I was partially right. The amphicoelias you were talking about was Amphicoelias fragillimus, the largest ever found, atleast it was at first. It has now been renamed and regrouped to Maraapunisaurus fragillimus, which whilst still large, didn’t quite reach the size of 60 meters, rather closer to 28. The way this mistake was made is that Amphicoelias was thought to have been a diplodocid, long but with rather thin bones. There had been only found a vertebrae and for a diplodocid it was massive. Now it is an rebaccchisaurid which had way bigger bones but were not as long. There are still species of Amphicoelias but they are way smaller.
This was my presentation on Amphicoelias, the lost giant.
I spent way too long writing this.