Re: On the Issue of Sprawling Dromaeosaurs (long)

[Tim Williams <twilliams_alpha@hotmail.com>]

Jaime Headden wrote:

> 2) the leg can be extended DOWNWARDS, where the feathers will point back
> and down ... this would obviously occur during "landing" or leaping
> maneuvers, but any aeodynamic performance at this point would be as in
> vertical vanes in planes, and not provide lift or thrust -- the point in a
> glider would be ... irrelevant, with the leading edge pointing downward;

Firstly, thank you for a very interesting post.

Secondly, the arguments over the function of the hindlimb feathers ("trouser 
wings") of _Microraptor_ have focused mainly on their role in lift- and 
thrust-generation.  But what if the broad feathers of these forms were 
associated with aerodynamic drag, not lift or thrust?  The asymmetric vanes 
have led to the assumption that the feathers on the forelimbs and hindlimbs 
functioned in airfoil generation, and therefore that _Microraptor_ was a 
glider or a flapper.  But there are alternatives to the idea that asymmetry 
= airfoil generation = gliding or powered flight:

http://www.cmnh.org/dinoarch/2003Mar/msg00146.html
http://www.cmnh.org/dinoarch/2001Mar/msg00823.html

If the forewings, hindwings and tail of _Microraptor_ functioned to maximize 
air resistance, then the creature may have used its appendages (forelimbs, 
hindlimbs, tail) to slow its descent in order to produce a softer landing.   
Thus, _Microraptor_ simply parachuted to the ground from the trees, and 
there was no airfoil generation necessary for gliding or powered flight.  
These animals were like four-winged shuttlecocks, with no need for the fore- 
and hindwings to be coplanar or contiguous while in the air.



Tim

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