20 OCT 2026 — Palaeontologists in China have described a bird from the Late Jurassic that appears to have lived on the ground and could not fly. The species, named Yuezhuornis yangyuanensis, was found in Fujian province and dates to roughly 148 to 150 million years ago. The paper was published in Nature on 14 October. Its authors are researchers at the Chinese Academy of Sciences' Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing, working with the Fujian Institute of Geological Sciences.
The IVPP describes it as the oldest bird known to have lost the power of flight. That matters because the standard account of early bird evolution treats flight as the main pressure that shaped the bird skeleton. A flightless bird this close to the base of the family tree suggests some early lineages went another way.
What the fossil is
The specimen, catalogued as IVPP V34427, is held at the institute in Beijing. According to the institute's Chinese-language release, the team found it in August 2024 in rock layers not far from the core fossil site of the Zhenghe Fauna, in Zhenghe County. The species name comes from Yangyuan Township, where that fauna was found. The genus name borrows a divine bird from ancient Chinese legend.
The animal was small. The publisher's press summary puts its weight at about 821 grams, and the institute describes it as crow-sized. By the publisher's account, its forelimbs were about a third shorter than the hind limbs.
A bird with a raptor's toe
The skeleton mixes features of birds with those of the small predatory dinosaurs closest to them. Its hips and hind limbs are bird-like. Its teeth are closely packed and serrated, a trait the institute says is typical of deinonychosaurs and not of birds. Its second toe could bend sharply upward and ended in a sickle-shaped claw, the hallmark of deinonychosaurs, the predatory group that includes Velociraptor.
"When we examined Yuezhuornis, we were struck by its extraordinary mix of features," said Wang Min of the IVPP, the study's corresponding author, in the institute's English statement. "It shows us that early bird evolution was far more complicated than we previously realized."
The Chinese release adds a detail rarely seen in an announcement. The dinosaur-like anatomy left the team itself unsure what they had, and the paper was at first rejected in review. When the researchers forced the animal into the deinonychosaur group in a test analysis, the family tree needed 14 extra evolutionary steps. The institute says that result, among others, persuaded the four reviewers.
Why researchers think it could not fly
The case for flightlessness rests on proportions. The team compared the limbs of Yuezhuornis with those of 377 living bird species. Its forelimbs fell well away from tree-dwelling, swimming and wading birds, and close to ground-dwelling birds and birds that have lost flight. The Chinese release says calculations across the dinosaur-to-bird transition rank it as the Mesozoic bird with the shortest forelimbs relative to its body yet known.
The authors read the whole package as a meat-eater adapted to running on land. Wang told Live Science, in an email interview, that there is no clean modern stand-in. "I think there are no directly comparable modern birds," he said.
Where it sits on the family tree
The team ran its phylogenetic analyses two ways: maximum parsimony and Bayesian tip-dating. "The results consistently placed Yuezhuornis firmly within Avialae (the group containing modern birds and their closest extinct relatives), just crownward of Archaeopteryx and as a sister taxon to Zhengheornis," said Zhou Zhonghe, a co-author, in the institute's statement.
The Chinese release goes further. It places Yuezhuornis and Zhengheornis together in a new family, Zhengheornithidae, and calls the new bird more primitive than Baminornis, a bird of the same age from the same fauna that carries a fused tail bone.
Nature ran a News & Views commentary alongside the paper by Fernando E. Novas of the Félix de Azara Natural History Foundation and CONICET in Buenos Aires, who was not involved. Its summary says flightless birds lived alongside known flying species. As quoted by Live Science, Novas wrote that "the ability to fly arose not once, but several times among disparate groups of carnivorous dinosaurs that are closely related to birds".
A fauna that keeps producing early birds
The Zhenghe Fauna is a recent find. It first appeared in Nature in 2023 with Fujianvenator, and the institute says its own fieldwork with the Fujian institute uncovered it. Baminornis followed in Nature in 2025 and Zhengheornis in Science Advances this year. The institute says the work behind them took more than 440 days of field excavation over four years. Its English statement argues that the run of finds makes the fauna a rare window on a stretch of bird history with few fossils.
What one specimen cannot settle
The publisher's summary is plain about the limits. Yuezhuornis rests on one partial skeleton, and further fossils will be needed to pin down how it lived and where it belongs. Flightlessness is an inference from limb proportions and shoulder bones, not a direct record. Even so, a bird that had given up on flight this early would mean the first birds were already spreading into very different ways of life.
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