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Re: Fixing dinosaurian carnivour question



In a message dated 5/27/99 10:54:20 AM EST, tkeese1@gl.umbc.edu writes:

<< I have heard of some phylogenies under which Mammalia would fall inside
 this group, but if that were the case I think (I hope) Amniota would have
 precedence as the name for this clade, and Reptilia would be abandoned. >>

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." If mammals are found to nest within Reptilia, one could still 
define the >class< Reptilia as the >clade< Reptilia minus the >clade< 
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; but this kind of 
subjectivity is precisely the same as the kind that attends the naming of 
"important" clades versus not naming "unimportant" clades in a strictly 
cladistic taxonomy wherein all the taxa are clades (monophyletic) and 
ranking, if any, is done by inclusion.

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.), so that we ultimately wind up with more 
higher-level taxa than we have species to be classified: like having seven 
managers for five workers.