An article published in the journal “Proceedings of the National Academy of Sciences” describes a research on a bird that lived about 130 million years ago called Eoconfuciusornis zhengi. A team of researchers from North Carolina State University, Chinese Academy of Sciences and Linyi University have found in this bird’s known fossil specimen traces of keratin and melanosomes and managed to prove that these are traces of its feathers.
The known specimen of Eoconfuciusornis zhengi was found in the Hebei Province in North China, in an area known for the good preservation of fossils dating back to the early Cretaceous period. The skeleton is almost complete and most of is plumage is well preserved too. It’s the oldest bird discovered with a beak containing keratin and no teeth, just like modern birds.
According to previous studies the feathers of primitive birds and feathered dinosaurs contained melanosomes, organelles that contain pigments that give feathers their color together with other pigments. The problem was to prove that those structures weren’t later contamination caused for example by microbes that had coated the feathers during the decomposition and fossilization stages.
In this new research, they used electron microscopic exams to obtain details of the surface of Eoconfuciusornis zhengi’s feathers and their internal structure. Gold particles were used because they get attached to antibodies that bind to particular proteins in order to make them visible in electron microscopy. This was needed to prove that the filaments inside the feathers were keratin.
If the very small structures were melanosomes, they had to be embedded in the keratin matrix because the feathers contain beta-keratin, a keratin protein version evolved from the scales of reptiles and dinosaurs. The analyzes needed required the destruction of some small parts of the fossil the size of a grain of rice but eventually the researchers found the structures they sought.
During the tests, the researchers also mapped copper and sulfur content in the feathers. The sulfur was widely distributed, reflecting its presence in the keratin and melanin in modern birds’ feathers. Copper, found only in modern melanosomes and not in keratin, was observed only in the fossil melanosomes. That means that during the processes of decomposition and fossilisation it didn’t get mixed with other elements.
The test results suggest that the body Eoconfuciusornis zhengi’s body was brownish or of a dark color. It’s a step forward in this type of research and could open the way for other types of analysis. The only problem is that it’s a destructive analysis so its use must be carefully assessed.
