Study shows dinosaur could fly
New evidence gathered from a major advance in X-ray imaging of fossils has established that the winged dinosaur called archaeopteryx could actually fly and had much the same sense of balance and sharp vision found in today's birds. And while its senses were a bit more primitive than its modern evolutionary descendants, the pigeon-sized archaeopteryx was certainly well equipped to navigate over land and forests looking for distant prey, scientists say. The evidence comes from a remarkable technology that allowed University of Texas researchers to scan in three dimensions deep inside the brain case of the priceless 247-million-year-old fossil dinosaur and reveal the workings of its most critical sense organs.
The technique -- somewhat similar to computerized CAT scans that doctors use to examine the brains and bodies of their patients -- has resulted in the first complete 3-D models of the interior of the ancestral bird's brain, and an equally detailed cast of its inner ear. Although both casts together are no larger than the end of a human's little finger, they have been enlarged sevenfold to reveal minute details of the animal's crucial sensory system, according to Timothy B. Rowe, a Texas paleontologist who studies the evolution of vertebrate animals.
Rowe, along with Angela Millner, the fossil's curator at the British Museum, and their colleagues are publishing the results of their work in today's issue of the journal Nature. The 1861 discovery of seven weird birdlike fossils -- later named archaeopteryx -- in a Bavarian limestone quarry touched off a huge scientific and popular uproar in Europe because Darwin's "Origin of Species" had just been published, and the mysterious origins of flight swiftly rivaled apes in the outcry over evolution. Ever since then, some scientists have doubted that archaeopteryx could even fly at all. But Kevin Padian, a noted dinosaur expert at UC Berkeley, said the report by Rowe's group clearly confirms for the first time that the feathered member of the dinosaur tribe could really fly. "It may not have been a strong flier, but clearly it was a flier," Padian said in an interview.
"Small as it was, its brain was substantially bigger than a dinosaur brain, and the structure of the brain, its optic lobes and its sensory-motor lobes also show that it clearly was not stupid -- so the term bird-brain should be a compliment for anybody," Padian said. To apply the new 3-D scanning technology to the study of archaeopteryx, Rowe and his colleagues received a National Science Foundation grant to bring Millner and the British Museum's tiny fossilized archaeopteryx brain to Rowe's laboratory in Austin. Millner carried the priceless bit of stone aboard a plane wrapped in tissue and encased in a box hidden in her shirt pocket, Rowe recalled in an interview.
The entire body of the fossil, feathers and all, is known as the London Specimen. It is by far the best-preserved of all the archaeopteryx specimens ever found, and its tiny brain and inner ear are so precious, Rowe said, "that I hardly dared hold it because it was so much like handling some sacred object. " Like standard medical computer tomography scanning, Rowe's X-ray device took images of 1,300 "slices" of the fossil bones and assembled them into one 3-D image. It then enlarged and printed the image with a device much like a standard ink-jet printer but which sprayed out 1,300 jets of wax instead of ink until, layer by layer, it built up a full wax model of the fossil with every detail intact. The images clearly show the bone structures that in life contained the bird's eye sockets, its blood vessels and the canals of its inner ear where its sense of balance kept its flight stabilized as it navigated from side to side and soared, Rowe said. By reconstructing the interior of the fossil's brain case in such detail for the first time, Rowe and his colleagues said, they were able to determine the volume, weight and form of the long-vanished soft tissue inside the animal's skull. Details of its inner ear also reveal how well archaeopteryx could hear, they said.
"Both an aerodynamic wing and a powerful central nervous system are integral to powered flight," the scientists concluded in their report -- and from their fresh evidence archaeopteryx certainly had both, Rowe said. Rowe's laboratory now maintains an entire computer library called Digimorph containing hundreds of 3-D images of birds, mammals, reptiles, fish and even dinosaurs, both common and obscure. It is accessible on the library's public Web site at www.digimorph.org
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