Chinese fossil reveals evolution of skin in feathered dinosaurs

A new fossil of the Cretaceous Period dinosaur Psittacosaurus, a dog-sized herbivore with a parrot-like beak, that was donated to a Chinese university came with a surprise - one revealed only after scientists viewed it under ultraviolet light

A new fossil of the Cretaceous Period dinosaur Psittacosaurus, a dog-sized herbivore with a parrot-like beak, that was donated to a Chinese university came with a surprise - one revealed only after scientists viewed it under ultraviolet light.

It retained large patches of beautifully preserved skin, down to its cellular structure, providing new insight into skin evolution in feathered dinosaurs. The fossil points to "zoned development" in the skin of these dinosaurs, researchers said, with Psittacosaurus and probably other feathered dinosaurs possessing scaly, reptile-like skin on body regions without feathers, with soft, bird-like skin on areas with feathers.

"Initially we didn't really have much hope of finding any soft tissues because, to the naked eye, our specimen appears to preserve only the bones. We didn't give up, though, because we knew that during fossilization soft tissues can be replaced by minerals, which may blend in with the sediments," said Zixiao Yang, a postdoctoral researcher in paleontology at University College Cork in Ireland and lead author of the study published on Tuesday in the journal Nature Communications.

"When I turned on the UV light, I could feel my heart almost skip a beat. Large patches of scaly skin, covering the chest and belly, were glowing in a striking golden-yellow color under the UV. The fossil skin looked really exquisite, covered by tiny, rounded scales of about one millimeter wide," Yang said.

Fossils of any soft tissues are rare. Skin fossils of this quality are rarer still.

Unearthed in northeastern China, the nearly complete fossil, dating to roughly 130 million years ago, is of a juvenile Psittacosaurus (pronounced SIT-ak-oh-sawr-us), about 2-1/4 feet (66 cm) long and approximately 3 years old when it died. It was donated in 2021 to Nanjing University from a private collection.

Psittacosaurus is an early member of the horned dinosaur lineage, called ceratopsians, that later produced large beasts like Triceratops. Psittacosaurus itself lacked horns. Its name means "parrot lizard" based on its protruding beak, adapted for eating plants.