RE: Defending grades (Was: Re: Archaeopteryx (rant))

[grossber <grossber@grinnell.edu>]

I have to agree, in principle, with my good friend Mike, but disagree with the 
suggestion that aves should not be a distinct class from reptiles.

While ancestral reptiles are also ancestral to aves, we should maintain this 
distinction.  Why?  Because by placing them in the clade of reptiles, we would 
have to do the same for mammals, and place reptiles under amphibians, etc.  It 
would go ad infinitum.  At a certain point, we must acknowledge things as a 
seperate clade, even at the family or genus level.  (Personally, I consider 
dinosauria as a distinct class.)

Classification is intended to ease our understanding of a species' origins.  
One can note that aves evolved from reptiles, while still maintaining them as 
a separate class.

We are imposing human constructs on nature.  There is no right or wrong.  
While classification is arbitrary, the standards have purpose.  Even without 
reconstructing the lineage, we often reclassify things.  Libraries do the same 
thing with books.  There is nothing wrong with this.

-Daniel Grossberg