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Re: Disney's Dinosaur Trailer


Norton, Patrick wrote:

As a bit of an aside, I've often wondered why birds have retained more
muscle mass in their wings (think of a tasty fried chicken wing) than
pterosaurs or bats, which have very little muscle mass within the wing
itself.  The wings of pterosaurs and bats were (are) mostly membrane and
bony struts controlled by tendons.
Pat, why do you say thatt birds have retained more muscle mass in their wings than pterodactyls?  I suggest you look at the muscle attachment markings on Qsp and Qn and some of the necessary skeletal deformations on Qn that were used to increase the contact area of the attachments.  I believe you'll change your opinion in short order.  I sure did, because the bones didn't match my preconceptions at all.  Think of one wing providing meat for a feast.  We are talking about the inner wing here, inboard of the wrist, not the outer wing which was mostly (but not entirely) tendon and membrane.  Also, in Qn, some of the tendon grooves in the inner wing receive tendons an inch or more in diameter.  Visualize the muscles required to generate the loads those tendons carried (or even better, compute the approximate muscle mass required to do so).
My guess would be that, per unit area
of wing surface, lifting the wing of a bird requires more energy than
lifting a pterosaur or bat wing.
Re pterosaurs, my guess is that it wouldn't.  Some birds can open their primaries during the recovery stroke to reduce the 'added' mass' effects (I have some photos showing them doing this).  Pterosaurs can't, though they do have the ability to invert camber in the outer wing during part of the recovery (having the ability doesn't mean they have to use it).  I have no opinion re bats, not having given much attention to their recovery stroke (but since, unlike birds and pterosaurs, they can't substantially reduce their span during their recovery stroke, there would be some increased cost of lifting the wing relative to a similar but partially retracted wing (bats can't significantly reduce either the moment of inertia or the 'added mass' during the recovery)).

All the best,