By understanding how pigments change during the fossilization process, researchers may have figured out a way to tell what the color an extinct animal was back when it was still alive. The findings, published in Proceedings of the National Academy of Sciences this week, also revealed the colors of two bat species that lived tens of millions of years ago.
In animals today, organelles called melanosomes contain melanin, the pigment that provides black to reddish-brown hues for hair, skin, eyes and feathers. “Different melanins are found in organelles of different shapes: Reddish melanosomes are shaped like little meatballs, while black melanosomes are shaped like sausages,” University of Bristol’s Jakob Vinther explained in a statement.
To see if this trend holds true for fossils, Vinther and colleagues aged melanin that was extracted from the feathers of nine living species of birds. By replicating the high temperature and high pressure conditions under which fossils form, they could observe the way fresh melanin changes during geologic burial and fossilization. “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,” first author Caitlin Colleary of Virginia Tech explained in a statement. Additionally, the team analyzed the molecular makeup of fossil melanosomes using an instrument called a time-of-flight secondary ion mass spectrometer.
The artificially aged melanin ended up resembling chemical signatures found in well-preserved fossils ranging in age from 20 million to 300 million years. “The correlation of melanin color to shape is an ancient invention,” Vinther said. “We now know how melanin is preserved and we have the methods to confidently detect it.”
The researchers then looked for spherical and oblong-shaped microbodies in the fossils of two extinct bat species, Palaeochiropteryx (pictured above) and Hassianycteris. The team determined that both bats – which lived in Germany between 56 million and 33.9 million years ago – were reddish-brown when they were alive. This is the first time the colors of extinct mammals were described through fossil analysis. Vinther’s team has previously reconstructed the colors of a feathered dinosaur.
"We have now studied the tissues from fish, frogs, and tadpoles, hair from mammals, feathers from birds, and ink from octopus and squids," Colleary said. "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."