Re: REALLY good introduction to cladistics!!

[philidor11@snet.net]

So they are willing to assume that direct ancestors can be identified 
in the second window discussion, but are unwilling to assume 
an amniotic egg for an animal that far up the amniotic branch? 
 Seems an inconsistent faith in the power of bracketing.
I have been trying to remember...
One of the characters they use to demonstrate that T. rex's share 
a more recent common ancestor with parrots than with caimans 
is the 'heel knob'.  This they note is unique to crocs.  Unless 
you're looking at the question of whether T. rex descended from 
a croc, I thought unique to a group characters were considered 
bad form.
Is this correct?
HP Holtz has had a lot more experience teaching and teaching 
cladistics than I, so if he says it's a good intro I accept it. 
 To me, the discussion doesn't lay out the logic of a cladistic 
argument about ancestry, concentrating on animals being treated 
as contemporaries, like T. rex and the parrot.  I'd be confused, 
but then I'm not the usual student.  (Hearing sighs of relief 
from the teachers in the group.)




= = = Original message = = =

----- Original Message -----
From: "philidor11" <philidor11@snet.net>
Sent: Tuesday, October 23, 2001 3:41 AM


> Oh, and amniotic egg is coded '?' for T. rex.  Be a major disappointment
if
> they laid eggs fixed to lily pads.

They are just puristic and code everything we don't actually 
know as "?".
After all, no *T. rex* eggs are known. Look at my matrix -- some 
"-" there
are rather idiotic, but it's better that way, and after all many 
aren't
nearly that certain. They could of course have used phylogenetic 
bracketing
to show that *T. rex* must have had amniotic eggs, but I think 
taking taste
is more fun... :-)

The site is the best (if not only) introduction to cladistics 
of that length
that I've ever seen, and it's better than many longer, more detailed 
ones.



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