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Paleontologists have long determined that modern-day birds evolved from smaller members of the two-legged, meat-eating theropods, such as velociraptors. However, for many years, the only transitional fossil linking the two had been that of the archaeopteryx — a bird-dinosaur hybrid that lived on Earth about 150 million years ago, during the late Jurassic period.
Now, the perfectly-preserved remains of a small feathered raptor, dating back 120 million years, is providing scientists a glimpse into how the feathered fauna appeared during the Cretaceous period, the third and final period of the Mesozoic Era. The new dinosaur species may also help researchers determine the early connections — and differences — between birds and dinosaurs.
"The new dinosaur fits in with an incredible radiation of feathered, winged animals that are closely related to the origin of birds," said study leader Ashley Poust, a postdoctoral researcher at the San Diego Natural History Museum. "Studying specimens like this not only shows us the sometimes surprising paths that ancient life has taken but also allows us to test ideas about how important bird characteristics, including flight, arose in the distant past."
Named Wulong (Chinese for "dancing dragon") bohaiensis for the artful pose of its impressively preserved fossil, the new species was discovered by a farmer in the Jiufotang Formation in China's Liaoning Province, about a decade ago. However, it lay unnoticed in the collection of the Dalian Natural History Museum until a few years ago when Poust, then a student at Montana State University, stumbled upon the rare find.
The raven-sized dinosaur had a narrow face filled with small, sharp teeth, winglike feathers on its arms and legs, and two plumes at the end of its elongated bony tail. When examining the fossil, Poust and his team, which included scientists from the Dalian Natural History Museum, noticed an anomaly. Poust said, "The specimen has feathers on its limbs and tail that we associate with adult birds, but it had other features that made us think it was a juvenile."
To determine the dinosaur's age, the researchers performed bone histology, which involved cutting up some of its bones and examining them under a microscope. The results proved their suspicions right — the "dancing dragon" specimen was a juvenile with adult feathers. This is in sharp contrast with modern-day birds, which typically do not get their adult feathers — particularly the tail plumage, which is usually used for mating — until they are fully-grown. "Either the young dinosaurs needed these tail feathers for some function we don't know about, or they were growing their feathers really differently from most living birds," Poust explained.
The Jiufotang Formation, where the "dancing dragon" remains were unearthed, is a treasure trove of fossil deposits. Once home to a wide variety of animals, it is one of the earliest-known bird environments, where birds, bird-like dinosaurs, and pterosaurs all shared the same habitat.
"There was a lot of flying, gliding and flapping around these ancient lakes," Poust said. "As we continue to discover more about the diversity of these small animals, it becomes interesting how they all might have fit into the ecosystem. It was an alien world, but with some of the earliest feathers and earliest flowers, it would have been a pretty one."
Resources: www.sdnhm.org, phys.org