Tyrannosaurus--what's with the arms?

[vibrotronica]

This question was discussed here:
http://boards.straightdope.com/sdmb/showthread.php?threadid=26377&highlight=tyrannosaurus+arms

and included this, which I still think is the funniest thing I’ve ever read on these boards:

It could wave them in the air, like it just didn’t care

[Emperor_Penguin]

*Originally posted by Darwin’s Finch *
**Keep in mind, however, that even if a fall were to be fatal, that does not imply that such falls were commonplace. In general, larger animals are likely to be more difficult to trip than smaller ones, and tyrannosaurs may well have been able to recover from most stumbles. Even if the occasional fall were fatal, that does not rule out potentially risky behaviour - particularly if the rewards (e.g., a meal) outweighed the danger (e.g., death).

Keep in mind, after all, that tyrannosaurs were fairly successful (Tyrannosauridae persisted for some 18 million years). If these animals fell every time they tried to move faster than a walk, and such falls were always fatal, we certainly wouldn’t expect them to have stuck around for very long. **

I agree. A T. rex is big, and anything big enough to trip up a T. rex would be highly visible to it, so fatal falls were probably uncommon. My post was more just to highlight the fact that if a T rex did manage to get tripped up, it was in a spot of trouble.

Also, much like Neurotik said, it was likely that the T. rex knew how to minimize the impact from a fall.

Another thing that came to mind, is that with these guys were built like the preverbal tank. Many injuries that we would consider disabling, seemed to only slow them down, if that. STAN, a T. rex found in South Dakota, exhibited a whole range of pathologies, including a broken neck that had started to heal, as well as a punctured skull, most likely caused by the tooth of a fellow T. rex, which had healed over as well.

Another T. rex, Sue also had signs of broken ribs, an infected leg and arm, as well as a bacterial infection that ate holes in her jaw. Despite all of this damage, she was considered to quite a healthy dino.

Of course, this is all beside the point, as I think both you and Sock Munkey nailed the question.

[Sock_Munkey]

(minor hijack)

I always suspected that the T-rex hunted like a komodo dragon:

Sneak up,
lunge in,
take one good bite,
let the animal run,
track its scent untill blood loss and infection to stop it,
scare away any other scavengers,
chow down.

The fact that it takes a lot of energy to move a T-rex sized body around looking for food is what makes me think that just relying on scavenging would not have supplied enough food for it.
A vulture, by contrast can search all day long gliding on thermals expending hardly any more energy than at rest making full time scavenging highly effecient for them.