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Tuesday, June 15, 2010

The chemical make-up of fossils

Archaeopteryx is the best-known example of the transition from land-dwelling dinosaurs to birds. Over the years, some beautiful specimens of Archaeopteryx have been found which clearly show features of both birds (feathers) and dinosaurs (teeth and bony tails). Now Roy Wogelius and his team from England’s University of Manchester and from the US Department of Energy's SLAC National Accelerator Laboratory have added chemical evidence to the proof that the animals were related to birds.

The scientists examined the Thermopolis Archaeopteryx, a very well preserved specimen that was first described in 2005. This specimen has been subjected to many noninvasive types of analysis, including CT scans. This time, the researchers used the Stanford Synchrotron Radiation Lightsource (SSRL), located at the SLAC National Accelerator Laboratory to create hair-thin, extremely bright x-ray beams. These x-rays allowed the scientists to determine the chemical make-up of the fossil.

The geochemists discovered that the feathery impressions visible in the fossil actually contain organic material, including chemical signatures of modern feathers, such as phosphorous and sulfur. Those chemicals were not found in the surrounding rock, disproving the possibility that the chemicals simply leached into the animal as it fossilized.

The authors expect this new ability to detect trace metals and chemicals in fossils to revolutionize paleontology.

Main panel: false color composite showing location of phosphorous, silicon, sulfur and iron.

Top left panel: anaglyph made from phosphorus and iron showing detail of skull and manus claw

Top right panel: phosphorous anaglyph showing fine detail of the skull.

Image created by K.G. Huntley from data produced at the Stanford Synchrotron Radiation Lightsource.