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RE: Similicaudipteryx feather ontogeny, in Nature



Jaime Headden wrote-

> 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*).

I disagree the Similicaudipteryx postcrania indicate it is a caudipterid.  He 
et al. referred it to Caudipteridae based on several characters. Most are 
symplesiomorphic for maniraptorans (low number of caudal vertebrae; deep pubic 
peduncle; unfused metatarsus; metatarsal III longest; metatarsals II and IV 
subequal in width; metatarsal II slightly shorter than IV; subarctometatarsal 
metatarsus), the proximally placed metatarsal I is also present in 
Protarchaeopteryx, and the preacetabular depth is intermediate between other 
oviraptorosaurs. In fact, Similicaudipteryx shares large anterior dorsal 
hypapophyses with caenagnathoids, and a pygostyle with Nomingia specifically 
(unknown in other caenagnathids).
 
I'm curious what the basis for referring the new specimens to Similicaudipteryx 
is, since most of the supposed diagnostic characters in the original 
description are flawed, and its presence in the Yixian Formation instead of the 
Jiufotang Formation suggests Caudipteryx instead.
 
Mickey Mortimer
The Theropod Database Blog- http://theropoddatabase.blogspot.com/