Dinosaur-Era Bird Could Fly, Brain Study Says

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"The question is, once it was airborne, was it just a glider, a weakly flapping flyer, or a strong flyer?" he said.

To answer this question, Milner joined Patricio Dominguez Alonso of Universidad Complutense de Madrid in Spain, and other colleagues. They applied modern imaging techniques to the first discovered Archaeopteryx fossil. One of just six in existence, the specimen is housed in London's Natural History Museum.

The team used x-ray technology called computed tomography. In this technique a computer combines a series of flat cross-sectional images to create a three-dimensional model of a body structure. The process allowed Milner and her colleagues to look inside the animal's tiny braincase and make a 3-D reconstruction of its brain and inner ear.

Earlier, Witmer and others had performed a similar study on fossils of the flying reptiles called pterodactyls, which are not related to Archaeopteryx. Published last year in Nature, the pterodactyl study showed that these reptiles had many of the same brain features as modern birds. The report suggested that certain brain features are minimum requirements for the development of flight.

Birdbrained

The new analysis by Milner and her colleagues shows for the first time that Archaeopteryx's brain had many of the features that birds use to hone their flying abilities today.

Archaeopteryx's brain was smaller, in proportion to its body size, than the average bird brain today. The ancient creature's brain, though, was around three times as big as the brains of comparably sized reptiles of the same time period.

Furthermore, the way Archaeopteryx's brain was organized was also very birdlike, according to the study. The cerebral hemispheres and other parts of the brain involved with vision and movement were relatively large. And the size and shape of Archaeopteryx's inner ear hint that the animal had a keen sense of balance and spatial awareness.

"Though less sophisticated than modern birds, Archaeopteryx appears to have had all the neurosensory mechanisms necessary for flight," Milner said. "It probably wasn't an endurance flyer but was certainly capable of proper, powered, flapping flight."

Finding that the brain is so sophisticated in this species is surprising. Though Archaeopteryx is the oldest bird known from the fossil record, the discovery suggests that flight must have begun long before and therefore much further back in time than expected, Milner said.

"Ground-dwelling animals live for the most part in two-dimensional space, but flying animals live very much in three dimensions," Ohio University's Witmer said. "So the ability to sense your position in space and use that information to make constant adjustments needs to be very well developed."

These pressures lead to the development of certain parts of the brain in both birds and pterodactyls, he said.

Analyzing the brains of some meat-eating dinosaurs for similarities to Archaeopteryx's brain may allow researchers to test a highly controversial theory that some dinosaurs are the "secondarily flightless" descendents of Archaeopteryx, Witmer said.

Some researchers have suggested that Archaeopteryx could in fact be the ancestor of a group of dinosaurs that includes velociraptors, made famous by Jurassic Park. Those carnivores have many similarities to Archaeopteryx but appear later in the fossil record.

The study by Milner and her co-authors will now "allow us to tease apart the transition between birds and dinosaurs in a whole new way," Witmer added.

For more dinosaur-era news, scroll down.

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