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RE: Tyrant stuff (no longer ranting) (was RE: Rant (was RE: Detai ls on SVP 20...



 
Dinogeorge wrote:

>In between those times, the regions were essentially isolated, and any 
> putatively "congeneric" species that occur there then are very likely 
>convergent or plesiomorphic rather than truly congeneric. 

You mean the Asian and North American _Saurolophus_ species are diphyletic?
Oh come on - surely this is not the most parsimonious scenario.

> If it was so easy to get across, why are there no ceratopine
> or centrosaurine ceratopians in Asia (for example)? Easy for one means 
> easy for all.

I'm assuming you're usage of "ceratopine" rather than "chasmosaurine" is
prompted by taxonomic correctness.  However, can you demonstrate that
_Ceratops montanus_ and _Chasmosaurus_ spp. belong in one and the same
"subfamily" of Ceratopsidae?  I only ask because, as Peter Dodson has
pointed out, _Ceratops montanus_ bears an uncanny resemblence to
_Avaceratops lammersi_.  _Avaceratops_ is neither chasmosaurine (=
ceratopine sensu Olshevsky) nor centrosaurine; and so therefore _Ceratops_
is likely not referrable to either subfamily.  At any rate, _Ceratops
montanus_ is probably not a valid species.

The moral of the story: the Centrosaurinae-Chasmosaurinae dichotomy of
derived ceratopsids should stand.  There is no compelling reason to rename
the latter Ceratopinae.  _Avaceratops_ and _Ceratops_ appear to basal to the
Centrosaurinae-Chasmosaurinae split.



Tim