Re: Powered Flight Definition (part of RE: Cost in Aquatic Birds (long))

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

Jaime A. Headden wrote:

> However, fossils
> indicate that *Archaeopteryx*, though a flapper, could not power-flap,

I'm curious about this, as the archie fossils don't indicate this to me at all. 
 What am I missing?

> I think I need to clarify what I mean by powered flight, however. The
> power flap, or power stroke, in the bird wing, also present in the bats,
> is a result of the presence of a triosseal canal. I previous indicated
> this. The reason being the condition is neccessary for the rotation of the
> humerus about it's long axis as it is being elevated above the horizontal.

This only appears to be needed if the animal must launch at low speeds, and in 
some but not all cases if it must land at a lower speed than it can run.  For 
an animal that can launch directly to or near cruise speeds, it doesn't really 
seem
to be necessary, assuming of course that the animal can also use one of the 
various alternate techniques for slowing to a satisfactory landing speed.  How 
does the triosseal canal work for the azhdarchidae when they are in powered 
flight?

> The nature of the scapulocoracoid glenoid and the acromion and joint
> between the scapula and coracoid show that until Enantiornithes, birds did
> not have a triosseal canal, nor did they have a particularly
> dorsally-apparent glenoid, that could be used to suggest the presence of a
> elevation-rotation phase of the wing-path, and thus a power stroke.

Are you saying that they could not perform the rotation, or that they could not 
'power' it?