The skull of "Scotty" and the dinosaur's likeness at the T. rex Discovery Centre in Saskatchewan. Credit: Brian Switek
Brian Switeck on his Laelaps blog has a great post that discusses why "Scotty" may NOT be the biggest T.rex. Our local favorite, "SUE" of the Field Museum has long been billed as the largest, oldest, and most complete T.rex ever found. There isn't any doubt in the "most complete" title. But, largest and oldest has been discussed with the recent plans to display "Scotty" at the Discovery Centre in Saskatchewan. However, Laelaps points out that while the estimates for size and weight for "Scotty" are very close to those of "SUE", slightly longer (42.6 vs 42.0) and heavier (+900 lbs), "SUE" is much more complete, which would yield better estimates. The estimated differences are within the expected margin of error for "SUE. "Scotty" is only 65% (vs 90% for "SUE"). That's quite a bit of missing material, so not so fast here! "SUE" might still be the overall king (or queen) of the T.rexes!
Scotty – known to researchers as RSM P2523.8 – is pretty exceptional as far as T. rex goes. That’s because the skeleton includes about 65% of the expected parts. And those fossils are at the center of a new study by paleontologists W. Scott Persons, Philip Currie, and Gregory Erickson that heralds this dinosaur as “An older and exceptionally large adult specimen of Tyrannosaurus rex.”
Dinosaurs are not just for display. In-depth studies like this offer basic information about individual animals that can help provide a clearer image of what a vanished species was like. This is especially critical when sample sizes are small. There are about 50 known partial T. rex skeletons from the dinosaur’s two million year reign. That’s pretty good for dinosaur standards, but imagine how little we’d understand if we only had such a sample size for animals like jaguars or spotted hyenas. Every piece is important.
At about 28 years of age, Scotty was undoubtedly old for a T. rex. That’s about the same age-at-death for the famous, nearly-complete “Sue.” But it’s the matter of size that has shone a spotlight on Scotty.
Scotty’s size estimate comes out to about 42.6 feet, just stretching past Sue. And the new weight estimate is almost 900 pounds heavier than that the researchers calculated for Sue. There’s no doubt that Scotty was a huge dinosaur that represents the ultimate in the evolution of non-avian predatory dinosaurs (partly because there weren’t any more after an asteroid dropped the curtain on the Cretaceous soon after Scotty’s time). But in the classic “my dinosaur is bigger than yours” contest, Scotty might not be the apex, after all.
There’s the basic fact that Scotty isn’t as complete as Sue – about 65% to about 90% in Sue’s case. That matters. A few inches here or there on this or that missing vertebra can add up, especially when the two individual T. rex are already so close. Bulk gets tricky, too. Paleontologist John Hutchinson has pointed out that previous mass estimates for Scotty have come out as comparable to Sue and are within the expected margin of error for these sorts of approximations. The difference between these two dinosaurs was likely a matter of ounces and inches.