A fossil site in Canada has yielded the heaviest Tyrannosaurus rex specimen ever foundan 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 thats 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 paradisebut life was no vacation. The dinosaurs remains include a broken and healed rib, a massive growth of bone in between two teetha sign of infectionand broken tailbones possibly maimed by another tyrannosaurs 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 wasnt 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.
PHOTOGRAPHY BY NOREBERT WU/ MINDEN PICTURES
As more specimens of those other theropods are found, were 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 sizepotentially to overlap or even surpass what we know from T. rex .
It has taken more than two decades, however, for scientists to come to full grips with Scottys remains. The animals massive bones were firmly stuck in very hard rock, making them extremely difficult to extract for study. But once Scottys bones were freed, Personss team could finally reconstruct the dinosaurs 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 Scottys size.
By studying many living animals, scientists have found that the wider an animals femur, the more weight that the bone tends to hold up. Scottys femur was a whopping eight inches acrosswhich means that Scottys two legs could hold up more than 19,500 pounds, give or take a couple tons. When the same methods are applied to Sue, the famously complete T. rex at the Field Museum, that fossil comes out about 900 pounds lighter.
Lean and mean
However, this bone-measuring method isnt foolproof. For one, animals dont use their skeletons to passively hold up their weight; bones also endure the forces of motion. Theres some evidence that tyrannosaurs may have been faster and more agile than other groups of large predatory dinosaurs, such as the earlier allosaurs. Perhaps tyrannosaur leg bones were slightly over-engineered to take the stress of running, which would lead researchers to overshoot Scottys actual weight.
In addition, body mass is just one way of parsing bigness, and not all predatory dinosaurs had the same dimensions. Tyrannosaurs such as T. rex appear to have had stockier builds, while other species had longer, more slender bodies. This variety, some researchers argue, may even hold within the T. rex species, which includes some more slender specimens.
No species demonstrates this conundrum better than Spinosaurus , a semiaquatic dinosaur that lived in whats now northern Africa about a hundred million years ago. The animal was about 50 feet long from its snout to the tip of its tail, which would make it longer than T. rex . But when estimating Spinosaurus s weight based only on femur size, it comes out at just 3,600 pounds.
Realistically, Spinosaurus almost certainly weighed more. The dinosaur is thought to have spent much of its time in the water, letting it get away with tinier hind limbs. Also, its bones were far denser than those in other predatory species, a trait that helps maintain buoyancy in living semiaquatic dinosaurs, such as penguins.
Spinosaurus is sort of breaking the mold, says Ibrahim, the National Geographic grantee who rediscovered the remains of Spinosaurus. Its a highly specialized theropod with a unique ecology and environmental contextits more like a river monster.
For now, Personss gaze will remain on land. Hes continuing to study Scottys remains in detail, starting with the tyrannosaurs dramatic eye crests and flaring horns on the sides of its skull.
The big thing that everyone is talking about is just how large this particular individual is, he says, but my favorite part of the specimen is actually the smaller detailsthe little bits of weirdness.
Also read: Rare fossil of crocodile cousin are found in Brazil
Source: www.nationalgeographic.com/
