Re: Stegosaur plates as protection......

[Randy King <randyk@informix.com>]

Dann Pigdon wrote:
> 
> Randy King wrote:
> >
> > A few animals may attack through the back, but most will attack the
> > soft vital organs; this is usually either the throat or the abdomen.
> > Animals with defenses based on the back tend to be smaller and can
> > protect their stomach and throat through other means, like the
> > armadillo or porcupine.  Otherwise, I think the soft areas are more
> > important to protect.
> >
> > Perhaps this is different for a therapod; though, that has the strength
> > to crush through the bones.  But that still assumes that the giant
> > therapods were the primary threat to teh stegasaur. This almost feels
> > like a circular argument to me: If the stegasaur was only preyed upon
> > by therapods, he would develop a therapod defense; the therapods would
> > go after easier prey; the stegasaur would lose the genetically costly
> > defense.
> 
> For a start there are no modern analogies that come close to the size
> of a large theropod. Lions may come close, and when attacking cape
> buffalo they DO attack the spinal colomn. They leap onto the hind
> quarters and bite and claw persistantly at the base of the tail.
> This way they avoid the pointy end of the beast and at the same time
> may cripple it so it can not run away so quickly.
> 

But the lion doesn't consistently attack the spine.  It will attack the
throat of most larger prey.  Perhaps it learns which to attack with what
method.  I do belive that the plates could offer some defensive value,
but
doubt that that is why they evolved - at least solely I suppose.  More 
attacks are to the soft areas of contemporary animals than not.  

I acknowledge that there is no contemporary analog to the therapods, but
that in itself doesn't mean they didn't attack soft tissue.  Nor is
there
any indication that stegasaurs were their prey of choice.  Most
contemporary
animals do attack the soft areas, even to the point of turning smaller
animals over to do so.  Although the scale is different, that does
indicate
how a larger animal my attack a smaller prey.  It seems that plates
would
only assist this maneuver.  

There are other extreems as well.  Some animals with powerful jaws can
go
through bone or shell without regard for passive defenses of many
animals.
In this case, there is no need to attack softer tissue.  Some therapods
may
well have fallen into this category, in which case plates wouldn't have
provided any direct defense either.  

Someone, a while back, suggested that the plates may have made the
animal
appear larger.  This is the only defensive value I feel would make
sense.

-Randy

> --
> ____________________________________________________
> 
>         Dann Pigdon
>         Melbourne, Australia
>         http://www.geocities.com/capecanaveral/4459/
> 
> ____________________________________________________

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Marc: http://www.cs.ruu.nl/~hansb/d.chessvar/makerule.html