The discovery will open the way for research into the evolution and function of colour in animals and is regarded as such a significant breakthrough that it was reported yesterday by the international journal Cell Biology.
The colourless fossil of a Spanish snake was analysed by a team of UCC scientists led by Maria McNamara, who found that, depending on their condition, some fossils can retain evidence of skin colour.
The scientists discovered fossilised snakeskin maintained the unique shapes of different types of pigment cells, which would have created yellows, greens, blacks, browns, and iridescence while the reptile was alive.
The pigments themselves are now decayed, but with the cell shapes, specific to each kind of pigment had mineralised, providing enough information to reconstruct their colours. In the case of the Spanish snake the team were able to determine it was green and black.
“When you get fossil tissues preserved with this kind of detail, you’re just gobsmacked when you’re looking at it under the microscope,” said Dr McNamara, a palaeobiologist at the UCC’s School of Biological, Earth, and Environmental Sciences. “I was astounded. You almost can’t believe what you’re seeing.”
She first came across the fossilised snake while conducting her PhD research on fossils at site in Leros, Spain, but only recently analysed the specimen.
Her team discovered the skin cells when viewing the fossil under a high-powered scanning electron microscope and then matched the shapes up with pigment cells in modern snakes to determine what colours they might have produced.
“For the first time, we’re seeing that mineralised tissues can preserve evidence of colour,” said Dr McNamara.
The researchers found the fossilised snakeskin had three types of pigment cells in various combinations: Melanophores, which contain the pigment melanin; xanthophores, which contain carotenoid and pterin pigments; and iridophores, which create iridescence. The snake was green and black, with a pale underside — colours that aided in daytime camouflage.
“Up until this discovery, the only prospect for skin colour being preserved in fossils was organic remains related to melanin,” said Dr McNamara. “But now we know colour can be preserved even for tissues that are mineralised.”
This discovery opens the door for reanalysis of many other fossils.