July 1, 2011

Researchers Uncover Traces Of Pigment In Ancient Birds

Researchers have uncovered chemical traces of a pigment, an important component of color, that once formed patterns in the feathers of fossilized birds.

The pigment is one of the coloring agents responsible for brown eyes and dark hair in many modern species.  This discovery would have been one of the factors that determined the birds' color patterns, along with structural properties of the birds' feathers and other pigments they ingested as part of their diets.

The discovery will help give textbook illustrators, diorama makers and Hollywood special-effects artists a more realistic palette for their depictions of ancient animals.

Understanding these pigments will help scientists understand a variety of behaviors like camouflage, communication and selecting mates.

"This is a pigment that evolved a very, very long time ago but is still actively synthesized by organisms on the planet, and we found a way to map it and show its presence over 120 million years of geological time passing," geochemist Roy Wogelius of the University of Manchester, one of the leaders of an international team that reported the discovery, said in statement. "It is a direct relationship between you, me, and some extremely old organisms."

Co-author Uwe Bergmann of the Department of Energy's SLAC National Accelerator Laboratory, said in a statement: "If we could eventually give colors to long extinct species, that in itself would be fantastic. Synchrotron radiation has revolutionized science in many fields, most notably in molecular biology. It is very exciting to see that it is now starting to have an impact in paleontology, in a way that may have important implications in many other disciplines."

The researchers examined two fossilized birds that lived over 100 million years ago, the Confuciusornis sanctus and Gansus yumenensis.

The team looked for chemical traces of the pigments with two sophisticated X-ray techniques developed at Stanford Synchrotron Radiation Lightsource.

The researchers unveiled traces of specific elements in and around the tissues, bones and surrounding rock of Confuciusornis sanctus. 

They said the most striking of these elements was copper, which can be toxic at high levels.  Bergmann said copper has persisted in the fossil in significant amounts, appearing in the images as a ghostly glow in places where feathers remained. 

The team used the second X-ray imaging technique to study the fossil of a single feather form Gansus yumenensis.  His analysis revealed that the copper in the fossil took the same form as copper trapped by eumelanin pigment.

The team found the same relationship between copper and pigments in samples from modern feathers and squid.

"These new techniques for teasing out evidence of pigmentation will take a lot of the guesswork out of reconstructing the appearance of extinct dinosaurs and birds," said renowned dinosaur illustrator James Gurney, author of the best-selling Dinotopia series.
The new discovery opens a window on the biochemistry of ancient creatures, which could lead to a greater understanding of what they ate and the chemistry of their surroundings.

"The fossils we excavate have vast potential to unlock many secrets about the original organism's life, death and subsequent events impacting its preservation," co-author Phil Manning, a paleontologist at the University of Manchester, said in a statement.

"In doing this, we unlock much more than just paleontological information. We now have a chemical roadmap to track similar pigments in all life."

The study was published Thursday in Science Express.


Image 1: Shown here is an artist's conception of the pigmentation patterns in Confuciusornis sanctus, an ~120 million year old species, the oldest documented to display a fully derived avian beak. Patterns are based on chemical maps of copper and other trace metals in several fossils of this organism. Trace metals, copper especially, are found to exhibit patterns which reveal eumelanin pigment distribution in the living organism. In the background is a picture of one of the fossils used to derive the artist's drawing. Drawing of C. sanctus is by Richard Hartley, University of Manchester. Photo by T. Larson, courtesy of the Black Hills Institute. Image created by Gregory Stewart, SLAC National Accelerator Laboratory.

Image 2: Synchrotron rapid scanning x-ray fluorescence image of the calcium distribution in a fossil specimen of Confuciusornis sanctus, an ~120 million year old avian species, the oldest documented to display a fully derived beak. Calcium is high in the bones as shown by the bright white areas, but calcium is also high in the areas corresponding to residue of downy feathers in the neck region. This is interpreted to be due to the distribution of calcium being controlled by eumelanin chelates in the neck feathers, indicating that these soft tissues were originally darkly pigmented. Data were collected at the Stanford Synchrotron Radiation Lightsource. Image created by Gregory Stewart, SLAC National Accelerator Laboratory.

Image 3: A collage of images. Top, optical images of: blue jay feather, squid, and fossil fish with feather. Bottom: x-ray images showing the distribution of copper (red) in the same organisms. Copper in the dark parts of the feathers, the fish eye, and the squid ink sack indicates the presence of eumelanin pigmentation and in combination with other elements can be used to map pigment distributions in fossils and existing organisms. Photos by Phil Manning/Nick Edwards/Holly Barden, University of Manchester. Data were collected at the Stanford Synchrotron Radiation Lightsource. Image created by Gregory Stewart, SLAC National Accelerator Laboratory.


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