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mass, momentum, & misc.



  I've been crawling around the Tyrrell Museum website (nice site, by the
way) and find myself once again vexed with questions about dinosaur physics.
Does the T. rex reconstruction there represent contemporary thinking about
how the rex most likely was built?
( http://tyrrell.magtech.ab.ca/tour/trex.html )
  I notice the forward view indicates the legs were placed very close to one
another.  This brought back to mind that question that has been pestering me
of where a rex would store a large meal (two tons, by at least one famous
estimate).  If the legs were indeed spaced this closely together, I would
think that would mean the bulk of a meal would have to be stored forward of
the legs--and far enough forward at that so as not to seriously impede the
motion of the legs.  Looking at the rex in profile, I find it hard to
imagine where you could hang a two-ton meal mass on that skeleton forward of
the legs without seriously front-weighting the rex.  I fail to understand
how it could have compensated.  (T.A., I thought your suggestion that maybe
the rex could have used its flexible neck to pull its head back some had
merit, but looking at that spine, my feeling is that this strategy would not
have gained much.  But perhaps someone out there has some actual figures as
to how much the rex could have retracted it's head by flexing it's neck.)
  I'm not just picking on the rex here, by the way.  Take a look at the
Albertosaurus reconstruction.
( http://tyrrell.magtech.ab.ca/tour/alberto.html ) 
  What is going on here?  Does that look like an animal built to carry a
heavy meal load up front?  From what I can tell, therapod experts don't seem
to think huge meals would have posed a balance problem for these guys.  What
do they (or you) know that I don't?

  While I'm going on about dinosaur physics, the Tyrrell had some displays
on pachycephalosaurs which I found curious.  
At  http://tyrrell.magtech.ab.ca/tour/stegocer.html we see a scene described
as "A male stegoceras prepares to butt a rival in the ribs."  I have often
heard pachycephalosaurs described as head-butters, much like bighorn sheep.
Does this strike anyone else as peculiar?  Look at that flexible curved
spine.  If the impact force decelerating that head is great enough to
require such a thick skull (far thicker in proportion than the bighorns seem
to need) wouldn't the momentum of the body following the head fold up that
spine like a wet soda straw?  I don't know.  If someone handed me a club
that was round and blunt on the end, but with knobs and spikes surrounding
the end, I think I would be more inclined to swing that club than thrust
it--particularly if the handle was flexible.  (But then, I like to do things
the easy way.)

  The Tyrrell brought up similar contests with regard to ceratopsians,
saying: "Ceratopsians had a variety of horns, with which they probably
battled members of their own species, just as deer and bighorn sheep do
today.  They also had large bony frills surrounding their necks. The frills
served as a means of display."
  What the hey??  I was under the impression that the horns and frills were
so that the ceratopsians could mass together, in the fashion of musk-ox, to
present a horny, armored barricade against any would-be predators.  Was I
just completely out in left field on that one?  And did female ceratopsians
differ significantly from the males in armor and weaponry?  (My thinking
being that sexual dimorphism would lend support to the notion that
ceratopsians battled one another in contests much like deer and bighorn do.)

Confused,

Nicholas (Wren)