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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 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.

>An aside............
>As a layman, I find it difficult to understand sometimes why animal/(read 
>dino) 
>behaviour is seen as primitive/simple/unsophisticated. Surely _any_ animal 
>which 
>survives for successive generations (ie successfully) is de facto an exhibitor 
>of extremely complex behaviour/adaptation in relation to its environment? 

Exactly my point.

Rob

***
Q.  What fossil fish is a blood relative?

A.  The antiarch.