Paleontologists in China have described a small, beforehand unknown Jurassic chicken whose quick tail provides new proof for a way the earliest birds traded their lengthy, dinosaur-like tails for the compact tailbone that helps residing birds fly.
Life reconstruction of Zhengheornis buyu. Picture credit score: Chung-Tat Cheung.
Trendy birds are distinctive amongst vertebrates in having a brief tail capped by a fused clump of bone known as the pygostyle, which anchors their fan of tail feathers and is important to flight.
Their dinosaur ancestors, in contrast, had lengthy, bony tails with dozens of vertebrae.
How and when that transition occurred has been troublesome to pin down, largely as a result of so few fossils seize birds in an intermediate stage.
The newly-identified chicken species, Zhengheornis buyu, seems to be a type of lacking items.
“As a result of long-tailed and short-tailed birds appeared practically concurrently within the early fossil document with out clear intermediates, evolutionary biologists have lengthy argued {that a} transitional species having an abbreviated however fully unfused bony tail was biologically inconceivable and unlikely to have ever existed,” stated Dr. Zhonghe Zhou, a paleontologist with the Institute of Vertebrate Paleontology and Paleoanthropology on the Chinese language Academy of Sciences.
The holotype specimen of Zhengheornis buyu was present in 2024 within the Nanyuan Formation close to Yangyuan village in Zhenghe nation in China’s Fujian province.
The fossil dates 148-150 million years again to the tip of the Jurassic interval, when a number of the earliest birds have been starting to diversify.
It’s the fourth chicken taxon now recognized from what paleontologists name the Zhenghe Fauna, becoming a member of Fujianvenator, Baminornis and an incomplete specimen represented by a single furcular (wishbone).
Based mostly on the circumference and size of its thigh bone, the authors estimate a physique mass of 74 to 163 grams — smaller than the diminutive specimen lengthy held up because the smallest known Archaeopteryx.
“The holotype of Zhengheornis buyu is, to our information, the smallest grownup particular person of non-pygostylian theropods recognized so far,” they stated.
The holotype specimen of Zhengheornis buyu. Picture credit score: Wang et al., doi: 10.1126/sciadv.aeb5202.
Zhengheornis buyu’s tail accommodates simply 15 vertebrae — far fewer than the 23 to 24 present in Archaeopteryx or the greater than 30 in different early chicken family members — but these vertebrae stay separate somewhat than fused right into a pygostyle.
The 2 last tail bones are unusually box-shaped, a function in any other case seen solely within the distantly associated dinosaur Caudipteryx.
The findings problem the notion that tail shortening and pygostyle formation occurred concurrently.
“This anatomical mosaic proves a stepwise evolutionary path: the vertebral discount and shortening preceded pygostyle fusion in early chicken evolution,” stated Dr. Min Wang, additionally from the Institute of Vertebrate Paleontology and Paleoanthropology on the Chinese language Academy of Sciences.
The staff’s evaluation additionally suggests Zhengheornis buyu was not clearly tailored to both tree-dwelling or ground-dwelling life, in distinction to different Jurassic birds discovered close by.
“The disparate physique dimension, skeletal structure, and area of interest preferences amongst co-occurring Zhenghe birds, various from the generalist Zhengheornis buyu to the cursorial Fujianvenator, present indeniable proof that avialans had already underwent a significant adaptive radiation by the very finish of the Jurassic interval,” the paleontologists stated.
“This landmark discovery successfully reconciles long-standing educational debates relating to the timing of the preliminary diversification of early birds.”
Their paper was revealed this month within the journal Science Advances.
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Min Wang et al. 2026. Jurassic avialan reveals stepwise evolution of bony tail in birds. Science Advances 12 (27); doi: 10.1126/sciadv.aeb5202
