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Re: Science feather strength debate



David Marjanovic <david.marjanovic@gmx.at> wrote:

> Regarding life in trees, how good a glider can *Archaeopteryx* have
> been when it had that gap between wing and body,


I'm not wholly convinced that _Archaeopteryx_ lacked humeral feathers
(= tertiaries or tertials).  Modern birds have three or four of these,
proximal to the innermost secondary feathers.  However, no known
_Archaeopteryx_ specimen exhibits feathers associated with the
humerus.  For example, the flight feathers in the Berlin specimen are
preserved on the distal forelimb right up to the elbow, where the
feathers stop dead: no tertiaries.  This has been cited in support of
the flight surface of _Archaeopteryx_ being discontinuous, with a gap
between the wing and the body wall where the tertiaries would
otherwise be (e.g., Garner et al., 1999 - the "Pouncing Proavis"
model).


However, two things make me skeptical about this interpretation.
Firstly, some crown-group birds from the Messel are also found without
tertiaries preserved, although the outer flight feathers are clearly
preserved.  In these cases, the absence of tertiaries is certainly
preservational.  So the same may be true for _Archaeopteryx_.
Tertiaries were likely not as firmly attached to the wing as primaries
and secondaries, and may have come loose.


Secondly, Mayr et al. (2007) mention what could be evidence of
tertiaries in the "Tenth Archaeopteryx".  They describe "marked, fuzzy
furrows at the ‘elbow joint’ which may stem from the tertiaries".  As
positive evidence goes, this is admittedly weak.  But overall, I
wouldn't write off the possibility that _Archaeopteryx_ had
tertiaries, and therefore the wing was complete, right up to the body
wall.



Cheers

Tim