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.”

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.

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.

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.

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.”

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.”