Birds are famous for their colorful feathers, which they use to fly, flirt and keep warm. But long before avians ever flapped their wings, flying reptiles called pterosaurs seized the skies.
Among paleontologists, it was a long-running assumption that the winged creatures lacked feathers. But a team of researchers has found what they believe to be tiny structures hiding in the fossils of two pterosaurs from China that they say are feathers — not as elegant, but comparable to the plumage on birds and dinosaurs.
More specimens may be needed to confirm the finding, which other paleontologists questioned. But if true, it would push back the origins of feathers by about 70 million years, and also be the first time that feathers have been identified on an animal that was neither a bird nor a dinosaur.
“The feather has deeper origins, not of a bird but maybe from the ancestors of birds, dinosaurs and pterosaurs,” said Baoyu Jiang, a paleontologist from Nanjing University in China and leader of the team that collected the fossils. Their research was published Monday in the journal Nature Ecology & Evolution.
Some pterosaurs towered as tall as giraffes and had wingspans as wide as F-16 fighter jets. While sometimes pictured as scaly beasts, the fossil record has long revealed fuzzy pterosaurs enrobed in fluffy coats made of tiny structures called pycnofibers. Unlike bird feathers, which contain a central shaft with smaller shafts branching off, pterosaur pycnofibers were thought to be simple strands, similar to hair or fur.
In the latest study, Dr. Jiang and Zixiao Yang examined fossils collected in China, of short-tailed juvenile pterosaurs that were about the size of pigeons.
Both specimens were mostly covered in hollow, unbranched pycnofibers that resemble fur. But the team then found one type of branched structure, which looked like a curved painter’s brush, on the neck, part of the forelimb and foot area and tail of one of the specimens. A second structure, found on the head of the same specimen, had a central shaft that branched off near the midpoint almost like a fraying rope. And the last, which was found on both pterosaurs’ wing membranes, looked straggly like down feathers on a chicken.
In contrast with the sleek, aerodynamically designed feathers seen on modern birds, these feathers were most likely for insulation, the researchers said.
Some paleontologists had previously pegged the origin of feathers to dinosaurs somewhere around 180 million years ago in the Early and Mid-Jurassic. While these pterosaur specimens were about 160 to 165 million years old, their lineage dated back to about 230 million years ago, and the new finding adds further evidence to the idea that there was a common ancestor of birds, dinosaurs and pterosaurs that was either feathered or at least had the genes to grow them.
The researchers shared their finding with Maria McNamara, a paleobiologist at University College Cork in Ireland who performed a scanning electron microscope analysis.
“When I first saw these specimens and the branching I didn’t believe it,” Dr. McNamara said.
Her views were changed, she said, when she saw the systematic arrangement of the feather-like branches. But other scientists have retained their skepticism.
“I would not say that the evidence is overwhelming, but certainly some of the images show what appear to be branching filaments,” said Matthew Shawkey, an evolutionary biologist at Ghent University in Belgium. “But of course many things in nature branch, such as branches on a tree, so this does not mean that they are in fact feathers.”
Others were less equivocal.
“I would not use the term feathers to describe these structures,” said Julia Clarke, a paleontologist from the University of Texas at Austin, who added she would prefer using another name for them, like branched filaments or branched integumentary structures.
Jingmai O’Connor, a paleontologist from the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences in Beijing, cautioned that it was difficult to interpret feathers and feather-like structures from flattened fossils.
“I don’t know if the described morphologies of the pycnofibers in this specimen are valid,” Dr. O’Connor said. “In dinosaurs, similar claims of unusual feather morphotypes have been made that are slowly being refuted one by one. Only time and better specimens will tell.”
But Michael Benton, a paleontologist at the University of Bristol in England and an author on the study, said the structures line up with feathers observed on birds and dinosaurs.
“These additional three types are branching,” he said, “and if you simply take the dictionary definition of a feather, that is a feather.”