Re: Psittacosaurus queries

["Steve Brusatte" <dinoland@lycos.com>]

On Wed, 3 Jul 2002 23:58:46   
 NJPharris wrote:
>In a message dated 7/3/02 6:03:35 PM Pacific Daylight Time, 
>dinoland@lycos.com writes:
>
>
>> >Moreover, in all the Psittacosaurus species the rostral bone
>> >contact the slender rostroventral processes of the nasal, a features absent
>> >in all the other Neoceratopsia, perhaps this is another diagnostic features
>> >of the genus.
>> 
>> It most certainly is.  
>
>Tough to tell the polarity on this one, though, since all outgroups to 
>{*Psittacosaurus* + Neoceratopsia} lack rostral bones altogether!

Most definitely.  It's next to impossible to discern the polarity of any 
rostral feature that differs between psittacosaurs and Neoceratopsia.  So, the 
condition in _Psittacosaurus_ might be the primitive condition, or it might be 
the derived condition.  Who knows.  However, I don't know of any 
neoceratopsians that possess the rostroventral process of the nasal contacting 
the rostal bone, so at the least we can say it is diagnostic of 
_Psittacosaurus_.  However, I'm unsure of state in _Chaoyangsaurus_ and 
_Liaoceratops_.  (And, thanks to Luc for posting the _Chaoyangsaurus link!).

Have a happy holiday (and for all non-Americans, er uh, have a happy ordinary 
day).

Steve

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