A crow-sized bird with dinosaur teeth that gave up flying 150 million years ago
What happened
Palaeontologists in China have described a crow-sized bird from the Late Jurassic that appears to have lost the ability to fly — making it the earliest known example of a bird lineage giving up flight. The study was published in the journal Nature and reported on 23 October 2026. The work comes from the Institute of Vertebrate Palaeontology and Palaeoanthropology at the Chinese Academy of Sciences, together with the Fujian Institute of Geological Sciences. The animal has been named Yuezhuornis yangyuanensis. It lived between about 150 and 148 million years ago. The fossil was found in Fujian Province in south-eastern China, in a group of fossils recently recognised as the Zhenghe Fauna. Two features of the skeleton stand out, and both look more like a dinosaur than a bird. Its teeth are closely spaced and serrated, very like the teeth of deinonychosaurs — the group of meat-eating dinosaurs that includes dromaeosaurids and troodontids. These are the animals most people picture when they think of raptors. Its foot is stranger still. The second toe bends backward unusually far and carries a curved, sickle-shaped claw. That is another deinonychosaur signature. Despite all that, when the team ran the fossil through two separate analytical methods — maximum parsimony and Bayesian tip-dating — both placed it inside Avialae, the group that contains birds. Specifically, just slightly closer to modern birds than Archaeopteryx, and as a close relative of another animal called Zhengheornis. Then there is the flight. The proportions of its limbs resemble those of modern ground-dwelling birds, and of some closely related dinosaurs, rather than those of flying birds. The researchers conclude it lived on the ground and could not fly. Min Wang, the corresponding author, said: "When we examined Yuezhuornis, we were struck by its extraordinary mix of features." He added that the find "shows us that early bird evolution was far more complicated than we previously realized"
Why this matters
The story most of us learn about bird evolution is a straight line. Dinosaurs develop feathers. Feathers become useful for gliding. Gliding becomes flight. Birds take to the air and never look back. Flightless birds, in that story, come much later. Ostriches, emus, penguins and kiwis are all descended from flying ancestors, and all lost flight long after birds were well established. Yuezhuornis puts a flightless bird right at the beginning. Archaeopteryx, the famous first-bird fossil from Germany, is about 150 million years old. This animal is the same age and sits just slightly closer to modern birds on the family tree. So within a few million years of birds appearing at all, at least one lineage had already stopped flying. That changes the shape of the story. Rather than a single push into the air followed by diversification, the earliest stretch of bird evolution looks like a crowded experiment: different body plans, different ways of living, some in the air and some on the ground, all at roughly the same time. The teeth and the sickle claw add to that. They suggest the boundary between early birds and the dinosaurs they came from was blurrier than a tidy diagram allows. Features we file under dinosaur and features we file under bird were being mixed and matched. The Zhenghe Fauna itself is part of why this is possible. It is a recently recognised set of fossils from a period and place that was poorly sampled before. New rock means new animals, and new animals mean the tree gets redrawn.
What the evidence actually says
This is a single-specimen description, and that is both its strength and its limit. The strength is in the method. The team used two independent approaches to place the animal on the family tree, and both agreed. Maximum parsimony looks for the simplest arrangement of shared features. Bayesian tip-dating also factors in the ages of the fossils. When two different techniques land in the same place, the result is more trustworthy than when only one does. The limits are real too. Flightlessness in a fossil is inferred, not observed. The argument rests on limb proportions resembling ground-dwelling birds rather than flying ones. That is a reasonable and widely used line of reasoning. It is not the same as watching the animal fail to take off. A single skeleton with unusual proportions could, in principle, be an individual rather than a species pattern. "Earliest known" is also a claim about the fossil record, not about the past. It means nothing earlier has been found. The record for this period is patchy, and the Zhenghe Fauna was only recently recognised, which is a reminder of how much is still missing. And the family-tree position, while supported by two methods, is close to Archaeopteryx. Small shifts in how features are weighted can move animals across that boundary. Future fossils may move it again. What the paper establishes well is that an animal existed 150 million years ago with a genuinely unusual combination: serrated dinosaur-like teeth, a sickle-clawed second toe, limb proportions suited to the ground, and a position inside the bird group on two separate analyses. That combination is hard to fit into the simple story, and that is the point. As Min Wang's co-author Zhonghe Zhou and the team argue, the early ecological diversity of birds is the headline — it is in the paper's title.
What to know
A new fossil bird named Yuezhuornis yangyuanensis, described in the journal Nature on 23 October 2026, lived 150 to 148 million years ago in what is now Fujian Province, China. It was about the size of a crow, had closely spaced serrated teeth like meat-eating dinosaurs, and had a second toe that bent backward with a curved sickle-shaped claw. Two separate analyses placed it inside the bird group, just slightly closer to modern birds than Archaeopteryx. Its limb proportions match ground-dwelling birds, so the researchers conclude it could not fly — the earliest known loss of flight in a bird lineage. Flightlessness is inferred from bone proportions rather than directly observed, and the finding rests on one specimen. "Earliest known" reflects what has been found, not necessarily what existed. The fossil comes from the recently recognised Zhenghe Fauna, a newly sampled window into this period. Sources: Nature, "Jurassic flightless bird reveals early ecological diversity of avialans", 2026, volume 658 issue 8136, page 690, DOI 10.1038/s41586-026-10972-z, https://doi.org/10.1038/s41586-026-10972-z; ScienceDaily, "This 150-million-year-old bird had dinosaur teeth and a strange secret", 23 October 2026, https://www.sciencedaily.com/releases/2026/10/261023023710.htm; Chinese Academy of Sciences, Institute of Vertebrate Palaeontology and Palaeoanthropology, http://english.ivpp.cas.cn. This article is for general information. It covers palaeontology research and contains no health advice; for any health question, speak to a doctor, pharmacist or other qualified healthcare professional.
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