Most pterosaurs, flying reptiles that lived during the Late Cretaceous 77 million years ago, were giants with wingspans of between 13 and 36 feet (4 to 11 meters). The biggest was as large as a giraffe, with a wingspan of a small plane.
But newly discovered fossils suggest they could also be much smaller. A new specimen had a wingspan of only about five feet (1.5 meters)—and was about the size of a modern cat. It’s the first of its kind to be discovered on the west coast of North America.
The new fossils are the first associated remains of a small pterosaur from this time and include a humerus, dorsal vertebrae (including three fused notarial vertebrae), and other fragments. They are the first to be positively identified from British Columbia, Canada, and belong to an azhdarchoid pterosaur, a short-winged and toothless flying reptile which dominated the final phase of pterosaur evolution.
Pterosaurs are the earliest vertebrates known to have evolved powered flight.
Previous studies suggest that the Late Cretaceous skies were only occupied by much larger pterosaur species and birds, but the new finding, reported in the journal Open Science, provides crucial information about the diversity and success of Late Cretaceous pterosaurs.
“This new pterosaur is exciting because it suggests that small pterosaurs were present all the way until the end of the Cretaceous, and weren’t outcompeted by birds,” says lead author Elizabeth Martin-Silverstone, a paleobiology PhD student at the University of Southampton.
“The hollow bones of pterosaurs are notoriously poorly preserved, and larger animals seem to be preferentially preserved in similarly aged Late Cretaceous ecosystems of North America. This suggests that a small pterosaur would very rarely be preserved, but not necessarily that they didn’t exist.”
The fossil fragments were found on Hornby Island in British Columbia in 2009 by a collector and volunteer from the Royal British Columbia Museum, who then donated them to the museum. At the time, it was given to Victoria Arbour, a then-PhD student and dinosaur expert at the University of Alberta. Arbour, as a postdoctoral researcher at North Carolina State University and the North Carolina Museum of Natural Sciences, then contacted Martin-Silverstone who sent the specimen for analysis in collaboration with Mark Witton, a pterosaur expert at the University of Portsmouth.
“The specimen is far from the prettiest or most complete pterosaur fossil you’ll ever see, but it’s still an exciting and significant find,” Witton says. “It’s rare to find pterosaur fossils at all because their skeletons were lightweight and easily damaged once they died, and the small ones are the rarest of all. But luck was on our side and several bones of this animal survived the preservation process.
“Happily, enough of the specimen was recovered to determine the approximate age of the pterosaur at the time of its death. By examining its internal bone structure and the fusion of its vertebrae we could see that, despite its small size, the animal was almost fully grown. The specimen thus seems to be a genuinely small species, and not just a baby or juvenile of a larger pterosaur type.”
Other researchers from the University of Portsmouth, North Carolina State University, and the University of Alberta, coauthored the work that was funded by the Natural Sciences and Engineering Research Council of Canada.
Source: University of Southampton