The head and neck of the 120-million-year-old fossil of Confuciusornis sanctus. The red highlights correspond to the distribution of copper, providing a reconstruction of dark-pigment shading (Image: R. A. Wogelius, University of Manchester; Gregory Stewart, SLAC National Accelerator Laboratory; E. Kaxiras, Harvard University)

Major new clues to the appearance of fossilised birds have emerged from X-ray scans, which reveal which parts of their plumage contained the black pigment eumelanin. The same technique could theoretically be applied to fossils of any animal, providing new insights into their appearance.

The scans show that the earliest-known beaked bird – the roughly 120-million-year-old Confuciusornis sanctus – had extremely dark plumage on the neck, breast and body.

Scans also revealed heavy eumelanin pigmentation in two fossilised feathers from Gansus yumenensis, the oldest-known modern bird, resembling a grebe, from about 110 million years ago.


Neither is as old as Archaeopteryx, the famous forerunner of birds dating from 150 million years ago, but the scans reveal for the first time the likely patterning of light and dark in the early birds’ plumage.

Hint of copper

This has been problematic before now, because like all organic material in fossils, pigments rapidly degrade away, leaving little clue to the colours and patterns of plumage in birds, or skin in dinosaurs.

Now, researchers have found a way around this. Although the eumelanin itself biodegraded millions of years ago, traces of it remain as non-degradable copper – a vital metal found within the pigment and also within the tyrosinase enzyme that manufactures it.

Because the copper survives in fossils, scans of its distribution match that of eumelanin when the birds where alive. “Wherever you find the copper, that’s where there was eumelanin,” says Roy Wogelius at the University of Manchester, UK, who heads up the team that analysed the fossils.

Pinpointing pigment

Wogelius and his colleagues revealed the distribution of copper by exposing the fossils to extremely high-energy X-rays at the SLAC National Accelerator Laboratory in Menlo Park, California. Although the X-rays are much more powerful than those used in hospitals, they don’t damage the fossils.

When the X-rays strike copper, the metal atoms fluoresce and produce a characteristic light spectrum. This enabled the team, co-led by Phil Manning also at the University of Manchester, and Uwe Bergmann of SLAC, to build up images showing the distribution of the copper in the whole fossil.

Although researchers have previously identified melanosomes, physical structures in fossils where eumelanin was formed, these can be detected only by taking tiny pinprick samples from the fossils and finding the melanosomes through magnification in an electron microscope. As well as damaging the fossils, this provides only a rough idea of the total distribution of pigments.

Combined approach

“This latest work is a really cool study,” says Jakob Vinther of Yale University, who developed the pinprick sampling technique. “It is able to reveal the extent of the black eumelanin across the whole organism in a less destructive way, whereas we rely on analysing several small samples.”

But Vinther says that whereas the X-ray scans can reveal the presence of black eumelanin alone, his sampling technique shows where plumage is grey, brown or iridescent as well, so the two techniques could complement each other to reveal more than either could alone.

Wogelius is searching for non-degradable remnants of other pigments, such as orange-coloured carotenoids and pheomelanin, the red-gold-blonde “cousin” of eumelanin, to give an even better idea of the skin and plumage colours of fossilised animals. “I have hope there will be chemical residues of other pigments,” he says.

Journal reference: Science, DOI: 10.1126/science.1205748