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Re: Re: Transitional Fossils



>In a message dated 95-10-03 09:08:54 EDT, Thomas_R_HOLTZ@umail.umd.edu (th81)
>writes:
>
>>An ancestral taxon will appear stratigraphically earlier than its
>>descendants, and (perferably) within the geographic range of the
>descendants.
>>
>>
>
>When did stratigraphy and biogeography get into cladistics?
>

AHA!  I think I've found the crux of the problem here...

I think we are talking about different things.  Although many people (myself
included) will  refer to a cladogram as a phylogeny, it is not actually
such.  A cladogram is a graphic representation of the distribution of
derived character states among taxa.  A phylogeny is the next step, the
transformation of a cladogram into a representation of the "family tree",
including stratigraphic and other data.  This distinction (between
cladograms and phylogenies) is address in almost every technical primer on
cladistics.

So, stratigraphy and biogeography are not used in the cladistic analysis per
se, but in the transformation of the resultant cladogram into a proposed
phylogeny.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist
Dept. of Geology
University of Maryland
College Park, MD  20742
Email:Thomas_R_HOLTZ@umail.umd.edu (th81)
Fax: 301-314-9661
Phone:301-405-4084