Re: DINOSAUR digest 1272

["Martin Barnett" <martin.barnett3@virgin.net>]

Eric Beyer wrote:
> Sounds silly but...How about simple theory.
>
> What if they where used to pick his teeth?  (Nothing more bothersome than
a
> slice of meat caught in your teeth.)
I don't think T. rex could reach it's teeth with those little things, but I
agree with you that we are looking for a simple theory.  Besides, can we
call those little arms "Special adaptations" to anything?  Even if we knew
their use, would that not mean they had been reduced until that's all they
did.  Take for example the mating idea - who said Tyrannosaurs are they only
ones to hold on during mating?  What if all theropods did it?  It'd lead me
to the idea that Tyrannosaurs struggled the least (Perhaps Therizinosaurs
were rougher).

Sam

"Wouldn't we be more scared if a cow could skeletonize a pirhana in
seconds?"

> -----Original Message-----
> From: Dann Pigdon [mailto:dannj@alphalink.com.au]
> Sent: Wednesday, January 26, 2000 5:05 PM
> To: dinosaur@usc.edu
> Subject: Re: DINOSAUR digest 1272
>
>
> Martin Human wrote:
> >
> > > From: Dann Pigdon <dannj@alphalink.com.au>
> >
> > > I like the idea that they were used to help the beast get up. If
> tyrannosaurs
> > > spent much time lying around (and that huge pubic boot is obviously
> there for
> > > some reason), they may have had to rock forward to get up in order to
> begin
> > > straightening their legs. Maybe the forelimbs were still there (rather
> than
> > > being lost entirely, or vestigialised like in Carnotaurus) to stop
them
> scooting
> > > forward on their chests before they could pivot their front section up
> to
> >
> > > I don't think much of the idea of the forelimbs being used during
> mating. Who'd
> > > want to antagonise a 6 tonne female by jabbing her with meat hooks at
> the
> > > critical moment? (please don't answer that question)
> >
> > Doesn't the latter statement contradict the first? If you want to push
> > yourself up, or stop yourself slipping forward when rising, why keep
> > "meathooks" as appendages? A flat strucuture with toes to dig in would
> > seem a better idea?
>
> Providing that was all the limbs were used for. I can't think of what else
> they
> could have done personally though. I've read that Tyrannosaur forelimbs
> couldn't
> straighten out at the elbow more than about 90 degrees (that is, couldn't
> straighten out at all). If this is not one of those Mesozoic myths (as
> opposed
> to urban myths) that has been endlessly repeated until assumed true, it
> certainly seems to fit in with the former of the two above mentioned
> theories.
> Imagine a Tyrannosaur lying down with its weight supported by its folded
> legs,
> pubic boot and chest. The position of the arms, and their c.90 degree
angle
> would probably put the forelimbs lying horizontally along the ground, with
> the
> claws digging into the earth. Being heavily muscled, and unable to
> straighten
> out any more than c.90 degrees (I'm still assuming this), they would seem
to
> be
> perfect for stopping the chest from scooting forward when the animal
> straightens
> up its hind limbs before rocking back and using the counter balancing tail
> to
> raise the front part of the body. Perhaps the large curved pubic boot
> functioned
> as a pivot early on in the process before the legs were straightened
enough
> for
> it to leave the ground (that is, enough to allow the centre of balance to
be
> moved forward to take some of the stress off the hind limbs to allow them
to
> begin the process of straightening, when the chest would be baring a bit
> more
> weight and perhaps require the forelimbs to prevent it scooting forward
with
> the
> change of weight/angle on the chest).
>
> I suspect the whole process would have been similar to how a goat rises to
> its
> feet (I'm assuming from memory that they rise back legs first). As to why
it
> retained curved claws, this could have been a holdover from earlier
> theropods
> who had more use of their forelimbs, or perhaps they did other things with
> them
> that we haven't thought of yet.
>
> Conjecture at its best (arguably).
>
> --
> ____________________________________________________
> Dann Pigdon
> GIS Archaeologist
> Melbourne, Australia
>
> Australian Dinosaurs:
> http://www.geocities.com/capecanaveral/4459/
> http://www.alphalink.com.au/~dannj
> ____________________________________________________