The British auction house Christie's announced this week that it would sell the largest and most complete known skeleton of a Tyrannosaurus rex in early October.
The auction house said the dinosaur skeleton is nearly 12 meters long and just under 5 meters tall. It has been known as Stan, named after amateur paleontologist Stan Sacrison, who discovered it in the upper Midwestern U.S. state of South Dakota in 1987.
Christie's science and natural history specialist James Hyslop said scientists that looked at the bones initially misidentified them as belonging to a triceratops, a more common dinosaur discovery.
It was not until Sacrison took the remains to the Black Hills Institute of Geological Research in 1992 that anyone realized what he had found.
Hyslop said the paleontologists from the institute carefully excavated and reassembled the skeleton, ultimately finding 188 of the estimated 300 total bones in a T. rex, more than for any previously found specimen.
Hyslop said Stan eventually went on tour to Japan between 1995 and 1996, and he later went on permanent display in Hill City, South Dakota.
Complete T. rex skeletons are very rare, and the last time one was put up for auction was in 1997, when the Field Museum in Chicago bought the now-famous Sue for $8.36 million. Hyslop said Christie's hopes to beat that price when Stan goes up for auction October 6.
Christie's will display the dinosaur until mid-October at its Manhattan auction house, making Stan visible to the public through Christie's windows.