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Re: Incredibly preliminary size estimate for new T. rex



> Date:          Sun, 21 Sep 1997 22:35:24 -0500 (CDT)
> Reply-to:      znc14@ttacs1.ttu.edu
> From:          "Jonathan R. Wagner" <znc14@ttacs1.ttu.edu>
> To:            Jeffrey Martz <martz@holly.ColoState.EDU>
> Cc:            dinosaur@usc.edu
> Subject:       Re: Incredibly preliminary size estimate for new T. rex

<snip>

> >     This is just speculation, but active lifestyles get more hazardous
> >the more massive you get; remember the numbers from Dr. Farlow's
> >"tripping T.rex" paper.      
>         Dr. Farlow (et al., wasn't it?)'s work is valuable in that it
> addresses such questions in a modern, thoughtful, and quantitative manner.
> This is clearly what we need. I still wonder why an animal seemingly "built
> to run" as it were would become so large as to endanger its life by the act
> of running. Nature is truly something.

Dr. Farlow's paper is well done, interesting, and thought provoking.  
However, looking at numbers often does not reveal what is in the real 
world.  There is no extant model for large theropods.  There is for 
"medium sized" ones-the ostrich.  They are fast, likely run 
"similarly" to theropods (as close as we have, but an assumption that 
might not be true either), and they do fall-not unoften.  When they 
do, they seem to slip and end up on their side, getting up very 
quickly usually without damage. And yes, there is orders of magnitude 
of difference between the inertia of an ostrich and a tyrannosaur. 

Now, before I am flamed (no incinerated), I realize this is not the 
equivalent of a large theropod in size, speed or perhaps running 
abilities, etc.  Hold this thought.

Elephants are not theropods, but perhaps medium sized sauropods.  
They can run fairly fast.  They do not fall often(hardly at all) and 
when they do fall they often hurt themselves.  They just don't fall 
often.  Perhaps this is because they are quadripedal, etc.

However, rhino do fall and they are built for it.  They are tanks 
with the black at one ton and the white at two.  They chase each 
other and topple one another at speed.  Are they modern day 
triceratops?

Hippos on average weigh more than rhino except large male whites and 
they run fast as well.  But when they fall they get sprains and such. 
They are not built for it like rhino.

So what's the point.  Well, you cannot compare with any certainty any 
large extant animal with a large theropod or perhaps any theropod.  
You can see that some extant animals  run well without falling 
much, some don't fall well, and some do.  You can say that prey today 
often herd if size and defensive weapons are not enough and run 
nearly as fast as their predators.  Defenses are numerous and vary.  
Predators compete for prey and with each other.  Predators have 
favorite prey depending on numerous factors. Differing predators 
occupy different niches.

As for T rex falling and running, look at the way it's built.  No 
this doesn't prove it was real fast, but it had to be able to move 
fairly well.  Falling exposes any animal to risk, but physics doesn't 
tell all.  A well placed strike at long bones requires little energy 
to break in humans.  But there is soft tissue and connective tissue 
involved. So injury in falling would involve a lot of complex 
variables not addressed with pure physics.  And perhaps they could 
slow themselves as someone else suggested then slip and slide without 
as much injury as thought. Or maybe they didn't fall much.   Of 
course maybe they did like lions often do.  Let the hyena of the day 
make the kill, see or smell the kill, then take it away. 

Michael