SAN JOSE, Calif. – Stanford scientists are using powerful X-ray beams on a rare feathered dinosaur that perished more than 150 million years ago in an effort to see its inner tissues and perhaps someday understand the anatomical split that sent birds and reptiles down different evolutionary paths.

At SLAC’s Stanford Synchrotron Radiation Lightsource in Menlo Park, Calif., the scientists are using the beams to scan one of the world’s most valuable fossils, delicately transported by pickup truck from its home in a Wyoming dinosaur museum.

The X-rays, generated by a particle accelerator, cause tiny amounts of a dozen chemicals to glow without harming the ancient fossil, believed to be the earliest representation of a bird.

Scientists hope the chemicals will correlate with organs, blood vessels and other interior parts of the creature, called archaeopteryx, or “ancient wing,” which has both reptilian and avian features. When compared with scans of other fossils, such anatomical information could help explain evolutionary changes.

“What we are hoping is that we will learn more information than just what you can see with your eyes,” said Uwe Bergmann, staff scientist at SSRL. “The body decays, but the chemical elements – silicon, calcium, potassium, iron, all the chemicals which make up living animals – some of them will be preserved.”

What is visible in stone is just a faint imprint of a physical feature, such as a feather, he said. But soft tissues have unique chemical characteristics that aid in their identification. For instance, calcium would suggest a bone; iron might mean blood. By measuring the distribution of these chemicals in a fossil, it may be possible to re-create anatomy – and hence, evolution.

The latest effort is not the first time the intensely bright X-rays, emitted by particles circulating near the speed of light, have been used to solve ancient mysteries. In 2005, they helped decipher a 10th century manuscript that contained rare copies of works by the mathematician Archimedes.

But the tool brings new possibilities to our understanding of archaeopteryx. Some of the 10 known specimens of the creature have previously undergone extensive visual analyses and even CT scans, but nothing as comprehensive as the X-ray imaging researchers are utilizing at SSRL.

Archaeopteryx holds a unique place in history. When the first specimen was discovered about a century and a half ago, just a year after Charles Darwin published “On the Origin of Species,” its shared reptile-avian features provided the strongest evidence yet for the theory of evolution.

The Jurassic-era fossil has a beaklike mouth, winglike forelimbs, long feathers and feet for perching. But it also has reptilelike teeth in its jaws, claws on its fingers and a long tail. A little over a foot long, it could probably fly – but without the grace of modern birds.

“If you want to find a single fossil which is a missing link in the evolution of dinosaurs into birds, this is it,” said University of Manchester paleontologist Phil Manning. “It’s a bird with sharp teeth, claws and a long bony tail. If you were to freeze-frame evolution, you would end up with archaeopteryx.”

Millions of years ago, the creature under study at SSRL sank to the bottom of a shallow lagoon and became entombed in limestone near Solnhofen, Germany. It is now owned by the Wyoming Dinosaur Center, located in Thermopolis, Wyo.

Last weekend, scientists packed the creature into a small wooden box, loaded it into the cab of a white Chevy Silverado truck and drove the 850 miles to SLAC. Upon its arrival Monday night, it was moved into a helium-filled tray for analysis.

The creature heads back home after the weekend. Then, for SLAC scientists, the real work begins.

“We could build up a library of samples,” Bergmann said. “We’d start out with parts of creatures that are still in existence – let’s say, a bird’s feather, or maybe the shells of turtles or skins of lizards. Then we could do more fossils. Once you have all that information together, it’s possible to compare.”

“I don’t see that one measure of archaeopteryx will provide all the answers,” he said. “But if we work hard and very broadly, studying lots of samples, I think we’ll be in for a surprise.”

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