A Tale of Two Tails

["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 AnkylosaurÕs is not necessarily the 
outcome of such pressures -- bony serrations or other light weight augmentations
are quite conceivable.  

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.  

Richard Dieterle

Science red in tooth and claw.