An article published in the journal “Nature Communications” describes a research on the skin of feathered dinosaurs. A team of researchers examined fragments of fossil skin of specimens of some species discovered in north-eastern China: Microraptor, Beipiaosaurus and Sinornithosaurus together with an early bird of the genus Confuciusornis. The conclusion is that those dinosaurs shed their skin in tiny flakes, like modern birds, and not all together like many modern reptiles.
Over the last few decades a number of discoveries and the help of modern technologies have been allowing to reconstruct the evolution of dinosaurs into birds, albeit slowly. Especially in China, the discovery of many species of feathered dinosaurs and early birds continues to provide new information. What was called Jehol biota, named after the Chinese province in which those fossils were found, is an ancient ecosystem in which between 133 and 120 million years ago there were also many species that are important to understand that transition.
A team of paleontologists from UCC (University College Cork), Ireland, wanted to study feathered dinosaur fossils from the Cretaceous period. The ones from the Jehol biota are ideal for the conservation state that allows to study their plumage using modern technologies such as electron microscopy but also chemical analysis.
The dinosaur specimens examined by the researchers belong to the genera Microraptor, which included some of the smallest known dinosaurs, Beipiaosaurus, which included some of the largest feathered dinosaurs, and Sinornithosaurus, which included rather small feathered dinosaurs. They were added a specimen of the genus Confuciusornis, an early crow-sized bird, the oldest found so far that had a beak.
By studying the specimens’ plumage, the researchers ended up finding small bits of materials present in the feathers and started analyzing some fragments. It turned out that these were the remains of cells called corneocytes, present in the outer layer of the skin that are periodically replaced.
The image (courtesy Maria McNamara et al. / Nature Communications) shows images of skin fragments examined at electronic microscope of Confuciusornis (a, e, f), Beipiaosaurus (b, g), Sinornithosaurus (c, h) and Microraptor (d). Basically, these are fragments of skin lost by the specimens examined very similar to those of modern birds. The difference is that the dinosaurs’ corneocytes don’t show traces of fats, instead present in modern birds’ cells. This suggests that those dinosaurs weren’t as warm as modern birds.
According to Maria McNamara, the article’s lead author, that mechanism of skin loss evolved following the presence of plumage, probably around the mid-Jurassic period. At that time there were quick changes that led to the emergence of many species of feathered dinosaurs. Those skin fragments can help to reconstruct that evolution.