The oldest known beaked bird had a dark body, dark neck, and dramatic patterns along its feathers, scientists have determined using a new, non-destructive technique to characterize pigments in fossils.
The study, published online today in Science, is the first to map the distribution of trace metals in fossils as a way to reconstruct pigment patterns. The findings suggest that pigment chemistry may be key to filling in the prehistoric color palette, which could provide a wealth of information about ancient species and the role of color in evolution.
“It’s more important that just color,” said Phillip Manning, a paleontologist at the University of Manchester and author on the paper. “We’re mapping biochemical pathways which were alive in an organism over 120 million years ago.”
“It is a really cool study,” said Jakob Vinther, a paleobiologist at Yale University who was not involved in the research, in an email. “It is a great supplement to [other] analyses, as they are able to study the extent of black [pigmentation] across the whole organism in a less destructive way.”
Last year, two teams, including Vinther and colleagues at Yale, reconstructed color patterns in dinosaur fossil feathers by analyzing the structure of melanosomes to extrapolate color. Melanosomes are pigment-containing organelles, like biological paint tins, preserved in many fossils. The process provided some pigment information about dinosaurs and early birds, but was limited to those pigments associated with only two melanosome structures, and the process required removing and destroying small samples from the fossils.
Manning, along with colleagues Roy Wogelius at Manchester and Uwe Bergmann at the SLAC National Accelerator Laboratory in California, decided to see if there were pigment residues present in fossils without relying on the presence of melanosomes. They specifically looked for traces of metals whose atoms are often incorporated into melanin, an important pigment molecule found throughout the plant and animal kingdoms, including in human skin.
Using the X-ray techniques available at SLAC, the team scanned whole fossils of extinct birds—without sampling or damaging them—and detected chemical residues of trace metals including copper, nickel, zinc, iron and more. “Whatever’s in that fossil, if we can excite that atom at a particular energy, we can then map it,” said Manning.
The 120 million year old C. sanctus is analyzed using the Rapid Scanning X-ray Fluorescence technique at the Stanford Synchrotron Radiation Lightsource. Courtesy of Phillip Manning, University of Manchester. From thescientistllc on Vimeo.
Copper had one of the most striking distributions across samples. Copper is associated with eumelanin, the most common form of melanin, responsible for brown or black coloration in dark hair and brown eyes in many modern species, including humans. Based on the presence of copper, the team was able to determine the eumelanin patterns in Confuciusornis sanctus, the oldest documented species with a beak, and Gansus yumenesis, the most ancient representative of the lineage that led to modern birds. The team also verified their technique on tissues from living organisms, such as fish, bird feathers and squid ink sacs.
While they were able to map patterns of dark pigment, scientists cannot yet diagnose true colors, said Manning. However, as research advances, scientists may be able to track other chemical signals using the X-ray technique, he added, and determine a greater array of fossil colorations.
R.A. Wogelius, et al., “Trace metals as biomarkers for eumelanin pigment in the fossil record,” Science, doi:10.1126/science.1205748, 2011.