Re: 4 winged dino NOVA

[Dann Pigdon <dannj@alphalink.com.au>]

Mike Habib writes: 

> The primary problems with the Chatterjee & Templin model stem from  
> feather position, which in turn seems to have (once again) derived  from 
> an insistence on making the hind limb feathers act as weight- supporting 
> airfoils during steady gliding.  I give C&T full points for  thinking 
> outside the box, but here are a few of the problems with the  model: 
>
> 1) The feathers on the hind limb are articulated in a manner unlike  
> anything seen in any other taxa (including living birds).  While not  
> impossible, this does make a broad range of assumptions about novel  
> feather anchoring.  They need more morphological evidence to support  this 
> model.

That was my thought too. Flight feathers on the forelimbs have the flow of 
air parallel to the central vein. In the bi-plane Microraptor model, the air 
flow would be perpendicular. What would prevent the feathers from being 
swept backwards and possibly breaking? Even if they bent instead of 
breaking, it would still ruin the aerofoil shape of the leg 'wings'. 

> 2) Unless the feathers could rotate, at their base, about the axis of  the 
> long bones (tmt, primarily) then they would be in a very  problematic 
> position for any non-gliding locomotion, including walking  and running.  
> This type of rotating ability would be even more  complicated and unusual 
> than the feather position itself.

Indeed. Forelimb feathers are usually anchored so as to have very little 
movement. If Microraptors bi-plane leg feathers couldn't rotate, then the 
animal would have to walk around with a set of broad sails impeding its 
steps (I'm envisioning a dinosaurian MC Hammer, only with feathers instead 
of parachute pants). 

The only other option would be to twist the feet 90 degrees inward at the 
ankles, which I don't think would have been anatomically possible. 

___________________________________________________________________ 

Dann Pigdon
GIS / Archaeologist              http://geo_cities.com/dannsdinosaurs
Melbourne, Australia             http://heretichides.soffiles.com
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