A fossil site in Canada has yielded the heaviest Tyrannosaurus rex specimen ever found—an animal that weighed an estimated 19,500 pounds in life, far heftier than most elephants alive today.
The dinosaur, unveiled last week in The Anatomical Record, consists of a skeleton that's about 65 percent complete, including the skull and hips along with some of its ribs, leg bones, and tail bones. Nicknamed “Scotty,” the tyrannosaur was a senior by this species' standards, making it to at least the age of 28.
Some 68 million years ago, the Canadian landscape Scotty knew was a subtropical coastal paradise—but life was no vacation. The dinosaur's remains include a broken and healed rib, a massive growth of bone in between two teeth—a sign of infection—and broken tailbones possibly maimed by another tyrannosaur's bite.
“It was not an easy life, even for the king of predatory dinosaurs, judging by all these injuries,” says Nizar Ibrahim, a paleontologist at the University of Detroit Mercy who wasn't involved with the study.
The find suggests that large predatory dinosaurs probably got older and bigger than paleontologists would have surmised based on currently available fossils. Among the known species, T. rex is one of the best represented extinct dinosaurs, with more than 20 fossil individuals identified.
“As more specimens of those other theropods are found, we're going to find their Scottys: their particularly large, particularly old individuals,” says study leader Scott Persons, a postdoctoral researcher at the University of Alberta. “It would not surprise me that those animals turn out to increase the range of body size—potentially to overlap or even surpass what we know from T. rex.”
Scotty has actually been known to paleontologists since 1991, when its bones were dug up at a site in Saskatchewan, Canada. To celebrate this T. rex's discovery, the field crew wanted to raise a toast to the creature. By that point in the field season, all they had on hand to celebrate the occasion was a bottle of scotch—hence the nickname.
It has taken more than two decades, however, for scientists to come to full grips with Scotty's remains. The animal's massive bones were firmly stuck in very hard rock, making them extremely difficult to extract for study. But once Scotty's bones were freed, Persons's team could finally reconstruct the dinosaur's age and size.
Cross-sections of its bones show that their structure is remarkably robust, resembling that of a different T. rex known to have died around the age of 28. And its main leg bone, or femur, in particular provided a vital clue to Scotty's size.
By studying many living animals, scientists have found that the wider an animal's femur, the more weight that the bone tends to hold
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