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

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

On Mon, 12 Jul 1999 Dinogeorge@aol.com wrote:

> This is merely a philosophical difference about the definition of "real." 
> Suppose we have a clade A and an included clade B. Use whatever criteria you 
> like to decide whether a species belongs to A or more specifically to B. The 
> same criteria will also tell you at once whether the species belongs to taxon 
> A-B. A-B is just as real as either A or B.

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.

In PT, however, every paraphyletic group is as easy to name as any other,
provided the clades used to define them are named and they exclude equal
numbers of clades. I find this much more useful. For example, you were
saying in one thread how much more useful it would be for "dinosaur" to
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. If we define Dinosauria as excluding
Aves, these groups become much harder to refer to, even though they are
equally as useful.

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