Which was the heaviest dinosaur?

The really large sauropodomorph dinosaurs such as Brachiosaurus, Ultrasaurus and Seismosaurus may have had extremely large bodies, but at the same time their bodies are lightened by having hollow bones. The bones of the spine are deeply pitted or honeycombed with holes in order to save weight, and rather like birds many of these holes may have had air cavities in them. In this way the really big dinosaurs may actually have been lighter than they might seem. The giant Brachiosaurus has often been quoted as weighing 77 tonnes, but inspection of the skeleton in Berlin suggests that it may have weighed less than 30 tonnes. Using this estimate, the heaviest dinosaur may well have been Seismosaurus, but it probably weighed little more than 50 tonnes at the very most. This is obviously well below the 130 tonnes of the largest ever animal - the blue whale.