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Re: Genetics and Morphology Collide



Chip Pretzman (02/09/96; 3:53p) cited this quotation from Nature, v. 379, 
Jan. 25, 1996:

>"...morphological 'synapomorphies'previously used to cluster rodents and 
>lagomorphs into Glires, may actually represent symplesiomorphies or 
>homoplasies that are of no phylogenetic value."

Then added his comments (partial):

>Perhaps there is an unexpected mix of character
>states that may be the root of confusion as to the exact relationships
>between dinos and birds and reptiles and mammals.

Of course, there is always the danger that synapomorphies used in 
constructing cladograms actually do not have phylogenetic significance.  
Perhaps that explains the mix of character states in theropods that force 
us to the conclusion that several significant character reversals 
occurred beginning with the second node beyond maniraptora (node 12 of 
Holtz, 1994), and force us to conclude that tyrannosaurs and ornithomimes 
have degenerate semi-lunate carpals.

Don't get me wrong, either (heaven forbid!).  The tremendous predictive 
value of cladistics must be clear to everyone.  It is to me.  But what 
are we predicting?  It gives us answers, but are they the right answers?  
Perhaps the pendulum needs to swing back a little.  Over-reliance on that 
one technique may result in "over-confusion."


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Norman R. King                                       tel:  (812) 464-1794
Department of Geosciences                            fax:  (812) 464-1960
University of Southern Indiana
8600 University Blvd.
Evansville, IN 47712                      e-mail:  nking.ucs@smtp.usi.edu