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

[rjmeyer@ix.netcom.com (Rob Meyerson)]

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.

>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.

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.

Shalom,

Rob Meyerson

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