Amphicoelias is believed to have been the largest dinosaur ever to live. Much bigger than Argentinosaurus or even a blue whale. Being discovered in the late 1800's and with only four bones ever found, early paleontologists had little time to study the large bones because they were crumbling at a fast rate. It was twice the length of a blue whale and twice the lengh of sauropods like Diplodocus . With absolutely no phyisical evidence other than notes taken by Edward Drinker Cope, the dinosaur is purely skeptical in topics about its measurement. Even without fossil evidence, photographic evidence left by the behemoth's discoveror, Edward Drinker Cope , has allowed paleontologist to make calculated guess estimates. It is believed to be 190 feet (58 m) long, and weigh at least 122.4 tonnes in recent estimates. This size exceed any other sauropod. It could have been the biggest reptile, sauropod and dinosaur yet. It could also be the biggest animal that ever lived, twice as long and slightly heavier than the most massive of blue whales!
On that picture we can see, how big it was, if we compare it with a blue whale and other animals, including man.