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Re: Lemurs and Feathers



David Marjanovic (david.marjanovic@gmx.at) wrote:

<This implies that the condition in the cf. *Sinornithosaurus*
specimen is basal. If either *Archaeopteryx* or *Caudipteryx* is
closer to Pygostylia than this one, then it either isn't the
basal condition, or wing feathers have evolved twice. What about
the wings of *Longipteryx* that look so similar to this?
Artifact of preservation? Preservation of ~contour feathers
during moulting?>

  In part because I helped perpetuate this idea by proposing it
in the first place, the paper states the prescence of feathers
and indicates them on the slab, well away from the arm and
"contour" arrangement. In this, there were real feathers, just
not carbonized traces of them, as in Confuciusornithidae, et
al..

<Perhaps, but *Unenlagia*, *Achillobator* and, more importantly,
*Archaeopteryx* don't have it. BTW, the pubes of basal
ornithothoracines like *Sinornis* are retroverted, but not as
far as in ornithischians and segnosaurs.>

  Well, in the later it seems to be irrelevant, and that it may
be corrolary to diet. If I have the chance, I will be working on
the dietary adaptations in segnosaurs and their role in
influencing evolution...

  Retroversion of the pubis ban be acheived in two ways,
remembering the lack of a pubic apron in some of these fellows:
The whole pubis is turned caudally, from the iliac contact; _OR_
the distal half is turned backward, possibly related to
respiration and thus metabolism. Carrier and Farmer show that
position of the pubis influences the most caudal air sacs;
without a pubic apron, this is acheived by the distal pubes, and
thus pelvic respiration occurs differently wether the whole
pubis or just the distal end is turned caudally, and the issue
is homogenous. Orientation of the proximal end of the shaft is
irrelevant if there's no apron and the distal end is flexed.

<Woodpeckers, however, have _specialized_ feet (zygodactyl!!!)
that have relatively big claws and are very strong, so that they
can _walk_ up tree trunks. No described non-pygostylian dinosaur
-- I'm looking forward to HP Tracy Ford's work -- has even the
long retroverted big toe of *Sinornis* or at least
*Confuciusornis*.>

  !

  Zygodactyly is a manipulation issue, and has very little to do
with scansorality, otherwise Parrots would be skipping up the
trunks of trees to their merry content.... In zygodactylous
birds, the fourth, outer toe is seldom used when everted, making
the bird functionally tridactyl (two forward, one back).
Something seldom described. True in climbing woodpeckers,
parrots, and the few other zygo birds...

=====
Jaime A. Headden

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

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