Chinese paleontologists have unveiled a remarkable discovery: a previously unknown small Jurassic bird. The short tail of this bird provides critical evidence that early avian species transitioned from long dinosaur-like tails to compact coccyges, facilitating flight in modern birds.
Modern birds stand out among vertebrates for possessing short tails comprised of a fused bony structure known as the coccyx, which is crucial for flight. In contrast, their dinosaur ancestors boasted lengthy, bony tails made up of numerous vertebrae.
Determining the timing and nature of this evolutionary transition remains challenging due to the scarcity of fossil evidence capturing intermediate stages.
The recently identified Jenhernis Buyu provides an important addition to our understanding of this evolutionary gap.
“Evolutionary biologists have traditionally argued that a transitional species with a partially fused bony tail is biologically implausible, as long-tailed and short-tailed birds appeared almost concurrently in the fossil record,” stated Dr. Zhou Zhonghe, a paleontologist from the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences.
The holotype specimen of Jenhernis Buyu was discovered in 2024 within the Nanyuan Formation near Yangyuan Village in Zhenghe Country, Fujian Province, China. This fossil dates back approximately 148 to 150 million years ago, during the late Jurassic period, when early bird species began to diversify.
Remarkably, this is the fourth taxonomic group of birds recognized within the Zhenghe fauna. The other identified specimens include Baminornis and an incomplete specimen characterized by a single wishbone.
Estimates based on femur circumference and length suggest that Jenhernis Buyu weighed between 74 to 163 grams, making it smaller than previously recognized tiny specimens like Archeopteryx.
The research team confirmed that Jenhernis Buyu is the smallest known adult non-pygostyle theropod identified to date.
Holotype specimen of Jenhernis Buyu. Image credit: Wang et al., doi: 10.1126/sciadv.aeb5202.
The tail of Jenhernis Buyu includes merely 15 vertebrae, whereas other early avian relatives contain over 30 verebrae that remain separate from the caudal column. The last two coccyges exhibit an unusual boxy shape, a feature observed only in distantly related dinosaurs such as Codypteryx.
This finding challenges the prevailing concept that tail shortening and caudal column formation were simultaneous processes.
“This anatomical mosaic indicates a gradual evolutionary pathway. In early avian evolution, the reduction and shortening of vertebrae preceded the fusion of the tail column,” commented Dr. Ming Wang from the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences.
The team’s analysis also indicates that unlike other nearby Jurassic birds, Jenhernis Buyu was not adapted for either arboreal or terrestrial living.
“The body size, skeletal structure, and ecological niches of the Zhenghe birds differ from those commonly observed. The discovery of Jenhernis Buyu provides compelling evidence of extensive adaptive radiation in birds by the end of the Jurassic period,” stated the paleontologists.
This groundbreaking discovery helps clarify longstanding academic debates regarding the timeline of early avian diversification.
For further details, refer to their published paper in this month’s issue of Scientific Progress.
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Wang Ming et al., 2026. Jurassic Birds Reveal the Gradual Evolution of the Avian Coccyx. Scientific Progress 12(27); doi: 10.1126/sciadv.aeb5202.
Source: www.sci.news
