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Re: A Tale of Two Tails



> From:          "Richard L. Dieterle" <Richard.L.Dieterle-1@tc.umn.edu>

> Perhaps the best reason that we have for thinking that Hadrosaurs did not use 
> their tails much in defense, especially against large carnivores, is this: if 
> it
> were effective to any degree at all, there would exist a constant selective 
> pressure for improvements in its disabling capacity to any degree consistent 
> with the presumed limited functional demands existing otherwise for Hadrosaur 
> tails (balance + ?).  A heavy tail like an AnkylosaurOs is not necessarily 
> the 
> outcome of such pressures -- bony serrations or other light weight 
> augmentations
> are quite conceivable.

This thread started out with the question of what defenses hadrosaurs 
had.  I think most people would agree, including me that herding was 
their primary defense. I suggested the possibility of using the tail 
as a defense.  See below.  
> 
> Whacking large carnivores, broom-like, with the tail as a whole unit is 
> another 
> possibility that has been raised.  The tendon-like stiffening rod running 
> down 
> the tail might have had enough lateral flexibility to give some slight 
> whipping 
> motion to the tail.   However, the problem is that collisions are in some 
> sense 
> symmetrical: is a Hadrosaur tail really tougher than a Tyrannosaur leg?  
> Whose 
> bones are going to crack first?  Where does the strongest muscle-padding lie, 
> in
> the Tyrannosaur leg, or the Hadrosaur tail?  Also, how many shots does a 
> Hadrosaur get?  If a backside mobbing were conjectured, the complexity of 
> coordinating such a blind-side defense would make it prima facie unlikely.  
> 
Let's say the prey is Edmontosaurus and it is about 40 feet long.  
Let's make the tail 15 feet long.  Let's say the base moves 45 
degrees/sec.  In rough math the end of the tail is moving 25 
feet/sec.  The energy is .5  * ?50lbs end of tail * 25*25=15625 
ft/lbs/sec. Cut it in half and it's still a lot.  Collisions are 
not symetrical.  The energy delivered would be absorbed by the 
area under the blow followed by a shock wave since it's traveling 
primarily thru water (bone excluded). Some energy goes back 
to the tail and perhaps the end of the tail was damaged some.  
But not as much as it could deliver.  Many rex fibulas show mid shaft 
fractures.  Was it all from stress/falls/ankylosaurs? It takes 14 
ft/lbs to take a human knee out.  And I agree that if I were a 
hadrosaur I would flee.  Maybe the mothers didn't though.  If I were 
a tyrannosaur, I would camp out beside a nesting site and when I got 
hungry I would get a snack.  That seems too easy for me.  Those 
mothers had to have protected themselves in some fashion.  I'm just 
imagining animal behavior.  I have no claim to omnipotence.  I'm I 
out in left field here, or is some of this valid?








As always, this is only an opinion, subject to
retraction and recall without notice, and with 
due respect to others opinions.

Thanks,

Michael Teuton MD