Ancient Loch Ness monster reptiles swam like penguins

Plesiosaurs, marine reptiles that thrived in the world's seas when dinosaurs ruled the land, swam much like penguins by using their flippers to "fly" underwater, scientists said on Thursday, resolving a debate that began nearly two centuries ago.

Plesiosaurs had four large flippers, and many had remarkably long necks. They lived from about 200 million years ago to 66 million years ago, disappearing in the same mass extinction that doomed the dinosaurs. Nessie, Scotland's mythical Loch Ness monster, often is portrayed as looking like a plesiosaur.

The researchers conducted a series of computer simulations based on the anatomy of a plesiosaur from 180 million years ago called Meyerasaurus to find the most effective swimming strategy for this body design.

The method that produced the fastest forward speed was flapping the two front flippers up and down in an underwater flying motion similar to penguins and sea turtles. The back flippers were probably used to steer and provide stability, said the researchers, whose work was published in the journal PLOS Computational Biology.

Plesiosaurs, which ate fish and squid, came in various shapes and sizes, some with shorter necks and others with lengthy ones like Elasmosaurus, a creature about 46 feet long. Meyerasaurus, unearthed in Germany, measured 10 feet long.

There have been some competing hypotheses, Smith added, with some researchers suggesting plesiosaurs moved their limbs mostly backwards and forwards, in a rowing motion. The underwater flying method is unusual because swimming creatures, including most fish and whales, tend to generate thrust using their tails, Smith said.