Re: four winged Archaeopteryx

["Jaime A. Headden" <qilongia@yahoo.com>]

Greg Paul (GSP1954@aol.com) wrote:

<Actually, it would be interesting to compare the total weight, drag and lift 
of the tails of the biggest tailed modern birds than can achieve flapping
flight to Archaeopteryx. The bony tail of Archaeopteryx was not really heavy,
it was a small minority of total mass. Even so it may have been less
aerodynamically efficient than that of a similar sized tail of a modern bird,
but that is to be expected in a basal flier.>

  Well, perhaps in a rather unspecialized flier.

  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. This would imply that the
tail MIGHT have been more or less passive with very, very little active
functionality in what birds might use their tails for today.

  So the best comparison for Archie's tail is with a bird doing nothing with
ITS tail during flight.

<We may never know whether the tail of Archaeopteryx was used to generate lift.
That depends upon whether Arch was tail heavy or not, and that depends upon the
relationship between the axis of wing lift and the center or gravity, and that
depends upon the distribution of body mass which is not reliably
reconstructable, and also upon the fore versus aft sweep of the wings which we
cannot determine because it depended upon the unknowable question of how the
beast held its wings.>

  Some of this data is actually knowable, as in the case of determining muscle
weight, inferrence of function of muscle to determine what kinds and thus how
heavy, and then the distribution of this weight in the limbs; the weight of
bone; the weight of the integument (with distribution of generalized feathers
over the body); and a neutral position of the wings. One can model the wings
and tail in various positions with all other variables static and arrive at a
likely mobile CoG, infer the CoL in a volant bird relative to various wing
positions and angles of attack in the wing and body, and extending the legs,
neck, etc., to arrive at various possible ranges for the CoG and thus body
attitude in flight. Since most of that work simply requires number crunching,
the remainder is available to us and others have performed the model work
neccessary to adapt into this study. There will be assumptions, of course, and
margins of errors can be expected for these variables, but the best way to
solve the issue is to do the work and play it against the expectation.

  For me, personally, I cannot see how Archie CANNOT have some flight ability,
but the effectiveness of this flight ability relative to expectations (that of
extant birds) is likely low (as Greg said, it's a basal flier, or a latent
flier).

  Cheers,

Jaime A. Headden
http://bitestuff.blogspot.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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