From Charles Weber:

Re: Tiny “T. rex” found (Sept. 17): I saw the portrayal of Tyrannosaur in the Science journal. They portrayed the dinosaur as holding its body horizontally and its legs vertical. I doubt very much if they were stupid enough to hold their bodies horizontally, but they could not hold their legs vertically. If they tried to do so, they would fall forward and either break their thin ribs or break their fall with that big head and extended hip bone, because their center of gravity is forward of their hips. Of course they could walk horizontally if they thrust their hips backward. You can verify this by bending forward at the hips (but I doubt if you have any intention of walking this way or that they did). I suspect that if they must fall, they would have preferred to fall back on that robust tail. If they had walked horizontally, almost certainly they would have evolved their hip bone forward of where they portray it.

You may find interesting a proposal as to why the herbivore dinosaurs declined in armor, teeth, and quite a bit in bony structure across the Cretaceous. I suggest it was due to a phosphorus famine created by erosion of the soil of the runways of plant smothering termites. You may see this discussed in more detail starting here and its links, which links explore the possible affect that ant evolution had upon them. The affects that soil phosphorus has had on Paleocene vertebrates and modern animals may be seen here.