Re: Conway's Velociraptor (and pterosaurs)

["James R. Cunningham" <jrccea@bellsouth.net>]

Jaime Headden wrote:
> 
> why was this lost in pterodactyloids if the foot/leg useage in the 
> uropatagium was the same?

To increase aspect ratio of the flight surface?  And was it lost in all
pterodactyloids?

> It would seem the
> use of the toe would have a distinctly advantageous usage that was lost in 
> pterodactyloids, but that the pterodactyloids retained
> some advantage by selectively repressing this feature early in their 
> evolution. If so, this seems to suggest that their relative
> "hind wing" function, if present, was different.

So that the hindlimb could play a more active roll in providing yaw
command authority as the length of the tail diminished?


> However, in the art of both John Conway (john@pterus.net) and Luc Aspidel, 
> these
> legs are drawn in the same position, knee forward and foot volarly-ventral 
> (pads down) (which I don't get anyway, given the
> mesotarsal ankle and un-twisted tibia).

The pads don't point down. In that position, they would point aft and
very slightly down, with the spreading such that the 4th toe would be
displaced (flexed) further aft than the 1st toe.  The pad orientation
would appear to be rotated about 70-80 degrees aftward of the ventral. 
Think beaver.  At a distance and at low resolution, the two positionings
appear much the same.  I preferred Aspidel's positioning because he
curved the toes more aftward to reflect the untwisted tibia and ankle in
a way that made it more apparent.

> I am curious why this is offered, or if the same leg position is provided for 
> pterosaurs generally?

I would expect some substantial variation between species as variations
on a theme, and variation within the same species to reflect the
'command' of the moment. One of the interesting things is that much the
same cruise leg positioning would apply to ramphorynchs and to
pterodayctlys, for both the broad and narrow wing models. However, the
effect on the wing membrane would be quite different between the broad
and narrow wing models.

Jim