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Re: tooth counts in systematics



chris brochu wrote:
> 
> Joshua Smith wrote:
> > 
> 
> >         I don't think polymorphic traits need to be thrown out--the
> > impetus behind this work was to begin accounting for variation in
> > characters, not to just look for characters can be simply coded as
> > bionomial states.  But as I work with teeth, I started here, and began
> > with the stuff that was unambiguous and easy to code first.  A lack of
> > rigorous testing of the characters before the analyses are run is the
> > whole point as far as I am concerned.
> > 
> What kind of "testing" are you advocating?  I think every serious
> systematist "tests" his or her characters, insofar as they look at every
> available specimen for each ingroup taxon.  (Yes, I know - not EVERYONE
> does.  Not all drivers wear seat belts, either.)
> 
        I was advocating a rigorous examination of the inter and 
intrataxonomic variation of the selected characters.  It has 
been my experience that most analyses (we are talking theropods only 
here--) don't really examine the amount of variation that exists within
the characters they describe and use, but rather describe the variation such as
"premaxilla very deep subnarially" or "key-hole" or "light bulb" shaped 
orbits or lower temporal fenestrae "very large".

        So, the other condition is lower temporal fenestrae very small?   
        What does that mean?  How is large defined vs. small?  Is it 
repeatable?  Is my definition of "large" the same as yours?  How can I go 
into my newly excavated skull and determine if the lower temporal 
fenestra is large or small when it looks to me to in the middle of the two? 
Seems really ambiguous to me.


-- 
__________________________
Josh Smith
University of Pennsylvania
Department of Earth and Environmental Science
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smithjb@sas.upenn.edu