RE: Sinosauropteryx feathers?

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

Michael Lovejoy (michael@palaeoproductions.fsnet.co.uk) wrote:

<Suddenly lots of replies! Thanks everyone, but now I have a couple more
questions. It's been suggested that body contour feathers are purely
aerodynamic, but a book I have says the are better for insulation and
impact protection than fibrous structures. Is this true (or relevant)?>

  Down is perhaps the last know developed feather morphotype, but contour
feathers do not have the same morphology, and are in fact pennaceous with
the same development as primaries and other vaned features. The book may
be confusion down with contour, maybe or maybe not.

<I've also read that bristle feathers are degenerate contour feathers. Is
there evidence that bristles came first?>

  Bristles and filoplumes are apparently pennaceous vanes that have been
arrested during development or were over-developed during the development
of barbs, so that barbulets do not form and the barbs occur at the tip
with an aftershaft in some. Not sure on the details. Maybe Alan Brush can
chime in if he's not too busy. Prum details the work in hypothetical
scenarios and a recent paper in Nature follows this with corroboratory lab
analysis on histogenesis and feather development. I have the paper
somewhere....

<Finally, these Stage II feathers that Jaime's talking about: are they
illustrated anywhere? They sound like a reasonable option if I'm denied my
beloved contours.>

  These stage II feathers are the structures so far identified in various
theropods, aside from the vanes seen in birds and *Caudipteryx* and
*Protarchaeopteryx*; Prum and Brush have both discussed the nature of
stages I--IV, which involve a single filament, development of multiple
filaments from a single folicle and/or fusion of these into a "fan-shaped"
structure, isolation or fusion of one set of filaments or one filament
into a rachis, from which feathers with after shafts come from, and
finally a pennaceous vaned feather. Other types of feather are present
only as variations of stages III and IV, which are known in extant birds.
Stages I and II, as well as III and IV, have been found in Cretaceous
dinosaurs and the the protobird *Archaeopteryx* (of course). These stage
II structures would not be as cohesive as countours in "sleeking" down the
body surface, and may instead have been rather "bushy".

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

__________________________________________________
Do you Yahoo!?
Yahoo! Mail Plus - Powerful. Affordable. Sign up now.
http://mailplus.yahoo.com