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subject material and Re: Dinosaur Discussion List Dictionary



Before returning to my conversation with George, I'd like to add my
agreement to Bonnie Blackwell's sentiments.  Just as a for instance,
do you *really* think that this list should house a discussion about
techno-geek humor?

I'm also unsure as to how much the discussion of cladistic terminology
needs to be here.  I tried to take part of it directly to George, but
he forwarded to the list my personal e-mail to him (without permission
-- as an aside, that's kind of a no no, by the way) and resurrected
the discussion here.  Well, since I'd also like to get some input from
some of the cladophiles (calling Tom Holtz -- Oh good, he seems to be
answering!) I'll keep the discussion here.  Protest if you think we
should work this out behind the scenes.

Anyhoo...  George asks:

> Here's what I wrote:
>
>> APOMORPHY--n. A character state present throughout a clade but
>> not present in any close outgroup of the clade.
>
>This is wrong?

I've double checked Robert Carroll's _Vertebrate Paleontology and
Evolution_*, and near as I can tell, the above is, in fact, wrong.  In
the first place, it implies that you can determine whether or not a
character state is apomorphic on the basis of that character state's
distribution alone.  A cladistic analysis must include suites of
characters in order for us to have any hope of it spitting out correct
answers.

On the more philosophical level (as I objected yesterday) comparison
of character states among various groups represents an attempt to
*measure* character state polarity.  According to George's definition,
comparison amongst outgroups *defines* whether or not a character is
apomorphic.  That's just not right because aside from comparisons of
character state amongst outgroups, character state polarity analysis
proceeds also by an examination of the fossil record in order to
determine the sequence of appearance of a character state, and by
studies of ontogenetic sequencing (a final remnant of Haeckel's
"recapitulation").  If you want to confirm, look at Bob Carroll's book
pg. 5 _et seq._.

* Author:         Carroll, Robert L.
 Title:          Vertebrate paleontology and evolution / Robert L. Carroll.
 Published:      New York, N.Y. : Freeman, c1988.


-- 
Mickey Rowe     (rowe@lepomis.psych.upenn.edu)