Back in the 1990s, it took nearly a decade for paleontologists in Canada to extricate the massive Tyrannosaurus rex skeleton known as “Scotty” from its solid sandstone casing.
Now, for the first time, researchers from the University of Alberta have taken Scotty’s detailed and accurate measurements. At nearly 42 feet long, the dinosaur weighed an estimated 19,555 pounds (8,870 kg) when it roamed prehistoric Saskatchewan some 66 million years ago, making it the world’s largest known T. rex, and the biggest dinosaur ever found in Canada.
Through painstaking work, paleontologists managed to recover about 65 percent of the specimen officially known as RSM P2523.8 after its discovery nearly 30 years ago. But until recently, the enormous fossil hadn’t been completely prepared for analysis. The new research, led by paleontologist Scott Persons from the University of Alberta, was published in the journal The Anatomical Record.
By measuring Scotty’s hip, leg and shoulder bones, Persons and his team were able to estimate the dinosaur’s nearly 10-ton body mass. Their study of Scotty was the first to take detailed measurements, and to compare the specimen to other known T. rex fossils, including the famous “Sue,” once considered the biggest T. rex skeleton ever found. Discovered in 1990 in South Dakota, Sue weighed in at 18,651 pounds (8,460 kg), around 5 percent lighter than Scotty.
“This is the rex of rexes,” Persons said in a statement. “There is considerable size variability among Tyrannosaurus. Some individuals were lankier than others and some were more robust. Scotty exemplifies the robust.”
Scotty, which got its nickname after researchers shared a bottle of Scotch on the night of its discovery, is not just the largest-ever T. rex, but also the oldest. By studying the growth patterns on the dinosaur’s bones, the paleontologists estimated that it died in its early 30s—an unusually long life, by Tyrannosaurus standards.
It was also a rough life. Scotty suffered broken ribs and a jaw infection, the researchers found. They observed what looked like bite marks on his tail, possibly battle scars incurred in a fight with another T. rex.
Though the size difference between Scotty, Sue and other known Tyrannosaurus specimens may not be that significant—and certainly lies within the margin of error for calculating the weights of such prehistoric predators—Scotty still pushes the threshold of the maximum T. rex size higher than previously thought. Paleontologist Thomas Carr from Carthage College, who was not involved in the new study, told Gizmodo that Scotty’s new weight calculation “changes our picture of what is within the range of possibility for these large animals and expands our understanding of the biology of large theropods at that extreme end of the size range.”