Pterosaurs may have flaunted colorful plumage long before the reign of dinosaurs

The idea that dinosaurs sported colorful feathers, once outlandish, has become conventional wisdom. Now, a new study of a Brazilian fossil suggests that pterosaurs—leathery winged, flying reptiles only distantly related to dinosaurs—were also clad in tiny feathers of varying hues. The finding suggests feathers may have evolved more than 150 million years before the heyday of the dinosaurs, probably for display, the authors say. “In their very earliest forms, feathers were colored … presumably for signaling,” says paleobiologist Maria McNamara of University College Cork, who led the study.

The paper “reinforces the idea that pterosaurs were ‘fluffy,’ and indicates at least some of them probably had complex colorful patterns—which is fantastic,” says Rodrigo Pêgas, a paleontologist at the Federal University of ABC, São Bernardo do Campo, in Brazil. But Pêgas is not convinced that feathers originated as early as McNamara thinks—and some other researchers doubt the structures are feathers at all.

How feathers arose has been a big question in paleontology for more than 150 years, since the first Archaeopteryx—a feathered dinosaur once thought to be the first bird—was found in Germany. Many researchers think feathers arose for insulation and were co-opted only much later for flight and other uses, such as courtship displays. As for pterosaurs, researchers had previously reported their bodies were covered in pycnofibers, single-stranded structures that formed a “fuzz,” presumably for warmth.

Then in 2018, McNamara and her colleagues reported that two well-preserved Chinese pterosaurs showed what seemed to be a defining feature of feathers: a central shaft with branches. Some paleontologists were skeptical, and McNamara says she understood why. “Their feathers were—to be honest—a bit weird,” she says. “They didn’t branch like modern bird feathers do.”

Now, she and her colleagues have cemented their arguments with a paper this week in Nature analyzing the soft tissue of an exquisitely preserved skull of Tupandactylus imperator—a pterosaur that had a majestic head crest and a 5-meter wingspan. It lived 113 million years ago in what is now the Araripe Basin in northeastern Brazil, although McNamara studied the fossil in Belgium. The team thinks it was poached from Brazil and kept in private collections until recently. Earlier this year, the Royal Belgian Institute of Natural Sciences repatriated the fossil to Brazil, where it will be displayed at the Earth Sciences Museum in Rio de Janeiro. “It is great that the fossil is back in Brazil,” Pêgas says.

On the pterosaur’s head crest, the researchers identified both single-stranded fibers and featherlike branching ones with a central shaft narrowing at the base. Under the scanning electron microscope, both skin and feathers had melanosomes, intracellular structures containing melanin that give pigment to skin, feathers, and fur in living animals, with differently shaped melanosomes conferring different colors. The pterosaur’s melanosomes had diverse shapes—ovoid, spherical, and elongated—something until now only seen in mammalian fur and dinosaur and bird feathers.

Tupandactylus imperator, a large pterosaur that lived in what is now Brazil, may have sported a colorful head crest, as seen in this artist’s illustration.© Bob Nicholls 2022

The researchers think Tupandactylus’s colored, branching structures were indeed feathers, which both kept it warm and enabled it to signal to other pterosaurs, perhaps as male peacocks do by displaying plumage during mating.

The finding means feathers must have evolved far earlier than was thought, McNamara says. “The most parsimonious explanation is that feathers were present in the common ancestor of [pterosaurs and dinosaurs],” about 250 million years ago during the Triassic period.

Some paleontologists say the evidence of feathers is persuasive. “We’re hammering it in with 7-inch nails with these findings,” says Jakob Vinther, a paleobiologist at the University of Bristol. Paleontologist Michael Benton, also at Bristol, agrees, but “I don’t think pterosaur feathers had any function in flight because they’re just fluffy little feathers.”

But paleontologist David Martill from the University of Portsmouth says the small branched structures “look nothing like feathers.” He thinks they are a different kind of keratinous covering, though he agrees they were probably spectacularly colored.

Even if they are feathers, pterosaurs may not have flaunted them like Mesozoic peacocks, Vinther says. He notes that the researchers didn’t infer the melanosomes’ color and says it’s possible the plumage was used for camouflage rather than display.

Nor is it certain that the pterosaur structures share an ancient origin with those of dinosaurs and their descendants, living birds, some researchers say. “We still need fossil evidence for feathers in the Triassic as well as unequivocal molecular evidence for the common origin between pterosaur pycnofibers and dinosaur feathers,” Pêgas says.

McNamara promises more evidence for her scenario. Her team is working to characterize the detailed chemistry of the Tupandactylus samples, which could reveal organic compounds in the feathers.

If the current findings hold up, they may shed light on the selection pressures that shaped early feathers, says Jasmina Wiemann, a molecular paleobiologist at the California Institute of Technology. “Thermal regulation has been the old hypothesis out there … [but] maybe there’s more to it.”

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