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RE: Fossil Discovery Threatens Theory of Birds' Evolution



> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> NJPharris@aol.com
>
> >  Please don't confuse "definition" with "diagnosis".
> Definition, in PT, is
> a
> >  statement of common ancestry.  Diagnosis remains a list of derived
> character
> >  states optimized at that particular node.
>
> Hey, now!
>
> Please read what I wrote.  This is a definition (albeit not a PT
> one), not a
> diagnosis.
>
> And I was very careful to state "the first ancestor *of modern
> mammals* to
> possess a single lower jaw bone" to avoid a potential
> polyphyletic mammalia
> should that feature prove to have evolved more than once.
>
> Nick P.

Fair enough; I guess I was responding to the person YOU were responding to,
and got mixed up in the process.  SOMEbody along the way had said that under
PT mammals were diagnosed as all descendants of the...

Oh, and by the way: your definition is a perfectly good PT definition.
Apomorphy-based phylogenetic definitions are most certainly allowable under
PT: I and some others have philosophical and operational problems with them,
but they are allowable.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-314-7843