150-Million-Year-Old Chinese Fossil Shows Gradual Bird Tail Evolution

A 150-million-year-old fossil discovered in China shows that birds lost the long bony tails of their dinosaur ancestors through a gradual evolutionary process. South China Morning Post reported the finding, which was described in a paper published July 1 in the peer-reviewed journal Science Advances.

The fossil fills a gap in understanding the transition to the pygostyle, a fused structure formed by the final few caudal vertebrae in modern birds.

This short tail anchors feathers and muscles and supports tail fanning along with aerodynamic advantages during flight. Researchers from the Chinese Academy of Sciences and the Fujian Province Geological Science Research Institute authored the paper.

They stated that early-diverging birds and birdlike dinosaurs remain exceedingly rare in the fossil record, which has complicated prior study of the change.

“The evolutionary assembly of the flight-adapted bird body plan encompasses some of the most profound morphological changes in terrestrial vertebrate history,” the team said. Birds represent the only dinosaur group that survived the mass extinction event 66 million years ago.

“A short pygostyle-bearing tail is functionally and ecologically vital to living birds, which enables tail fanning and conveys aerodynamic advantages,” the researchers added.