An farily recent find, Dreadnoughtus ranks among the largest dinosaurs known from a relatively complete skeleton. Adults measured in at some 80-85 feet in length and could weigh over 30-40 tons. Initial estimates suggested much higher weights, but subsequent studies have since revised these. It was still so huge, it would have had few, if any, predators. Dreadnoughtus lived in South America roughly 65-85 million years ago.