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Re: bloated T. rex



Jaime,
Thank you for your extended response.  This is definitely helping.

>But this is about a rex, so I'll use another specimen (AMNH 5027 for 
>example) to illustrate this: say, 17 cubic feet (big skull), that's over 
>seven cubic feet inside, and it's strait down the gullet where the 
>pectoral girdle would have allowed such a volume (remember JP?) and then 
>to the gut. There was a smaller degree of expansion on the rex as there 
>was on the daspletosaur, but it was a much larger creature, fully 
>one-third bigger, and this is not the biggest rex specimen, but I use it 
>for its relatively complete trunk. _Nine_ of us could end up down there 
>(1440 lbs or over 650 kg) and this is with an expansion possibility of 
>one-seventh volume or so. That's a third of a hadrosaur of relatively 
>average size at 30 feet and four tons or so in the time it would take a 
>small family (seven or so, given mine) to eat a roast turkey and taking 
>time to swallow and wipe one's lips.

Excellent.  I think I see where my problem lies.  The figure that was quoted
to me from GSPaul's _Predatory Dinosaurs of the World_ was that the rex
would have had a meal capacity of two tons.  I was figuring that would have
been two *short* tons--meaning 4,000 pounds, or approximately three times
the capacity you just suggested--because that was the most favorable
interpretation I could come up with (as opposed to two metric tons at about
4400 lbs. and two long tons at 4480 lbs.)

So, assuming the two ton quote was accurate (not absolutely certain, since I
don't yet have a copy of this book), I think that means one of the following
is true:

Either a ton for paleontologists is about half what it is in common parlance
or you and GSPaul disagree by a *huge* margin about the meal capacity of a
rex.  (Your estimate seems a great deal more reasonable to me, IMHO.)  

Or was there a third option I have overlooked?

>A duck waddles because it is front heavy, I assume,

That, and the legs are spaced widely apart.

>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,

Okay, ignoring the ton issue until we can get that cleared up, I can see
this form of compensation working IF the rex was capable of rotating the
front half of the body up (and thus, toward the center of gravity) while
keeping the tail horizontal (as otherwise, the tail rotates down toward the
center of gravity in the same proportion as the front, accomplishing almost
nothing--and this doesn't even get into the problem of tail dragging.)  This
raises two obvious questions.  1) Was the rex spine in the pelvic region
flexible enough to bend like this? and 2) Was the musculature above the
spine strong enough to accomplish this bend?  I'm assuming the rex spine was
spring loaded to resist gravity so that the rex would not have had to expend
much energy to maintain it's flat cantilevered body position (I've always
assumed this spring loading is what causes the classic therapod death pose)
but I'm guessing the "springs" involved were ligaments which would have
slacked off as the spine bent upward--shifting the body load to the muscles
pulling the spine in this direction.  Also, assuming the spine was
relatively uncompressible, I think there would have been added resistance to
bending the rex body from having to stretch the lower regions of the body
longitudinally (ie. around the outer circumference of this bend).

I think I will wait to find out whether I am proceeding from incorrect
assumptions before heading off into the rest of your letter.  If anyone out
there can see where I am heading off course, feel free to bat me in the
right direction.

Nicholas (Wren)