Feather pigments revealed in 150-million-year-old fossils

The distribution of pigments in feathers in three Archaeopteryx fossils has been examined by non-destructive X-ray methods that indicate that they have survived over 150 million years. In a cross European-US study, synchrotron rapid scanning X-ray fluorescence was used to derive maps of trace metals and organic sulphur while sulphur X-ray absorption near edge structure spectroscopy revealed the sulphur oxidation states.

The distributions of the various metal species like copper, which are biomarkers of the pigment eumelanin, can be used to infer the original colour of the feathers. In one fossil, the outer vane and tips were darker than the inner vane which had little pigmentation.

These non-destructive methods are important for studying these rare and valuable fossils. In this case, revelations about the colour distribution, which conflict with published work, have implications for the evolution of bird feathers.