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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.  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?  Did oviraptorosaurs and birds
independently produce barbules from a "simple" barbed rachis, while
_Sinornithosaurus_' deinonychosaur ancestors never exhibited this
character?  Or did barbules evolve in an ancestor common to
oviraptorosaurs, deinonychosaurs, and avialians, only to be secondarily
lost within the deinonychosaur clade leading to _Sinornithosaurus_?  Are
oviraptorosaurs closer to birds than deinonychosaurs, in spite of
cladistic diagnoses to the contrary?

Although I seriously doubt that we will be able to settle this matter in
this forum, I would be interested in seeing comments on this topic.  And
please correct me if I have made any errors in the above post.

-- Ralph W. Miller III   ralph.miller@alumni.usc.edu