[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Longipteryx chaoyangensis (Aves, Enantiornithes?)



Pat Norton (ptnorton@email.msn.com) wrote:
 
<I've wondered for a long time why researchers haven't raised
more questions about the apparent absence of quill knobs on
Archaeopteryx in particular, given all the work that has been
done analyzing its flight capabilities. Implicit in all the
analyses of Archie's flight capabilities is the assumption that
the elongated feathers of the arm formed a rigid airfoil. The
only way that is possible is for those feathers to be anchored
to the arm bones---and feathers anchored to bone would almost
certainly leave some osteological evidence.>

  No test has been performed that demonstrated (to my knowledge)
that the ulnar ridge or quill knobs perform any added function
to resisting stresses from feather raches.

<Perhaps that evidence simply hasn't been preserved in all
cases.>

  Or is absent period, and that flight does not require them. No
test... I would think that the degree of preservation in
*Iberomesornis* and un-knobbed Liaoning birds (which is
remarkable) would attest against the lack-of-preservation being
a factor in the absence of these features.

<But it seems that one would need an entirely novel explanation
of the mechanics of feathered flight to argue that those animals
flew using feathers that weren't somehow anchored to the bones
of the arm.>

  Or that tendonous or ligamentous or collagenous fibers are
sufficient in their binding of the bases of raches to prevent
the feathers from reacting to stresses distally, instead of
transfering forces to the ulna. This is done regardless. Do the
forces of the airpressure against the feather outweigh those of
the soft-tissue base's abaility to control the feather's
rigidity? That's the question, I think.

=====
Jaime A. Headden

  Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
  Where the Wind Comes Sweeping Down the Pampas!!!!

__________________________________________________
Do You Yahoo!?
Get personalized email addresses from Yahoo! Mail - only $35 
a year!  http://personal.mail.yahoo.com/