Dinosaur feather changes suggest moulting

Two fossils of juvenile feathered dinosaurs found in China suggest that their feathers changed dramatically over their lifetimes, just as those of birds do.

Researchers led by Xing Xu at the Chinese Academy of Sciences found two fossils of the dinosaur species Similicaudipteryx, one a young juvenile and the other one older.

Similicaudipteryx was about the size of a peacock, and was a member of the Oviraptor family of bird-like dinosaurs.

The scientists found the fossils in the Yixian Formation of western Liaoning, China, dating back to the early Cretaceous period, about 125 million years ago.

They found that the feathers of the two individuals, visible in detail in the fossils, were different in shape.

The wing and tail feathers of the younger specimen were ribbon-like, while those of the older one were shaped like quills. The younger dinosaur's wing feathers were also much smaller than its tail feathers, while the difference in size in the older dinosaur wasn't as noticeable.

"The existence of these two different morphotypes suggests that Similicaudipteryx displayed moulting of feathers during development, as in modern birds," the authors wrote this week in the journal Nature.

The particular change in feather shape, from ribbon-like to quill-like, is no longer seen in birds, the researchers said, suggesting that some feather shapes have been lost over evolutionary time.