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re: PAUP vs. MacClade



Dave Peters (davidrpeters@earthlink.net) wrote:

<I've been fooled many times, as I've discovered recently as I make
corrections. But, the thrill is in the learning -- and I am learning about
burrowing snakes, turtle kin and ichthyosaurs -- things I admired but
never studied until now. Hence the earlier questions about snake diphyly
(sp?) which is becoming more and more interesting evrery day. I can see
where the arguments have their strengths, but again, I think the arguments
can be solved by expanding the taxon list.>

  On this, I am loathe to comment, but feel my response may be more
constructive than not. Only a fool should beleive their analysis holds the
truth, or an ounce of it. It is a product of a what you put into the
analysis, how you treat characters, WAHT characters you're putting in,
etc., not to mention how many species you put in. It doesn't matter if
your analysis of any size always comes up with a single MPT, you need to
analyze WHY the result appears as much as the input and the output, and
reminding yourself of that long-understood axiom of GIGO would go a long
way to solving this, as this is a cornerstone of scientific self-checking
and hypothesis formation.

  Similarly, NEVER a priori decide that you have "enough" taxa or
characters. MORE data is better than LESS data, and the idea that if
you're finding a single MPT means your analysis is good and you can stop
adding characters is actually wrong on so many levels I wouldn't know
where to begin but look back up to what I write and *hope* it makes some
sort of sense.

<One thing I have noticed is a vast emptiness in the literature when it
comes to extant lizard skeletons.>

  http://www.Digimorph.org/ houses an extensive (and expanding) collection
of skeletal and cranial data on lizards and some snakes. I highly
recommend this site as well as the sources otherwise listed. Similarly,
never forget to go to a local museum which should have more than a few
species of lizards and snakes on file, running between gekkotans,
iguanians, "anguimorphs," etc. Maybe even a tuatara or two. Which reminds
me: the marvelous variability of rhynchocephalians from clevosaurs to
sphenodontids to the highly modified aquatic pleurosaurs/paleopleurosaurs.
Marc Jones has a poster assessing cranial variation and deformation planes
reflecting it at the 2004 SVP, wonderful group of animals.

  Cheers,

Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


                
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