We now know for a fact that many dinosaurs sported feathers. But until recently, scientists have not been able to definitively tell whether they were hot pink or jet black.
Within the last decade, scientists began identifying color-conferring structures called melanosomes in fossilized dinosaur feathers. Using these clues, they were able to piece together a better picture of what the dinosaurs really looked like. The problem was, some scientists claimed that the structures aren't melanosomes from the dinosaurs, but microbes that happened to become fossilized along with the dinosaur.
Now, a new study published in the journal Scientific Reports confirms that the fossilized structures found in a 150 million-year-old dinosaur known as Anchiornis huxleyi indeed belonged to the dinosaur and not to nearby microbes.
"We have integrated structural and molecular evidence that demonstrates that melanosomes do persist in the fossil record," study co-author Ryan Carney, a graduate student at Brown University, said in a statement. "This evidence of animal-specific melanin in fossil feathers is the final nail in the coffin that shows that these microbodies are indeed melanosomes and not microbes."
First, researchers used electron microscopes to get a closer look. The rod-shaped structure of the potential melanosomes was a sign that they were indeed a valid indicator of the feathers' color, but that evidence wasn't enough on its own.
As a second line of evidence, the researchers also conducted two types of chemical analysis, called time-of-flight secondary ion mass spectrometry and infrared reflectance spectroscopy. Both of these tests reveal information about the chemical signature of the melanin pigments in the melanosomes.
Since melanin from animals has a chemical signature distinct from that of microbes, the scientists were able to compare the signatures found in the fossils to those found in the melanin produced by modern animals. The signatures were a match.
This work settles the debate over whether the melanin in fossils really belonged to the dinosaurs, but melanin is just one type of pigment. It is the pigment that darkens skin and eye color in humans as well as in other animals.
In birds, the colors – such as flaming pink – in their feathers come from the foods they eat rather than pigment, so some aspects of the dinosaurs' appearance may forever remain a mystery. But for now, it seems safe to say that Anchiornis huxleyi at least had some dark black feathers.