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Re: Sinornithosaurus & Caudipteryx feathers



----- Original Message -----
From: "Dino Guy and Computer Gal" <gbabcock@best.com>
To: <dinosaur@usc.edu>
Sent: Wednesday, March 21, 2001 6:21 PM
Subject: Sinornithosaurus & Caudipteryx feathers


> As much as I am very pleased with the recent paper in _Nature_ on
> _Sinornithosaurus_ feathers, it intrigues me that these structures are
> apparently simpler than the integumental (or is it integumentary?)
> structures present on _Caudipteryx_ specimens.  I say this because the
> arrangement of _Caudipteryx_ fibers suggests a central rachis with barbs
> branching off which are presumably held in place by barbules as in the
> case of modern avian remiges and rectrices (flight feathers), albeit
> without the aerodynamic asymmetric barb pattern.

At the moment, the feathers of *Sinornithosaurus* are the best-investigated
Mesozoic body-covering feathers. The "contour" feathers of *Caudipteryx* are
not illustrated in its description and referred to as "plumulaceous", and
those of *Archaeopteryx* seem not to have been investigated so closely. The
wing and tail feathers of *Caudipteryx* seem to lack barbules, judging from
the good illustrations I have (but IIRC, people who have seen actual
specimens are onlist). *Sinornithosaurus* lacks wing and tail feathers (I
asked onlist why it was so incompletely prepared -- it has been prepared now
for the _Nature_ paper.) What is most interesting to me is that *S.*
apparently has two different types of feathers -- "protodowns", which
consist of barbs joined at the base, and "proto-contour feathers" that
consist of short barbs branching from a rachis and are reminiscent of kiwi
contour feathers.

> That _Caudipteryx_, a
> putative basal oviraptorosaur, should have more advanced feather design
> than _Sinornithosaurus_, a basal deinonychosaur, is surprising because
> deinonychosaurs are believed to have a more recent common ancestor with
> Avialae than oviraptorosaurs.
>
> If this is so, what does it suggest?  [...] Are
> oviraptorosaurs closer to birds than deinonychosaurs, in spite of
> cladistic diagnoses to the contrary?

This would fit my cladogram (which clearly is a minority view...):

--+--+--*Archaeopteryx*
    |    |--*Rahonavis*?
    |    `--Dromaeosauridae "sensu lato"
    `--+--Arctometatarsalia
         `--+--Oviraptorosauria (including *Caudipteryx* and maybe
*Protarchaeopteryx*)
              `--+--Alvarezsauridae
                   |--Avimimidae
                   |--*Yandangornis*
                   `--Pygostylia