Re: Pro(to)avis

[jrc <jrccea@bellsouth.net>]

----- Original Message ----- 
From: "Michael Habib" <mhabib5@jhmi.edu>
To: <david.marjanovic@gmx.at>
Cc: "DML" <dinosaur@usc.edu>
Sent: Friday, September 16, 2005 6:08 PM
Subject: Re: Pro(to)avis


> 1) The limbs may have been held subhorizontal, but still held close enough 
> to a horizontal plane to generate lift.

If the outboard feathers were less stiff than the inboard in bending, it 
would enhance this effect.

> 2) The hindlimb feathers may have more important to increasing passive 
> stability than to generating lift.

To be passively stabilizing with anhedral, the hindlimb feathers would need 
to be creating a download rather than upwardly directed lift.  Some aircraft 
do that, but I doubt that an animal would deliberately create a substantial 
download for any extended period of time.

>  A number of different hindlimb orientations (other than splayed 
> horizontal) might accomplish this goal, either by producing some 
> differential lift laterally when the animal tilts,

This would require dihedral if the hindlimb feathers were lifting; or the 
anhedral you postulate, if the hindlimb feathers were downloading.

> or by simply increasing posterior drag such that the animal had a tendency 
> to stay facing forward.  (The problem with these ideas is that the 
> increased drag would make it harder to stay in the air).

Creating lift with the hindlimbs either lifting or downloading in a 
subhorizontal orientation would do this anyway, due to the increase in 
induced drag as the hindlimb aspect ratio decreases.

> 3) It could simply be a developmental constraint, or be unrelated to 
> flight...but I'm not sure how to demonstrate these very conclusively.

Me neither.

>