Arctometatarsalia [was: Re: Dinofest Report #2 (and final)]

["Jonathan R. Wagner" <znc14@TTACS.TTU.EDU>]

At 06:29 AM 4/27/98 -0400, J. Woolf wrote:
>Then the definition of the taxon is tautological and conveys no useful
>information.
        Pardon? It contains exactly as much information as is necessary for
the naming of a taxon. Specifically, it answers the question: "How do I tell
which taxa are memebers of the Arctometatarsalia." If this is not useful
information, then I certainly do not understand taxonomy. As for
"tautological", why should it be tautological because it always exists?
        Bear in mind that PT is a different way of taxonomic construction.
Your idea of taxa might be that they represent ideas about the phylogenetic
structure or morphology of the group in question, but this is not
everybody's idea. The entire point of PT is to assure stability of taxonomic
nomenclature (but not taxon composition, which changes with phylogenetic
hypothesis in *anybody's* system) by providing a set method for recognizing
taxon composition given a phylogenetic hypothesis.
        As such, the only useful information is that which determines taxon
membership. Linean taxonomy accomplished the same task using morphological
characters. PT is simply one step removed from this, by using phylogeny
(which is, of course, derived by various means, including morphological
characters). You don't even have to be a cladist to use PT. Philosophically,
it is a more objective approach to taxonomy.

>>For example, if two clades evolved an arctometatarsus independantly
>> ("convergently" or whathaveyou), how would you determine which one evolved
>> the character first?
>
>Very good.  That's my exact question.  Unfortunately, you haven't given a good
>answer yet.
        If you read on in my post, you will note that an answer is not
necessary for the current definition, because the definition was changed
from apomorphy-based to stem-based by Holtz (1996).

>No matter what alternatives, evasions, exceptions, riders, and other
>1040-grade complexities you introduce, you cannot get away from the fact that
>ultimately, organisms are classified based on physical characteristics,
PT is not "classification" per the arguments of De Quiroz and Gauthier. To
crudely paraphrase, classification is the devision of objects along crudely
arbitrary boundaries. PT is a system of applying names to groups which fall
naturally out of the process of ancestry and descent.
        As such, PT does *not* directly assign taxon names based on
morphology. PT assigns names based on inferred evolutionary relationships.
Such relationships *may* be derived from analysis of morphology. However,
that is a function of how you got the relationships, not how the taxonomy is
applied.

>and only
>physical characteristics can tell us if a given organism belongs in a given
>taxonomic group.
        Actually, according to recent postings by Dr. Brochu, molecular data
are just as good at developing phylogenies. Once we have a phylogeny, a PT
definition will allow us to determine what named taxon the animal belongs to.

>If the feature(s) used to classify the organism are not
>apomorphic, then the classification will be flawed.
        Using traditional Linnean taxonomy, perhaps. However, as I made
clear before, we are not using traditional Linnean taxonomy.

>Question: how does one tell if a given organism meets this definition?  If you
>answered, "by analyzing its characteristics," go to the head of the class.  All
>useful taxonomic definitions are ultimately character-based.
        I answer the question: "By developing a phylogenetic hypothesis."
For all your singing and dancing, you have only here demonstrated that you
do not understand the point:
        Morphology or DNA or imagination => Phylogeny
        Phylogeny => Phylogenetic taxonomy

        The ultimate taxonomic position is dependant on the analysis of
(hopefully derived) characteristics. However, the characters do not make the
taxon.

>>         3) Synapomorphy does not require that the character evolved only
>> once.
>Semantic hairsplitting.  I think everyone who read my post knows what I
meant, >and also knows you're just trying to cloud the issue.
        Ah, yes, evil Wagner excercises his power to cloud men's minds.
        Seriously though, yes, we all knew what you meant, but words have
power, and by misusing the word you sought to use the power behind that word
to support your point. This is improper. It's the sort of thing
non-scientists do all the time to snooker the laymen into believing various
"theories".
        So, I'll try not to cloud the issues with the truth if you agree to
try not to cloud the issue with falsehood.

>>         5) That the character evolved more than once does not imply that
>> some or all of the taxa formerly included in the group don't still
>> constitute a clade exclusive of other taxa.

>Irrelevant to my original point: if the characteristic for which the taxon
was >named is not a synapomorphy for ALL species within the taxon, the name
is >inconsistent with the facts.
        Birds have wings on their fingers, should we thus invalidate
Pterodactyloidea? Carnivora aren't the only animals that eat meat.
Brachiopods and Ostracods are not molluscs, yet we allow Bivalvia to soldier
on unchanged. Why, Ornithiscians aren't even closer to birds than sauropods
are. Heck, Sauropods... how many lepidosaurs have "lizard feet"? As I said
before, "A rose by any other name would smell as sweet."

>>         10) What is then "the relationship after which the clade was named"?
>> As noted below, a clade cannot be named based on a set of taxa, because
>More semantic evasions.
        Actually a very important point which you fail to understand. If you
say the world is flat, and I say it is round, you could just as easily say I
am making a "semantic evasion". However, the difference, although perhapos
semantic in that words are used to describe it, is very real and of grave
consequence for all of science.

>>Therefore, a P. taxon can never be "invalid" (unless we goof up
>> the process of defining it somehow.
>Technically, no.  But if the definition is goofed to the extent that the
clade >has no useful meaning,
        What the buckyballs do you mean? The definition is absolutely fine!
        Oh, and, in case you didn't notice my extensive earlier commentary,
*clades* do not have "meaning", because they are natural entities. Taxa may
have meaning, because they are artificial applications of names to natural
entities, and therfore some meaning may have been imparted in the naming.

>both name and clade should be dropped from the literature and declared passe.
        And then what? If we proceed with your plan the literature will be
cluttered with a bazillion names erected for a bazillion different purposes.
The Principle of Priority was created (in part) to avoid that sort of crud
(even though some workers seem to enjoy flagrantly ignoring it). Besides, as
I interpreted it earlier, the taxon still lives up to its original intent
(although this is irrelevant for priority).

>you and other hardcore cladists don't care if what you do makes any
rational >sense.
        It does not make sense because you don't understand. My apologies
for not making things clearer, but I'm afraid I have other things on my mind
(writing "delta oh-eighteen" out four hundred times...). Now, if you don't
mind, I have to get back to teasing up my hard-core parsimony spikes and
spraying a cladogram on the back of my hard-core leather.

>Claiming that characteristics don't matter when defining taxa
>is prima facie irrational --
        Unless your taxa are set up so that characters are not part of the
definition. This does not mean that characters are not used at some level,
as noted above.

>with most organisms and all fossil organisms,
>characteristics are the only things we can use for definition of taxa.
        You are dead wrong. As De Quiroz and Gauthier demonstrated, we can
use phylogeny. It even works better, once you get the hang of it.


>You can use any doubletalk you like to evade that fact -- "crown-based
clades," >"stem-based clades," or whatever -- but it all comes back to
characteristics.
        You are still having a fundamental problem distinguishing between
how we deduce phylogeny and how we define clades. Please read any article by
De Quiroz and Gauthier (ref.s in the archeives) before you continue. Then
perhaps we can continue this as a true discussion.

>Sometimes I wish dinosaur paleontologists were more like 'amphibian'
>paleontologists
        All wet? :)
----------------------------------------------------------------------------
    Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
                    "...To fight legends." - Kosh Naranek