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

[Chris Campbell <sankarah@ou.edu>]

Rob Meyerson wrote:
> 
> Chris Campbell writes;
> 
> >I've always been skeptical of the idea of using the horns for
> >intraspecific competition for two main reasons: first, those horns are
> >long and sharp.  Aside from the obvious problems of breakage due to
> >direct contact with the frill, the risk of injury in such exchanges
> >would be quite high.  Look at modern ungulates who exhibit head-butting
> >behavior; all of them have either antlers or recurved horns of some
> >type.  This reduces the chances of both breakage and injury to a
> >minimum, while allowing the animals to charge one another full force.
> >Also, look at other head-butters among the dinosauria; pachycephalosaurs
> >come to mind -- even though the method is different, the effect is
> >similar.  Maybe an argument can be made for, say, locking horns and just
> >shoving one another (which has been suggested in various sources), but I
> >can't see that working in many species; it'd make sense in _Triceratops_
> >and other long-horned, solid frilled species, but something like
> >_Chasmosaurus_ or _Torosaurus_ would just wind up skewering its
> >opponent.
> 
> There is physical evidence for intrapecies combat damage in Triceratops.  
> The skeletal mount in the museum here in Minnesota has a puncture wound 
> below the left eye that is interpreted to be horn related (the animal 
> survived 
> the encounter; the wound is pretty well healed.

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.
 
> >The second reason I'm skeptical is the fact that many ceratopsians had
> >holes in their frills; even covered with skin or cartilage these would
> >make the frill rather dubious protection against horns.  It'd still work
> >pretty well against predators, though.
> 
> I still hold that the holes in the frills were places for muscle attachment.
> 
> Even if the frills were covered, they are placed at the back of the head.  
> They are well away from "the scene of the crime" where the horns would 
> come into play, and are protected.

Some of those holes ran the length of the frill; they'd be quite
dangerous in a fight.
 
> I know we are starting to go soft on mammal/dinosaur analogies, but consider
> how rhinos fight.  The majority of these "fights" are actually bluff 
> displays, 
> with actual contact occurring when the two animals are relatively matched.  
> In watching a rhino fight on The Discovery Channel, it appeared that the 
> horns 
> were used more as levers; they lock horns on either side of their heads, and 
> attempt to push their opponent into submission (the horns were never used as 
> a sword).  IMO, ceratopian combat was similar in nature.  These animals 
> probably 
> never charged each other like a big-horned sheep; the results would be fatal 
> to 
> one or both of the animals.

Yeah, that's essentially what I was getting at.  I think if the horns
were strictly for intraspecies use they'd be shaped quite a bit
differently; as is, they have to be multipurpose to make sense.  When
you look at the rest of the animal's biology you can see they'd be
excellent for defense; the only use in dominance would likely be display
or maybe horn-locking tugs of war.

Chris