Pterosaurs Had Four Types of Feathers, New Study Shows
Pterosaurs lived side by side with dinosaurs, some 230 to 66 million years ago. They were the first vertebrates to achieve true flapping flight, but in the absence of living species, many questions concerning their biology and lifestyle remain unresolved. It has long been known that they had some sort of furry covering called ‘pycnofibers,’ and it was presumed that it was fundamentally different to feathers of dinosaurs and birds. An analysis of two pterosaur specimens with well-preserved pycnofibers shows that these flying reptiles had at least four types of feathers: simple filaments (hairs), bundles of filaments, filaments with a tuft halfway down and down feathers.
Birds have two types of advanced feathers used in flight and for body smoothing, the contour feathers with a hollow quill and barbs down both sides.
These are found only in birds and the theropod dinosaurs close to bird origins. But the other feather types of modern birds include monofilaments and down feathers, and these are seen much more widely across dinosaurs and pterosaurs.
“Our discovery has amazing implications for our understanding of the origin of feathers, but also for a major time of revolution of life on land,” said University of Bristol’s Professor Mike Benton, senior author of the study.
“When feathers arose, about 250 million years ago, life was recovering from the devastating end-Permian mass extinction.”
Professor Benton and co-authors studied two pterosaur specimens from the Middle-Late Jurassic Yanliao Biota (around 165–160 million years ago) in Inner Mongolia, China, and found many examples of all four types of feathers.
“We were able to explore every corner of the specimens using high-powered microscopes, and we found many examples of all four feathers,” said Nanjing University paleontologist Dr. Zixiao Yang, first author of the study.
“Some critics have suggested that actually there is only one simple type of pycnofiber, but our studies show the different feather types are real,” said co-author Dr. Maria McNamara, a researcher at University College Cork.
“We focused on clear areas where the feathers did not overlap and where we could see their structure clearly. They even show fine details of melanosomes, which may have given the fluffy feathers a ginger color.”
“We ran some evolutionary analyses and they showed clearly that the pterosaur pycnofibers are feathers, just like those seen in modern birds and across various dinosaur groups,” Professor Benton said.
“Despite careful searching, we couldn’t find any anatomical evidence that the four pycnofiber types are in any way different from the feathers of birds and dinosaurs. Therefore, because they are the same, they must share an evolutionary origin, and that was about 250 million years ago, long before the origin of birds.”
The study was published in the journal Nature Ecology & Evolution.
Zixiao Yang et al. 2019. Pterosaur integumentary structures with complex feather-like branching. Nature Ecology & Evolution 3: 24-30; doi: 10.1038/s41559-018-0728-7