It’s possible that all dinosaurs had feathers. Scientists previously believed that only avian dinosaurs — that is, the direct ancestors of our modern birds — sported feathers along with their scales. But the discovery of fossilized feathers on a newly identified dinosaur far removed from the bird lineage means that feathers likely were more widespread in the dinosaur world.
The discovery, published Thursday in Science, could change scientists’ understanding of how and why feathers evolved.
Several partial skeletons of the new dinosaur, called Kulindadromeus zabaikalicus, were discovered in a recent geological survey of the Kulinda Valley in Siberia. A plant-eating dinosaur that lived during the Jurassic period and only reached about five feet long, it didn’t use its feathers for flying.
“It’s impossible that they flew,” said lead study author Pascal Godefroit, director of earth and life sciences at the Royal Belgian Institute of Natural Sciences. “They were bipedal and had long legs with very, very short arms.”
Their feathers varied from quite primitive — structures like bristles or hair — to downy feathers much like those seen on modern birds, Godefroit and his colleagues reported. The bristles most likely served as insulation, indicating that it was warm-blooded, Godefroit said.
The more advanced feathers, which were found around the legs of the dinosaur, were probably decorative. “To us that implies that they had some kind of social life,” he said, and that they used the more elaborate plumage to attract mates.
This adds further weight to previous theories about feathers — that they originally evolved for something other than flight. “Flight is the latest stage in feather evolution,” Godefroit said. Even after bird ancestors developed truly bird-like feathers, he said, they were gliding instead of flying.
University of Calgary assistant professor of geoscience Darla Zelenitsky, who wasn’t involved in the study, agrees. “This discovery suggests that feathers became a useful tool early on in dinosaur evolution, whether it was for camouflage, display or insulation,” she said. Seeing feathers on a dinosaur so far removed from a bird, Zelenitsky said, suggests to her that they could have been found on most dinosaurs.
One area still ripe for exploration is large dinosaurs. “We’ve learned in recent years that feathers in dinosaurs were diverse in form, and evolved initially for things other than flight,” she said, “but because most known feathered dinosaurs are relatively small, we still know very little about the nature or presence of feathers in larger dinosaurs.”
Unfortunately, scientists might never make the leap from “could have been” to a definitive answer on dinosaur feathers. “It must be proven by the discovery of fossils with preserved evidence of feathers, which is very difficult,” Godefroit said.
The preservation of feathers seen in Kulindadromeus zabaikalicus, which researchers said was particularly remarkable, was a complex and lucky accident. The combination of volcanic material and lake sediment that covered them allowed for exceptional soft tissue preservation, Godefroit said. But such specimens are rare, and without them researchers are left guessing.
“We don’t know when new feathered dinosaurs will be discovered,” Godefroit said. “Such big discoveries are made only by chance.”