What made the oldest plesiosaur a strong swimmer

London: An analysis of the fossil remains of the oldest-known plesiosaur, an unusual underwater reptile that lived 201 million years ago, has revealed that the species was a very effective swimmer.

Whereas sea turtles mainly use their strong forelimbs for propulsion, the plesiosaurs moved all four limbs together, resulting in powerful thrusts, researchers found. 

The 237-cm long skeleton of plesiosaur, discovered by a private collector Michael Mertens during quarrying in a clay pit in Germany in 2013, lived during the youngest part of the Triassic period, according to the researchers.

"I could not believe that there was a plesiosaur from the Triassic, given that these animals had been studied by paleontologist for nearly 300 years and never was there one older than Jurassic," said Martin Sander, a paleontologist from the University of Bonn.

The study showed that these long extinct animals propelled themselves through the world's oceans by employing "underwater flight" - similar to sea turtles and penguins.

Instead of laboriously pushing the water out of the way with their paddles, plesiosaurs were gliding elegantly along with limbs modified to underwater wings.

Their small head was placed on a long, streamlined neck. The stout body contained strong muscles keeping those wings in motion.

Compared to the other marine reptiles, the tail was short because it was only used for steering. 

"This evolutionary design was very successful, but curiously it did not evolve again after the extinction of the plesiosaurs," Sander said.

For the study, detailed in the journal Science Advances, the team studied a bone sample. 

Based on the growth marks in the bones, the researchers recognised that the species were warm-blooded and a fast growing youngster. 

"At the end of the Cretaceous, a meteorite impact together with volcanic eruptions led to an ecosystem collapse, of which plesiosaurs were prominent victims," Sanders said.