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Gliding reptiles have been taking to the skies for 260 million years
Researchers have reconstructed one of the first gliding reptiles in extraordinary detail.
By studying several specimens of the Permian reptile Coelurosauravus elivensis, scientists have been able to discover how and why these early gliders evolved.
Modern gliding reptiles take to the skies in much the same way their predecessors did some 260 million years ago.
Researchers found that Coelurosauravus elivensis, a small reptile that existed millions of years before the first dinosaurs, would have extended its membranous 'wings' to glide between trees while grasping the leading edge to keep them steady.
PhD student Valentin Buffa, who led the research, says, 'Like contemporary Draco gliding lizards, C. elivensis was able to grasp its patagium, or wing membrane, with its front claws, stabilise it during flight and even adjust it to allow for greater manoeuvrability.'
'While their habits were likely similar, there are subtle differences. C. elivensis had an additional joint in one finger that may have enhanced its capability to stabilise its flight, and could have been a necessary compensation for the lower positioning of its patagium which probably made it more unstable.'
The findings of the study were published in the Journal of Vertebrate Palaeontology.
Modern gliding lizards fly in a similar way to their ancient predecessors. Image © NeagoneFo/Shutterstock.
What are the weigeltisaurids?
The gliding reptile C. elivensis is an example of an animal called a weigeltisaurid, one of a group of gliding lizards that lived during the Late Permian between 260 and 252 million years ago. The group contains some of the first reptiles to take to the skies, predating the earliest known pterosaurs by around 30 million years.
Despite this notable achievement, the group's exact identity has been somewhat uncertain. Features such as frills, similar to Triceratops, have led to suggestions they were related to dinosaurs, but more recent analysis suggests they are actually closer to the ancestors of modern reptiles.
The researchers behind the current study, based at the Muséum national d’Histoire naturelle and the Staatliches Museum für Naturkunde Karlsruhe, decided to reassess all known specimens of C. elivensis to help infer more about the species and its wider grouping.
By examining several fossils, they were able to create an almost complete skeletal reconstruction to figure out how it might have looked and behaved.
They found that the lizard sat very flat to the surface, with limbs of similar lengths to help it remain close to the bark of trees. This body shape would help ensure it didn't fall, aided by sharp curved claws to dig into the tree itself.
While these characteristics are similar to modern gliding reptiles, C. elivensis' wings were very different. Unlike modern reptiles, they were not supported by bones that extend from the ribs.
Instead, the patagium extended from either the body's muscles, or from an arrangement of bones in the skin that covers the belly of some reptiles known as the gastralia. The ancient reptiles would, however, likely have adopted a similar posture to modern gliding lizards, with bent hindlegs to increase stability.
The reptile Coelurosauravus elivensis is one of the first reptiles that took to the air. Image © Buffa et al./Journal of Vertebrate Paleontology.
How did gliding reptiles evolve?
The researchers suspect that gliding came about as a response to changes in the environment when the world passed from the Carboniferous Period into the Permian around 300 million years ago.
'The forests of the Late Carboniferous, or Pennsylvanian, subperiod were comprised of a variety of tree species of different heights, but had rather open canopies with spatially separated trees, resulting in little crown overlap,' Valentin says. 'In contrast, Cisuralian forests show evidence of denser communities suggestive of more continuous canopy strata.'
'Such changes in forest structure could explain why no gliders have been reported prior to weigeltisaurids, even though several arboreal or scansorial amniotes have been described from Pennsylvanian and Cisuralian deposits.'
Gliding would have allowed C. elivensis to glide from tree to tree without walking across the ground, which it was poorly adapted for. It would also have facilitated a quick escape from predators or competitors if necessary.
The researchers now hope to work further on deciphering where the weigeltisaurids sit in the overall tree of life. Having described C. elivensis in unprecedented detail, they hope comparisons of its features, along with those of its relatives, will bring greater understanding of the weigeltisaurids' phylogeny.
