteryx (one of the earliest known birds) and closely related non-avian dinosaurs.

As a result, they were able to calculate the total volume of each digital brain case, as well as determine the size of the cerebrum, the cerebellum, the optic lobes, and other major anatomical regions of the brain.

They discovered, in terms of volumetric measurements, the Archaeopteryx was not unique as a transitional species bridging the gap between non-avian dinosaurs and modern birds. In fact, Balanoff and her colleagues learned several other non-avian dinosaurs, including bird-like oviraptorosaurs and troodontids, actually had larger brains relative to their body sizes than the creature once believed to be the oldest known bird.

"Archaeopteryx has always been set up as a uniquely transitional species between feathered dinosaurs and modern birds, a halfway point," Balanoff told Gray. "But by studying the cranial volume of closely related dinosaurs, we learned that Archaeopteryx might not have been so special: 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."

Unfortunately for the Archaeopteryx, this is another blow to its once proud legacy, as Carl Zimmer of National Geographic pointed out on Wednesday. Once viewed as the "crucial fossil for scientists wanting to understand how reptiles evolved into feathered flyers," Zimmer said its importance has been drastically reduced as more studies have been conducted and more fossils have been discovered by investigators.

For the past several decades, experts have agreed birds evolved from a suborder of bipedal saurischian dinosaurs known as theropods, but it has become increasingly uncertain exactly where Archaeopteryx fits into the equation, he said. It could still be closely related to the ancestors of modern birds, or there could be other non-flying theropods which share a closer genetic link with living avians.

"It's possible that the common ancestor of Archaeopteryx and other close relatives of birds had already evolved a more bird-like brain than other dinosaurs. It's also possible that the different linages of dinosaurs that were closely related to birds evolved even bigger brains in parallel," Zimmer said.

"If a bird-like brain was essential for the mental challenge of flying through the air, then these other dinosaurs had what it took for flight," he added. "It will be up to future paleontologists and ornithologists to figure out how flight shapes the brain, and how well other feathered dinosaurs could fly. But Archeopteryx will only be one among many species that they consider when they tackle those questions."