Structures In Fossil Dinosaurs Confirmed To Be Animal Pigments

The fossil of Anchiornis huxleyi, a bird-like dinosaur, preserves the details of feathers, and even pigment structures. Credit: Thierry Hubin/RBINS
Josh Davis 27 Aug 2015, 10:33

Debate has been raging over the past few years as to whether it is possible or not to determine the color of an animal from its fossils. It all centers on whether pigment-containing structures in animal cells can indeed be observed, or if the scientists are actually just looking at preserved bacteria that were feeding on the dead animal before it was fossilized. Well, now it seems that the debate can be settled once and for all: the pigment of fur and feathers can be deduced from the fossils.

One of the structures found in skin, feathers, and fur that is known to contain common color-producing pigments – called melanin – is known as a melanosome. Only within the last few years have scientists suspected that certain structures in well-preserved fossils that were originally thought to be microbes might actually be melanosomes. However, there has been a lot of debate about their legitimacy.

“This paper is the final piece of evidence, the final nail in the coffin that really shows that these microbodies are indeed melanosomes and not microbes,” Ryan Carney, co-author of the study published in Scientific Reports, explained to IFLScience. “We detected molecular melanin in the feathers of the dinosaur Anchiornis, and this is important because it allowed us to tie this chemical evidence to the actual microscopic structures which are melanosomes.”

The new research, carried out by scientists at Brown University, decided to see if they could settle the debate using chemistry. They looked to see whether they could find traces of the animal “eumelanin” pigment by putting small samples through a secondary ion mass spectrometer and infrared reflectance spectroscopy in order to determine the molecular signature of the fossilized structures. They then compared this with the molecular signature of modern-day animal eumelanin.

They found them to be virtually identical. “Now that we know that they are actually melanosomes,” said Carney. “And now we know we find melanin and melanosomes in a variety of tissues – from the eye, the skin and from the feathers. And in a variety of taxa, from fish, reptiles, dinosaurs, over close to 200 million year range and in different environments. We now have this mountain of evidence that melanin does persist through the fossil record.”   

Just to make certain that these pigment traces were derived from animals, they then compared their spectral signature – or how much electromagnetic radiation the structures reflected or absorbed – with pigments produced by bacteria. These results confirmed that “the melanin was animal specific melanin, and not microbial melanin,” he added.

This opens the door to allow paleontologists to detect, and then start to reconstruct, the coloration of long-extinct animals. More than that, it can allow inferences about their paleobiology. Melanin has another function as structural support in feathers, so if it is present in the trailing edge of an animal’s wing, it could add to evidence and help researchers figure out if that animal could support itself with its wings or not. “It’s an amazing time to be a palaeontologist,” says Carney. 

Image in text: Melanosomes confirmed to be from animals found in the fossil dinosaur as seen under a microscope. Credit: J. Lindgren et al.

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