U. PENNSYLVANIA (US) — Trace metals in fossils are offering clues about the pigmentations of creatures dead for more than a hundred million years.
Researchers have long studied fossils of the earliest birds, including Confuciusornis sanctus, which lived 120 million years ago and was one of many evolutionary links between dinosaurs and birds, and Gansus yumenensis, which is considered the oldest modern bird and lived more than 100 million years ago.
“Every once in a while we are lucky enough to discover something new, something that nobody has ever seen before,” says Roy Wogelius, a geochemist at the University of Manchester and the paper’s lead author.
The team’s discovery, reported in the journal Science, is rooted in a new technique, using technology based on synchrotron radiation to identify copper-bearing molecules in the fossilized feathers of these ancient birds.
“There is an intimate relationship between trace metals and organics. When you’re getting a good suntan, melanin forms in your skin. There are many forms of melanin, and some are found in the dark feathers of birds, but copper is always bound into its structure,” says Philip Manning, adjunct professor at the University of Pennsylvania.
“You can see this in living animals, but it’s only since we’ve been using a synchrotron—a vast accelerator that generates intense X-rays a hundred million times brighter than the sun—that we can see the chemical detail in fossils and show that the copper complexes we found were originally part of the animal.”
Metallic compounds can survive in fossils for hundreds of millions of years because they are unpalatable to microorganisms. But to distinguish the copper that was bound in melanin with copper that might have been geochemically produced requires the precision that only a tool like the synchrotron can provide.
By measuring the energy released by atoms when they are bombarded with high-powered X-rays, researchers can get an accurate picture of the molecules in which they reside.
“We’re able to map absolute quantities, to parts-per-million levels in discrete biological structures, which we compare with living organisms and see they are comparable,” Manning says.
The new technique paints a richer picture of the lives of these ancient creatures.
“While our work doesn’t yet allow you to diagnose color, you can get the concentration and distribution of pigments,” Dodson says. “In other words, you can work out monochrome patterns, which may tell us something about camouflage or other traits relevant to natural selection of the species.”
“If we could eventually give colors to long extinct species, that in itself would be fantastic,” says co-author Uwe Bergmann of Stanford University.
“But synchrotron radiation has revolutionized science in many fields, most notably in molecular biology. It is very exciting to see that it is now starting to have an impact in paleontology, in a way that may have important implications in many other disciplines,”
Further research with this technique is expected to fully diagnose color via fossil chemistry, among other applications.
“This synchrotron research is really important as it gives us the first clue to really understanding what happens with organic debris when you bury it in the ground,” Manning says.
“For example, there are huge implications for understanding the mass transfer of buried waste; trace metals can be bad if you get too much of them, so we can spatially map and give images of exact loadings of these metals in both living and extinct organisms.
“No one else can do this. It’s not just contributing to a field, it’s creating a whole new discipline.”
Support for the research was provided in part by the United Kingdom’s National Environmental Research Council.
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