Re: Preview of new stegosaur plate paper

[Mike Taylor <mike@miketaylor.org.uk>]

> Date: Wed, 18 May 2005 08:33:19 -0700 (PDT)
> From: don ohmes <d_ohmes@yahoo.com>
> 
>>> Engineering and mass allocation considerations indicate that the
>>> relative size of passive defense structures must scale negatively
>>> with body size.
>> 
>> How so?
> 
> Muscle-to-mass ratios decrease with body size.  Assuming mass
> specific power is equal, as mass increases, the relative muscle
> power available to "tote that bale", or shield, or armor plate, or
> shell, or .45 ammo, or anything with mass decreases. Big guys tote
> bigger shields than small guys, but small guys can carry more shield
> per kilo.

OK, but isn't that smaller proportion of muscle just a reflection of
the fact that larger animals tend to be less athletic than smaller
ones?

>>> Intuitively, it seems to me that the relative size of display
>>> structures might scale negatively with body size.  Does anyone
>>> have enough data from extant animals to comment on this?
>> 
>> I don't have references to my fingertips, but I do recall that,
>> surprisingly, this is often incorrect.  For example, the
>> ludicrously big antlers of the recent deer _Megaloceros_ ("Irish
>> Elk") scale _positively_ with body size, so that large specimens
>> have proportionally larger antlers than smaller individuals.
> 
> Megaceleros' antlers may not have been even partially for
> display... deer in rut are EXTREMELY aggressive.  What evidence do
> you have that the (I grant you) apparently ridiculous size of irish
> Elk antlers is a "display" trait?

Only that you'd just asserted that defence structures _must_ scale
negatively.  If you're withdrawing that assertion, then, yes,
_Megaloceras_ antlers (and the many other positively allometric
structures in extant beasts) could be defensive.

 _/|_    ___________________________________________________________________
/o ) \/  Mike Taylor  <mike@miketaylor.org.uk>  http://www.miketaylor.org.uk
)_v__/\  "If you don't know what your program is supposed to do, you'd
         better not start writing it" -- Edsgar Dijkstra.  ("Though it's
         a great way to find out" -- Mike Taylor.)

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