On August 12, 1990, Sue Hendrickson, a fossil hunter with the Black Hills Institute of Geological Research, set out across the scorching plains of western South Dakota to explore an outcropping of rock while her team worked on fixing a flat tire. After hours of hiking in foggy conditions with her golden retriever, Hendrickson reached a 60-foot-high bluff and scanned the ground with no luck. Then, she glanced up—8 feet above, three massive bones jutted from the rock face.
She eventually showed the bones to Peter L. Larsen, the president of the Black Hills Institute, a fossil dealer in Hill City, South Dakota. The six-member team then began the painstaking process of extracting all the bones from the site. Only when they finished 17 days later did they realize the significance of their discovery: They had just uncovered the most complete Tyrannosaurus rex skeleton to date.
Their excitement, however, would be checked when, two years later, a dozen F.B.I. agents assisted by members of the National Guard led a surprise raid on the institute and seized the T. rex fossil. Larsen had paid Maurice Williams, a member of the Cheyenne River Sioux tribe on whose land the fossil was found, $5,000 for the right to excavate and remove the bones. But because the land was “in trust” to the Federal Government, it was off limits to fossil collections except by special permit—which Larsen lacked.
After years of legal disputes, the dinosaur fossil, which became known as “Sue” (after Hendrickson), was auctioned at Sotheby’s in New York City on October 4, 1997. In only nine minutes, it fetched a record-breaking $8.36 million, the highest price ever paid for a fossil at the time. The winning bid came from the Field Museum in Chicago, backed by contributions from McDonald’s Corporation, Walt Disney World Resort and private donors.
Sue, who is also known as Specimen FMNH PR 2081, made its debut at the Field Museum’s Stanley Field Hall in 2000, and in 2018, moved to the museum’s Griffin Halls of Evolving Planet.
“Scientifically, Sue is the ‘Rosetta Stone’ for this species, and provides some of the very best evidence for what this iconic dinosaur was like,” says William Simpson, the head of fossil vertebrates at the Field Museum.
“Millions of people have seen it, been inspired by it, learned from it, and scientists, too,” says Stephen Brusatte, a paleontologist at the University of Edinburgh, who first saw Sue when he was 16 years old. “We now understand so much more about T. rex as a bus-sized, bone-crunching predator because of the skeleton of Sue.”
Here are seven remarkable facts about Sue the T. rex.
1. Sue is the most complete adult T. rex ever found.
While more complete immature T. rex specimens have been uncovered since Sue’s discovery, Sue remains the most complete adult T. rex ever found, explains Jingmai O’Connor, a Field Museum paleontologist.
By bone volume, Sue is 90 percent complete, with 250 of the approximately 380 known bones in the T. rex skeleton, including rare ones such as the furcula (wishbone), stapes (an ear bone), and gastralia (belly ribs).
“Consequently, it gives us an excellent way of understanding the proper proportions of a single T. rex individual, rather than looking at a composite of multiple separate individuals,” says Thomas R. Holtz Jr., a vertebrate paleontologist at the University of Maryland. “Imagine trying to figure out human anatomy using isolated body parts of a gymnast, a linebacker and supermodel.”
2. Sue had an extreme teenage growth spurt.
Dinosaur bones, like trees, have growth rings. Using a diamond-tipped drill, Tom Cullen, a quantitative paleontologist and ecologist at Auburn University, extracted a small cylinder from Sue’s left thigh bone (it’s since been filled in with putty, but if you look closely enough, you might be able to spot it).
By examining thin slices of the bone under a microscope, he identified growth rings that revealed how new bone was added each year. Cullen’s analysis showed that Sue had a period of extreme growth during adolescence—likely gaining 35-45 pounds per week—until reaching adult size by age 20.
3. Sue is one of the largest T. rexes discovered.
At 40.5 feet long and weighing an estimated 9 tons—or nearly the weight of four pick-up trucks—Sue was long considered the largest-ever T. rex ever found. But after more than two decades of excavation and analysis, a fossil found in Saskatchewan, Canada, in August 1991 challenged that title. In a 2019 study, the specimen, nicknamed “Scotty,” measured nearly 42 feet long and was estimated to weigh 9.8 tons, edging slightly past Sue.
Still, some experts, like John Hutchinson, an evolutionary biomechanics expert from the University of London’s Royal Veterinary College, have noted that earlier mass estimates for Scotty have come out as comparable to Sue, and that the differences fall within the margin of error for such approximations.
4. Sue is also one of the oldest T. rexes ever found.
A dinosaur excavated in Montana in 2013—initially referred to as “Grandma Rex” before it received the name “Trix” after Beatrix, the former queen of the Netherlands—claimed the title of being the oldest T. rex that ever lived at roughly 30 years at the time of death. But studies of bone growth rings have also shown that Scotty and Sue lived to be roughly the same age, with Scotty reaching its early 30s, and Sue an estimated 33 years.
5. Sue had a hard-knock life—even for a T. rex.
Scientists examining Sue's skeleton have identified a number of debilitating ailments that likely plagued the dinosaur during its lifetime. Among the dinosaur’s afflictions are gout, a torn tendon, bone infections, broken ribs (which then healed) and arthritis in its tail.
As O’Connor says, “Sue was in a lot of pain at the end of its life.”
6. Sue ignited the fossil trade.
Some argue Sue’s biggest impact on the paleontological community was the steep price it fetched at auction. Since Sue sold for $8 million in 1997, prices for dinosaur fossils have only soared upwards. “These days $8 million for a T. rex would be a bargain,” says Nick Longrich, a paleontologist at the University of Bath.
“That was when dinosaurs became worth serious money, and that’s led us to where we are now,” he says, pointing out that a stegosaur sold in July 2024 for more than $40 million.
Since fossils can now fetch high sums, commercial exploitation has taken a toll. “We have lost about half of the T. rex sample size to the market,” explains Thomas Carr, a paleontologist at Carthage College, who has found about a 50/50 split between the number of T. rex fossils in AAM-accredited museums and those in commercial or private hands.
“Obviously commercial and scientific interests don’t always align,” says Longrich. “It’s a complex legacy, but if it wasn’t Sue, I’m sure it would have been some other dinosaur.”
