For the first time, paleontologists have been able to analyze fossils and derive the colors of extinct mammals.
Virginia Tech and University of Bristol scientists analyzed microscopic structures in the fossils of two bats that lived 50 million years ago and determined what their coloring would have been in life -- a reddish-brown.
The researchers say the technique can be used on well preserved fossils up to 300 million years old. The finding, then, could help scientists figure out the real colors of a great many extinct species whose coloring has until now only been guessed at.
The structures the team studied in the bat fossils were once believed, in a long-running debate, to be fossilized bacteria. But the researchers say they are actually melanosomes, cell structures that hold melanin, the substance that brings color to skin, hair, feathers and eyes.
The study's senior author, University of Bristol paleontologist Jakob Vinther, has worked with fossil melanosomes since 2008, when he first described them from a fossilized feather, a discovery that led to the identity of colors in some dinosaurs. And now mammals are having their turn at a kind of color restoration.
Vinther and his colleagues found that different melanosome shapes indicate different colors. "Reddish melanosomes are shaped like little meatballs, while black melanosomes are shaped like little sausages," he explained in a press release.
"This means that this correlation of melanin color to shape is an ancient invention, which we can use to easily tell color from fossils by simply looking at the melanosome's shape," Vinther said.
The team also determined that fossil melanosomes are chemically distinct.
"We were able to see how melanin chemically changes over millions of years, establishing a really exciting new way of unlocking information previously inaccessible in fossils," Virginia Tech doctoral student Caitlin Colleary, the study's lead author, explained.
Learning about ancient animal colors is important, said Massachusetts Institute of Technology Earth Science Professor Roger Summons, who was not involved in the research. "For complex animal life, color is a factor in how individuals recognize and respond to others, determine friend or foe, and find mates," he said. "This research provides another thread to understand how ancient life evolved."
"We have now studied the tissues from fish, frogs, and tadpoles, hair from mammals, feathers from birds, and ink from octopus and squids," said Colleary. "They all preserve melanin, so it's safe to say that melanin is really all over the place in the fossil record. Now we can confidently fill in some of the original color patterns of these ancient animals."
The team's work has just been published in the journal Proceedings of the National Academy of Sciences.