Robotic flippers reveal how plesiosaurs swam

Plesiosaurs roamed Earth’s oceans for nearly 150m years, until their extinction 66m years ago. They were propelled by four equal-sized flippers, unlike any animal alive today. A question that has long bothered palaeontologists is, did all four flap up and down, or were they rowing rather than flapping, or did the back ones steer rather than flap or row? As he reports in the Proceedings of the Royal Society, Luke Muscutt of Southampton University, in England, has now answered this definitively. By testing robotic replicas of plesiosaur flippers in a water tank he has shown that all four flapping up and down is by far the most efficient and powerful arrangement.