Scientists have discovered how ancient flying lizards were able to reach colossal sizes
A team of palaeobiologists has carried out extensive analyses of the structure and proportions of virtually all known pterosaur forms, covering their entire evolutionary history.
The study revealed how these flying lizards were able to reach colossal sizes, occupy a variety of ecological niches and acquire unique anatomical features. The paper is published in the journal Current Biology.
Pterosaurs were the first flying vertebrates on Earth. They appeared in the late Triassic period about 227 million years ago and existed until the end of the Cretaceous period, about 66 million years ago, when a mass extinction event occurred.
During their existence, pterosaurs achieved an amazing variety of shapes and sizes. In early 2023, a well-preserved skeleton of Balaenognathus maeuseri, a pterosaur with jaws studded with small bristle-like teeth resembling a comb, was discovered in Bavaria. This species had a wingspan of just over one metre. A similar structure was previously known in the pterosaur Pterodaustro, which had bristles only on the lower jaw.
Some pterosaurs of the Cretaceous period reached truly gigantic sizes. For example, representatives of the azhdarchid family, such as Aramburgian and Hacegopteryx, had wingspans of up to 11 metres. Some of them had skulls up to three metres long, making them some of the largest flying creatures ever to have lived on Earth.
British and American palaeobiologists have studied the history of changes in the limbs of pterosaurs to understand the development of their locomotor system. They analysed the structure, length and proportions of the phalanges of the first three fingers of the forelimbs, which ended in claws, and the bones of the first four fingers of the hind limbs. It was these fingers that were used by pterosaurs when travelling on various surfaces.
Early pterosaurs were adapted for climbing trees, having tenacious fingers similar to the feet of modern birds. However, during the Middle Jurassic period, about 160 million years ago, some species, such as Propterodactylus and Douzhanopterus, began to shift to a terrestrial lifestyle. Their limbs changed, allowing them to move efficiently on the ground on four legs.
The transition to living on the ground removed the body mass limitations that were associated with climbing trees. This allowed pterosaurs to grow significantly in size and occupy new ecological niches. The terrestrial lifestyle paved the way for the development of a variety of adaptations and allowed these lizards to successfully compete with other species.
Study author Robert Smith, a researcher at the University of Leicester, said:
'Understanding how pterosaurs moved not only in the air but also on the ground helps us to further understand their evolution and role in ancient ecosystems. Flight is only part of their story; studying ground behaviour opens up new horizons in palaeontology.