I’ve previously written about work identifying the colors of feathers in fossil dinosaurs (birds, of course, evolved from feathered dinosaurs). These colors were assumed by looking at the shapes of melanosomes (pigment granules) in the fossils and judging the color from the shape of the granules—assuming granule shapes were conserved between fossil and modern birds. Now, however, according to a new paper in Science by Wogelius et al., we can guess the colors more directly by a method (Synchrotron Rapid Scanning X-Ray Fluorescence, or SRS-XRF) that can detect trace metals that are attracted by some pigments. Using this, the authors found that a fossil bird, Confuciusornis sanctus, appears to have had had the pigment eumelanin, which is blackish-brown.
C. sanctus is the first known bird that had a true beak, and lived about 120 million years ago. The fossil is to the left below (A, images from the paper) and the SRS-XRF scan, with false color, to the right (B). Copper shows up as red, and is in especially high concentration in the neck feathers. This, along with other analyses, suggested that those regions had high concentrations of the pigment eumelanin, which binds copper.
When they examined the copper-rich region of the neck feathers with scanning electron microscopy, they found the region full of bodies that looked like “eumelanosomes” (pigment granules containing eumelanin). These granules were also found in some of the flight feathers. Here’s one of the copper-rich granules.
To verify that these were not artifacts, they looked at a variety of material from other living or fossil species, including other animal parts known to be high in copper (fish eyes) and feathers of living birds, which also showed a correlation between eumelanin pigment density and high copper detected by SRS-XRF.
Conclusion: C. sanctus had the pigment eumelanin in its neck feathers, so it probably had dark downy feathers, shading into lighter colors at the tips of the flight feathers, where copper concentration is lower. The distal flight feathers had no trace metals, and so were probably white or another color. Our best guess, then, is that this ancient bird was parti-colored.
Wogelius, R. A. et al. 2011. Trace metals as biomarkers for eumelanin pigment in the fossil record. Science (early view): 10.1126/science.1205748
h/t: Greg Mayer