An article published in the journal “PLoS Biology” describes the discovery of fossils of six new species of pterosaurs, the flying reptiles that lived at the time of the dinosaurs. Researchers led by the University of Bath examined them concluding that this group of reptiles went exinct suddenly together with the dinosaurs at the end of the Cretaceous period, while the prevailing theory was that they started declining from the mid-Cretaceous.
Pterosaurs – order Pterosauria – appeared in the Late Triassic period, almost 230 million years ago. These reptiles were the first flying vertebrates and were very successful because they diversified occupying a number of niches during the Cretaceous period with very variable sizes so that their wingspan could go from 50 centimeters to more than 10 meters.
The discovery of a lower amount of pterosaur fossils dating back to the second part of the Cretaceous period compared to the previous ones suggested a decline at least partial. It was perhaps a misconception due to a scarcity of available fossils and not to a real decline of these reptiles.
This is a common problem in the field of paleontology and in some cases it’s particularly serious. Pterosaurs had hollow bones that were lightweight and therefore were an advantage in their ability to fly, similar to those of modern birds. Dr. Nick Longrich of the University of Bath, the study’s first author, pointed out that unfortunately this characteristics makes their fossilization more difficult.
The discovery of new pterosaur fossils in northern Morocco could significantly change the ideas of paleontologists regarding these flying reptiles’ history. Their examination shows that at the end of the Cretaceous period in that region lived seven species of pterosaurs of three different families: Pteranodontidae, Nyctosauridae and Azhdarchidae.
The new species discovered are from mid to large size, with a wingspan ranging from just over 2 meters to almost 10 meters with a weight that could reach 200 kg for the largest species. In addition to size, there are differences also in various parts of their bodies such as their beak shape, their neck length and their wings proportions.
The image (courtesy Nick Longrich et al. / PLoS Biology) shows two of the fossils discovered in Morocco. At the top there’s the mandible of a relatively small pterosaur of the species Alcione elainus. At the bottom there’s a part of the ulna of a much larger pterosaur tentatively attributed to the genus Arambourgiania.
In essence, the fossils discovered in Morocco show that at the end of the Cretaceous there was still a considerable diversity among the existing pterosaurs. It’s a greater diversity than expected and above all greater than what’s expected of a group of organisms that were already falling to extinction.
Together with Professor David Martill of the University of Portsmouth and Dr. Brian Andres of the University of Texas at Austin, Dr. Nick Longrich analyzed the fossils discovered in Morocco emphasizing their diversity. Their conclusion is that pterosaurs were not slowly brought to extinction during the Cretaceous period by competitors such as birds, but large species continued to thrive until the mass extinction wiped them out along with dinosaurs.