A Bird as Old as Archaeopteryx May Have Already Abandoned Flight, Carrying a Raptor-Style Sickle Claw

A crow-sized bird that lived roughly 150 million years ago, in the same era as Archaeopteryx, appears to have already given up flying. The fossil, named Yuezhuornis yangyuanensis, was described in a study published Oct. 14 in Nature. It combines a bird's hips and legs with serrated teeth and a curved, sickle-shaped claw on its second toe, features long associated with small predatory dinosaurs.

The specimen comes from the Zhenghe Fauna in Fujian Province, southeastern China, and dates to the Late Jurassic, about 148 to 150 million years ago. The research was led by teams from the Chinese Academy of Sciences' Institute of Vertebrate Paleontology and Paleoanthropology and the Fujian Institute of Geological Sciences. The authors call it the earliest known bird lineage to lose flight, a notable claim because flight is usually treated as the defining step in early bird evolution.

The animal is an odd assembly. Its pelvis and hind limbs look like a bird's. Its closely spaced, serrated teeth resemble those of deinonychosaurs, the meat-eating dinosaur group that includes Velociraptor. Its second toe bends back unusually far and carries the sickle claw, a trait known from dromaeosaurids and troodontids but not previously from birds. Corresponding author Min Wang said, according to ScienceDaily, that the team was struck by the extraordinary mix of features. The study estimates a body mass of about 821 grams, roughly 1.8 pounds.

The case for flightlessness rests on proportions. The forelimbs are about one-third shorter than the hind limbs, according to a Nature press summary. The team compared its limb measurements statistically with 377 living bird species. The closest matches were ground-dwelling birds such as pheasants, along with some bird-related dinosaurs.

That is circumstantial evidence, not direct observation. No feathers or flight muscles are preserved to settle the question, so the conclusion comes from skeletal ratios. The species is also known from a single incomplete specimen, and the authors say more fossils are needed. Its place on the family tree was tested with two methods, maximum parsimony and Bayesian tip-dating. Co-author Zhonghe Zhou places it one step more advanced than Archaeopteryx, as the closest relative of another Zhenghe bird, Zhengheornis. Such placements can shift as new fossils turn up.

Archaeopteryx, found in Bavarian limestone in Germany beginning in 1861, has been the iconic Jurassic bird for more than 150 years. It had feathered wings and is generally thought capable of at least some flight. Edinburgh paleontologist Steve Brusatte once called it the textbook example of a creature caught in the act of evolution, in comments to Reuters about another Zhenghe find. Yuezhuornis lived around the same time but seems to have invested in strong legs and a predator's foot rather than wings.

That other find was Baminornis, described in 2025: a quail-sized bird about 150 million years old from the same area. It had a short, fused tail bone like modern birds, unlike Archaeopteryx's long, reptile-like tail, and lived in a swampy landscape alongside the meat-eating dinosaur Fujianvenator, turtles and fish. Until then, Reuters reported, Archaeopteryx was the only unquestioned Jurassic bird. Together, the Fujian fossils suggest Late Jurassic birds came in several body plans, some built for better flight and at least one apparently built for the ground. If so, early birds were not a single march toward the sky; some lineages may have tried flight and then specialized elsewhere, as ostriches, kiwis and penguins did tens of millions of years later.

The teeth and claw point to an active hunter. Small raptor dinosaurs with similar features likely used the claw to pin or grip prey, and a crow-sized ground bird so equipped may have chased insects, lizards or other small animals on the forest floor. The authors frame this as inference from anatomy, not direct evidence such as stomach contents. The Zhenghe Fauna itself is recently recognized and still poorly understood.

The study is peer-reviewed, but it depends on one partial skeleton and statistical comparison, and the earliest-flightless title could change if older fossils emerge or new specimens alter the limb picture. Next, paleontologists will search Fujian's Jurassic rocks for more Yuezhuornis specimens and other birds.