Jurassic bird fossil from China suggests some early birds were ground-dwellers

Centre · 2Researchers have described a nearly complete fossil of a new Jurassic bird species, Yuezhuornis yangyuanensis, found in Fujian Province, south-eastern China. 1 2 Centre · 1The fossil is about 148 million to 150 million years old. It was found in August 2024 and named by Min Wang of the Chinese Academy of Sciences and colleagues after Yuezhuo, a mythological Chinese bird. 1 Centre · 2The animal was about half a metre tall and weighed just over 800 grams (1.8 pounds), roughly the size of a large crow. Wang suspects it lived in a swampy environment and was probably a good runner. 1 2

Centre · 2Its forelimbs were shorter than its hindlimbs, as in modern ground-dwelling birds such as pheasants. The researchers compared its anatomy with nearly 400 living birds (377 species, according to The Times of India) and found it most similar to terrestrial species. 1 2 Centre · 2It had dinosaur-like features: closely packed, serrated teeth like those of deinonychosaur dinosaurs, a long tail like that of Archaeopteryx, and a sickle-shaped claw on its second toe. Wang calls the claw "highly functional" and says it was probably used to catch prey. It resembles the claws of relatives such as Velociraptor, which modern birds have lost. 1 2 Centre · 1Other features, including its hip bones and fibula, resemble those of later Cretaceous birds. Wang describes the result as a "mosaic" of primitive and derived features. 1

Centre · 2Archaeopteryx, from roughly the same period, has forelimbs longer than its hindlimbs and probably flew better. New Scientist reports that the researchers' analysis places Archaeopteryx as more primitive than Y. yangyuanensis. 1 2 Centre · 1The researchers argue that bird evolution was more complex and rapid than thought, with early species quickly exploring different niches, including lifestyles without flight. Wang says this challenges the idea that selection for flight almost exclusively drove the early avian body plan. 1 Centre · 2The coverage differs on flight ability. New Scientist calls the species flightless and says it may have never flown or abandoned flight almost immediately after evolving it. The Times of India, citing Reuters, says it had fully developed wings but probably could not sustain powerful flight and likely flew only when it had to. It adds that the wing was about a third shorter than the legs. 1 2

Centre · 2The Times of India says the fossil does not settle how flight evolved. Other early birds may have had different survival strategies, or may have descended from flying ancestors and become more ground-dependent. New Scientist adds that recent finds, including a bird-like dinosaur from China that evolved flight from a different lineage, are disrupting the view of a straight-line path to flight. 2 1