Fossil feathers hint at color

Signs of color preserved in stone?: Fossil feather from Brazil (left) displays similarities with recent woodpecker feather (right)
Signs of color preserved in stone?: Fossil feather from Brazil (left) displays similarities with recent woodpecker feather (right)Courtesy J.Vinther/Yale
Researchers at Yale University are reporting the discovery of pigmentation within the fossilize feather from a bird or dinosaur. Using a powerful electron microscope, paleobiologist Jakob Vinther and his team claim that particles seen in the 100-million-year-old fossil appear to be similar to those seen in the feathers of living birds. This could mean that color - a characteristic long-thought lost in the fossil record - could someday be determined from the remains of pigment.

Vinther’s colleagues included Yale paleontologist Derek E. G. Briggs and Yale ornithologist Richard O. Prum. The results of their study will appear in an upcoming issue of Biology Letters. The research shows that dark stripes in the Cretaceous-aged feather display many similarities to the make-up of black melanin particles found in modern bird feathers. Melanin compounds determine color in plants and animals, a trait useful for such things as camouflage, species identification, and courtship display. In humans, melanin colors our skin and also protects us from overexposure to sunlight.

For a long time, the dark granules seen in fossilized feathers were thought to be the carbon remains of bacteria that had worked at decomposing the organism prior to fossilization. But advances in electron microscope technology have given scientists a closer - and clearer – picture of the feather’s structure, and instead show them to be fossilized melanosomes containing melanin pigment.

"Feather melanin is responsible for rusty-red to jet-black colors and a regular ordering of melanin even produces glossy iridescence,” Vinther said. “Understanding these organic remains in fossil feathers also demonstrates that melanin can resist decay for millions of years."

Under the scope, the lighter bands of the fossilized feather showed only the rock matrix, while the darker bands displayed traces of residue closely resembling the organic compounds found in the feathers of modern birds.

“You wouldn’t expect bacteria to be aligned according to the orientation of the feathers,” said Vinther.

Another bird fossil showed similar organic traces in the feathers surrounding its skull. The 55-million-year-old fossil from Denmark also preserved an organic imprint of the eye that showed structures similar to the melanosomes found in eyes of modern birds.

Nanostructure studies could one day provide paleontologists with evidence of colors other than just black and gray tones, and not just in fossil feathers. Vinther figures other organic remains such as fur from prehistoric mammals or fossil skin impressions from dinosaurs could prove to be the remains of the melanin.

ScienceNews story
Yale website story
Cosmos magazine website story
Melansome info

Your Comments, Thoughts, Questions, Ideas

Anonymous's picture
Anonymous says:

very interesting

posted on Tue, 08/05/2008 - 12:31pm
Anonymous's picture
Anonymous says:

I don't buy this hypothesis. These structures seen in fossil feathers look like bacilli-form bacteria also. They never really give a good scientific explanation to why they aren't. Furthermore, melanin only accounts for about ~1.5% of a pigmented feather, yet fossil feathers appear to be completely replaced by these structures. Where is the room for the keratin? Also, these structures have been preserved in what appears to be reproduction/cytokinesis. As far as I know, melanosomes undergo more of a synthesis.

I think more work needs to be done other than comparing a few SEM images before something as important as interpreting dinosaur color is released to the public. It seems weak at best. The authors have a lot of explaining to do.

posted on Tue, 08/12/2008 - 4:22pm

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