Re: Gaia theropod follow-up: a "new" phylogeny

["Jeffrey Martz" <jeffmartz@earthlink.net>]

Dinogeorge wrote...
>Is it just me, or do other people find this endless hunt for ever more
>"characters" just plain CRAZY? The computer will, of course, grind out
trees
>as long as you give it "characters" to chew on, but do you really BELIEVE
in
>the resulting phylogenies, or are they just so much nonsense, to be
discarded
>when the next batch of computer-generated trees, crunching even more
>"characters," emerges?

    But they aren't entirely discarded George.  If every phylogeny produced
for a group different completely different tree, this attitude might be
understandable, but there are patterns which can hold in different
phylogenies.  Look at previous trees, try to understand WHY the characters
produce the pattern that they do, and WHY different phylogenies differ.  Why
would we ever NOT want to incorporate as much information as possible into
our hypotheses?  You seem to think that a cladistic analysis just involves
writing down big lists of stuff without thinking about what it means, but a
good analysis thinks hard about the morphological features it includes and
what they might mean (for example, considering the effect of purely
size-related characters on
the placement of tyrannosaurs within the theropods).
    Also keep in mind that cladistic analyses have supported many
phylogenetic hypotheses that I doubt you would disagree with; for example,
placing birds in theropods.  I also seem to remember you once denouncing
cladistic placement of therizinosaurs within the theropods.

>If so, why not hold out until you've found ALL
>possible "characters," grind out the one big tree and be done with it?

    Sure.  And Colbert should have waited until every single specimen of
Coelophysis that is still buried in Triassic sediments had been found and
fully prepared before writing about it.  2,000 years of intesive searching
and massive quarrying involving stripping off all the overburden covering
Triassic exposures in the southwest and we might get them all.
    This philosophy takes procrastination to a pretty wacky and paranoid
extreme George.  Do you think we will ever reach the point where somebody
has noticed every single feature of potential interest?  I find it hard to
believe you have never realized that people publish on new specimens of
previously known taxa that preserve stuff that hasn't been seen before (an
can be used in cladistic analyses).  Are we really supposed to wait until
every single specimen that MIGHT preserve something new has been uncovered,
and every potential character of potential interest (including the ones we
don't relaize are releveant yet) are noticed before we start thinking about
what we have already noticed means?  The world won't implode if we make a
mistake George.
    Archaeologists are still learning things about ancient Sumer, so they
haven't collected all the possible information yet.  According to your
philosophy, there should still be a complete absence of litterature on
ancient civilizations because we don't have all the data.  Somebody could
make a mistake discussing the Sumerians before we have found every artifact,
you know.
    Sit down with all the real specimens of Coelophysis and start looking
for all the characters, let everyone know when you have found them all.  In
the meantime we will pretend the material doesn't exist and has no
information to offer on theropod evolution.

>But
>then how would you CHECK this tree against reality? Are synapomorphy wars
>what the search for truth in paleontology is really like?

     Do you think that historians and nuclear physicists and chemists and
astronomers and members of every other field of study that has to infer
about its subject without observing it directly are running a fools errand?
I've never seen a sample of methane gas from Jupiter, but I'm willing to
trust atronomer's means of inferring its presence indirectly.
    If the synapomorphy wars bother you, try taking apart a few analyses
character by character to try to understand how they work.

LNJ
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Jeffrey W. Martz
Graduate student, Department of Geosciences, Texas Tech University
3002 4th St., Apt. C26
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