Re: "Flight theory has legs"

[Graydon <oak@uniserve.com>]

On Sun, Jul 13, 2003 at 02:22:32PM -0700, James R. Cunningham scripsit:
> Graydon wrote:
> > > Once aerodynamic power supplants leg power, reduction of hindlimb mass
> > > would have enhanced the distance and control over this hunting style.
> 
> Why?  Wouldn't hindlimb mass (in the form of muscle) still be useful for
> those animals that used a leaping launch?

My guess is that is a complex three variable optimization between
pouncing range, slicing effect, and mass distribution.

> > > No trees need be involved.
> 
> I'd agree with that.  But I wouldn't exclude them either.
> 
> > Especially as the second toe sickle claw a)only works down and b)has a
> > force limit; you can't apply more than will start shoving the dromeosaur
> > away from the prey.
> 
> Yes, you can.

Ok, yes, there's the springing away phase.

> Applying additional force will tear through the prey with
> more vigor, just as it moves the predator away from the prey with more
> vigor.

Not if the other two toes touch, and not if the claw rotates out of a
slicing angle and into a holding angle.

My visualization of all this is very shakey, but portion of the possible
leg stroke to drive the sickle claw where neither of those things has
happened seems quite short.

> > "Hang time", and some aerodynamic means of counterbalancing a
> > downward force, would be selected for in any dromeosaurid that
> > regularly hunted large prey.
> 
> I'm sorry, I don't understand what you are saying. 

I'm not surprised, I botched that.  Sorry.

> Will you elaborate please?

Well, if the predatory stroke with the feet is directed down, you have
to jump up to apply it to large prey.  (Small prey you're effectively
stepping on.)

This presumably starts with leaping and slashing, but you're better off
if you can extend the leap and pick _where_ to slash a little better.
But since your feet are off the ground, you have to use aerodynamic
means to add energy to get that 'hang time' in the leap.

What I was also trying to say is that you're also trying to provide a
counterbalancing downward force so you can slice harder without going
springing away; you've made contact, you want to stay and keep slashing,
not go springing away again.  (Since the best place not to be kicked,
trampled, tail slapped, or land badly is on top of the prey animal.  It
probably still sucks for being scraped off with a branch, but one can't
have everything.)

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