Re: Fate of Protoarchaeopteryx

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

  Zdráste,

Ekaterina Amalitzkaya (eamalitz@hotmail.com) wrote:

<Also the pygostyle of Nomingia now seems to be a purely
convergent feature suggesting that the large features may have
initially evolved only for display and then recyckled for
flight.>

  Current research has lead me to consider some the following
about pygostyles in birds and in *Nomingia*:

  The form of the pygostyle is derived in birds for the purpose
of providing the rachis of the retrices a point from which to
orient, and to anchor caudal muscles and flesh that form the
fleshy tail, so that the "fan" can operate as a locomotor module
in connection with the dis-attachment of the caudofemoralis
longus. Similarly, the earliest fused pygals in archosaurs
general appear to be stress-correlators, rather than part of a
locomotor module (this came second, in birds). There is
reasonable expectation to view the fusion of distal caudal
vertebrae (pygals) into a single structure as a means of dealing
with excess stress on the bones: fusion alleviates the stress on
an individual element, and spreads it out; this continues as the
stress increases, for whatever reason (more feathers or whatever
are being incorporated, ankylosaurs are getting more bang for
their buck, etc.).

  Related ness of type of pygostyles depends on use; we can
posit that the tails of ankylosaurs and *Nomingia* are not
comparable, but can we posit the same for *Nomingia* and birds?

  I would love to hear discussion on this,

=====
Jaime A. Headden

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

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