"At close to 50 feet long and up to three tons, Elasmosaurus was one of the biggest plesiosaurs of the Mesozoic Era, though still not a match for the largest representatives of other marine reptile families (the ichthyosaurs, pliosaurus and mosasaurs), some genera of which could weigh up to 50 tons."

Also, apparently, Elasmosaurus was part of something called the "Bone Wars" which was instigated by a bitter feud between two paleontologists!

Read some more facts about the Elasmosaurus here .