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Liaoceratops yanzigouensis gen. et sp. nov.




The exact citation is:

Xu, X., Makovicky, P.J., Wang, X, Norell, M.A. and You, H. (2002).  A
ceratopsian dinosaur from China and the early evolution of Ceratopsia.
Nature 416: 314-317.

A few things caught my attention:

_Liaoceratops_ shows characters found in some (but not all) _Psittacosaurus_
species, e.g. weak ventral flange on the dentary; infratemporal fenestra
that is wider ventrally.  This may have repercussions for a question much
discussed on this list: should the half-dozen or so species of
_Psittacosaurus_ all be considered a single genus?

There is some support for considering _Chaoyangsaurus_ a psittacosaurid, a
topology that is recovered when ordered (but not unordered) characters are
used.

The article (incl. Suppl. Info.) refers to both _Microceratops gobiensis_
and _Graciliceratops gobiensis_.

Xu et al. find support for a restricted Protoceratopsidae (_Proto_ +
_Baga_), with the more traditional and more exclusive Protoceratopsidae
coming out as paraphyletic:

Neoceratopsia 
  _Liaoceratops_
  Clade 1
    _Archaeoceratops_
    Clade 2 
      new "family" (includes _Asiaceratops_, _Montanoceratops_,
_Leptoceratops_, _Udanoceratops_)
      Clade 3 - contains trichotomy of:
        _Graciliceratops_
        Protoceratopsidae (_Protoceratops_, _Bagaceratops_)
        Clade 4 
          _Zuniceratops_
          Ceratopsidae

Notes: 
_Liaoceratops_ is regarded as a neoceratopsian by Xu et al.; however, I am
not aware if this clade has been defined using anchor taxa.
Clade 2 - would this be called Ceratopsoidea?
Clade 3 - would this be Coronosauria?
Clade 4 - would this be Ceratopsomorpha?



Tim


------------------------------------------------------------ 

Timothy J. Williams 

USDA-ARS Researcher 
Agronomy Hall 
Iowa State University 
Ames IA 50014 

Phone: 515 294 9233 
Fax:   515 294 3163