An international research team led by scientists at University College Cork, Linyi University, and China’s Institute of Vertebrate Paleontology and Paleoanthropology has found and analyzed dandruff fragments preserved amongst the plumage of Cretaceous feathered non-avian dinosaurs, revealing the first evidence of how dinosaurs shed their skin.

A pair of Beipiaosaurus dinosaurs. Image credit: Pavel Riha / CC BY-SA 3.0.

The team discovered the fossilized skin of three feathered non-avian dinosaurs (Beipiaosaurus, Sinornithosaurus and Microraptor) and an early bird called Confuciusornis.

These creatures lived approximately 125 million years ago (Early Cretaceous epoch) and were important members of the famous Jehol Biota, a rich ecosystem preserved in a rock formation cropping out in several Chinese provinces.

The paleontologists studied the fossilized dandruff, and dandruff from modern birds, with powerful electron microscopes.

“What’s remarkable is that the fossil dandruff is almost identical to that in modern birds — even the spiral twisting of individual fibers is still visible,” said co-lead author Dr. Maria McNamara, from the School of Biological, Earth and Environmental Sciences at University College Cork, Ireland.

“The fossil cells are preserved with incredible detail — right down to the level of nanoscale keratin fibrils.”

Colorized electron images of fossil soft tissue in Confuciusornis (a, e, f), Beipiaosaurus (b, g), Sinornithosaurus (c, h) and Microraptor (d). Image credit: McNamara et al, doi: 10.1038/s41467-018-04443-x.

The 125-million-year-old dandruff is the first evidence of how dinosaurs shed their skin.

“Beipiaosaurus, Sinornithosaurus and Microraptor clearly shed their skin in flakes, like Confuciusornis and also modern birds and mammals, and not as a single piece or several large pieces, as in many modern reptiles,” the researchers said.

“It’s unusual to be able to study the skin of a dinosaur, and the fact this is dandruff proves the dinosaur was not shedding its whole skin like a modern lizard or snake but losing skin fragments from between its feathers,” added co-author Professor Mike Benton, from the School of Earth Sciences at the University of Bristol, UK.

Just like human dandruff, the fossil dandruff is made of tough cells called corneocytes, which in life are dry and full of the protein keratin.

“This modern skin feature evolved sometime in the late Middle Jurassic, around the same time as a host of other skin features evolved,” the study authors said.

“There was a burst of evolution of feathered dinosaurs and birds at this time, and it’s exciting to see evidence that the skin of early birds and dinosaurs was evolving rapidly in response to bearing feathers,” Dr. McNamara said.

“Modern birds have very fatty corneocytes with loosely packed keratin, which allows them to cool down quickly when they are flying for extended periods.”

“The corneocytes in the fossil dinosaurs and birds, however, were packed with keratin, suggesting that the fossils didn’t get as warm as modern birds, presumably because they couldn’t fly at all or for as long periods.”

Source: sci.news