Over 200 million years ago, during the Triassic period, plesiosaurs first appeared in the ocean. The swimming, flippered reptiles lived for several million years, until the mass extinction that wiped out the dinosaurs, but like their land-dwelling counterparts, plesiosaurs are still a source of fascination for scientists and prehistoric-animal enthusiasts. These particular reptiles present a particular challenge for scientists, however, because until now, no one has been able to figure out quite how plesiosaurs managed to swim. Most flippered animals have two distinct sets of flippers: the ones in the front are designed to produce thrust, while the flippers in the back are used for steering.
Fossils, however, have shown that the plesiosaur had four nearly identical flippers, which means that however the plesiosaur got around, it was quite different than any other flippered animal, according to experts. It’s been unclear how exactly plesiosaur mobility worked, but thanks to a robot with 3D printed flippers, researchers at the University of Southampton and the University of Bristol may have finally figured it out.
PhD student Luke Muscutt led a team of researchers who constructed a robot and attached 3D printed flippers, designed based on plesiosaur fossils. They also used X-rays of currently existing flippered animals to determine what kinds of movements the robot would need to make.The team then ran a set of experiments on their simulated plesiosaur in a water tank.
If the plesiosaur’s method of mobility was ineffective, the species would have either evolved or gone extinct much sooner, so scientists studying the reptile have been aware that their flippers did work well – the question has been how. Experimenting with the robot in the water tank, Muscutt and his team made an interesting discovery: the front flippers created swirling movements in the water, which increased the thrust of the back flippers by up to 60 percent and their efficiency by up to 40 percent when both sets of flippers worked together as opposed to when they moved independently. This indicated that all four flippers were used to propel the plesiosaur through the water, which differs from the movement of, for example, a turtle. The experiments also showed exactly how the flippers would need to have moved in relation to each other in order to create the most effective propulsion.
“Fossils by themselves don’t tell us much about how plesiosaurs actually moved. Short of genetically engineering a plesiosaur, our best available option was to create a robot to show how it might have happened,” said Muscutt. “The results were amazing and indicate why plesiosaurs were such a successful species, retaining four flippers for more than 100 million years. If this wasn’t the case, it’s unlikely the four-flipper system would have been maintained for so long.”
Muscutt plans to further his studies by examining different types of plesiosaurs and how their movements may have differed from each other. He’s also interested in how the motion system of the plesiosaur could be adapted for modern applications, such as submarines.
“Understanding how an animal might have moved gives us a better understanding of the animal as a whole – for instance, how far it can travel, what animals it can predate on, and what it might have fallen prey to,” he said. “Our observations of tandem flipper systems such as the plesiosaur’s might also eventually have a real-world application – as a propulsion system for undersea vehicles, for instance, that could help make them more manoeuvrable, efficient and quieter.”
The research was documented in a paper entitled “The four-flipper swimming method of plesiosaurs enabled efficient and effective locomotion,” which you can read here. Authors include Luke E. Muscutt, Gareth Dyke, Gabriel D. Weymouth, Darren Naish, Colin Palmer, and Bharathram Ganapathisubramani.
[Source: University of Southampton]