An artists impression of the pigmentation of C.Sanctus, a bird that lived 120 million years ago.
Credit: Richard Hartley, University of Manchester; T. Larson, Black Hills Institute; Gregory Stewart; SLAC National Accelerator Laborato
LONDON: Minute traces of metals on bird fossils have given scientists an unrivalled picture of what prehistoric birds looked like, according to a new study.
An international team used these metals to determine the pigmentation patterns on the bodies and wings of birds that lived as much as 150 million years ago.
Understanding these pigmentation patterns could be a first step in revealing new details of how prehistoric animals lived - for example how they remained camouflaged or communicated through their colourings.
"These are extinct animal behaviours that people thought were probably beyond reach but now we might just be able - if we built up a database - to get some hint of the evolutionary pressures, and how pigmentation has evolved in certain species," said Roy Wogelius, from the University of Manchester in the UK, who lead the study published in the current issue of Science.
X-ray precision
Previous attempts to map the pigment patterns of prehistoric birds used techniques such as electron microscopes to look for melanosomes - the part of the cell that produces the dark pigment melanin.
The problem is that these structures often break down over time, so they can be impossible to find. What's more, these techniques can be time consuming, and can only be used to study small samples, so it is harder to identify patterns over an entire specimen.
Now, Wogelius and his team are harnessing the power of super bright X-rays as an alternative method. Last year they used this technique to scan the surface of a fossil of the ancient bird Archaeopteryx and found something unexpected.
"We discovered that there was still some residue from the feathers," Wogelius said. "That had never been seen before in 150 years of study."
Traces of metal remain
The unexpected find led the team to study other exceptionally preserved fossils for chemical residues of pigments.
"The reaction that your body uses to make the dark pigments in your hair and in your skin involves a chemical that has copper in it," Wogelius explained. The team thought that the traces of metal might remain, even when the pigments themselves had degraded.
By scanning ancient fossils for these traces and comparing them to modern day samples, the team discovered this was the case - even when the melanosomes disappear, the metals can stay in quantities so small they are lost in the background using standard imaging techniques.
