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Re: Therizinosaur systematics



At 08:00 PM 3/10/97 -0500, George wrote:
>According to whose rules? Who said "phylogenetic" definitions must take
>priority over non-"phylogenetic" definitions regardless of publication date?
        George makes a point upon which I must stand corrected. My wording
was egregiously imprecise. Therizinosauroidea does not have *taxonomic*
priority over Segnosauria, unless we define the two to be the same clade.
Were Segnosauria to be defined phylogenetically as = {+ _Alxasaurus_, +
Therizinosauridae } (ie. the same as Therizinosauroidea) it would have
*taxonomic* priority (barring nuances of the ICZN code). Until it is
defined, however, we are better off using a defined monophyletic group in
discussions of phylogeny.
        What I should have said was: as far as this discussion is concerned,
we must use Therizinosauroidea because Segnosauria is not defined in a
phyloegentic context. If it were defined, as I believe it should be, as a
stem based clade, it would still be inappropriate for the discussion as
Segnosauria may include _Microvenator_, eg. Holtz 1996b (abstract of SVP),
and no "segnosaurs" (sensu Barsbold and Perle) outside of Therizinosauroidea
have yet been identified.
        On a strictly casual basis, George may be right, the group might
best be termed "segnosaurs" and not "therizinosaurs". If we are to refer to
the group as a phylogenetic taxon (and since we are discussing phylogeny,
this is appropriate), "therizinosauroids" is the correct term (and not
"therizinosaurs"). My apologies for the confusion.

>When and if "phylogenetic" definitions are accepted and codifed [...]
        See Gauthier 1992(?) for a discussion of priority in phylogenetic
taxonomy.

>[...] cladist-arrogance to make that assertion.
        Probably more like me not paying attention. Again, my apologies.

>Segnosauria, see Barsbold & Perle's paper, 1980, also Barsbold's 1983
>published dissertation.
        I am really not at all concerned with the diagnosis of Segnosauria,
as diagnosis and definition are two seperate animals (if you'll pardon the
expression :).
        I will respond to any further permutations of this thread off-list.
+--------------------------------------------------------------------------+
| Jonathan R. Wagner                    "You can clade if you want to,     |
| Department of Geosciences              You can leave your friends behind |
| Texas Tech University                  Because your friends don't clade  |
| Lubbock, TX 79409                               and if they don't clade, |
|       *** wagner@ttu.edu ***           Then they're no friends of mine." |
|           Web Page:  http://faraday.clas.virginia.edu/~jrw6f             |
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