So T. rex is considered to be a bit of a slow poke now.....what about Gorgosaurus, Albertosaurus, Daspletosaurus?

[andrewsaurus rex]

could they run, or were they just fast walkers?   Gorgosaurus and Albertosaurus are the most likely runners I guess as the were more lightly built.

[GojiraGuy1954]

T. rex was a very specialised animal, being an endurance-based predator. Other tyrannosaurs were likely faster as they still tended to rely on running down their prey in shorter bursts. You can even see it by comparing the proportions of T. rex to G. libratus, A. sarcophagus, etc.

[Newt]

I'm sure subadult Tyrannosaurus were good runners too, and they were built more like the Campanian tyrannosaurids. 

There's an analogous situation with bears. All bear species are good tree climbers when young, but brown bears have to give up climbing when they reach adulthood as they're just too bulky; it's harder for them to climb and they're more likely to be injured if they fall. Other bears don't reach that critical size, so they can keep on climbing (except polar bears, who don't spend much time in forests in any case). The size differential between brown bears and the various other forest bears is similar to the size differential between Tyrannosaurus and its Campanian cousins.

[Takama]

Forgive me for being out of the loop. (Way out if you can consider that) but does T.rex being a "Fast Walker"  only apply to members of its family? (Tyrannosaurs) or does it apply to other Theropods like Allosaurus?

[Bread]

I still find it not at all crazy to think that Tyrannosaurus, as well as a majority of large Tyrannosaurs did not really run, but "speed walk" when in pursuit of prey.

Majority of their prey has always been large ceratopsian and hadrosaur. Both species tending to not really be fast in general.

[Newt]

Forgive me for being out of the loop. (Way out if you can consider that) but does T.rex being a "Fast Walker"  only apply to members of its family? (Tyrannosaurs) or does it apply to other Theropods like Allosaurus?

Not even all the tyrannosaurids, just the really big ones. Scientists have been going back and forth on this topic for many years. The bigger an animal is, the more dangerous it is for it to run. A mouse can scamper and tumble all day and never be hurt, but one bad step by an elephant can lead to a fractured leg or worse. 

On the other hand, the long legs of tyrannosaurids are clearly built for speed. Not just their length, but the proportions (short, muscular thigh, longer and less muscular lower leg and foot) and the restricted mobility of the joints - these are running adaptations. So the reasoning goes that most tyrannosaurids were runners, but the adults of the really big ones (Tyrannosaurus, Tarbosaurus, Zuchengtyrannus) probably didn't run so much. Not to say they couldn't - elephants do, after all - but it wasn't a typical part of their lifestyle.

The idea that Tyrannosaurus couldn't run was key to the old idea that it was a dedicated scavenger, but that isn't necessarily so. Even a non-running tyrannosaur was probably about as fast as the larger herbivores in its environment and likely could pursue them until they were too exhausted to escape. This is a strategy wolves use sometimes.

This argument could also be applied to other super-sized theropods, like the big carcharodontosaurids. I don't know if any scientist has explicitly made the argument for non-running in these non-tyrannosaurid clades.

I'm personally pretty ambivalent about Tyrannosaurus's running capabilities and habits. I'm certain it had the ability (again, elephants can run, and they are not built for running the way a tyrannosaur was), but it also faced inherent risk. But just because a thing is risky doesn't mean animals don't do it.

[Tecovas]

Forgive me for being out of the loop. (Way out if you can consider that) but does T.rex being a "Fast Walker"  only apply to members of its family? (Tyrannosaurs) or does it apply to other Theropods like Allosaurus?

Not even all the tyrannosaurids, just the really big ones. Scientists have been going back and forth on this topic for many years. The bigger an animal is, the more dangerous it is for it to run. A mouse can scamper and tumble all day and never be hurt, but one bad step by an elephant can lead to a fractured leg or worse.

On the other hand, the long legs of tyrannosaurids are clearly built for speed. Not just their length, but the proportions (short, muscular thigh, longer and less muscular lower leg and foot) and the restricted mobility of the joints - these are running adaptations. So the reasoning goes that most tyrannosaurids were runners, but the adults of the really big ones (Tyrannosaurus, Tarbosaurus, Zuchengtyrannus) probably didn't run so much. Not to say they couldn't - elephants do, after all - but it wasn't a typical part of their lifestyle.

The idea that Tyrannosaurus couldn't run was key to the old idea that it was a dedicated scavenger, but that isn't necessarily so. Even a non-running tyrannosaur was probably about as fast as the larger herbivores in its environment and likely could pursue them until they were too exhausted to escape. This is a strategy wolves use sometimes.

This argument could also be applied to other super-sized theropods, like the big carcharodontosaurids. I don't know if any scientist has explicitly made the argument for non-running in these non-tyrannosaurid clades.

I'm personally pretty ambivalent about Tyrannosaurus's running capabilities and habits. I'm certain it had the ability (again, elephants can run, and they are not built for running the way a tyrannosaur was), but it also faced inherent risk. But just because a thing is risky doesn't mean animals don't do it.

Agree with you there. Triceratops and Edmontosaurs don't look too spry either.