Meet The Newly Discovered Cousin Of Velociraptor That Probably Glided On Four Wings

For more than 40 years, researchers digging in a remote corner of northwestern China found bird fossil after bird fossil, and assumed that was the whole story. Then a set of arm bones turned up that didn’t belong to any bird.

Scientists have formally identified a new species of small, bird-like dinosaur from the Changma Basin in Gansu Province, China. Named Jian changmaensis, the animal belongs to the same family as Microraptor, the celebrated four-winged dinosaur that could likely glide or fly. What makes this find so unexpected is where it came from: a site that had yielded more than 100 fossilized bird skeletons over four decades, yet had never produced a single non-bird dinosaur bone fossil until now. The findings appear in the Annals of Carnegie Museum.

Even its name carries its own story. “Jian” refers to the Jiān, a mythological one-winged bird from Chinese folklore, a nod to both the animal’s bird-like anatomy and the fact that only its arm bones were recovered. “Changmaensis” refers to the village of Changma, near where the fossil was found. Microraptorines are a group of small, bird-like dinosaurs closely related to the evolutionary lineage that eventually gave rise to modern birds, and until now every confirmed member of the group had been found in northeastern China, roughly 2,000 miles away.

Jian changmaensis Was a Medium-Sized Member of a Bird-Like Family

What survives of the animal is a partial left shoulder and arm: the shoulder blade and its attached bone, the upper arm bone, and the two lower arm bones. The hand, wrist, and the rest of the skeleton are gone. Despite being fragmentary, the bones tell a reasonably detailed story. Their surface texture is smooth and “finished,” a sign the animal had stopped growing, and the shoulder blade and adjacent bone were fully fused together, another marker of skeletal maturity. This was an adult, or close to one, with an upper arm bone just over four inches long, placing it midway in size between smaller members of its group and larger ones.

Three Bone Features Set Jian changmaensis Apart From Every Known Relative

Three physical features set Jian apart from every other known member of its family. First, a bone connecting the shoulder to the chest was unusually long relative to the upper arm, longer, proportionally, than in any other member of this group on record. Second, the joint surfaces at the lower end of the upper arm bone faced straight forward rather than angling downward, a configuration seen in birds but not in its closest dinosaur relatives. Third, a well-developed hole was found on the underside of the upper part of one of the lower arm bones, a feature that has not been reported in any other dinosaur of this type.

One additional feature helped researchers place Jian firmly within the microraptorine group: a large oval opening in a bone near the shoulder joint. This kind of opening has been found in only a handful of other dinosaurs, all of them microraptorines from northeastern China.

Because the fossil was partially crushed by millions of years of burial, the team used high-resolution scanning to look inside the bones without damaging them. The scans showed hollow areas in the forearm bones and a thin-walled radius, signs of a lightly built limb. Those air spaces fit with the idea that Jian may have had a light, bird-like body, although the fossil is too incomplete to say whether it could fly or glide.

What Jian changmaensis Reveals About a 120-Million-Year-Old Ecosystem

Perhaps the most surprising part of this story has nothing to do with the bones themselves. Rocks in the Changma Basin date back roughly 120 to 124 million years, and for decades that site has been dominated by a single ancient bird species, Gansus yumenensis, the first bird from the age of dinosaurs ever found in China, discovered in 1981. Many of those bird fossils preserved soft tissue including feathers and skin, yet in all that time not a single non-bird dinosaur bone had ever turned up. A fossil site in northeastern China called Sihedang shows a remarkably similar pattern: dominated by a single bird species closely related to Gansus, and also home to microraptorine dinosaurs. Both locations may have preserved similar lakeside habitats, but the authors stress that more fossils and environmental studies are needed to test that idea.

For more than four decades, the Changma Basin seemed to offer only one answer to the question of what lived there. Jian changmaensis is a reminder that a fossil site is never fully read, and that 120 million years ago, the boundary between dinosaurs and birds was far less clear than the one we draw today.

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