BEIJING, July 5 (Xinhua) -- Chinese researchers have recently discovered a new Jurassic bird fossil that overturns a long-held assumption about how the avian tail evolved, according to findings published online in the journal Science Advances Thursday.
The fossil, named Zhengheornis buyu, was unearthed by a joint research team from the Institute of Vertebrate Paleontology and Paleoanthropology under the Chinese Academy of Sciences and the Institute of Geological Sciences in east China's Fujian Province.
The researchers' study shows that the bird had a tail of only 15 shortened caudal vertebrae, with no fused pygostyle at its terminal end. In contrast, other long-tailed birds have significantly more caudal vertebrae.
The pygostyle is a structure formed by the fusion of multiple terminal tail vertebrae. It is a key part of the modern bird skeleton and plays a vital role in flight, while the shortening of the tail is one of the most profound morphological transformations in the transition from dinosaurs to birds.
Weighing merely 74 to 163 grams and measuring about 20 centimeters in length, it is the smallest known long-tailed bird to date. The unique combination -- a short tail with no fused pygostyle -- is exactly what makes the discovery so significant, as it challenges the long-held assumption that no such transitional form existed.
Previous fossil records indicated that the earliest birds with a pygostyle appeared during the Late Jurassic, about 150 million years ago, when other birds and their dinosaurian relatives all still had long tails.
The researchers noted that body size miniaturization is one of the key driving forces behind the dinosaur-to-bird transition, suggesting that some birds underwent more rapid size reduction at the dawn of their evolution than previously believed. ■
