Re: A sure sign you're launching an unscientific discussion (was Re: Taxonomic philosophy)

["Jerry D. Harris" <dinogami@hotmail.com>]

Ken Kinman wrote (and Tracy Ford posed similar sentiments):

>     Well, I suspect this is the first time on this list that there has 
> been
> a serious discussion of whether Aves should be given Class status (correct
> me if I am wrong).

...and Chris Brochu responded quite well, but never summarily stated the 
heart of this issue, which is:  "What is a Class?"  That is, what features 
of a group make it a class?  What features make an Infraclass, or and Order, 
or a Phylum?  Is it number of members?  Clearly not, as others pointed out 
that, in Linnaean systematics, there are many "orders" (etc.) with only one 
member and others with thousands.  Essentially, it boils down to "degree of 
difference."  Well, if so, then we need to have explained the criteria by 
which those "degrees" are calculated.  As explained previously by many 
persons, character possession becomes problematic for this as new taxa with 
varying character possession are found.  Dr. Kinman (unless I am grossly 
misinterpreting him here) believes that "Class" can be applied to Aves, so I 
ask "why?"  What features of Aves make it a "Class?"  Why not an Infraclass, 
Order, Phylum, Subkingdom, or any other rank?  If you can argue that Aves 
deserves the rank of class, then we need to know what Aves has that makes 
them worthy of that one, but not other, ranks.  Following that, of course, 
we need to know precisely which taxa get put into Aves and which don't (as 
they do or do not possess whatever "degrees" of difference may exist to 
define the "Class" rank).

  This is why ranks are pointless and should be abandoned.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jerry D. Harris
Dept of Earth & Environmental Science
University of Pennsylvania
240 S 33rd St
Philadelphia PA  19104-6316
Phone: (215) 898-5630
Fax: (215) 898-0964
E-mail: jdharris@sas.upenn.edu
and     dinogami@hotmail.com
________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com