Re: Tyrannosaur stance Question

["Allan Edels" <edels@email.msn.com>]

My response to Dwight's question, and to Dann's answer:

1)    Most modern mounts of _T. rex_ try to show the animal in an active
pose, probably running.  This means that the tail will be straight back,
parallel to the ground, with the head leaning closer to the ground than it
likely was at rest.
2)    The mounts are supported by steel posts, and sometimes by guy wires
from the ceiling.
3)    Many of the latest models are based on the modern mounts, i.e.
running.
4)    Look carefully at the pubic boot.  It is nearly 60% the length of the
skull, and it is a bit more solid than the skull. It is a large, heavy
construct.  It gave _T. rex_ a low center-of-gravity, and as Dann mentions,
the tail was heavy, and fairly solid, whereas the front of the animal would
have lungs and other air sacs, etc.
5)    The tail, like many other dinosaurs, probably had a set of strong
tendons that ran most the length of the tail, stiffening it.  (Some dinos
had ossified tendons there, but it may be that we don't have an old enough
_T. rex_ to show them - and those _T. rex_s that were old enough, the
tendons were not collected).
6)    The likely true standing pose of _T. rex_ would be with the tail
drooping 5-10 degrees towards the ground (below parallel), and with the ribs
and shoulders lifted around 12 degrees above the parallel to the ground.
The head would most likely be a bit above that angle.  Standing like that,
a properly built _T. rex_ model wouldn't fall over.
7)    WAY BACK (but not quite Mesozoic) when I was a child, I used to prop
my toy _T. rex_ leaning over the back of _Triceratops_, too.  However, I
just thought that it would look better that way - who knew that they would
change the stance to match my preferred pose?

    (As an aside to point 4 above:  R. MacNeil Alexander, in his great
(short) book about dinosaur and other extinct animal mechanics, used plastic
models [from the British Museum, I believe] to determine the correct center
of gravity, the specific gravity, and the displacement of each animal.  To
be sure about the center of gravity, he drilled out an area equivalent to
location and size of the lungs.  He used different models to measure the
displacement.  Greg Paul told us (DML) that he [GSP, that is] would take the
best reconstructed model, modify it as he thought it should be, then grind
up the plastic to determine displacement, and thereby, how much the animal
weighed).

    Allan Edels


-----Original Message-----
From: Dann Pigdon <dannj@alphalink.com.au>
To: dinosaur@usc.edu <dinosaur@usc.edu>
Date: Saturday, September 19, 1998 7:50 PM
Subject: Re: Tyrannosaur stance Question


>Stewart, Dwight wrote:
>>
>> I have a question that I have been attempting to get a clear answer on
for
>> some time.
>>    So, here's my question: what features have led to the conclusion that
>> Tyrannosaurus rex walked, ran, and (perhaps) primarily stood with its
body
>> almost horizontal?  Do you agree with this paradigm?  And, if
Tyrannosaurus
>> rex did move & stand in this posture, COULD he (or she) have stood more
>> erect.
>> I understand (I think :-)) that the paradigm that birds tend to hold
their
>> bodies at that angle (some birds, anyway) could open the question up, but
>> the physics of the very horizontal stance look awkward to my eyes.  By
that,
>> I mean that if one takes the hip structure as the fulcrum, then the front
>> end of the Tyrannosaurus rex appears to be over-balanced with respect to
the
>> tail.
>> I know the T. rex head had many air pockets and that the small arms would
>> also tend to damper this effect.  Nevertheless, the tail doesn't seem
quite
>> long or robust enough to balance out the structures anterior of the hips.
>> Am I missing something here?
>
>Okay, I'll try to say something remotely scientific here (gasps of
>horror). The tail would have been solid bone, muscle, sinew, etc,
>whereas the body had lungs and connected air sacks, and various
>weight saving features. A model tends to be solid all the way through
>(or hollow all the way through, depending on the size I expect).
>That said, I too tend to reconstuct a standing Tyrannosaur with a
>VERY SLIGHT upward tilt of the body towards the front. Not as extreme
>as in birds (which lack counter balancing tails), nor as extreme
>as the near-bipedal tail-dragging reconstructions that once abounded.
>However when moving, at a brisk walk or at a run (if that was
>possible - no that isn't a topic for a new thread, just let it go),
>I suspect the body would have levelled out (even blackbirds do
>this when they run across a lawn).
>
>> What made me ponder this is that I collect
>> 1/40th scale museum quality dinosaur models and the Bataat model was
touted
>> to me as the most accurate representation of what the T. rex looked and
>> stood like.  SO, I bought one and it has this rather nasty habit of doing
a
>> nose dive when it stands alone.  I asked my friend at the Dinosaur World
>> Store about this and he stated; "Gee, they ALL do that."  :-)  My
solution
>> was to pose my Tyrannosaurus lurking over (propped up) on the back of my
>> Triceratops.
>>
>> Dwight
>
>Have you ever tried to balance a Barbie doll on its feet (or any
>doll for that matter)? Yet we know that humans can stand in a bipedal
>fashion. A dead, static model does not have the complex
>inner ear arrangement of a living creature (surprise surprise). I
>wonder how much luck you would have trying to get a model of a
>sleeping flamingo to stand upright on one foot?
>
>--
>____________________________________________________
> Dann Pigdon
> GIS Archaeologist
> Melbourne, Australia
>
> Australian Dinosaurs:
> http://www.geocities.com/capecanaveral/4459/
> http://www.alphalink.com.au/~dannj
>____________________________________________________
>