Oldest plesiosaur was a strong swimmer: study

Scientists have revealed that plesiosaur, an unusual underwater reptile that lived 201 million years ago, was a powerful swimmer.

Numerous fossils documented a global distribution of the group during the Jurassic and Cretaceous periods.

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

"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 from the University of Bonn in Germany.

The scientists bestowed the name Rhaeticosaurus mertensi on the unique fossil.
 

According to the findings published in the journal Science Advances, the reconstructed length of the skeleton is 237 centimetres.

These long extinct "paddle saurians" 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, the researchers studied a bone sample. Based on the growth marks in the bones, the researchers recognised that species was a fast growing youngster.

They compared the thin sections with those from young plesiosaurs from the Jurassic and Cretacous.

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