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Re: four winged Archaeopteryx

On Sun, Sep 24, 2006 at 04:59:49PM -0700, Jaime A. Headden scripsit:
>   However, I think tghere is a difference to be shown here between
>   _aerodynamic efficiency_ and _aerodynamic functionality_. The tail
>   in *Archaeopteryx*, unlike those of modern birds, cannot get wider
>   than it already is, and cannot fan out. It is likely that, based as
>   it is on a nearly rigid spar (the tail core itself), the ability of
>   the tail to twist about its base axis (as in extant birds) is
>   extremely limited, and the ability to expand or diminish its aspect
>   is likely VERY limited, if it existed at all.

What keeps Archie from folding the tail feathers against the central

Do that with the feathers down one side and not the other and the lever
arm of the long rigid tail would result in a strong turning moment.

Whether it's going to be roll or yaw or both, I couldn't say, but I'd
expect that was adjustable based on how much rake which feathers got.