(CN) – Hundreds of new fossils reveal that pterosaurs died off abruptly during the same mass extinction event that ended the reign of dinosaurs, according to a study published Tuesday in the journal PLOS Biology.
Pterosaurs – commonly known as pterodactyls – were giant prehistoric flying reptiles with skin wings supported by a single large finger. They were one of the largest animals ever to fly.
While scientists previously believed pterosaurs were declining prior to the mass extinction event at the end of the Cretaceous period around 66 million years ago, the new fossils show the creatures were actually thriving.
The fossils, discovered at sites in Northern Morocco, show that the region supported seven pterosaur species – including six that were recently identified – from three different families.
The new pterosaurs ranged in wingspan from more than 6 feet to 30 feet – nearly three times bigger than the largest living bird – and weighed up to 440 pounds. Besides the diversity in size, the species also differed significantly in the size and shape of parts of their bodies including neck length, wing proportions and beak shape. This suggests they occupied distinct ecological niches, according to the team.
“To grow so large and still be able to fly, pterosaurs evolved incredibly lightweight skeletons, with the bones reduced to thin-walled, hollow tubes like the frame of a carbon-fiber racing bike,” said lead author Nick Longrich, a researcher at the Milner Center for Evolution and the department of biology and biochemistry at the University of Bath in the United Kingdom.
“But unfortunately, that means these bones are fragile, and so almost none survive as fossils.”
As a college student, Longrich dreamed of studying pterosaurs. Years later, he came across a single, small bone mixed in with fossil fish retrieved from a phosphate mine in Morocco.
“It was like a light went off,” Longrich said. “I remembered back to the Illustrated Encyclopedia of Pterosaurs, a book I'd practically memorized as an undergraduate. And I thought, 'That's a nyctosaur.'”
It had not been proven that nyctosaurs, a family of small pterosaurs, survived until the end of the Cretaceous. The discovery led Longrich to look for more pterosaurs.
He ended up finding other species including Tethydraco, a member of the pteranodontids family that researchers thought had disappeared 15 million years earlier. Besides the single species previously found in the area, six more species turned up.
“I believe there are many more species to find,” Longrich said.
The rarity of pterosaur fossils from around the end of the Cretaceous led many researchers to conclude that the species went extinct slowly. However, the new findings show that the data had been misleadingly affected by the lack of fossils and that pterosaurs at this point were actually far more diverse than previously thought.
“Exciting discoveries are being made all the time, and sometimes, just the smallest of bones can radically change our perception of the history of life on Earth.” said co-author David Martill, a professor of paleobiology at the University of Portsmouth in Britain.
Co-author Brian Andres, a research associate at the University of Texas at Austin, added: “The Moroccan fossils tell the last chapter of the pterosaurs' story – and they tell us pterosaurs dominated the skies over the land and sea, as they had for the previous 150 million years.”
Nour-Eddine Jalil, a paleontologist at the Museum of Natural History in Paris, also highlighted the significance of the findings.
“This is a fabulous discovery of pterosaurs from Morocco – they tell us their amazing diversity while we thought them in decline,” said Jalil, who was not involved in the study.
“The Moroccan phosphates are an open window on a key moment in the history of the Earth, one that shortly preceded the global crisis that swept away, among others, dinosaurs and marine reptiles.”
The authors received no specific funding for the study.