T. Rex Tail Made For Running, Maybe

"T. Rex Tail Built for Speed"
Jennifer Viegas, Dinosaur News, Discovery News (November 17, 2010)

"Tyrannosaurus rex was one of the world's fastest moving hunters, suggests a new study of this dinosaur's muscular tail.

"The study, published in The Anatomical Record, shows that T. rex's long tail didn't just serve to counterbalance the up-front weight of the massive carnivore's extremely large head. Paleontologists had previously suspected that was the tail's primary function.

"Instead, the new research led by University of Alberta researcher Scott Persons reveals that T. rex's powerful tail muscles helped to give this dinosaur super speed...."

We don't have any living T. rex to study, so paleontologists need to work out what the critters were like from their fossilized bones - also the occasional fossilized soft tissue, and in one case unfossilized goo.

Anyway, paleontologists compared the T. rex tail to that of contemporary reptiles like crocodiles and Komodo dragons. The T. rex tail's 'ribs' were higher than those of today's reptiles: which gave more room for muscle.

"...He now believes that previous estimates of the muscle mass in this dinosaur's tail were underestimated by up to 45 percent. This explains why earlier researchers thought T. rex was more of a plodding animal that couldn't run very fast...."

The Lemming would have liked to see more discussion on why and how a well-muscled tail translates into a faster T. rex - but I suppose it's a matter of being able to balance better? Or maybe something else. That sort of detail would have been really nice to have.

On the other hand, there's this nifty video:

"T Rex Run"

TIMELESSTHEGAME, YouTube (July 4, 2009)
video, 0:06

"The popular scientific theory is that the Tyrannosaurus, while large and fearsome, was a scavenger and not a predator. This means that it probably did very little running, and when it did, it did not entirely leave the ground. It most likely achieved a 'fast' walking pace.

"The Speed of an animal is often determined by the scale difference between the femur and the lower leg bones. Animals with shorter femurs tend to be faster while those with longer more 'human-like' leg bones are on the slow side. The T-Rex had a very large femur, nearly equal in length to it's lower leg bone. It's top speed was most likely around 17.9 mph- that's fast enough to outrun our fastest sprinters."

Okay: the critter in the video doesn't seem to be going all that fast. But remember: T. rex was big. The one in the drawing here shows the high end of T. rex size - sort of the dinosaurian equivalent of a football player. But even a 'small' T. rex would be a whole lot of animal.

Look at the video and imagine someone whose head just about reaches the T. rex's belly, and the speed becomes a little more obvious.

Somewhat-related posts:

• "Ancient Galloping Crocodile"
  (November 19, 2009)
• "Tiny T. Rex Fossil, China, Paleontology, and International Law"
  (September 18, 2009)
• "Bringing Back the Dinosaurs: Not a Crazy Idea Any More"
  (June 29, 2009)