Sunday, August 30, 2009

Fossil Bird Feather Shows Its Colours

Structural coloration in a fossil feather. 2009. J. Vinther et al. Biological Letters.

Image: Jakob Vinther/Yale University
Paleontologists have discovered evidence of vivid iridescent colors in feather fossils more than 40 million years old.
Iridescence is the quality of changing color depending on the angle of observation, such as the rainbow of colors seen in an oil slick. The simplest iridescent feather colors are produced by light scattering off the feather's surface and a smooth surface of melanin pigment granules within the feather protein. Examining feather fossils from the Messel Shale in Germany with an electron microscope, scientists have documented this smooth layer of melanin structures, called melanosomes.

"These feathers produced a black background with a metallic greenish, bluish or coppery color at certain angles—much like the colors we see in starlings and grackles today," said Richard Prum.

For more than 25 years, paleontologists have found microscopic tubular structures on fossilized feathers and hair. These were long interpreted as bacteria that had digested the feathers at the time they were fossilized. The team had previously discovered that these structures were in fact not bacteria but melanosomes, which then allowed them to document the original color patterns.

The discovery could pave the way for determining color features of other ancient birds and even dinosaurs, the team said. link