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Re: Coelurosauravus: glider? or bluffer?



>
> Jaime wrote:

>
>   And ... the amount of stress being exerted on a given area for a given
> mass decreases with a decrease in size, so that *Coelurosauravus* is not
> really under a whole lot of stress gliding. The same amout of pressure
> would affect *Draco,* who does just fine.
>
>   Dave questioned the use of the spars in *Coelurosauravus* because they
> are of a dermal origin, but I'd like to point out that so are all
> vertebrate ribs. Forming extra dermal structures is not going to decrease
> the viability of these spars as an airfoil. Both the fossil *Icarosaurus*
> and the living *Draco* show adequate mechanisms for controlling stress on
> their expanding ribcages, so *Coelurosauravus* shouldn't be that much
> different.
>
>

I think this is tradition talking again. You can't imagine that old picture of 
Coelurosauravus in Carroll 1988 with the ribspars sticking out horizontally 
like an old-fashioned tv antenna. That reconstruction has gone by the wayside. 
And
it would be different if somehow the limbs were involved, like Batman holding 
his cape in the movies.

The ribs of Draco and Icarosaurus are firmly attached to the vertebrae. They 
can only move anteriorly and posteriorly in the former. They can't move at all 
due to fusion in the latter. Draco has no extradermal spars supporting a 
membrane.
Icarosaurus does have extradermal spars, but as Colbert noted ,the cylindrical 
vertically-oriented hinge permits only anterior-posterior movement, like a door 
hinge. Great support. Such a wing will never fail. And exactly the sort of
support/hinge that is lacking in the more primitive Coelurosauravus with its 
wire-like spar bases connecting to traditional, non-specialized wire-like rib 
tips.

Flexibility is one thing. But every airplane wing, from the Wright Flyer on up, 
has a rigid wing spar.

dp