Re: Cursorial adaptations (was T.rex and elephants)

[Chris Campbell <sankarah@ou.edu>]

Jonathon Woolf wrote:
> 
> Chris Campbell wrote:
> 
> <large snip>
> 
> > This doesn't argue for the wrestling scenario you give below, though;
> > perhaps the individual in question just pissed off an adult while it was
> > a juvenile, eh?  Alternately, the short-frilled ceratopsians (with
> > short, bony frills) might have done the head-butting thing while the
> > long-frills (having holes in 'em) didn't.
> 
> Could this be the evolutionary _reason_ for the long-frills?  As best I
> recall, short-frills came first and long-frills later.  Long-frills also
> have the openings in locations that make them look sort of like
> eye-holes in a mask.  In THE HORNED DINOSAURS, Peter Dodson sketches
> complete _Triceratops_ heads and frills with a multicolor scheme that
> places mock-eyes on the skin over the holes, so that when the head drops
> and the whole frill is facing forward, it looks like a very large face.
> 
> So maybe we could reasonably envision a scenario something like this:
> Short-frills spar with horns at mating time -- an active method of
> settling conflicts.  Because of the potential for serious injury to both
> parties, this isn't a very good method of settling disputes.  So, over
> time the long-frills develop so that the active conflict can be replaced
> by less direct passive conflicts of displays.  Whoever has the most
> impressive display wins.  Only in two very well matched individuals
> would the old method of active combat come into play.

That makes sense, and fits with most of the data presented.  However, as
George points out the frills came before the horns.  I think this can be
explained, though; if the frills and proto-horns were used for shoving
matches and defense, the growth of horns can be explained.  We have to
keep in mind that the horns and frills wouldn't serve only one function;
the frills might start off as defensive, but then be combined with horns
for intraspecific competition.  As the horns get longer (possibly in
response to predation pressures) the intraspecific uses become more and
more dangerous, so the display functions take over.  The horns remain
nice and long, though, because they're great as defensive items. 
Meanwhile, those who stuck with nose horns would go on with their
wrestling and respond to threats with head butts, bites, and short
charges.  Makes sense, but I dunno how well it'd stand a rigorous
analysis.

Chris