Stanford University scientists said they used an X-ray beam to confirm that Archaeopteryx, the "flying dinosaur," really had feathers.

The scientists in San Francisco identified key chemicals in the dinosaur's 150 million-year-old bones and wings, and in its soft tissue, the San Francisco Chronicle reported Tuesday.

The presence of the chemicals means the feathery impressions in the rock that fossilized Archaeopteryx actually were left by real feathers that had evolved for flight.

The scientists report they now have a tool to investigate fossilized tissues of other prehistoric life forms.

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

"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," said Bergmann.

"The important thing 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," said University of California dinosaur expert Kevin Padian.

The Chronicle reported that some paleontologists insisted the feather material in the fossils was really some other sort of tissue, and they still think that birds are not "modern dinosaurs."