Re: Archaeopteryx not the first bird, is the earliest known (powered) flying dinosaur

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

Greg Paul (GSP1954@aol.com) wrote:

<The arm wing area/total mass ratio of Microraptor is in the middle of the
range for flying birds of its mass, adding the hind wings doubles this value.>

  The longest, most inboard feather preserved in the holotype of *Microraptor*
is almost as long as the ulna, but slightly shorter, and is 32% the length of
the longest primary, when drawing a line along the curve of the rachis from tip
to base. This longest "secondary" feather has a rounded, slightly "pointed" tip
and it is possible it is fully preserved, but it may have been truncated, and
thus longer in life. Other feathers are preserved inboard, but their dimensions
are less distinct, but none seem to attain the length of the chord acheived in
the (last? second to last?) secondary noted. Is this the same shape inferred in
your drawing Greg?

<Assuming that the leg wings could be splayed out sufficiently close to
horizontal to generate close to the maximum possible lift, the distribution of
wing loading could be easily adjusted by adjusting the fore-aft sweep of the
two sets of wings as needed.>

  If we assume the hindwings could take even 25% of the wingloading off the
forearms, we would have to assume the robusticity Greg infers for the forearms
is compensated in somehow for a function (furious flapping?); otherwise,
lessening of the loading the arms had to undergo would permit the arms to act
in a more passive function, rather than active.

  Let us also be concerned that the skeleton of these specimens have been
crushed, and that fractures in the bone do not always correspond to perfect 3D
bones. The right humerus of the holotype of *M. gui* is certainly broken in
half, with the smooth concave interior surface exposed on the mainslab, so I
assume the inner surface of the other half is on the counterslab; the proximal
end is obscurved by te cervicals. The left humerus is not splity, but shows
features of deformation due to crushing of the interior marrow cavity, and a
large "foramen" is visible as in *Sapeornis* which is not apparent on the other
humerus, with the deltopectoral crets margin incomplete, indicating sections of
the humerus have broken away; collapse of the interior results in widening of
the shaft of bone much as you get when flatting a paper-towel core. This would
interfere with our ability to project muscle attachment sites not obvious at
adductor, abductor, pectoral, and biceps points on the humerus.

  Concerns over projection of femoral excursion will be saved for further
discussion, since this has been covered extensively.

  Cheers,

Jaime A. Headden

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

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