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RE: true semilunate on one side??

Ken Kinman wrote:

>I don't understand why Tim is arguing about how "easy" or difficult
>coming up with an osteological definition will be.  I looked at my post,
>and I didn't use the word "easy" in there at all.  

The implication of your post (indeed, of the entire "Kinman System") is that
apomorphy-based definitions are inherently more stable than node- or
stem-based definitions.  Ken, you've cited the Mammalia as a sort of "Gold
Standard" in the alleged stability of apomorphy-based definitions.  The
definition of Mammalia using characters of the middle-ear is (using your
words) "clear-cut".

However, even the briefest perusal of mammal phylogenies over the past 50
years will tell you that the definition of "Mammalia" is NOT "clear-cut".
The difference between what IS and IS NOT a mammal on the basis of
osteological evidence has proven to be extremely controversial.  The
Mammalia did not rise Phoenix-like from the ashes of Reptilia.  Nor did the
Aves, irrespective of whatever character(s) you use to define it.  As Mike
de Sosa said, moving the label "Aves" up or down the tree resolves nothing:
the phylogeny will be just as muddled wherever you stick that particular
label.  It's part and parcel of trying to use apomorphy-based definitions.
It's never going to work! 



Timothy J. Williams 

USDA/ARS Researcher 
Agronomy Hall 
Iowa State University 
Ames IA 50014 

Phone: 515 294 9233 
Fax:   515 294 3163