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Analytical Chemistry

Prehistoric Pigments Found In Fossilized Feathers

Paleochemistry: Analytical methods confirm Mesozoic melanin survived in dinosaur remains

by Matt Davenport
September 14, 2015 | A version of this story appeared in Volume 93, Issue 36

Fossilized dino with melanin.
Credit: Johan Lindgren/Sci. Rep.
Researchers say this Anchiornis huxleyi sample is exceptionally preserved.

Humanity may never know what colors dinosaurs were, but scientists now have the strongest evidence to date that clues about prehistoric hues are preserved in the fossil record.

Researchers led by Johan Lindgren of Lund University, in Sweden, used a battery of analytical techniques to scrutinize the molecular makeup of a fossilized Anchiornis huxleyi specimen. This dinosaur is a distant relative of today’s birds, and its remnants were preserved for about 150 million years in what is now northeastern China.

The researchers’ thorough analyses have allowed them to conclude that some of the dinosaur’s melanin, or pigment molecules, and melanin-producing organelles have also survived the intervening epochs (Sci. Rep. 2015, DOI: 10.1038/srep13520).

Scientists have previously observed signs of similar biomaterials in fossils, but studies have lacked sufficient evidence to rule out the idea that these materials come from bacteria or other microbial intruders.

Using methods including infrared spectroscopy and time-of-flight secondary ion mass spectrometry, Lindgren and his colleagues have shown that the sample’s fossilized feathers contain substances that closely resemble modern animal—not bacterial—eumelanin, the pigments responsible for brown and black coloration.

Photograph and overlayed IR spectrum of fossil sample.
Credit: Sci. Rep.
IR spectroscopy reveals that eumelanin (deep red regions on right) appears in the darker regions of the dino’s feather material (shown in photo on left).

“We will never know what color the dinosaur was for sure,” Lindgren says. Some pigments and other colorizing features may have degraded over time, and researchers can’t account for what isn’t preserved, he explains. “There is a dark component to the color, though. We can say that for sure.”

But the fossil was also rich in calcium phosphate, a mineral that suggests bacterial activity. This study thus confirms that dinosaur biomolecules can be preserved in fossils, but it doesn’t automatically discredit the microbial hypothesis, Lindgren adds.

Each fossil must be subject to careful analysis, like that developed by Lindgren’s team, to ascertain the source of its biomaterials, say North Carolina State University paleontology researchers Mary H. ­Schweitzer and Alison Moyer, who were not involved with the study.

“The really exciting thing is that paleontology is increasingly moving from a descriptive science to an analytical one,” they write in a message to C&EN. “The whole field will benefit from a cautious application of new methods to old fossils.”



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