The true colors of a 10 million-year-old snake have been revealed for the first time ever thanks to an innovative study led by paleontologists from the University College Cork in Ireland.
Nearly all fossils are devoid of their original color. Previously, researchers relied on melanin - a pigment that is linked to the color of skin, eyes and hair - to determine the color of fossilized remains. However, this method is limited to just brown, black and muddy red color pigments, as no other pigments have been shown to survive fossilization.
In the latest study, researchers analyzed a 10 million-year-old snake fossil found preserved in calcium phosphate. While the snake's pigments are no longer there, the cells where the pigments were lying are fully intact.
Fossilized snakeskin contains different types of cells shaped specifically based on whether they were yellow, green, black, brown or iridescent pigments. Advances in scanning technology allowed researchers to analyze these unique cells, revealing what the animal would have looked like when it was alive.
"When you get fossil tissues preserved with this kind of detail, you're just gobsmacked when you're at it under the microscope," said Maria McNamara, a paleobiologist at University College Cork. "I was astounded. You almost can't believe what you're seeing."
The snake was originally unearthed from a fossil site known as Libros in Spain. It was not until recently, however, that McNamara and her team were able to analyze them in great detail, using a high-powered scanning electron microscope. Researchers then matched their findings to the shapes of pigment cells found in modern snakes to determine what colors the fossilized cells might have produced.
"For the first time, we're seeing that mineralized tissues can preserve evidence of color," McNamara added.
Snakeskin contains three different types of pigment cells: iridophores, xanthophores and melanophores, each of which have different type of granules that correlate to different colors. But the distribution of these pigment cells varies across the body and result in different color patterns in different regions.
Based on the multiple structures they spotted, researchers suggest that the underside of the snake was pale and creamy, while its back and sides were likely green with brown-black and yellow-green blotches. Having this color pattern is believed to have aided in daytime camouflage.
"Up until this discovery, the only prospect for skin color being preserved in fossils was organic remains related to melanin," McNamara explained. "But now that we know color can be preserved even for tissues that are mineralized, it's very exciting."
The researchers also suggest that other similar fossils may yield similar clues, including aspects of extinct animals' behavior and evolution.
"It'll mean re-evaluating a lot of specimens that might have been overlooked," McNamara added.
Their study was recently published in the journal Current Biology.