Small pterosaurs ‘bar vaulted’ to escape water, study suggests

An analysis of a small pterosaur fossil has provided more evidence that Jurassic flying reptiles used their long arms to rock back and forth to “pole vault” themselves into the air.

The research, recently published in the journal Scientific reportsassessed a small pterosaur fossil from rocks dated to the late Jurassic period of about 163 million years to 146 million years ago, unearthed in Germany.

Scientists who have studied pterosaur fossils since they were first discovered over two centuries ago have reasoned that the physical characteristics of the flying reptiles, including a “forward center of gravity,” prevented them from a bird-like running launch.

Scientists have theorized a launch from water bodies for pterosaurs, similar to a method seen in modern water-feeding birds and bats.

However, direct physical evidence of such a mechanism has been elusive, until now.

In the new study, researchers including Michael Pittman from the Department of Earth Sciences and University College London analyzed the fossil remains of a type of pterosaur called aurorazhdarchid unearthed from the Jurassic rocks of Germany with well-preserved soft tissues, including a wing membrane and webbed feet.

Their analysis suggests that the soft tissues were primary propulsive contact surfaces needed for the pterosaur’s water launch with a quadrupedal bar vaulting mechanism.

With previous studies indicating that pterosaurs were not strong swimmers, researchers say the soft tissues likely helped launch from water rather than being swimming adaptations.

When folded, the pterosaur’s wings may have helped the reptile push off from the surface of the water.

The findings “reveal that quadrupedal water launch was theoretically possible and that webbed feet significantly affected launch performance,” according to the researchers.

They were also able to identify key factors limiting water-shooting performance in all pterosaurs, including “available propulsion contact area, range of extension, and extension force around the shoulder”.

Researchers believe that the new findings also offer comparative context for further investigations of water-dwelling potential and evolution in pterosaurs.

“Although many small pterosaurs probably had enough contact area, range of motion, and power to escape the water surface, it is quite likely that more terrestrial taxa may have been unable to water, especially if a lack of pedal webs limited the range of propulsive contact,” they wrote in the study .

The new findings follow a collection of studies published last year, in which researchers considered the fossil to be a giant pterosaur Quetzalcoatlus which weighed over 250 kg and had a wingspan of almost 12 metres.

The 2021 research suggested that giant pterosaurs probably jumped and jumped at least 2.5 meters into the air before lifting off.

Scientists have called for further analysis of more samples in the future to decode the evolution of flight across pterosaur species.

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