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Re: L'origine et l'évolution des oiseaux, with a twist

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----- Original Message ----- From: "David Peters" <davidpeters@att.net>
To: "jrc" <jrccea@bellsouth.net>
Cc: <dinosaur@usc.edu>
Sent: Thursday, January 29, 2009 4:28 PM
Subject: Re: L'origine et l'évolution des oiseaux, with a twist

The beauty is, it's never slack. Embedded with chord-wise fibers, so virtually no flagging.

If chordwise and stiff enough to inhibit flagging, they have to function as compression battens like a bat's fingers. I suspect that they don't have significant compression capability due to excessive length/dia ratio. I would expect them to operate in differential tension more like a pterosaur patagium and would expect the distal pattern to be more nearly semi-spanwise than chordwise, again more like a pterosaur.

As an aside, a strut with a thickness of about 2 inches
will usually have a chord of roughly about 4 to 6 inches.
For the same drag, struts are a lot bigger than circular

I'm not shooting for similar drag ratios. Simply less drag. And really, drag is not the issue while running in this taxon, not as big a deal, as every step is another unit of thrust. And the >uropatagia become wings when lateral.

I agree with that last sentence. :-)

The key to this thread is long legs (longer tibia than femur) = cursor.

Possible, but not a given.

Not sure about leaping, other than that last arboreal fling before becoming airborne.

Why would you expect them to run to takeoff speed ? Like most everything else that small, it would appear at first blush that they could probably leap to takeoff speed. If so, why do it the hard way.

All sister taxa tracks (Rotodactylus) indicate narrow-gauge, often bipedal, proximal phalanges elevated along with metatarsus-type locomotion.

David Peters davidpeters@att.net