Re: Dino Birds (was Re: Dinosaur = extinct animal)

["T. Mike Keesey" <tkeese1@gl.umbc.edu>]

On Sun, 18 Jul 1999, Stanley Friesen wrote:

> At 11:47 AM 7/13/99 -0400, T. Mike Keesey wrote:
> >The problem with the traditional system is that once you recognize one
> >paraphyletic group, it rules out many others from ever being recognized --
> >others, which, by your criteria, are just as real. For example, if we
> >define Reptilia as (Amniota - Mammalia) - Aves, then we are incapable of
> >naming Amniota - Mammalia, or (Tetrapoda - Mammalia) - Aves, or any other
> >number a paraphyletic groups.
> 
> Yes, this is strictly true.  But, just as cladistic taxonomists choose to
> name only a subset of the clades in a cladogram, so in a hybrid system the
> taxonomist chooses which paraphyletic groups are sufficiently interesting
> to name.  The main criterion is utility.  The taxa which have the highest
> biological information content are the ones that are most worthy of
> recognition.

But naming a traditional paraphyletic taxon can exclude other taxa (para-
or monophyletic) from ever being recognized, whereas naming a phylogenetic
taxon never precludes the possibility of naming other clades. No
possibilities are ruled out. 
 
> You might want to look at my discussion of this issue in:
> http://www.crl.com/~sarima/dinosaurs/philosophy/infocontent.html
> and
> http://www.crl.com/~sarima/dinosaurs/philosophy/linnaean.html

I'll have a look.
 
> >mean "non-avian dinosaur". Yet I find that a lot of times when I go to say
> >"non-avian dinosaur", I really mean something else -- "non-neornithean
> >dinosaur", "non-avialan dinosaur", "non-paravian dinosaur",
> >"non-maniraptoran dinosaur", etc.
> 
> Well, as I would use the name Aves for what you call Avialae, I would use
> that definition anyhow.

This doesn't address the other terms. I find myself using "non-neornithean
dinosaurs" at least as much as I use "non-avian dinosaurs". Under
traditional taxonomy, one has to use the rather clumsy phrase
"non-neornithean avians and dinosaurs". "Non-maniraptoran dinosaurs" 
becomes "non-maniraptoran dinosaurs and avians", etc. You gain efficiency
for one, and only one, designation ("dinosaur" instead of "non-avian
dinosaur"), and lose it for a thousand others. 

--T. Michael Keesey
tkeese1@gl.umbc.edu | THE DINOSAURICON: http://dinosaur.umbc.edu/
AOL IM:   RicBlayze | WORLDS:    http://www.gl.umbc.edu/~tkeese1/