Evrim Yazgin
Cosmos science journalist
Researchers may have solved the centuries-old mystery of how plesiosaurs swam by constructing a robot to test the biomechanics of the extinct creatures.
Plesiosaurs are marine reptiles, not dinosaurs, though they did live at the same time as the dinosaurs. The creatures died out during the mass extinction event 66 million years ago which spelled the end of the “Age of Dinosaurs”.
The giant reptiles are distinguished by their long necks and small heads with pin-like teeth used for catching fish.
Some believe plesiosaurs are the inspiration behind the myth of the Loch Ness monster.
Understanding how long-extinct animals got around is difficult based on fossils alone. It’s particularly challenging with plesiosaurs who have no modern equivalent to base their assumptions on.
So a team of researchers from Japan and the UK created a robot to test different swimming patterns of plesiosaurs. Their findings are published in Scientific Reports.
Plesiosaurs got around using 4 large flippers – this means they represent a form of a long-disputed issue in biomechanics: the four-wing problem.
“The four-wing problem in plesiosaur locomotion focuses on the coordination patterns between the pectoral and pelvic wing-like flippers,” the authors write. “Living tetrapods [four-limbed animals] with flippers (e.g., sea turtles, penguins, and sea lions) generate propulsive forces by the large wing-like fore limbs and steer their bodies by the smaller hind limbs. In contrast, the two pairs of flippers of plesiosaurs have very similar sizes and this allows a greater range of possibilities for thrust generation via suitable inter-flipper coordination.”
Previous research on this problem has focused on the hydrodynamics of plesiosaur bodies.
“Instead of focusing solely on how water interacts with plesiosaur bodies – that is, the hydrodynamics of swimming – we decided to examine how these animals controlled their movement,” says senior author Akio Ishiguro, a professor at Tohoku University. “This is because plesiosaurs must have been able to swim at different speeds and in varied conditions.”
Akio’s team drew inspiration from inter-limb coordination behind the flexible gait patterns of other four-limbed vertebrates, such as dogs and cats. They developed an autonomous decentralized control system for a plesiosaur-like robot.
Such “palaeo-robots” have become a new method for researchers to understand how ancient creatures moved.
The robot successfully coordinated its hind and front flippers in response to flapping cycle and form.
“Our new approach reconstructs the way extinct animals can adjust their movement patterns in a flexible, situation-dependent manner,” says first author Akira Fukuhara, an assistant professor also at Tohoku. “It also means we can start investigating the complete locomotion repertoires of other extinct animals and learn more about their lifestyles.”
“We hope to create models that incorporate the roles of the neck, head, and torso in controlling these ancient creatures’ movements.”
