Avaceratops and Ceratops (was RE: First International Phylogenetic Nom...)

[Tim Williams <twilliams_alpha@hotmail.com>]

Jaime A. Headden wrote:

>   To use *Triceratops,* the next oldest available taxon that is considered
> valud, one could just name a new clade Triceratopsia, or define the clade
> as an apomorphy-based taxon,

Why would we need to go to all this trouble?  Ceratopsia can be a valid 
name, irrespective of whether or not _Ceratops_ is a valid genus.  
Ceratopsidae (+Ceratopidae), on the other hand...  (To cite an analogous 
example: Titanosauria, but not Titanosauridae, can be valid names if 
_Titanosaurus_ is a nomen dubium.  Ditto for Hadrosauria/Hadrosauridae.)

> On the other hand, some
> HAVE suggested *Ceratops* may be valid ... I think Dodson suggested
> *Avaceratops* and *Ceratops* may be synonyms or sister-taxa. I forget.

Here's what I wrote over 4 years ago 
(http://www.cmnh.org/dinoarch/2000Jan/msg00354.html), regarding 
_Avaceratops_, based on new cranial material:

Penkalski and Dodson's paper contains a few interesting tidbits.
(1) The orbital horns of this new skull show a striking resemblence to the
horn cores of the type of _Ceratops montanus_, in their shape and
orientation (directed outwards at quite a large angle).  Could _Avaceratops_
be a juvenile _Ceratops_?  (For those who believe that _Ceratops_ is a
defunct genus, read on...)

(2) Even if this new skull does not belong to _Avaceratops_ it belongs to a
closely related genus, probably a basal ceratopsid like _Avaceratops_.
Maybe _Ceratops_?  (_Ceratops_ is considered a nomen dubium by Penkalski and
Dodson, but I've heard of good material from the "Milk River" site that may
pertain to this genus.  Anybody know about this?)

(3) In another paper in the same issue of JVP, Sereno calls the sister-group
to the Centrosaurinae Ceratopsinae rather than Chasmosaurinae.  [snip]  At 
any rate,
there's no good evidence that _Ceratops_ is a chasmosaurine (see (1) and 
(2)).



Tim

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