Chemical traces left 150 million years ago by feathers from the first known bird have been recovered by scientists.
The discovery shows that feather shapes found in an Archaeopteryx fossil are more than just rock impressions.
They include tiny amounts of phosphorous and sulphur, elements that exist in the feathers of modern birds.
Copper and zinc, both of which are needed by birds to stay healthy, were also found in bone material from the fossil.
British and US scientists uncovered the elements by firing intense X-rays generated by synchrotron particle accelerators at the fossil specimen.
Roy Wogelius, from the University of Manchester, said: "We talk about the physical link between birds and dinosaurs, and now we have found a chemical link between them.
"In the fields of palaeontology and geology, people have studied bones for decades. But this whole idea of the preservation of trace metals and the chemical remains of soft tissue is quite exciting.
"We're able to read so much more into these organisms now using this technology -- we're literally touching ghosts.
"Chemistry is the real key in the future of palaeontology."
The findings were reported yesterday in the US journal Proceedings Of The National Academy Of Sciences.
They showed different concentrations of elements in the fossil and surrounding rock, confirming they were from the bird and not due to natural contamination.
Archaeopteryx, which was about the size of a magpie, lived alongside the dinosaurs at the end of the Jurassic period and is considered the earliest known true bird. It had dinosaur-like features such as teeth and a long, bony tail, but also feathery wings.