[medved]

Aside from any questions about gravity then and now, there are three models for a predatory existence worth considering. To successfully take on animals its own size, a predator generally has to be able to gain control of the prey animal's body while trying to inflict a fatal bite or strangle the animal, and this requires more than just teeth; thus big cats with their combinations of claws and teeth can do this. It also requires the predator to roll and tumble with prey and a tyrannosaur would be too heavy to do that; elephant-sized animals cannot sustain falls (at least in our gravity).

The second modus operendi to look at is that of wild dogs and wolves, who compensate for lacking weaponry other than teeth by hunting in packs; it's a bit much to picture tyranosaurs hunting in packs.

The third method of operation may actually be the one primarily used by tyranosaurs, and that is the method favored by storks and a number of wading birds. This method depends on the fact that most prey animals don't spend a whole lot of time looking upwards for eyes and teeth; basically, you just stand there and wait for something short and stupid (a democrat or an evolutionist perhaps)to walk by, and then you snap it up. Teeth and patience are all which is required.

[RoughDobermann]

I could be wrong, but I believe that the latest "thinking" regarding T-Rex hunting is that they may in fact have been ambush hunters. One T-Rex would scare up the game, they'd start running towards the hiding T-Rexs, who'd then pounce. I've no idea how they came up this theory though. And, it'll probably be replaced by another theory tomorrow!

[RightWhale]

T-Rex would have preferred a modification of Method 1. It would tromp on its prey and then rip the roadkill into bite-size morsels at its leasure.

[Thud]

Yeah, I just don't see how T-Rex could immobilize large prey long enough to get in a good bite, without sitting on 'em.

[Bonaparte]

An elephant can chase you down at 30 mph and then trample you. Why couldn't T-Rex have simply stomped his prey like an elephant?