"Stan" (NHMAD 2020.00001, formerly BHI 3033) is a Tyrannosaurus rex fossil found in the Hell Creek Formation in South Dakota, just outside of Buffalo in 1987, and excavated in 1992. It is the fifth most complete T. rex fossil discovered to date, at more than 70% bulk. In October 2020, the fossil was sold for $31.8 million at auction, making it at the time the most expensive dinosaur specimen and fossil ever sold. This record stood until July 2024, when the Stegosaurus fossil Apex sold at auction for $44.6 million. The Abu Dhabi Department of Culture and Tourism acquired Stan and displayed the fossil at the Natural History Museum Abu Dhabi which opened on November 22, 2025.
Discovery Stan Sacrison, an amateur paleontologist, was responsible for the initial discovery of Stan's bone fragments in 1987, and as a result is the namesake for the T. rex. He was out looking at plant life in South Dakota when he spotted Stan's pelvis visible in the side of a cliff. At the time, Sacrison was doing freelance work for the Black Hills Institute of Geological Research. Originally, it was thought that the fossil was that of a Triceratops. The excavation itself required the skills and resources of the Black Hills Institute; it officially began on 11 July 1992, led by Peter Larson (the lead paleontologist on the excavations of many other T. rex specimens like Sue and Trix as well as the institute's president). The institute's team removed the rock above Stan's skeleton with a Bobcat and finer removal was done manually with picks and brushes until the fossils could be plotted and diagrammed with the help of a grid placed over the dig site. The bones were then wrapped in burlap and plaster and brought to the Black Hills Institute.
Description
The most notable aspect of Stan is his nearly complete and perfectly preserved skull. It is widely regarded as the best T. rex skull ever discovered. Although the bones were separated from each other before excavation, they were in pristine condition and ideal for study by researchers. According to Pete Larson of the Black Hills Institute, Stan's skull has enabled scientists to learn more about the T. rex's cranial kinesis, or movement of the skull bones, than any other T. rex specimen. Because of Stan's narrow pelvis, some paleontologists interpret the specimen as being male, though this method of determining sex in T. rex is controversial. Stan is around 11.78 m (38.6 ft) in length as measured by the Hutchinson et al. 2011, Stan, measured another way, was 12 m (39 ft) long, 3.7 m (12 ft) high at the hips, and is estimated to be around 66 million years old. Body mass estimates for this specimen include 7.6 tonnes from Bates et al. in 2009, 5.9 to 10.8 tonnes in Hutchinson et al. 2011, and 7.2 tonnes in Sellers et al. 2017.
Preparation
The bones of Stan the T. rex were cleaned and prepared at the Black Hills Institute where resident paleontologists and paleobotanists continued to study him and the fossilized plants he was discovered with. The institute has performed two additional excavations of the site that Stan was discovered, yielding 199 of the 350 known bones of the T. rex, more than 70% in bulk, which made Stan the second most complete T. rex until 2017. Since then, additional excavations for other known T. rex specimens, as well as new discoveries regarding the T. rex "Scotty" (RSM P2523.8) in 2019, have made Stan the fifth most complete T. rex. However, "Stan" is still one of the most famous T. rex discoveries, and more than 60 casts of the skeleton are on display and requested by museums all around the world.
Life and death Stan's fossils show notable signs of wear and indication that the dinosaur experienced multiple attacks and illnesses throughout his life. Puncture wounds on the back of his skull and rib indicate that he was at one point bitten by another T. rex. Other bite marks at the base of his skull suggest his neck was once broken and caused the fusion of two vertebrae, resulting in a loss of mobility and pain for the rest of his life. The injury spurred the growth of excess bone around his neck, showing a remarkable recovery. Other irregularities in Stan's skull include non-symmetrical holes on either side of his jaw with smoothed edges, which are indications that these are more healed wounds. According to the Black Hills Institute, Stan likely lived in a family unit of other T. rex. His mate could have been the cause of some of his injuries. Stan likely ate hadrosaurids, also known as duck-billed dinosaurs, such as Edmontosaurus. It is unknown what exactly caused Stan's death, but many theories suggest that it could have been the result of old age, starvation due to limited mobility from his injuries, or even parasitic infections that many T. rex exhibit signs of. In 2005, the BBC program The Truth About Killer Dinosaurs used Stan's skull as a model for their hydraulic test of the T. rex's bite force and estimated that it exceeded 6.8 tonnes. Additional tests, like those published by Karl T. Bates and colleagues in 2009, used Stan's remains to study the weight distribution of T.rex, as well as how their mass and proportions would have affected their movement. Bates et al. estimated that Stan was larger than previously believed, at around 16,875 pounds (7.6 tonnes); they also concluded that Stan, as well as other Tyrannosaurus rex specimens, were much more robust than commonly believed.
Exhibition
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