Tyrannosaurus rex is arguably the most famous of all the dinosaurs, but the tyrant lizard king is known from only about two dozen semicomplete specimens, making it difficult to determine how large T. rex could really get.
Now, a specimen first discovered in Saskatchewan in the early 1990s but only recently described has unseated Chicago’s Field Museum’s Sue as the largest known T. rex.
Nicknamed Scotty for the Scotch researchers toasted with in celebration of its discovery, the newly described tyrannosaur is one for the record books. At 13 meters long and over 8,800 kilograms when alive, Scotty would have dwarfed the largest African elephant. Scotty is also an important specimen because he was pushing 30 at the time of his death, making him the oldest known tyrannosaur, says Scott Persons, a paleontologist at the University of Alberta in Edmonton and lead author of the new study, published in the Anatomical Record.
“T. rex was a dinosaur that lived hard and died young,” Persons says. “Scotty represents the most extreme data point we have for tyrannosaurs in terms of how big they could get if they lived to full maturity.”
As huge as dinosaurs were, they may have been able to grow even bigger.
“The fossil record gives us relatively few examples of fully grown dinosaurs,” says Jordan Mallon, a paleobiologist at the Canadian Museum of Nature in Ottawa, Ontario, who was not involved in the new study. “Most of the specimens we have were not fully grown when they died. The new Scotty specimen is significant because it is one of the oldest and one of the few we can point to and say, ‘This is what a fully grown T. rex looked like.’”
Whether Scotty’s impressive size had anything to do with his sex is unknown—despite nicknames like Scotty and Sue, tyrannosaurs cannot be sexed. Females can sometimes be identified by the presence of spongy medullary bone inside long bones that is used as a source of calcium during eggshell formation, but this uniquely female feature has been found in only a handful of dinosaur specimens.
Birds and reptiles often show sexual dimorphism in which one sex is notably larger than the other. But this relationship has never been proven in dinosaurs, Mallon says. Some paleontologists have tried to group the known T. rex specimens into two body types, robust and gracile, which may represent male and female, but with only around 25 specimens, there aren’t enough to produce a statistically significant distribution, Mallon says.
Towering Display in Saskatchewan
In May, Scotty will go on display at the Royal Saskatchewan Museum in Regina in a two-story exhibit fit for a king.
“Museums want people to be able to see the tyrannosaur’s skull and teeth clearly, so many specimens are positioned in a head down position, bending over or crouching,” Persons says.
To showcase Scotty’s height, the museum took out the ceiling on the first floor to create a balcony view of Scotty. “As you come in at ground level you’ll be at knee height, able to look up and be impressed by the sheer size of this specimen, but then you can go upstairs and look at Scotty head-on. It’s a real thrill to see it on display.”
10 April 2019: This article contains a correction to where the new T. rex display will open in May.