In 1994, farmers in Liaoning Province in northeastern China began finding exquisitely preserved fossil birds representing a new species, Confuciusornis. They were discovered in fine-grained Early Cretaceous sedimentary deposits near the village of Sihetun. Many were so well preserved that even their feathers could be seen. Several kinds of fossil birds were found, but Confuciousornis was the most common. Other fossils were also found, including splendid examples of fish and plants. So many fossils were found, and are still being found, that a thriving market has developed in exporting them out of China-a market that the Chinese government considers illegal smuggling.
In 1996, the skeleton of a small dinosaur came to light at Sihetun. Complete practically to the last bone, it belonged to a new kind of theropod about three feet long named Sinosauropteryx prima. In size and anatomy, it closely resembled the small European dinosaur Compsognathus, but it showed distinct traces of short, brushy structures along the neck, back, and tail. After some arguing back and forth, most scientists now believe that the brushy structures are indeed feathers, somewhat different in structure than those of modern birds. Sinosauropteryx is thus the first feathered non-avian dinosaur ever found.
Even as Sinosauropteryx was being studied, more feathered dinosaurs turned up in Liaoning: Protarchaeopteryx, a larger theropod five feet long, with very birdlike feathers visible along the tail; Caudipteryx, a very birdlike theropod about three feet tall, showing good feather impressions along forelimbs and tail; Sinornithosaurus, a troodontid-like theropod about the same size as Sinosauropteryx, with hairlike feathers; and Beipiaosaurus, a theropod more than six feet long, the largest-known theropod with feather impressions (also hairlike). The smallest feathered Liaoning theropod was Microraptor, less than 1.5 feet long, classified as a dromaeosaurid. All these feathered dinosaurs had relatively large, powerful hind legs, obviously suited for fast running, and hands with large claws. None had wings.
The discovery of feathered theropods strongly supports the theory that birds are theropod dinosaurs that evolved the ability to fly. But perhaps the most interesting thing about the Liaoning feathered theropods is that they represent several different theropod families. This means that the origin of feathers is not closely linked to the origin of birds, and offers evidence that many different lines of theropod dinosaurs may have had feathers of some sort, not just those most closely related to birds. Depending on how widespread the structures were among theropods, even such giants as Tyrannosaurus rex may have had feathers.