Tyrannosaurus questions?

"I have heard people say that if a Tyrannosaurus fell ... while running they might be crushed under they're own weight. Is there any truth to this, or are these just rumors, or do we really not know?"

This is a prediction based on estimates of how an animal that size and shape might be affected by a fall at full speed. That may be accurate, but without actually watching live Tyrannosaurs we really have no certain idea how they managed. Falling at high speed is a risk for many animals - look at race horses, for instance. And yet, these animals continue zipping around (except the ones who fall down and break something, of course). This conclusion is used by people who contend that big Tyrannosaurs must have been scavengers because hunting would be too dangerous. I don't buy that myself, although I'm afraid my reasoning is more Calvinian (it just wouldn't be cool to have them be sluggish scavengers) than objective. Still, it seems far more plausible to me that these were active hunters who may have scavenged as well (like most of the big predators we know of today) than that they just wandered around hoping they'd find a big dead thing.

As for the arms/standing thing, unless they stood up all their adult lives, which just seems really unlikely, they must have been able to get down and get up again - otherwise you posit an animal that automatically dies if it falls down. Hard to see how such an animal could have been so hugely successful for so long. Maybe the arms helped, maybe they used their heads as anchors when getting up, maybe they only slept leaning against trees - we're likely never to actually find out for sure.

The arms, by the way, seem to have been pretty strongly muscled (based on muscle attachment scars on the bones), so even though they were relatively tiny, they presumably had some use that kept them strong. What that use might have been is still open for speculation, though.

This is the guy to go to for really authoritative Tyrannosaur answers, though:

http://www.geol.umd.edu/~tholtz/

although you might want to try to find out as much as you can in reference books first so that you can focus your questions.

From what i remember when we studied dinosaurs in primary school, the Tyrannosaurus did in fact have a use for its arms. Although theyre not entirely strong, it could still lift its upper body if it fell down, but it wouldnt be able to carry its own weight completely, so usually if something like that did occur it would 'crawl' to another location where it could climb something for assistance, such as a tree or the side of a mountain.

in most cases tho this is not necessary. this dinosaur may have pretty much useless arms but it had extremely powerful legs. unless stranded in a ditch it could usually twist its body and balance back on its hind legs, making it possible for it to sleep and get up in a hurry if it needs to.

i think the more probable reason behind t-rex having such useless arms, was its speed running and powerful legs and jaw, something to gnaw on just to give the herbivores a fighting chance, t-rex had to rely on its speed and jaws to catch prey. if it could grab them as well, the herbivores wouldnt have a fight chace, or so i am to believe.

An adult T. rex weighed several pounds, so I suppose if it fell over, it might injure itself. This is supported by the fact that most T. rex skeletons have broken and healed ribs. (The same is true for most large dinosaurs.) But there's also strong selective pressure for being careful - if you trip a cheetah at full sprint, it would probably be killed. Elephants could also easily hurt themselves if they fell over. The benefits to their size outweighed the risks.

As for the arms - no one knows why they were that short. Chances are, the animals got big and the arms just didn't get big along with them - they were using their jaws for processing food and didn't need long arms.

well you are right we really don't know but if you look at birds when they fall they are able to get back up and a tyrannosaurus body is similar to a birds body, or penguins for instance... and if they fell it would be hard to believe that they would crush under their own weight.. look at elephants they fall and get back up now the small arms i really don't know their use but use your imagination and i am sure something will come up

I don't know for sure, but I can imagine that they would be able to use their powerful neck to force their head to act as a "third leg" to get up after falling.