Chinese researchers have identified Zhengheornis buyu, a 150-million-year-old fossil that reveals birds shed the long, bony tails of their dinosaur ancestors through a step-by-step process, rather than a sudden evolutionary transition as previously believed. Discovered on March 24, 2024, in Fujian province, this Late Jurassic specimen fills a critical gap in scientists’ understanding of how dinosaurs’ elongated tails evolved into the compact tails of modern birds. The findings, published in the peer-reviewed journal Science Advances on July 1 (and reported online Thursday), confirm that the reduction in tail vertebrae occurred before the remaining vertebrae fused into the pygostyle—the bony structure that characterizes the tails of modern birds—helping resolve a long-standing debate in evolutionary biology.
The Institute of Vertebrate Paleontology and Paleoanthropology Unearths Zhengheornis buyu
A Missing Link in Avian Evolution
The transition to a short, feathered tail was one of the most important steps in the evolution and survival of birds, the only living group of dinosaurs to survive a mass extinction event 66 million years ago. The evolutionary assembly of the flight-adapted bird body plan encompasses some of the most profound morphological changes in terrestrial vertebrate history,
a team of Chinese researchers said in their paper. The fossil was unearthed by a joint research team from the Institute of Vertebrate Paleontology and Paleoanthropology under the Chinese Academy of Sciences and the Institute of Geological Sciences in Fujian Province.
The study shows that the bird had a tail of only 15 shortened caudal vertebrae, with no fused pygostyle at its terminal end. In contrast, other long-tailed birds have significantly more caudal vertebrae. The pygostyle is a structure formed by the fusion of multiple terminal vertebrae. This fossilized remains, named Zhengheornis buyu, appear to be the smallest known long-tailed bird from the Late Jurassic.
Professor WANG Min Investigates the Fragmentary Fossil Record of Archaeopteryx
Evolutionary Context and Morphology
Birds are the most diverse land vertebrates, and some studies suggest their earliest diversification dates back to the Jurassic period, around 145 million years ago. However, the early history of birds is unclear due to a fragmentary fossil record, with Archaeopteryx being the only widely accepted Jurassic bird. Although Archaeopteryx had feathered wings, it looked like non-avialan dinosaurs because of its long, reptilian tail. Recent studies have questioned whether Archaeopteryx is an actual bird, raising the question of whether there are any clear records of Jurassic birds. A research team led by Professor WANG Min from the Institute of Vertebrate Paleontology and Paleoanthropology has been working to address these gaps.
Modern birds are unique among vertebrates in having a short tail capped by a fused clump of bone called the pygostyle, which anchors their fan of tail feathers and is essential to flight. Their dinosaur ancestors, by contrast, had long, bony tails with dozens of vertebrae. The newly-identified bird species provides new evidence for how the earliest birds traded their long, dinosaur-like tails for the compact tailbone that helps living birds fly.
Baby Yingliang and Fujianvenator prodigiosus Expand the Chinese Paleontological Record
Comparative Discoveries and Scientific Challenges
The research landscape in China has been bolstered by other significant finds. For instance, a 66-million-year-old dinosaur embryo now dubbed ‘Baby Yingliang’ was recently discovered in southern China. A joint study from the University of Birmingham and China University of Geosciences found that the Oviraptorosaur fossil was in a curled-up position similar to that of modern bird embryos. Additionally, another fossilized remain, Fujianvenator prodigiosus, was unearthed in 2022 and described in Nature; it is as old as Archaeopteryx and might have specialized in running or wading instead of flying.
Reconstructing these ancient animals remains difficult.
The Identification of Baminornis Clarifies the Theropod Dinosaur Lineage
The discovery of Zhengheornis buyu, alongside other recent breakthroughs, highlights a productive period for paleontology. As noted in recent reports, 2025 has been a great year for the field, both in actual discoveries and in first-described publications. The identification of Baminornis, another Jurassic bird, further illustrates the ongoing effort to tie modern birds’ ancient lineage to theropod dinosaurs. By analyzing these fossils, researchers are gaining a deeper understanding of the early development of flight and the complex morphological shifts that defined the transition from the Jurassic era to the modern avian form.
Related reading
