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



MBell16766@aol.com wrote:
> 
> Dear Chris, I really think you have the right idea about ceratopsian
> locomotion. The everted elbowed, semi-erect (not sprawling) front limbs
> revealed in the trackways, is another adaptation for pivoting. If you have
> read Osborn's 1933 paper on the AMNH mount of T."elatus", this is covered.
>  Punctures in Triceratops skulls show that they could develop decent
> velocities. I like your idea of a brief charge. I've speculated and have
> developed some restorations of Triceratops going bipedal for a step or two at
> the culmination of a charge. I think most of their offensive activity was
> directed at each other, however.

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.  

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.

Chris