BUENOS AIRES (AGENCIA CTYS-UNLAM).- It is the largest elasmosaurid in the world, similar in appearance to the Loch Ness monster. With a body mass that exceeded 12 tons, it doubles in size the majority of reptiles of his family known until now. According to the researchers, they would have developed a form of feeding similar to that of whales.

The paleontologist José O'Gorman of the Museum of La Plata (MLP) and CONICET assured the CTyS-UNLaM Agency that "a very important specimen was extracted in the Marambio Island; It is the largest elasmosaurid in the world. "

"Due to the large size of this specimen, its rescue was carried out during successive campaigns of the Argentine Antarctic Institute and its rescue culminated in 2017", explained the main author of this study published recently in the scientific journal Cretaceous Research.

In addition, this giant reptile stands out for being the elasmosaurid closest to the extinction of dinosaurs that has been discovered on the white continent. Dr. Marcelo Reguero, researcher of the Argentine Antarctic Institute and the MLP, said that "this fossil is very close to the end of the Cretaceous, when it is estimated that a large meteorite fell and caused the disappearance of many species."

The remains of this giant reptile are in the Museum of La Plata. Part of his spine has been found, part of his anterior and posterior fins and some elements of the scapular waist. While his skull has not been found, researchers have analyzed what feeding strategy he might have had to develop such a large size.

It is estimated that the length of this reptile was between 11.2 and 12 meters. "It weighed between 10 and 13 tons, so it is well above those that were known until now, which had a mass of between five and six tons," said Dr. O'Gorman.

The elasmosaurids are part of the great family of plesiosaurs, those extinct reptiles in what possibly inspired the collective imagination to create the monster of Loch Ness.
Within the elasmosaurids, this giant reptile is part of the subfamily of aristonectinos, which had a slightly shorter neck, much more robust vertebrae and a much larger skull.

"The hypothesis that could explain the great size of this new specimen, and that seems to be progressively supported by the evidence, is that the aristonectinos had a way of capturing their prey different from the rest of the elasmosaurids; We believe that, instead of capturing their prey individually, these animals opened their mouth and captured a large number of small prey at the same time, such as small crustaceans, for example, "O'Gorman said.

This type of capture is similar to the one applied by the current whales. Dr. O'Gorman said that "the whales take advantage of a roughness they have on the palate to catch the microplankton, while we consider that the aristonectinos used the battery of teeth as a kind of trap".

"It seems that evolution repeated certain patterns of development between these two groups that have no relationship," O'Gorman analyzed. And he differentiated: "Plesiosaurs are reptiles and have nothing to do with cetaceans that are mammals."

The rescue of the giant reptile and its babies
Dr. Marcelo Reguero highlighted the logistics and work that made possible the rescue of this specimen as well as other fossils in Antarctica.

In this site located towards the center of the Marambio Island, sediments of an ancient shallow marine environment are found. "There we have also found very small vertebrae of baby plesiosaurs; at that moment, there was a fairly calm sea" Reguero said. to the Agency CTyS-UNLaM.

In these deposits, flying seabirds and dinosaurs of different groups have also been found. Reguero appreciated that "whenever international congresses are held where the results of the research in Antarctica are exposed, the studies in paleontology of vertebrates carried out by the Argentine scientists are in very well positioned".

This new giant reptile specimen was discovered in 1989 and was recently completed in 2017. "The collection was carried out over many years and many teams have participated; this evidences the need for a support of the scientific activity that the Argentine Antarctic Institute has maintained over time, "said Dr. O'Gorman.

In addition to José O'Gorman and Marcelo Reguero, the researcher of the Argentine Antarctic Institute Sergio Santillana and the paleontologist Rodrigo Otero of the Laboratory of Ontogenia and Phylogeny of the University of Chile participated in this study that unveiled the world's largest elasmosaurid known so far.