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RE: Similicaudipteryx feather ontogeny, in Nature



  The piece is accompanied by an illustration from Lida Xing and Song Qijin of 
an *Incisivosaurus*-headed caudipterid. This is not normally the depiction of a 
typical caudipterid, but it is certainly consistent with the fact that the 
older of the two new specimens possesses a skull that is very close in 
appearance (general, rather than specific) to that of *Incisivosaurus*. Senter 
proposed that *Incisivosaurus* was a synonym of *Protarchaeopteryx,* and while 
this may be true, these fossils imply there may be an extra quality to this 
story.

  For one, it may suggest that *Protarchaeopteryx* is a caudipterid, and that 
*Incisivosaurus* was one two, expanding the range of cranial variation in the 
group and certainly consideration of the skull-shape changes that occured in 
just this one small group of oviraptorosaurs (not one, but two [or maybe even 
three?] progressive losses of dentition in Oviraptorosauria!?). It may also 
imply that *Similicaudipteryx* is not a caudipterid, which certainly 
contradicts the skeletal evidence as the postcranial seem fairly constrained in 
this respect. And it may imply an even more implosive taxonomic scheme in which 
someone will lump all of these taxa into *Protarchaeopteryx*! (Or variations on 
a theme, as it is possible only *Incisivosaurus* and *Similicaudipteryx* are 
*Caudipteryx*). 

  Of course, unless the specimens do NOT fall into a complex within types 
defined already in *Caudipteryx*, I won't be satisfied, as the metric for the 
genus remains unknown (contrary to some authors' opinions).

  The skull itself appears to possess a short, ventrally curved mandible 
without teeth, although this is based on the papers online figures' resolution, 
not a trusthworthy examination medium. There arte two skull morphotypes known 
for *Caudipteryx,* and one of them is a deeper and more rectangular in 
appearance than the other, while the former is very triangular. They roughly 
correspond to the same-sized animal, but one of them is effectively larger than 
the other, implying a proportionately larger skull in the boxy-ish type of 
skull. Both are referred to the same species. The new skull of 
*Similicaudipteryx* (there is only one) has the appearance of the boxier skull 
type, and is even more boxier with a higher and less triangular premaxilla (as 
in *Incisivosaurus*), and this certainly gives us the concept of a gradient 
from a squared to a triangular skull. If true, it implies that there was an 
progressive loss of teeth in caudipterids convergent with loss of teeth in 
other oviraptorosaurs.

Cheers,

Jaime A. Headden
The Bite Stuff (site v2)
http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)





----------------------------------------
> Date: Wed, 28 Apr 2010 17:15:48 -0400
> From: tholtz@umd.edu
> To: dinosaur@usc.edu
> Subject: Similicaudipteryx feather ontogeny, in Nature
>
> Xu, X., X. Zheng & H. You. 2010. Exceptional dionsaur fossils show
> ontogenetic development of early feathers. Nature 464: 1338-1341.
> doi:10.1038/nature08965
> http://www.nature.com/nature/journal/v464/n7293/full/nature08965.html
>
> Abstract: Recent discoveries of feathered dinosaur specimens have greatly
> improved our understanding of the origin and early evolution of feathers,
> but little information is available on the ontogenetic development of early
> feathers1, 2, 3, 4, 5, 6, 7. Here we describe an early-juvenile specimen and
> a late-juvenile specimen, both referable to the oviraptorosaur
> Similicaudipteryx8, recovered from the Lower Cretaceous Yixian Formation of
> western Liaoning, China9. The two specimens have strikingly different
> remiges and rectrices, suggesting that a radical morphological change
> occurred during feather development, as is the case for modern feathers10.
> However, both the remiges and the rectrices are proximally ribbon-like in
> the younger specimen but fully pennaceous in the older specimen, a pattern
> not known in any modern bird10. In combination with the wide distribution of
> proximally ribbon-like pennaceous feathers and elongate broad filamentous
> feathers among extinct theropods, this find suggests that early feathers
> were developmentally more diverse than modern ones and that some
> developmental features, and the resultant morphotypes, have been lost in
> feather evolution.
>
> News item: http://www.nature.com/news/2010/100428/full/news.2010.208.html
>
> Thomas R. Holtz, Jr.
> Email: tholtz@umd.edu Phone: 301-405-4084
> Office: Centreville 1216
> Senior Lecturer, Vertebrate Paleontology
> Dept. of Geology, University of Maryland
> http://www.geol.umd.edu/~tholtz/
> Fax: 301-314-9661
>
> Faculty Director, Earth, Life & Time Program, College Park Scholars
> http://www.geol.umd.edu/~jmerck/eltsite/
> Faculty Director, Science & Global Change Program, College Park Scholars
> http://www.geol.umd.edu/sgc
> Fax: 301-314-9843
>
> Mailing Address: Thomas R. Holtz, Jr.
> Department of Geology
> Building 237, Room 1117
> University of Maryland
> College Park, MD 20742 USA
>
                                          
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