Re: Incredibly preliminary size estimate for new T. rex

["Michael" <tons@ccs.netside.com>]

> Date:          Mon, 22 Sep 1997 11:35:12 -0600 (MDT)
> From:          Jeffrey Martz <martz@Holly.ColoState.edu>
> To:            Michael <tons@ccs.netside.com>
> Cc:            "Jonathan R. Wagner" <znc14@ttacs1.ttu.edu>, dinosaur@usc.edu
> Subject:       Re: Incredibly preliminary size estimate for new T. rex

>     Probably.  And also, they would not need to run as aften as a
> predator which also reduces thier chances of falling significantly.

Well, that's likely true.  But elephant don't have any real natural 
predators left to run from.  However, they did.  Does anyone look at 
elephantine fossils like Darren does dinosaurs for evidence of 
falls/trauma?  Maybe they did fall more, but that begs the point.  
They are not anything like a tyrannosaur that would have evolved 
(presumptively) to survive most falls if it evolved to run fast.  Now 
that statement is unable to be proven or disproven, but I wouldn't 
want to debate otherwise. 

Or it didn't fall much either, or didn't get hurt as much.  Now 
that's an opinion, but it makes more sense than anything else, except 
tyrannosaurs didn't run very fast.  Additionally, look at rhino.  
They can weigh two tons and are built to take falls.  Do we know that 
T rex weighed 1.5-4+x this much for sure?  Looks like they did, but 
no one knows.  I'm not taking sides but pointing out some things, as 
I suspect we agree more than not about this.

In
> other words, T.rex is running more often and a biped and so at greater
> risk of falling;

Presumptively, but not necessarily.  It could just as easily be the 
other way around.  

 and as you 
noted, an elephant sized animal WILL hurt
> itself if it falls, even if it doen't die.

I said often does but rarely falls, so evolution has created a 
"stable" form of locomotion for this animal and weeded out the 
clumsy, allowing the species to propagate more efficiently, if you 
allow another way to look at it.

>      Whether or not Dr. Farlow's numbers are dead on, the illustrate well
> that the force of impact of a falling animal increase IMMENSELY with
> increasing mass.

If it's a ball falling to earth then it's easy to work it out.  If 
it's a living breathing animal reacting to a fall, would it be the 
same?  How many times to we look at models only to find that they are 
not supported by the real evidence.  OTOH, if T rex weighs several 
tons it's going to have immense inertia when it falls.  Now it's 
a matter of how it falls and how often.  It isn't going to be exactly 
like an ostrich.

I'm not sure I agree with the amount of damage that would necessarily 
occur.  Obviously, it's not the best thing for the animal and may 
have been very serious or fatal.  The human body (and chimps) can 
withstand 10-12 gees easily without tearing any internal organs 
despite their dropping 1/2 foot within the body.  Surrounding tissues 
give bone a great deal of support.  It's an interesting debate with 
no real answer.  Closed head trauma and cervical injury happen in 
some accidents with little force and not all in 100mph collisions.  
So go figure.   
> 
>      Physics can tell us the forces involved with a given mass hitting the
> ground; and it can also give us some idea as to the tensile and impact
> withstanding abilities of tissues.

Yes, but not in a T rex and not in a T rex running and falling.  

>       Yes, T.rex was likely a to a large degree a RUNNING PREDATOR for
> reasons that have already been discussed on this list.  However, the
> dangers posed to it as a running bipedal predator of its size were
> probably very significant.

Yes, it would have to evolve a way to deal with those forces to 
survive if it had to run fast to survive with high energies involved 
in falling, fell often enough as a species for it to matter, and 
wasn't built to withstand a fall, couldn't withstand a fall at speed 
and/or didn't know how to fall. 

Michael