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Re: Sprawl, speed etc



> 
> >Sorry, I'm a bit lost with these sprawl/upright mixes/speeds/stances. Rob, I 
> >think, has said that sprawled front limbs add stability and a sprawl means 
> >an 
> >aniimal does not have to slow down in a turn, whereas an upright animal does 
> >not. Having spent a good deal of time on horsback (and being thrown off) I 
> >can 
> >assure you that an upright animal does not loose speed on a turn; it simply 
> >"changes foot" ie adjusts its pace to lead with the foot that is on the 
> >outside 
> >of the turn, leans over so that centrfugal forces (laymans term?) holds it 
> >in 
> >place on the turn, and carries on running/galloping/whatever. Equally it 
> >does 
> >not loose manoeuvrability; it uses a hind foot to pivot (and can do this so 
> >unexpectedly/fast that the rider falls off). 
> 
> True.  However, based on automobile test runs, it has been shown that the
> farther out one puts the wheels, the better the handling (take a look at some 
> of
> Chrysler's new models, for example).  This doesn't mean that a high 
> speed/erect
> posture animal won't be able to evolve adjustments to a more upright form, 
> just
> that the upright form will be more unstable (creating different 
> opportunities).
> This is simply adapting to differing evolutionary pressures.  I suggest that 
> the
> ceratopians were simply more *efficent* at high speeds, due to their inherent
> stability.
> 
I think one of the main problems a few of us are having here is that Rob
is continually comparing the ceratopians to automobiles.  They were not in
possession of wheels.  A four legged creature has an entirely different system
of locomotion than a four wheeled automobile.  An animal can turn sharply
because its feet are not always in contact with the ground; it can put one foot
down, shift its weight and pivot on that foot.  Whereas a car's wheels are all
on the ground at all times (at least unless they're doing stunts or having an
accident), they cannot shift their weight in a different direction because the
have no muscles to contort their bodies. Also, even if they could shift their
weight on one wheel, the wheels spin, making the hypothetical shift in direction
(which is already impossible) that much more difficult.

> >I don't understand Rob's concept of "dune busting" at all. For an animal to 


> >survive on  soft surface it needs big big feet to stay _on top_ of that 
> >surface. 
> >The only reason I can see where a sprawl would help would be where the 
> >diameter 
> >of its feet got so large they would collide with each other if held under 
> >the 
> >body.
> 
> I'm afraid that dune buggy manufacturers disagree.  Tires on these vehicles 
> only
> make contact with the ground at four relatively small points (relative to
> vehicle size).  I simply make the suggestion that the two morphologies are
> analogous to each other, evolving/designing to overcome the same conditions.
> 
I'll be the first to admit that I'm completely oblivious when it comes to dune
buggy stats, but aren't they built to be light, thus they wouldn't need large
tires to support their weight and also leading to their "dune busting" design,
so that strong gusts of wind coming over the dunes wouldn't blow them over.
While I don't have any figures on me right now, it is my impression that
ceratopians were supposedly quite heavy.


R. Scott Kowalke
- sorry about the excess spaces and nonessential paragraphs, I haven't quite
figured out this editor yet.