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Re: [Re: Birds, Fish, and the Class Ceratopsia (was RE: Response to Gould?)]



"Thomas R. Holtz, Jr." wrote:
> On the other hand, I can see an appeal to using morphological
> distinctiveness as a means of classificiation. However, I wish that    >
users of a rank system would truly stick to their guns and REALLY use
> morphological distinctiveness. For example, Class Aves (excluding
> dromaeosaurs and troodontids and other classic theropods) was at one   >
time separated by a morphological gap (in our knowledge of small       >
theropods and their integument!), but now there is no anatomical       >
structure found in _Archaeopteryx_ which is not also found in some     > other
small theropods. In contrast, Ceratopsia is characterized by a    > rostral
bone. This is a neomorph, folks: it is a whole new bone that no > other animal
has! If whole new anatomical elements aren't grounds for   > very high level
classification, than what is?
>
>
> So, I would like to see gradists support me (;-) in elevating >Ceratopsia to
Class rank. If they truly accept morphological distance as >a guiding
principle, let's seem them do it.  If in fact they are simply >maintaining an
old tradition for its own sake, regardless of the        >supposed guiding
principle, then they will keep Ceratopsia an >Infraorder.

+++++++++++++++++++++++++++++++++++++++++++++++++++++

Though I believe it should be a suite of characters and never just one
character, to define a taxonomic grouping (e.g. I think the 30+ characters
needed to become a new genus is the best way to do these things), I do
heartily agree with your statement. If a new bone is found only in the
Ceratopia and if that is what is needed to warrant a class status then by all
means do it. Ceratopians are no longer dinosaurs and now are Ceratopians. 

Yes, they descended from a dinosaurian ancestor, just like birds did, but just
how all members of Aves have more in common with one another than they do any
dinosaur, the Ceratopians too share more with one another  (including that all
important rostral bone) than any other dinosaur that they deserve a new
ranking. 

Hell, I'm willing to write to the ICZN to have this formally noted. It sounds
perfectly fine to me. It even makes the cladistic distinction (all animals
between Aves and _Triceratops_) all the more interesting.

Jura

Jurassosaurus's Reptipage: A page devoted to the study of and education on,
the reptilia:

http://reptilis.net

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