150-million-year-old bird fossil suggests it could not fly

A newly described bird from China's Fujian province may have spent its life on the ground rather than in the air. The fossil, named Yuezhuornis yangyuanensis, dates to the Late Jurassic, about 150 million to 148 million years ago. A study published in Nature on October 14 argues that its anatomy provides strong evidence of a flightless lifestyle.

The animal was found in the Zhenghe Fauna of southeastern China. Live Science reports that the researchers discovered the specimen in 2024.

Its skeleton combines features associated with early birds and their dinosaur relatives. The study describes unusually short forelimbs, a mixture of bird-like and troodontid-like skull characteristics, and a second toe capable of bending strongly upward. Researchers interpreted this combination as evidence of a terrestrial animal, challenging a simple picture in which every early bird evolved toward increasingly capable flight.

Yuezhuornis belongs to Avialae, the evolutionary group containing living birds and their closest extinct relatives. The Chinese Academy of Sciences says the fossil's limb proportions resemble those of ground-dwelling birds and some related dinosaurs. That comparison helps explain the flightlessness interpretation, but the bones cannot show the animal's movements directly.

Study co-author Min Wang told Live Science that the animal was probably about the size of a crow. The finding adds another body shape and possible lifestyle to a sparse Jurassic bird fossil record, suggesting that early bird evolution involved several ecological paths rather than a uniform march toward flight.

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