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Re: Is *Amargasaurus sattleri* a Parent Clade for Dicraeosaurines?




>  I feel rather put down by those who feel that
>revising whole phylogenies based on such a perspective
>of the natural occurrence of paraphyletic parent
>groups and the apparent nature of genera that are
>ancestral to other ?genera,? would be so difficult or
>time consuming, or mind-bogglingly immense, that we
>should just not do it.


    The "mind bogglingly immense" thing and my argument against scrubbing
genera were two different things, although they are connected.  My argument
goes like this:

1. Any system of taxonomy is entirely artifical and based on arbitrary
distinctions.  If we in our minds combine organisms that lived at different
times and in different places as a "clade" or a "family" or whatever, we are
creating a concept that didn't exist before we thought it up.  T. rex and
T.bataar and Gorgosaurus and Albertosaurus never thought of themselves as
being united as something, and neither did anything else until we came
along.  Nor was there flash of lightning and a puff of smoke when two
divergent populations become different enough to be called different
"species".  The crappy fossil record removed all the intermediates, so our
little pattern identifying primate brains can find a distinction between two
populations when they become divergent enough without being confused by the
hundreds or thousands of almost generations which are indistinguishible or
almost indistinguishible from the ones beffore and after.  Even the concept
of an individual organism is rather arbitrary since we are really a huge
symbiotic colony of cells (which has to do with my "mind bogglingly immense"
post).

2. These distinctions may be artificial, but they are still useful.  People
seem to be interpreting my point to mean that just because taxonomy is
artificial, it shouldn't be used.  I don't mean that at all.  In order to do
science, the human brain needs to be able to categorize and simplify.  We
simply need to be in touch with the artificial nature of the system and not
let it overpower how we veiw reality.

3.  Since taxonomy is an artificial system created for our convenience, it
is both pointless and counterproductive to eradicate useful taxonomic
categories in order to make the system "more natural".  The system will
NEVER be really natural, but it can be made either more or less useful to us
as a means of categorizing.  Genera, monophyletic or not, are completely
arbitrarily chosen taxa.  They are still assigned based on MORPHOLOGICAL
characters, even as monophyletic groups in phylogenetic taxonomy.  When a
taxonomist puts a genus name in front of all the species in a clade, the
reason he draws the line at thier sister taxa has nothing to do with common
descent; he sees some specific feature or features in that clade that is not
possessed by the sister taxon that he FEELS is an important distinguishing
point.  So what purpose will eliminating paraphyletic genera but keeping
monophyletic genera serve?  Genera are useful as conceptual tools, not as
reflections of sharp, real life distinctions between evolutionary lineages.

>individuals may be distinguished.  We put names on end
>products we perceive as unique biological organisms
>(UBEs).

    The key phrase is "we perceive".  But they are only "unique" if we just
want to look at living organisms and pretend that evolution never happened
(even that isn't always true; many living species have blurry lines drawn
between them whoose placement is not always agreed upon among biologists).
If we want a system of classification that reflects phylogeny however, we
need to recognize that they only look unique to us because all the
intermediates are dead.  This is also my response to Betty Cunningham's
post.

>Linnaeus coined the usage of binominal
>taxonomy as a way of distinguishing forms and
>variations of forms. Perhaps we should dump species,
>and keep genera. Name supra-generic groups, and name a
>?species? or subgroup of ?genus? when it appears there
>are two forms within the UBE we?ve given a name to.
>*Tyrannosaurus* is a widely recognized UBE with two
>apparent subtypes, a North American *T. rex* form, and
>a Mongolian *T. bataar* form.

    Wagner was bemoaning monotypic genera before, so he might partially
agree with this system, although I get the impression that he might want to
do away with the genus concept altogether, even "for two forms within an
UBE".  I think that the (artificial) genus concept is useful enough to keep,
but since monotypic species don't contribute anything by having two names,
it wouldn't hurt the value of taxonomy in my opinion to eliminate species in
monotypic forms.
    From a practical standpoint, a forsee a problem with trying to get this
system top catch on.  If somebody describes a new genus, eliminating species
in monotypic forms means that he can't get credit for the type species as
well, since he isn't supposed to name one.  That means that if somebody
later describes a secod species, THEY would also get to apply a species name
to the type form in order to distinguish them, and get credit for both
species names.  The original author might feel a bit miffed about this.


LNJ
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Jeffrey W. Martz
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