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SYFY WIRE dinosaurs

Prehistoric sea monster could probably beat Michael Phelps at the breaststroke

By Elizabeth Rayne
Jurassic World: Fallen Kingdom

You know that scene in Jurassic World when a ginormous sea monster leaps out of a pool like a dolphin at Sea World and devours an entire cow carcass? That’s a mosasaur. We’ll never know if they were trainable, but now scientists have found out something similarly cool.

Mosasaurs were real prehistoric sea monsters who terrorized late Cretaceous seas. Some have even theorized a surviving mosasaur to be slithering around at the bottom of Loch Ness, though what was thought to be Nessie may just turn out to be a bunch of giant eels. It’s still no wonder this 50-foot behemoth was thought to be some sort of cryptid. None of these creatures survived extinction, but now a new study suggests that they could possibly have done the breaststroke back in the day.

Monitor lizards and snakes are just vestiges of what mosasaurs once were. Imagine an ocean-dwelling creature with two rows of dagger teeth that could shred its victims without mercy (think back to when even the fearsome Indominus rex ended up in its jaws in Jurassic World). As if that weren't fearsome enough, it could apparently compete in the dinosaur Olympics: Its skeletal structure has revealed that it might have been capable of doing the breaststroke, which would have given it bursts of speed no prey could escape.

"We know that mosasaurs most likely used their tails for locomotion. Now we think that they also used their forelimbs, or their tail and forelimbs together," study lead Kiersten Formoso, a Ph.D. student in vertebrate paleontology at the University of Southern California, explained in a statement.


If they really did breaststroke through the ancient seas and use their tails to propel them, mosasaurs would have been unique among tetrapods (four-limbed creatures). While the mosasaur’s notably huge pectoral girdle, or group of bones supporting the forelimbs, had been noticed in previous studies, it was just assumed that it swam mostly with its tail. That style of tail-driven swimming, seen in extant creatures like alligators and sharks, is called “cruising.” The breaststroke is more of a “burst” motion.

"Like anything that swims or flies, the laws of fluid dynamics mean that burst versus cruising is a tradeoff," co-author Mike Habib, assistant professor of anatomical sciences at USC, said in the same statement. "Not many animals are good at both."

The researchers closely studied the fossil of one species of mosasaur, the Plotosaurus (pictured above), and used measurements of mosasaur pectoral girdles from other studies. They determined these aquatic lizards probably could swim the breaststroke because of what they say was an “unusually large and low-placed pectoral girdle,” which is believed to have supported large muscles. Their asymmetrical bone structure was also a sign of adduction, a downward-pulling motion that suggested mosasaurs used their forelimbs to get around.

“Mosasaurs swam unlike anything else,” Formoso said.

More research on muscle and bone structure (there was obviously no flesh to work with, and some bones were missing), morphology, measurements, and fluid dynamics is needed to be sure these sea monsters could breaststroke across the ocean — and how fast. Could it (theoretically) have challenged Michael Phelps?

Please note: SYFY WIRE contacted Professor Formoso, and she noted that at this time, the research is ongoing and there may eventually be new developments.

(via University of Southern California)