Archaeopteryx is not the "earliest bird" anymore? New discovery by Chinese scientists pushes back the history of bird evolution by 20 million years!

A Chinese research team recently discovered a 150 million-year-old bird fossil, the "Zhenghe Bamin Bird", in the "Zhenghe Fauna" in Fujian. This is one of the earliest known birds in the world and the only confirmed Jurassic bird. This discovery advanced the appearance of the pygostyle, a key feature of modern birds, by nearly 20 million years, rewriting the history of bird evolution. The relevant results were published in the international academic journal Nature on February 13.

Rewriting the history of bird evolution

Starting from 2021, researchers Wang Min and Zhou Zhonghe from the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, and the Fujian Institute of Geological Survey have cooperated to form a field team to carry out systematic paleontological and stratigraphic surveys in Fujian Province. In September 2023, the joint team reported in Nature the first dinosaur bone fossil discovered in Fujian, the strange Fujian dragon (Fujianvenator prodigiosus), and named it the "Zhenghe Fauna", providing a new window for studying the evolution of East Asia's late Mesozoic terrestrial ecosystems. In November 2023, the field team discovered two incomplete reptile fossils in the "Zhenghe Fauna", one of which had only part of the shoulder girdle bones exposed from the surrounding rock.

Ecological restoration map of Zhenghe Bamin Birds and Zhenghe Animal Group (drawn by Zhao Chuang)

After a year-long indoor restoration and research and analysis of the fossil, the research team determined that the fossil belonged to a bird and named it "Zhenghe Bamin Bird" (Baminornis zhenghensis). Its genus name "Bamin" is the ancient name of Fujian.

The holotype specimen of Zhenghe Baminornis (Photo provided by Wang Min)

The most special thing about Bamin Bird is that it has a fused pygostyle, which is the cornerstone of the modern bird's body shape. The most significant difference between birds and other reptiles is that birds have very short tails. Not only are the number of caudal vertebrae reduced, but the last few caudal vertebrae are fused into a structure called pygostyle, which is crucial to the forward shift of the body's center of gravity, the independent movement of the hind limbs and the coccyx, and the improvement of flight ability.

The shortening of the tailbone is one of the most radical morphological changes in the evolution of dinosaurs to birds. When it comes to the origin of birds, Archaeopteryx, which was discovered in the Late Jurassic in Germany, is widely known, but some studies believe that Archaeopteryx belongs to Deinonychus rather than birds. Because "potential Jurassic birds" including Archaeopteryx and Anchiornis still have the same long tailbone as dinosaurs, from this point of view, they are very different from birds at least in terms of body shape.

It is speculated that the Zhenghe Bamin bird was similar in size to today's cockatoos, weighed about 100 grams, and lived in an environment similar to lakeside swamps. The discovery of Bamin bird revealed for the first time that the body size of modern birds had already appeared in the Jurassic period, pushing the origin of birds back to the late Middle Jurassic period, 172 million to 164 million years ago, rewriting the history of bird evolution and further demonstrating the great potential of Zhenghe fauna for exploring the evolution of East Asian late Mesozoic ecosystems.

Is Archornis no longer the “earliest bird”?

In the view of Zhou Zhonghe, an academician of the Chinese Academy of Sciences and a researcher at the Institute of Vertebrate Paleontology and Paleoanthropology, the Zhenghe Bayunbird represents the oldest bird fossil known in the world except for the controversial Archaeopteryx. "This is a landmark discovery."

Academician of the Chinese Academy of Sciences and director of the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, Researcher Xu Xing said that the only bird known in the Jurassic period before was Archaeopteryx, which also lived about 150 million years ago, but Archaeopteryx was more like a dinosaur with feathers. The Zhenghe Bayinornis was only about two to three million years later than Archaeopteryx, but it already showed the body configuration of modern birds, which is of great significance for studying the origin and early evolution of birds.

"Compared to Archaeopteryx, Zhenghe Minnice is more bird-like overall." Wang Min said that phylogenetic analysis based on parsimony and Bayesian methods both support the bird classification position of Zhenghe Minnice. "On the evolutionary tree, Zhenghe Minnice is the earliest differentiated bird lineage after Archaeopteryx. So, if there is doubt about the bird classification of Archaeopteryx, Zhenghe Minnice is the only confirmed Jurassic bird at present."

The origin of birds may be further advanced

It is understood that in addition to the discovery of Baminornis, the research team also found a separately preserved forkbone. The results show that the forkbone is very similar to the modern birds of the Cretaceous (the earliest modern birds appeared 130 million years ago), but is clearly different from Zhenghe Baminornis and other Jurassic birds and dinosaurs.

Due to the lack of more information to determine its classification position, the research team has temporarily classified the furcula into the large classification unit of birds. However, the discovery of the furcula confirms that at least two types of birds lived in the Zhenghe fauna. If the furcula does belong to the modern bird type, then the origin of birds will be further advanced.

"We found clavicles similar to those of birds aged 130 million years in strata dating back 150 million years. This shows that the origin and appearance of birds as a whole are earlier than previously thought. We can now speculate on the time when the earliest birds appeared even earlier," said Wang Min.

Source: BRTV News, Xinhuanet, Voice of the Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Science and Technology Daily, China News Network