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Re: The origin of flight: from the water up (still short!)
David Marjanovic wrote:
> , birds have 4 segments per wing whose proportions can
> respond to different demands: upper arm, forearm, hand and primaries, while
> pterosaurs have 7: upper arm, forearm, metacarpus and the 4 wing phalanges,
> so pterosaurs may be able to distribute the stress differently.
10 -- the scapulo-coracoid can also respond to some extent, and in Quetz at
least, the carpals also increase quite disproportionally. Pterosaurs do
distribute the loads quite differently from birds.
> That's it -- moving a long, stiff plate (Archie's tail) through water is
> harder than moving it through air,
Isn't this making the presumption that archie's tail is a stiff plate? I agree
that it is long -- I don't know whether it is effectively stiff or not -- that
depends upon several other factors in addition to skeletal mobility or lack
thereof. Re the difficulty of moving it through the water, that depends upon
the speed at which it is happening in each medium -- it may be more or less
difficult (again, bear in mind that I don't believe that archie deliberately
spent much if any time in the water, but that isn't relevant to this particular
> and the longer the plate is the harder that becomes. Doesn't it?
Prouty doesn't seem to think it has to do so. My guess would be that it depends
upon several factors and could go either way, depending. I just wouldn't want
to make assumptions that aren't necessarily so (unless doing so deliberately).
> No AFAIK, and I didn't suggest that. I just imply that Archie's tail was
> most mobile at the base, while the rest was a pretty stiff rod, like in
I've got no argument with that, but is it possible that the feather attachments
themselves had adequate mobility to allow deliberately varying dynamic loads on
the feathers to move the tail? I have no opinion on whether that was the case
in life, I just wouldn't want to say it was impossible without investigating the
> (and the difficulty to get a cormorant... there are some in the nearby
> national park, though), I
> won't do it anytime soon. :-)
Aw shucks. I liked my visual image of the expression on the cormorant's face
while he was performing that experiment. :-)Sort of like the expression on the
face of the bear in 'Lake Placid'.