High-energy X-ray confirms feathered dinosaur

Scientists at Stanford have aimed a high-energy X-ray beam at a fossil specimen of Archaeopteryx, the famed “flying dinosaur,” and identified key chemicals in the creature’s 150-million-year-old bones and wings, and even in its soft tissue.

The chemicals, the scientists said, settled definitively that the feather-like impressions in the rock that entombed Archaeopteryx truly were left by real feathers evolved for flight.

By chemically separating the creature’s bony feathers from the chemicals in the rock around it, the scientists report they have found a powerful new tool to explore tissues long entombed in fossils of many other ancient life forms.

A report on the work was published Monday in the Proceedings of the National Academy of Sciences by a group led by Ewe Bergmann, a physicist at the Synchrotron Radiation Light Source SLAC National Accelerator Laboratory.

The powerful X-rays from the light source, beamed directly at the fossil bird embedded in its rocky shroud, mapped the extremely faint presence of chemicals such as sulfur and phosphorus in what was once the creature’s feathers and soft tissue, and traces of zinc and copper retained in its bones.

The first Archaeopteryx fossil was discovered in Germany in 1855, and only nine more have been found since. The one analyzed at Stanford was hand-carried secretly by car from the Wyoming Dinosaur Center in Thermopolis, Wyo., a year ago, where it is on display and is known as the Thermopolis specimen. The analysis took only two days, Bergmann said, before it was just as carefully returned.

“The sensitivity of the light source can tell us so much about the chemical composition of whatever we shine it on that we’re really excited about the future of what we can do,” Bergmann said.

“The important thing,” said Kevin Padian, the noted dinosaur expert at UC Berkeley, “is the finding of original feather material in the specimen, plus establishing that you can get good signals of things like iron, sulfur and phosphorus from fossils hundreds of millions of years old.”

In an interview, Padian said he hoped that Bergmann’s team would be able to shine their intense light on the “Liaoning fossils” – the feathered dinosaurs discovered more than 10 years ago in China that sparked a controversy.

The imprint of those feathers on the rocks in which they were fossilized helped establish as fact that dinosaurs are the ancestors of modern birds. But a few die-hard paleontologists insisted the feather material in the fossils was actually some other kind of tissue, and they still deny that birds are “modern dinosaurs.”

Padian’s wish is already in Bergmann’s plan. He plans to work with Chinese scientists to focus the synchrotron light source on some of those feathered fossils to analyze their chemistry.

One of Bergmann’s colleagues on Monday’s report is Roy Wogelius, a geochemist at the University of Manchester in England. In a phone interview Monday, he described it as “amazing” to think that even soft tissue can show its chemical nature after 150 million years.

“It should clearly be possible to use the same X-ray light source to determine the chemicals in the soft tissues in fossils of even older organisms,” he said – perhaps the early invertebrates that evolved without any bony structures at all.

David Perlman
E-mail David Perlman at dperlman@sfchronicle.com.