 When first described in 1991, discoverer David Gillette calculated it may have been up to 52 m (171 ft) long, making it the longest known dinosaur (excluding those known from exceedingly poor remains, such as "Amphicoelias").Some weight estimates of this time ranged as high as .The estimated length was later revised downward to and later on to  based on findings that show that Gillette had originally misplaced vertebrae 12–19 as vertebrae 20–27.