Fossil evidence suggests tiny pterosaurs the size of house cats
In the age of dinosaurs, ancient reptiles called pterosaurs soared through the skies of the Earth. To date, most fossil evidence of this flying reptile had wingspans that were as wide as 10 m (33 ft). Now, newly examined fossils suggests a smaller form of the vertebrate – about the size of a house cat – that could rewrite the evolutionary history of this ancient creature.
"It's quite different from other animals we've studied," says Elizabeth Martin-Silverstone of the University of Southampton, UK and lead author of the study. "There hasn't really been evidence before of small pterosaurs at this time period."
The fossils of the tiny creature consist of an upper arm bone and vertebrae, which were discovered in Hornby Island in British Columbia, Canada. The wingspan of the specimen is just 1.5 m (5 ft) and its height is on par with that of a common house cat.
Microscopic analysis of a thin slice of the arm bone called the humerus – as well as observations of the vertebrae beginning to fuse together – led Martin-Silverstone and her team to conclude that the despite the small size of the animal, it was almost fully grown at its time of death.
Pterosaurs' bones were hollow and possessed thin walls, making their preservation and discovery in fossilized form rare. In addition, smaller sized pterosaurs are difficult to identify. These roadblocks have made it hard for scientists to paint a clear picture of the animals' diversity and evolution up until their extinction, and the small number of fossils in the current study means that it's still not definitive that tiny pterosaurs roamed the skies alongside larger ones.
"I praise the authors for their efforts, but the specimen is not very complete," says Alexander Kellner, a paleontologist at the National Museum of Brazil in Rio de Janeiro. "If they had a skull, jaw or neck bones, that would help. The classification? I don't know. It could be anything."
Despite the uncertainty, if the fossils do prove to have originated from smaller-sized pterosaurs, the implications for the mass extinction of this order at the end of the Cretaceous period would be interesting. This particular extinction typically affected larger species, while smaller animals such as birds were able to tough it out and continue their evolution. If smaller pterosaurs did exist, it would suggest that small size wasn't the only factor connected to the success or failure of animals in the face of the Cretaceous extinction, as they too were wiped out.
"They have plenty of new material to determine that this is a new species of pterosaur," says Michael Habib, a paleontologist at the University of Southern California in Los Angeles. "If there's one, there were probably others. Then we'd need to rethink what we previously thought about survivability of these little ones."
The findings were published in the journal Royal Society Open Science.