Like most birds, penguins fly. In the ocean at least. And millions of years ago in the Mesozoic seas, plesiosaurs flapped their flippers and swam like penguins, according to computer simulations reported in PLOS Computational Biology this week.
Ever since the first complete plesiosaur skeleton was described in 1824, researchers have puzzled over how the four-flippered aquatic reptile got around. These were apex predators for more than 135 million years, from about 205 to 66 million years ago, yet no swimming animal today has that same body plan.
Without any modern analogues to draw insights about their swimming style, many questions remained. Did all four flippers move synchronously, or did the forelimbs and hindlimbs move separately? Was the motion a rowing one (like with oars) or was it more of a flapping one like the flight stroke of penguins, turtles, and sea lions?
To investigate, Georgia Tech’s Greg Turk and colleagues constructed a 3D model based on the Lower Jurassic fossilized skeleton of Meyerasaurus victor from what’s now Germany. And then they ran thousands of computer simulations to figure out what the most effective swimming strategy would be.
Plesiosaurs, the researchers found, likely used an underwater flight motion with a penguin-like flapping of the two front flippers. And according to the simulations, the rear flippers didn’t contribute that much to their forward speed. "Our results show that the front limbs provide the powerhouse for plesiosaur propulsion while the hind limbs are more passive," study co-author Adam Smith of Nottingham Natural History Museum said in a statement. Those hindlimbs likely helped the plesiosaur steer and stay stable, though.
In this very cool animation below, you can see how if the back flippers didn’t move at all, the plesiosaur still made its way forward with ease. That wasn’t the case if only the hindlimbs were working.