Re: bloated T. rex

[augwhite@neosoft.com (Toby White)]

>>>>2) have been due to having to rotate the thighs forward to keep the 
>>>>feet under a forward-displaced center of gravity? (Squat-walking, 
>>>>in other words.)
>
>>I didn't know whether to attach any significance to your lack of 
>>comment on this one. My impression is that you were attributing the >T. 
>rex's mobility impairment primarily to volumetric expansion >interfering 
>with the action of the legs, or is that an >overextrapolation of your 
>view? In other words, do you think putting >a couple of tons of meat in 
>the stomach would have had any effect on >the rex's center of gravity? 
>Just looking at a rex skeleton, (eg. the >one at 
>http://tyrrell.magtech.ab.ca/tour/trex2.jpg ) it is hard for >me 
>personally to imagine the stomach having been located far enough >back 
>that this kind of weight would not have seriously tipped the rex 
>>forward. I notice the balance problem in large carnivorous therapods 
>>doesn't seem to particularly bother most people in the field, (take a 
>>look at http://tyrrell.magtech.ab.ca/tour/alberto.html for what looks 
>>to my inexperienced eyes to be a *serious* case of imbalance) and I >am 
>trying to figure out why. I'm assuming the most likely explanation >is 
>that the experts know something about this issue that I don't, and >I'm 
>trying to find out what that is.
>
>A duck waddles because it is front heavy, I assume, but I think I've got 
>it right. No counterbalancing tail, for instance. And while a rex would 
>be front heavy with 1.5 tonnes of hot, fresh (or rotting) meat in front 
>of it's hips, all he would have to do would rotate his body up in the 
>front, the tail swinging back and forth behind like a tightrope-walker's 
>balancing pole, and waddle forward, and this position may be a reason 
>why the legs and hips are so broad and developed for muscle, to support 
>the forward-heavy body.  Normally, the center of gravity is right under 
>the preacetabular bar of the ilium, but with all that extra weight put 
>on, it moves forward about two feet (.45 meters) or so, and to 
>compensate, the rex must move it back or he's ("she" in the case of Sue, 
>we assume) in trouble of toppling. The duck waddle would be one of the 
>few gaits allowable under such conditions, for it requires little 
>femoral movement. The tibia and fibula support this as well, for they 
>are very strait compared to the relatively curvaceous shins of smaller 
>and lighter tyrannosaurs like *Albertosaurus* and *Daspletosaurus*, who 
>would be less hindered by such balance-altering mass compsumption.

Doesn't John Hutchinson work on T. rex locomotion?  This looks to be a
serious problem, if I recall the thread on toppling tyrranosaurids.  

  --Toby White