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

[Chris Campbell <sankarah@ou.edu>]

Augustus T. White wrote:
> 
> Chris Campbell wrote:
> > and that tells me that the nice, free-moving shoulderblade doesn't in
> > any way imply adaptations for cursorial motion.  Consider this
> > alternative use for those heavily built hind limbs (suggested to me in
> > private e-mail by another on the list): what if they were used as pivot
> > points, allowing the multi-ton animal to turn around quickly?  This
> > would make those horns somewhat useful against predators, as the animal
> > could bring them to bear very quickly.  The small forelimbs and hindward
> > center of gravity throw a lot of support to this idea.  It definitely
> > makes more sense to me than the notion of developing a massively heavy
> > head assembly as you simultaneously develop adaptations for speed.
> 
> The idea seems very plausible, and I think I've seen it elsewhere.
> However, the ceratopsians are relatively long.  Even given the rearward
> center of gravity, where does it get the force to make the spin?  The
> ceratopsian tail seems inadequadely massive or flexible for this purpose.

I'm not sure, but don't reconstructions show the musculature of the
limbs to be exceptionally strong?  That seems to be an argument in favor
of their running, but if you look at those massive hind limbs that
muscle might be just as useful for spinning the animal around.  This is
definitely CVA territory, though.

> Perhaps it would make more sense to think in terms of herd-level
> defensive behavior.  Even a small *circle* of ceratopsids, with the
> ability to make short lunges, would be pretty formidable.

Yes, agreed, and the whole spin deal might help out in overall mobility
when it comes to herd tactics.  Combine it with the nicely balanced head
(the ball and socket neck joint) and you have an excellent predator
response strategy.  I just don't see running figuring into it (other
than, perhaps, a *very* brief charge/lunge), and I think you'd need a
herd to make it useful; separated animals would be very vulnerable,
especially to a pair or more of attackers.

Chris