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Re: Science feather strength debate



 Scott Hartman <skeletaldrawing@gmail.com> wrote:

> Heh, people can "refudiate" me all they want, but let's be clear what
> that implies:


I heard about this new word "refudiate", and I love it.  What
silver-tongued wordsmith came up with this wonderful verb?  ;-)


> 1) 10 specimens, most with at least faint feather impressions, several
> with excellent and easily seen impressions, all with the flight
> feathers ending in the same location at the elbow (i.e. no variation
> in the end point that would imply randomness or missing elements)


The argument raised by myself and others is that the tertials had a
fairly loose attachment to the humerus, especially compared to the
primaries and secondaries which may have had a more secure attachment
to their respective distal forelimb elements.  (This is certainly the
case in extant birds.)


Only one _Archaeopteryx_ (the Berlin specimen) shows faint impressions
of hindlimb feathers, so they may have suffered the same fate as the
tertials in most specimens (including the Thermopolis specimen).  So
this suggests that the differential retention/preservation of certain
types of feathers was not random.  Some kind of decompositional
hierarchy was at play.


> 2) An exceedingly low-energy depositional environment (i.e. no
> plausible environmental mechanism for removing the tertials),
> corroborated in the best preserved specimens as there's no evidence of
> any displacement to the other feathers of the arm and tail.


Presumably, the agent responsible for removing the skin, muscle,
viscera, and other 'soft' tissue was also responsible for detaching
the tertials.  The agent would not need to consume the tertials,
merely the surrounding fleshy bits that held them in place.  The
tertials would then float up and away, and be lost to posterity.


As I said previously, it's my understanding that there are birds from
Messel that have primaries and secondaries, but no tertials.  As
crown-group avians, the absence of tertials is certainly an artifact.


> Honestly...if the tertials are so easy to remove that it happened in
> all the speccimens, even those with undisturbed tail and wing
> feathers, how would they stay on during flight?


This is assuming that _Archaeopteryx_ could actually fly...


If Christiansen and Bonde (2004) are correct in discerning contour
feathers on the hindlimb of the Berlin specimen, then we might ask a
similar question to yours: Why did these come off in all but one
specimen?



Cheers

Tim