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Re: A NEW REF, SOME TETRAPODS, AND CLADISTICS & PT



Tetanurae@aol.com wrote:

> TETRAPODA
> I don't get this discussion at all.....  Tetrapoda has never had any sort of
> coloquial usage like Reptilia.  There has never been a lable "tetrapod" that
> excluded stuff like snakes or birds because they don't have feet.  In
> elementary textbooks when they introduce the term tetrapod, they show a
> picture of a snake without fail.

True.  I didn't understand what Wagner was getting at with that bit either.  
I've
always seen "Tetrapoda" used as the name for the group consisting of all
land-dwelling vertebrates.  Until the cladists got hold of it, anyway.

> CLADISTICS AND PT
> Jonathon Woolf wrote:
> <<c), as you point out, is the cladistic one, and the cladists can have it
> for all I care.  Any definition that says _Seymouria_ isn't a tetrapod has no
> rational basis as far as I can tell..>>
>
> To which Jon Wagner responded:
> <<We've been through "rationality" and taxonomy before. Please check
> the archieves under "Arctometarsalia".>>
>
> Which caused Jonathon Woolf to answer with:
> <<So we have, and you're still wrong. Without some reason applied to it, any
> "classification method" is simply a recipe for manufacturing meaningless
> collections of random syllables.>>
>
> Alas, I do not wish to further this "discussion," but I feel we need to remind
> everyone of a few things:
> 1) scientific names are just labels and needn't tell you ANYTHING
> "a rose by any other name would smell as sweet..."

True enough, within limits.  However, scientific names are nearly always
manufactured from pieces of words in some language or other -- usually Greek or
Latin, but more and more often they're from other languages.  So the name itself
has a meaning in whatever language it's taken from.  That meaning is part and
parcel of the name.

As I see it, a name can have either a positive information content, zero
information content, or negative information content.  I have no problem with
either of the first two.  I only object when the name has a negative information
content -- that is, when the name implies X is included, but the definition 
says X
is not included.  Or vice versa.  If the thing has all the diagnostic features 
for
the group, it should be included in the group.  What could be simpler?
_Seymouria_ has all the diagnostic features for being a tetrapod, so how can it
not be in Tetrapoda?   _Morganucodon_ has all the diagnostic features (all the
skeletal ones, at least) for being a mammal, so how can it not be in Mammalia?

On the other hand, as far as I know _Marasuchus_ and _Psuedolagosuchus_ don't 
have
all the features used to diagnose Dinosauria.  Therefore, they aren't dinosaurs
and chouldn't be included in Dinosauria.

> 2) there is no reason to have 'reason' applied to it, as long as everyone
> agrees to what something means, then that is what it means

I think that statement just might make my case all by itself, but no matter.

> <<Since reason is something that's noticeably lacking in the way many alleged
> experts in the field apply cladistics, the method itself is effectively
> worthless.>>
>
> SAYS WHO!?  You have continually claimed that cladistics is worthless without
> any proof.  HOW is cladistics useless?  The application of cladistics is
> almost universally accepted and used by everyone in any field of biology.

The fact that it's widely accepted doesn't mean it's right.  Remember, thirty
years ago everybody thought dinosaurs were big, dumb, slow lizards and birds
descended from some other archosaur.  Did you hear about the molecular trees 
that
place birds and mammals in a clade with dinosaurs as an outgroup?  Did you hear
about the three or four different analyses of elephant shrews -- all of equal
parsimony -- that assigned them to as many different places in the overall
mammalian tree?  Robert Carroll almost got lynched at a conference a couple of
years ago because he dared to point out that cladistic methods were not
infallible.

As far as I'm concerned, there's enough contrary data floating around out there 
to
question cladistics as it's currently being applied and used.  Until that's no
longer true, until all that contrary data is taken into account and explained, 
I'm
not going to accept cladistics blindly.


> Cladistics is not the same as phylogenetic taxonomy.  Cladistics is filling
> out matrices, chugging them through a computer and coming up with a tree etc
> etc.  Phylogentic Taxonomy is the application of formal names with unambiguous
> definitions to clades.

Fine, so what we've been talking about is "phylogenetic taxonomy."  The problems
still exist, no matter what you call it.

> Woolf:
> <<If membership in a group can't be diagnosed, the group is effectively
> useless -- and in a number of cases there is no known way to distinguish
> members
> of a crown-based clade from their immediate ancestors.>>
>
> Yes, that is probably true of their IMMEDIATE ancestors, but most of the time,
> you can distinguish whether or not they fall within a clade or are outside of
> it.

"Most of the time" isn't all the time.  So why do people treat phylogenetic
taxonomy as being infallible, and either ignore or rationalize away the
exceptions?

> <<There is a long, long string of fossil forms from the latest Triassic up
> through the mid Cretaceous that look mammalian in every detail -- but can't be
> called mammals because they date from before the last common ancestor of
> Monotremata and Theria.>>
>
> SO WHAT?  Why does this make crown-clades useless?

It makes them useless because they can't be relied on to do what they're 
supposed
to do: identify a _diagnosable_ monophyletic evolutionary group.  If you can't
tell what organisms belong to a group, then the group has no practical use.  If
Hopson is right that monotremes and placentals share a MRCA in the Mid Jurassic,
then nothing earlier than that can be a mammal -- including such animals as the
morganucodonts, which have every feature that could reasonably be used as an
apomorphy for mammals.  On the other hand, if the idea that monotremes are
descended from a different line of therapsids than all other mammals is correct,
then crown-clade Mammalia would have to include a number of therapsids that
_don't_ have many of the mammalian apomorphies.  Which is why Hopson, in his
article "Synapsid Evolution and the Radiation of Non-Eutherian Mammals" in 
_Major
Features of Vertebrate Evolution_ doesn't even give a phylogenetic definition 
for
Mammalia.

> These are the rules, if you don't like them use your brand of reasoning and
> make new ones and publish them.  If they catch on, they catch on, if they
> don't, then use these ones because these are the ones that everyone uses.

Uh-huh.  In other words, the cladists want me to ignore the evidence and just 
take
their word for it.  Sorry, I don't work that way.  I know "experts" who worship
cladistics.  I know other "experts," just as qualified if not more so, who say
that cladistics and phylogenetic taxonomy as paleontologists use them are crap.
When I hear conflicting opinions from two different groups of "experts," I throw
away all their opinions and go back to the facts.  And the facts, to my eyes, 
say
that the cladists are wrong.

-- Jon W.