A 150-million-year-old bird with dinosaur teeth and a sickle claw is the earliest known bird to lose flight
Birds are famous for flight, yet a crow-sized Jurassic bird from southeastern China may have given it up around 150 million years ago. Scientists have described Yuezhuornis yangyuanensis, an early bird with serrated teeth and a sickle-shaped toe claw like those of small predatory dinosaurs. Its limb proportions resemble those of modern ground-dwelling birds, which suggests it lived on the ground. If that holds up, it is the earliest known example of a bird lineage losing the ability to fly.
A new bird from Fujian Province
The fossil comes from the Zhenghe Fauna in Fujian Province, southeastern China, and dates to between about 150 and 148 million years ago, in the Late Jurassic. That puts it in the same era as Archaeopteryx, the famous feathered fossil from Germany that scientists often treat as an early bird benchmark.
A team from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences and the Fujian Institute of Geological Sciences described the animal in the journal Nature on 14 October 2026. The paper is titled “Jurassic flightless bird reveals early ecological diversity of avialans.” Min Wang is the corresponding author, and the specimen is catalogued as IVPP V34427.
A strange mix of features
What stands out about Yuezhuornis is the combination. The skull mixes bird-like and troodontid-like traits. Its teeth sit close together and carry serrations, a feature reported in deinonychosaurs, the group of small meat-eating dinosaurs that includes Velociraptor. The second toe bends back unusually far and ends in a curved, sickle-shaped claw, another trait shared with those dinosaurs.
Even so, the researchers place the animal firmly among birds. Their analyses used two methods, maximum parsimony and Bayesian tip-dating, and the results put Yuezhuornis within Avialae, the group that contains birds and their closest early relatives. It sits just closer to modern birds than Archaeopteryx does, and it is a sister taxon to another Zhenghe bird called Zhengheornis.
“When we examined Yuezhuornis, we were struck by its extraordinary mix of features,” said Min Wang. Co-author Zhonghe Zhou added that the results consistently placed the animal firmly within Avialae.
Why scientists think it stayed on the ground
The key clue is the limbs. The paper describes markedly short forelimbs, and the team says its limb proportions match those of modern ground-dwelling birds. Using phylogenetically informed analyses, the authors report strong evidence for a terrestrial, flightless lifestyle. In other words, this bird most likely walked and hunted or foraged on the ground rather than taking to the air.
That matters because short forelimbs are common in non-avialan theropods, so this animal may have lost flight, or may have come from a lineage that never flew well, in a way that scientists can now test against other early birds.
What it says about early bird evolution
A common picture of early bird evolution is a steady march toward better flight. Yuezhuornis complicates that story. The authors argue that its short forelimbs point to several divergent ecological paths among early birds, rather than powered flight alone driving every change. Some lineages may have pushed toward the sky while others moved back to the ground.
Modern flightless birds such as ostriches and kiwis show that giving up flight can work well for a bird. This fossil suggests that experiment started far earlier than the fossil record previously showed, back when birds were still new.
Caveats and open questions
The flightless conclusion is an inference from skeletal proportions, not a direct observation, and the claim of “earliest known” depends on the current fossil record. A new find could change it. The full paper sits behind a paywall, so details such as exact limb ratios, body size and the rock formation were not available for this article. The sickle-claw detail comes from the press coverage of the study, and readers should check the paper for the full anatomy.
Researchers will also want more specimens. A single skeleton cannot show how common flightlessness was among Jurassic birds, or whether Yuezhuornis represents a dead end or a lasting branch.
For now, the fossil offers a vivid reminder that early birds were more varied than their reputation suggests. Some of them kept the teeth and claws of their dinosaur ancestors and chose the ground over the sky.
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