130-Million-Year-Old Bird Fossil Reveals Clue to Oldest Red Pigment

Researchers have found evidence of the oldest red pigment in the feathers of a 130-million-year-old bird.

A study titled Molecular evidence of keratin and melanosomes in feathers of the Early Cretaceous bird Eoconfuciusornis published in the Proceedings of the National Academy of Sciences of the United States of America found fossil evidence of feather structural protein (beta-keratin) surrounding microscopic pigment pods called melanosomes.

Eoconfuciusornis is a genus of the extinct bird that lived 131 million years ago during the Early Cretaceous of China. These prehistoric birds have pointed toothless beaks and long legs.

The discovery of the old pigment shows that original molecules may be preserved for longer periods of time. Researchers have long debated over the small round structures found in the fossils to be melanosomes, but without enough evidence, it may just as well be microbes which coated fossilized feathers over time.

Co-author Mary Schweitzer, NC State professor of biology with a joint appointment at the North Carolina Museum of Natural Sciences, stated, "If these small bodies are melanosomes, they should be embedded in a keratinous matrix since feathers contain beta-keratin," Schweitzer says. "If we couldn't find the keratin, then those structures could as easily be microbes or a mix of microbes and melanosomes -- in either case, predictions of dinosaur shading would not be accurate."

To settle the argument, a team from the Chinese Academy of Sciences composed of paleontologists from the Nanjing Institute of Geology and Paleontology (NIGPAS), the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), Linyi University, and North Carolina State University led the research.

Using scanning and transmission electron microscopy, the team took note of microscopic details of the feather's external and internal structure. They also adopted various molecular and chemical methods, including immunogold labeling, wherein gold particles are attached to antibodies that bind to particular proteins in order to make them visible in electron microscopy, to show that filaments within the feathers were keratin.

In a report by North Carolina State University, Yanhong Pan, corresponding author of the study, explained that "the study is the first to demonstrate evidence for both keratin and melanosomes using structural, chemical, and molecular methods." He added that "these methods have the potential to help us understand -- on the molecular level -- how and why feathers evolved in these lineages."