A newly described four-winged dinosaur from northeastern China is adding weight to the idea that flight-related features evolved separately in its group and in birds, rather than coming from a single flying ancestor. The fossil, named Norellraptor barsboldi, belongs to a group of small, feathered dinosaurs called microraptorines, which lived close to the evolutionary branch that produced birds.
The specimen was found in the Jiufotang Formation near Lamadong Town in western Liaoning, China. Researchers described it as a nearly complete skeleton measuring about 57 centimeters (22.4 inches) long, with preserved traces of feathers. Bone development and skeletal fusion indicate the animal was past its earliest juvenile stage when it died.
Norellraptor had several features seen in other microraptorines, including a lightweight build, specialized hands and feet, and structures linked with movement through the air. The preserved plumage is incomplete, but researchers reported probable asymmetrical flight feathers near the hand, along with feathers around the tail and hind limb.
‘Four-winged’ dinosaur shows a different flight path from birds
The study focused on whether these similarities with birds came from a shared flight system inherited from a common ancestor or developed separately as the two groups evolved. The analysis found that about 30% of the anatomical features identified as distinctive in microraptorines also appeared independently in the bird lineage.
More importantly, the order in which those features appeared was different. In microraptorines, changes to the fingers came early, while features involving the wrist, chest and upper arm appeared later. In birds, researchers found a different sequence. That mismatch argues against both groups following the same inherited developmental path toward flight.
The four-winged dinosaur lineage therefore appears to have assembled its flight-related anatomy through a separate evolutionary route from birds, according to the study. The authors said the results support multiple, independent pressures shaping aerial movement among paravians, the broader group that includes birds and their closest dinosaur relatives.
Bone growth adds evidence for a separate evolutionary route
Microscopic examination of a forearm bone also showed an unusual growth pattern. The radius had periods when growth stopped and later resumed, and its development differed from patterns reported in some related dinosaurs.
Researchers said this may point to a distinctive way the forelimbs developed in microraptorines, although the evidence remains preliminary.
Norellraptor also adds a new branch to the microraptorine family tree. Researchers placed it close to Zhongjianosaurus and said its anatomy helps show that the equipment needed for aerial movement did not appear in one single step.
Instead, different flight-related traits were added gradually and in a sequence separate from the one seen in early birds.
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