In the fossil of an ancient squid, X-rays generated by the Stanford Synchrotron Radiation Lightsource trigger chemical traces of the animal’s body left behind in the limestone; at right, the tentacles are clearly visible. The same technology is being used to learn more about Archaeopteryx, the famous bird-dinosaur hybrid found in Germany about 150 years ago. (Credit: SLAC)

STANFORD (US)—High-powered X-rays of the famous “dinobird” fossil could reveal unseen details about the evolutionary hybrid that died some 150 million years ago. Generated by the Stanford Synchrotron Radiation Lightsource (SSRL) in California, the X-rays cause chemical elements to glow, exposing the ghost of soft tissue or feathers.

In addition to offering a new view of a long-extinct animal, this work may also reveal more about fossilization itself and how ancient organisms evolved.

“What you normally can’t see are the chemical elements from the original organism that might still be present in the fossil,” says SSRL senior staff scientist Uwe Bergmann. “Using X-ray fluorescence imaging, we can bring these elements to light, getting a better look at the fossil and learning more about the original animal.

“These X-rays work a thousand times better than what you could do with a commercial X-ray machine. Only a synchrotron can do this,” Bergmann explains.

Recently the famous fossil—the Thermopolis specimen of Archaeopteryx lithographica—made its way by truck from the Wyoming Dinosaur Center to the SSRL, a building-sized device created for physics research. When the fossil was discovered in Germany during the 19th century, it was celebrated as proof of Charles Darwin’s then-new theory of evolution.

“If you want to find a single fossil that is a missing link in the evolution of dinosaurs into birds, this is it,” says University of Manchester paleontologist Phil Manning, a member of the research team. “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.”

It was brought to London soon after Darwin published On the Origin of Species in 1859. With perfect timing, the old bones played a major role in the controversy Darwin had stirred up.

“This fossil was the savior of Darwin,” Manning says. “As soon as it arrived in London, all of Darwin’s supporters realized that this was an intermediate animal, an evolutionary freak that they needed to study. It was halfway between dinosaur and bird. This is the single most important fossil in paleontology for that simple reason.

“It was used to beat the living daylights out of the nonsense which had been put forward as to the reason for why animals were present on this planet. Here, Darwin’s theory of descent with modification was hammered home with this one example of transitionary form, of an animal between dinosaur and bird.”

The fossil research is one example of how SSRL is shining new light on fields as diverse as paleontology, medicine, and the history of mathematics. SSRL’s hair-thin X-ray beam has been used, for example, to make visible the hidden writing in a medieval copy of a mathematical treatise from the Greek mathematician Archimedes. Tuned to specific energies, the X-rays produced images of phosphorus and calcium from the ink used on the papyrus document, which had been covered with paint.

Earlier this year, at the request of Stanford library officials and an academic researcher, the laser-like X-ray beam was used to scan a score by the Italian composer Luigi Cherubini (1760-1842). Portions of the work had been covered over with carbon-black ink, but after the scan, “the researcher was able to look right through the ink and read the score,” says Mary Miller, a Stanford preservation librarian.

“This is the very infancy of this new scientific method,” says paleontologist Peter Larson of the Black Hills Institute in South Dakota. “We don’t even know enough about this to know the right questions to ask yet. All of a sudden, we can look at fossils in a very different and new way.”

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