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Re: Tyrannosaur paleopathologies, updates.



Darren Tanke wrote:

> I have seen, fibular fractures in tyrannosaurs are not that
> rare, perhaps 10-15% so affected. I want to give a higher percentage number
> but I am being cautious here.
> I know of no femur or tibia fractures showing any sign of healing. 

     You mean they died right around the time thier legs were broken? 
Hmmmmmm...
     So what you are saying is that a broken fibula can heal, but the breaking
of the big weight bearing leg bones is associated with death?  Not very 
surprising.  It sounds like breaking a leg is a pretty risky 
proposition.  Even if they survived the fall (assuming that is how the 
break occurred), starving to death is BAD.  
 
>  5. Tyrannosaurs were obviously built for speed. 

     For such a big animal, yeah.
 
> bigger they are the harder they fall". Some fell and died or were injured.
> Don't deny it. Some were even killed by their prey (it happens today). But
> such events were rare and had no real impact (no pun intended) on the
> tyrannosaur population structure as a whole. 

     Why do you say that?  If they weren't common, it might have 
something to do with the fact that T.rexes who didn't modify 
thier speed were being selected agianst.                 

> If falls were so detrimental to tyrannosaurs, they would have
> evolved a "safety device" long ago or gone extinct from falling down
> all the time.

     You mean a safety device like being really really careful and 
watching thier speed?  Again, I'm willing to bet a sparrow could fly 
faster out in the open then it does in the forest.  Behavior can be 
moidified according to the circumstance.  
     There seems to be a curious ambiguity to some of the responses 
during this discussion.  Some admit that falling was dangerous, but not that 
this was a selective pressure (??!?)  Others have shrugged off the 
increased and inter-propagating dangers of huge size, bipedality, and high 
speed, by providing analogies that would apply to much smaller animals whose 
concerns on these matters would be relatively infinitessimal.  Others 
have provided "safety behaviors" to break a fall, in my opinion without 
appreciating limitations is the effectiveness of such maneuvers would 
decrease with increased size.  T.rex lifts its head away from the impact, 
it still crushes its torso.  Neck muscles that keep a couple hundred (?) 
lb head up under normal circumstances are still going to have to cope with a 
much greater RELATIVE magnitude increase in force then a smaller falling 
animal would.   
     If an activity is dangerous, then there will be selective pressures to 
modify the behavior or anatomy to reduce the danger as much as 
possible.  Yes, animals did and do engage in dangerous activities in 
thier day to day life, but if they do they are careful.  
Ourangutans don't do back flips in the trees, and sparrows don't 
fly at thier flat out, top potential speed when moving through a 
forest.  T.rex could run, and on a fairly regular basis, but 
instincts for NOT running at the top possible speed could be 
selectively ingrained.            
   
LN Jeff
O-