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Re: Fixing dinosaurian carnivour question



At 02:44 PM 5/27/99 -0400, Dinogeorge@aol.com wrote:
>Taxonomists seem to overlook the fact that once clade A is defined, and clade 
>B within clade A is defined, one can unambiguously define a taxon A-B by 
>subtracting (removing) clade B from clade A. This is what cladists are forced 
>to do when they talk and write--informally, of course--of "non-avian 
>dinosaurs."

Glad to hear I am not entirely alone :-)

>Mammalia (which = class Mammalia). There is no subjectivity in such 
>paraphyletic definitions except as concerns which clade to subtract from 
>which and how the taxa thus formed should be ranked;

And on top of that Peter Ashlock and his students have developed a
mathematical method for determining an optimal choice of which clade to
subtract, based on information theory.  [The method also helps *rank* the
resulting taxa].

>Where cladistic taxonomists and I really part company is over the idea that 
>taxa must >only< be clades. This arbitrary rule, along with differentiating 
>stem-based and node-based definitions, results in a truly unnecessary 
>proliferation of taxonomic names ("dinosauromorpha," "eudinosauria," 
>"eusaurischia," etc., etc.),

I also feel that the cladistic approach tends to change taxon memberships
too easily when cladograms are reanalyzed.

--------------
May the peace of God be with you.         sarima@ix.netcom.com