Re: Dinosaur Taxonomy (was Re: Re: dinosaur flatware)

[pharrinj@PLU.edu]

On Tue, 16 Jan 1996, Stan Friesen wrote:

> From: pharrinj@PLU.edu
>  > On Mon, 15 Jan 1996, Stan Friesen wrote:
>  > > 
>  > > Not if the defining characters of Herrerasauria do not include any
>  > > uniquely derived characters found only in the known herrerasaurs.
>  > 
>  > If that is the case, then no taxon Herrerasauria should ever be 
>  > diagnosed, and the points discussed here become moot.
> 
> Yes it can - it just is diagnosed on a combination of theropod
> apomorphies and the plesiomorphic condition of the characters used
> to diagnose the "higher" theropods.  This is *always* how one
> diagnoses a paraphyletic taxon!!  It is still a "differntial
> diagnosis", as it still specifies how the taxon differs from all
> coordinate taxa.

I never claimed that the Herrerasauria (or any other parataxon) COULN'T 
be diagnosed, just that it SHOULD'T, for the simple reason that, if the 
Herrerasauria is paraphyletic, then they are not each other's closest 
relatives.

As I said, the whole argument becomes moot if one allows parataxa.

     Nick