Protein in Ancient Reptile Skin Imaged

A nondestructive infrared imaging technique has exposed organic compounds (amides) surviving in 50-million-year-old fossilized reptile skin, revealing intricate chemical patterning that previous methods had overlooked.

Produced by University of Manchester paleontologists and geochemists, the images map the fossilized tissue of the preserved reptile that was discovered in the rocks of the Green River Formation in Utah.

These infrared maps are backed up by the first-ever element-specific maps of organic material in fossil skin generated using x-rays at the Stanford Synchrotron Radiation Lightsource at the SLAC National Accelerator Laboratory in California.

50-million-year-old reptile skin from the Green River Formation in Utah. A team of researchers led by the University of Manchester used modern infrared technology to show that protein residue has survived within the remarkably preserved skin. The small sample is about 8 cm long. (Image: N.P. Edwards)

Chemical details are clear enough that the scientists from the School of Earth, Atmospheric and Environmental Sciences (SEAES) at the University of Manchester are even able to propose how this exceptional preservation occurs.

When the original compounds in the skin begin to break down, they can form chemical bonds with trace metals. Under exceptional conditions, these trace metals act as a “bridge” to minerals in the sediments. This protects the skin material from being washed away or decomposing further.

“The mapped distributions of organic compounds and trace metals in 50-million-year-old skin look so much like maps we’ve made of modern lizard skin as a check on our work, it is sometimes hard to tell which is the fossil and which is fresh,” said Roy Wogelius, geochemist at SEAES. “These new infrared and x-ray methods reveal intricate chemical patterns that have been overlooked by traditional methods for decades.”

The infrared light causes vibrations in the fossilized skin, and a map of where these vibrations occur can be obtained from a fossil by using a trick — a tiny crystal (like an old phonograph record stylus), which moves from point to point in a programmable grid across the surface.

Highly detailed x-ray maps produced at the Stanford Synchrotron Radiation Lightsource of trace metal distributions in 50-million-year-old reptile skin (left) and the molted skin of a gecko lizard (right). Trace metal inventory in the fossil is original to the ancient organism and may be compared to modern species. (Image Courtesy of the Royal Society)

At each point where the tiny crystal touches the fossil, an infrared beam that shines through the crystal reflects off of the crystal base, but a small amount of the beam probes beyond the interface, and if organic compounds are present, they absorb portions of the beam and change the reflected signal.

This allows the team to nondestructively map large fossils that do not themselves transmit or reflect the beam — a revolutionary process for paleontologists.

The University of Manchester team said this imaging technique could even aid in understanding what happens to buried waste over long periods of time.

For more information, visit: www.manchester.ac.uk