Scientists in China have pushed the timeline of avian evolution back by 20 million years with the discovery of the world’s earliest known bird, Baminornis zhenghensis. Unearthed in the Jurassic rock layers of eastern China’s Fujian province, this fossil challenges previous assumptions about the origins of birds, offering a new glimpse into the ancient roots of modern bird species.

The fossil of B. zhenghensis, a bird from the late Middle Jurassic period, was unveiled by the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, alongside the Fujian Institute of Geological Survey, on Thursday.

The discovery of the fossil, dating back 172 to 164 million years, was published in Nature on Thursday. Paleontologist Stephen L. Brusatte from the University of Edinburgh called it the most important bird discovery since Archaeopteryx in 1861, which is considered the first bird fossil and a key link between dinosaurs and modern birds.

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The discovery challenges previous beliefs about early bird fossils, including Archaeopteryx, which some studies suggest could belong to a group of dinosaurs rather than true birds. The newly identified B. zhenghensis shares key features with modern birds, such as a short tail fused into a pygostyle, which typically supports the tail feathers.

A photograph and interpretive line drawing of the new fossil. Image by Wang Min, from The Paper

This adaptation is crucial for shifting the body’s center of gravity forward, enabling independent movement of the hind limbs and tail and refining flight capabilities. “The shortening of the tailbone was one of the most profound changes in body structure during the transition of dinosaurs into birds,” said researcher Wang Min from the Chinese Academy of Sciences, according to state-run China Daily.

Since 2021, Wang and academician Zhou Zhonghe from CAS have been uncovering dinosaur fossils in Fujian province, leading to the identification of the “Zhenghe Fauna,” a prehistoric ecosystem rich in tortoise, fish, and plant fossils. It is the southernmost site where late Jurassic Avialae, or “bird wings,” fossils have been found.

A 2023 fossil find confirmed the existence of at least two bird species in the region. “These discoveries offer new insights into the process of biological evolution. It overturns the previous assumption that Archaeopteryx was the only bird found in the Jurassic Period,” Zhou told the state-run Xinhua News Agency.

(Header image: An artist’s rendering of B. zhenghensis, with preserved bones highlighted. Image by Zhao Chuang, from The Paper)