When we see birds winging their way across the sky, we are really looking at living dinosaurs—the only lineage of these mighty beasts that survived mass extinction. Yet before they went extinct, many dinosaurs sprouted wings themselves. Researchers now report finding the largest ever winged dino in China, a sleek, birdlike creature adorned with multiple layers of feathers all over its arms and torso that lived 125 million years ago. It almost certainly could not fly, however—an important confirmation that wings and feathers originally evolved to serve other functions like attracting mates and keeping eggs warm.
Over the past 20 years, thousands of specimens of feathered dinosaurs have been found in China’s northeastern Liaoning province, adding greatly to researchers’ understanding of the origins of flight. One of the most important of these Liaoning groups is the dromaeosaurs, which include Velociraptor of Jurassic Park fame and Microraptor, one of the few dinosaurs that scientists widely agree could probably fly. That leaves open the question of what function dinosaur wings and feathers originally served if they were not used for taking to the air.
Now, reporting online today in Scientific Reports, paleontologists Junchang Lü of the Chinese Academy of Geological Sciences in Beijing and Stephen Brusatte of the University of Edinburgh in the United Kingdom describe the largest known dinosaur with birdlike wings and feathers. The new, nearly complete specimen, which the pair has named Zhenyuanlong suni (after Zhenyuan Sun, a representative of the local museum where the fossil is kept who obtained it from a local Liaoning farmer; “long” means dragon in Mandarin Chinese). The dino was about 1.65 meters long, a little longer than a modern condor, but at an estimated 20 kilograms, it was probably nearly twice as heavy as that bird.
That weight, along with its very short arms compared to most dromaeosaurs, almost certainly indicate that it could not fly, Lü and Brusatte say. And yet unlike most feathered dinosaurs, Zhenyuanlong sported a full set of wings and complex, quill-like feathers typical of those of modern birds.
What were they used for? One possibility, the researchers say, is that Zhenyuanlong evolved from dinosaur ancestors that could once fly, similarly to the way that flightless birds like today’s ostriches and penguins evolved from flight-capable forebears. But more likely, they think, the wings and feathers served some other function, such as appealing to the opposite sex—much as peacocks do today—or keeping itself or its eggs warm.
“This specimen is particularly important because it helps confirm that the evolution of dinosaur wings, and therefore the wings of birds, was not necessarily tightly coupled to the evolution of flight,” says Michael Habib, a paleontologist at the University of Southern California in Los Angeles. On the other hand, Habib says, its wings could still have helped it jump down from ledges or run up steep inclines, so-called “wing assisted” behaviors seen in flightless birds today.
Alex Dececchi, a paleobiologist at Queen’s University in Kingston, Canada, agrees with the authors’ suggestion that Zhenyuanlong’s feathers and wings might have been used for sexual display or other kinds of signaling. “We know that large feathers appeared even earlier in the lineage leading to birds, as did brightly colored plumage. This suggests that display likely had a big role in the lives of dinosaurs.” If so, it might have helped one lineage of dinosaurs, the birds, wing their way through the mass extinction that wiped out all the others.