A remarkably preserved 150-million-year-old bird fossil discovered in China is challenging long-standing ideas about how birds evolved. Rather than developing increasingly sophisticated flight abilities, some of the earliest birds appear to have taken a very different evolutionary path, including losing the ability to fly altogether. The newly identified species, Yuezhuornis yangyuanensis, lived during the Late Jurassic period (150-148 million years ago).
Described in a study published in Nature, the crow-sized creature provides evidence that early bird evolution was much more complex than scientists once believed. Instead of evolving primarily to become better flyers, ancient birds were adapting to a variety of environments and ways of life, including those that favored living on the ground. Researchers from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences (CAS) and the Fujian Institute of Geological Sciences uncovered the fossil in the recently recognized Zhenghe Fauna of Fujian Province in southeastern China.
According to their findings, Yuezhuornis represents the earliest known example of a bird lineage losing its ability to fly. An Ancient Bird With Dinosaur Teeth and Claws One of the most remarkable features of Yuezhuornis is its unusual combination of bird and dinosaur characteristics. Although it possessed skeletal features associated with birds, it also retained anatomical traits that would have been familiar among small predatory dinosaurs.
Its jaws contained closely spaced, serrated teeth resembling those of deinonychosaurs, a group of meat-eating dinosaurs that included agile predators related to birds. Such teeth are not normally associated with early birds. Even more striking was its second toe, which could bend backward unusually far and carried a curved, sickle-shaped claw.
This specialized feature is strongly associated with deinonychosaurs, including dromaeosaurids and troodontids, two groups of predatory dinosaurs. "When we examined Yuezhuornis, we were struck by its extraordinary mix of features," said Dr. Min Wang, corresponding author of the study.
"It possesses bird-like pelvic and hindlimb structures yet retains the specialized predatory foot and teeth of a small meat-eating dinosaur. It shows us that early bird evolution was far more complicated than we previously realized." Where Does This Strange Jurassic Bird Fit in Evolution? To understand how Yuezhuornis was related to other prehistoric birds and dinosaurs, scientists carried out detailed analyses of its evolutionary relationships.
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