Aristonectes

Aristonectes is one of the biggest and heaviest plesiosaurs ever found. One Antarctic specimen may have weighed as much as 13.5 metric tons (about 15 tons), as heavy as a large school bus.1

Unlike most plesiosaurs, which had very long necks, Aristonectes had a short neck and a big, bulky skull. Scientists put it in a special group called Aristonectinae because of this.1

Aristonectes probably migrated between Patagonia and Antarctica, just like many whales do today. Its fossils are found in both places.1

The first fossils of Aristonectes were discovered in Argentina in 1941, but scientists had a hard time studying them because the bones were not well prepared. It took decades to figure out what kind of plesiosaur it was.1

Aristonectes had a mouth that could open very wide, letting it gulp a huge amount of water and food at once. It fed by mixing prey with sediment from the seafloor, a method called benthic suction feeding.1

Like other plesiosaurs, Aristonectes probably swallowed stones called gastroliths. These may have helped grind up food in its stomach or helped control its buoyancy in the water.1