RE: Bakker & whiptails - jog my memory please!

["Scott Hartman" <scott_hartman@hotmail.com>]

> > > One of my questions regarding the supersonic sauropod tails regards the 
> > > fraying you see in a bullwhip.  The tip of a bullwhip travels so fast it 
> > > breaks the sound barrier, true, but because it cracks so fast, the ends 
> > > of the whip eventually begin to fray.  Not only that, but a bullwhip is a 
> > > continuous piece of material. <<<

    The continuity of material is an interesting question.  Of course, 
bullwhip continuity is really a matter of scale.  The tissue that makes up 
the bullwhip is made of different layers, as well as individual cells.  I 
bring this up, not because I think tht this data influences bullwhip motion, 
but because sauropod tails are so much larger.  So from a mechanical point 
of view, those huge sauropod verts are going to be smaller in the context of 
a butt-whip.  I'm not sure (and I don't think anybody's sure) what the 
maximum size is that individual mechanical units can have while still 
funtioning as a whip, although the study done by our fellow lister did 
simulate the length and inferred mobility of each vertebrae, so that's a 
start.  Estimating mass and required muscle/tendon strength would provide 
some limits on what cannot be done with animal tissue.  Masters project, 
anyone?
    As for the frayed whip end.  This isn't just a sternght of materials 
problem, because that fraying is actually intergral to releasing energy (in 
terms of sound) when the end breaks the sound barrier.  Basically, the 
difference between a non-frayed and frayed tail is the difference between a 
loud pop and a theropod-ear-melting boom.  Because of the behavior of dermal 
tissue upon damage, Ken Crpenter doesn't think sauropod tails could break 
the sound barrier (as presented in Eggs, Nests, and Baby Dinosaurs).  
However, in at least some diplodocids, there appears to be a row of "spiny 
things."  I don't believe that any histological evidence was preserved, but 
my best guess is that they were keratin.
    And to conclude briefly (hah!), if keratin was already present in 
sauropod caudal dermal evolution, then I see know particular barrier to 
evolving a softish continually growing tuft on the end of the tail.  This 
is, of course, speculation, but at least there is no biological barrier to 
sauropods evolving a "popper," should the biomechanics end up consistent 
with a supersonic whip.

Scott
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