The new specimen is also very interesting because it dates so close to the end of the Cretaceous-just 30,000 years before the mass extinction event that wiped out the non-avian dinosaurs about 66 million years ago. A lot of marine life would have needed to thrive there to satisfy the appetite of such a large creature, so the fact that these animals continued to exist so late in the Cretaceous adds to the evidence that the aquatic world, at least, was doing just fine right up until the sudden mass extinction.
While the animal's exact diet can't be known without fossilized stomach contents or other evidence, O'Gorman says that it likely fed on crustaceans and small fish, based on the small size of its teeth. And work on the bones unearthed over the past few decades has just begun; now that they are housed in a museum. The excavation finally finished in 2017, yielding a substantial portion of the animal's skeleton, which O'Gorman and his colleagues describe in their recent paper in Cretaceous Research. They estimate that the as-yet-unnamed elasmosaur weighed between 11.8 tons and 14.8 tons, with a head-to-tail length of nearly 40 feet. While some previously known Aristonectes have weighed about 11 tons or so, most other elasmosaurs only come in at around five tons.
José O'Gorman, a paleontologist with the National Scientific and Technical Research Council of Argentina who is based at the Museum of La Plata near Buenos Aires said, there is a lot of other research that can be done on this ancient specimen.For years it was a mystery ... we didn't know if they were elasmosaurs or not. They were some kind of weird plesiosaurs that nobody knew. We don't have a skull, but we have a lot of pieces of the specimen.
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