Source: Unexplained Mysteries

Originally discovered on Antarctica’s Seymour Island during an expedition all the way back in 1989, the record-breaking specimen, which is the heaviest of its kind ever found, took years to unearth.

Believed to date back to the Cretaceous era, this prehistoric ‘sea monster’ was an elasmosaur – a type of plesiosaur that looked a bit like a large manatee with a very long neck and four flippers.

Measuring almost 40ft in length and weighing in at 15 tons, this enormous creature would have been a force to be reckoned with in the ocean at a time when Tyrannosaurus rex roamed the land.

The discovery adds to the growing body of evidence suggesting that there existed a diverse and thriving marine ecosystem in the years prior to the mass extinction of the dinosaurs.

“Even in Antarctica, there were lots of happy elasmosaurs,” said palaeontologist Anne Schulp.