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Re: Nitpicky cladistics



        While I expect Dr. Holtz would like a crack at this, my knee-jerk
nature got the better of me...
        [see notes at bottom]

At 11:52 AM 11/17/96 +1030, Norm King wrote:
>Wouldn't a non-cladistic taxonomic category still exist if part of it
>were removed?
        As would a cladisitc taxon.  Part of it is *never* removed, so long
as all life on Earth constitutes a monphyletic assemblage.  Phylogenetic
taxa are not limited by what group they are nested in, they simply become
more or less inclusive with changing phylogenetic hypotheses.

>What happens to maniraptor if you use cladistics to make a case that
>birds are descended from an ornithosuchian?  (Granted, that would require
>some new fossils to be found, but, again, the question is conceptual.)
        [See notes at bottom]
        Just for the sake of example, if Ornithosuchia are more closely
related to crocodiles than to birds, Maniraptora {+ Aves, - Ornithomimus}
will be the sister group of the "ornithodirans" {+ Dinosauria, - Eosuchia},
which suddenly becomes... drumroll please, the Arctometarsali!  Pseudosuchia
{+ Eosuchia, - Aves} will be a more inclusive clade within the Maniraptora.
        (I am not currently in possesion of documentation, so some of these
definitions should be taken with a grain of salt)
So we have:
[Newick notation here, implies compostion, not clade definition.]
        Archosauromorpha: (basal "archomorphs", (Maniraptora, Arctometatarsali)
        Maniraptora: (basal animals not part of the {+ Eosuchia, + Aves}
clade, Archosauria)
        Archosauria: (Pseudosuchia, Ornithodira [which does not include
dinosaurs, but does include the birds])

        In other words, Maniraptora becomes crocodiles, birds, other
crocodile-like forms, Arctometatarsali becomes dinosaurs, pterosaurs, and
other fun stuff.  In this case, all of a sudden, dinosaurs lie outside of
the Archosaurs.

>I
>assume one could define a new cladistics-based category, perhaps the
>"Thecoavia" or even "Ornithornithia," which, BY DEFINITION would include
>birds.
        For what clade?  As you see above, there are *PLENTY* of
bird-outgroup clades already named.  No need for any new ones.  The magic of
Phylogenetic Taxonomy!

>Cladistics-based taxonomic categories seem poised to dictate our concepts
>of reality, whereas it should be our concepts of reality that dictate the
>taxonomic categories.  Cladists have become prisoners of their own rules.
        Au contraire, they decribe our concepts of reality, which are
dictated by phylogenetic analysis, just as traditional taxa described our
concepts of reality based on whatever voodoo analysis they were based on
(this is a joke.  I mean no disrespect to the thousands of perfectly
scientific taxonomists who have gone before).  You misunderstand
Phylogenetic taxonomy.  The idea is that each taxon describes a real group,
a clade.  Our understanding of the phylogeny may change, such thatthe
group's composition or autopomorphies may change, but the clade is always
going to describe a real group.  It is very flexible, yet also stable.

> Non-cladistics-based taxa are superior from the standpoint of not
>requiring any particular view of the course of evolution to be valid.
        And yet traditional taxonomists try very hard to incorporate
phylogeny into their taxonomy, which has resulted in the instability of the
Linean system.  What if the traditional Pachydermata end up being a real
group?  What will you folks do?  Change your heirarchies and change your
taxa, and go through a flurry of feather ruffling.  the cladist will just
allow the clades to fall where they are defined (maybe define some old taxa
phylogenetically to incorporate the old with the new), and get on to more
important matters.

>Maniraptora seems to be a legitimate grouping of dinosaurs, whether one
>uses cladistics or not, or whether birds are included or not.  So, any
>non-cladist ought to be able to use it.  It's not a forbidden term for
>them.  They might have to redefine it, but that happens all of the time
>in taxonomy.  No reason why it can't happen to terms established by
>cladists.
        Since tradtional systematicists seem to do whatever they want with
whatever taxa they want, I guess you can do this.  But the taxon *was*
DEFINED to include birds, and emphasize the relationship between birds and
certain dinosaurs.  Maybe Dr. Holtz or George know some of the old rules
which may preclude this.  I would personally think it would be a bit
insulting to Dr. Gauthier to use his taxon outside of the spirit in which it
was intended, but that's just me.

>Have I missed something here?    :-S ?
        Yup!  I respectfully suggest you go back and read the references in
Holtz 1996, as a starter.

        The Cladisitic Assassin

        "Tick, you're alive, tock, you're dead..."
                -Lorien

NOTES:
As an aside, I am experimenting here with a shorthand for phylogentic
taxonomic definitions.  {} invokes common ancestry (elipsis and straight
brackets are not used to avoid confusion with editorial comments and the
Newick Standard (Felsenstein 1993)), + is inclusiveness, - exclusiveness.
Thus, a stem-based taxon might read {+group A, -group B}, a node-based taxon
{+A, +B}, and an apomorphy-based taxon {+group A, +Apomorphy X} (the first
member of group A to evolve apomorphy X, and all of it's decendants).

Felsenstein, J.  1993.  PHYLIP (Phylogeny Inference Package) version 3.5c.
      Distributed by the author.  Department of Genetics, University of
      Washington, Seattle.
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| 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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