Fossil of a 15-tonne marine creature found in Antarctica: ENVIRONMENT & CLIMATE: Science Times

It took decades of fighting the weather on a small, desolate island in the Antarctic Peninsula. But now, scientists have finally unearthed the heaviest known elasmosaurus, an ancient aquatic reptile that swam in the Cretaceous seas alongside the dinosaurs. The animal would have weighed up to 15 tons, and it is one of the most complete ancient fossil fossils ever found in Antarctica.

The team believes that the newly described heavy weight belongs to the genus Aristonectes, a group whose species has been viewed as an aberrant species compared to other elasmosaurs because it differs so much from the fossilized specimens found in the United States. This genus, which is found in the southern hemisphere, is characterized by shorter necks and larger skulls.

"For years, it was a mystery … we did not know whether it was elasmosaurous or not," says Jose O. Gorman, National Council palaeontologist scientific and technical research of Argentina, based at the Museum of La Plata near Buenos Aires. "They were a kind of strange plesiosaur that no one knew."

The excavations were finally completed in 2017 and have recovered a significant portion of the animal's skeleton, which O & Gorman and his colleagues have described in their recent article in Cretaceous Research.

"We do not have a skull, but we have a lot of pieces of the specimen," said O & # 39; Gorman. They estimate that the elasmosaurus, whose name is still unknown, weighed between 11.8 and 14.8 tons, with a head length at the tail of nearly 40 feet. While some known Aristonectes weighed about 11 tons, most other elasmosaurs only reach about 5 tons.

He thinks the job is well done and that he is happy that the team did not jump to hasty conclusions. O & # 39; Gorman even hesitates to say if the species really belongs to the genus Aristonectes, as new evidence could place it in a new genre. fully.

The new specimen is also very interesting because it dates so close to the end of the Cretaceous, barely 30,000 years before the mbadive extinction that wiped out non-avian dinosaurs about 66 million years ago. It would have taken a lot of marine life there to thrive to satisfy the appetite of a creature of such a size. The fact that these animals persisted so late in the Cretaceous adds to the evidence that the aquatic world behaved well until the sudden mbad extinction.

Although the exact diet of the animal can not be known without a fossilized stomach content or other evidence, O & G Gorman says that he probably feeds on crustaceans and small fish, because of the small size of his teeth. And the work on the bones uncovered in recent decades is just beginning; O & # 39; Gorman explains that, now that they are housed in a museum, much research can be conducted on this ancient specimen.