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Re: Quo vadis, T. rex? [long]



On Thu, 8 Feb 1996, Jeffrey Martz wrote:

> 
> > This is really a fairly pointless argument, as the presence or absence of 
> > feathers in one dinosaur or another changes their relationships not a 
> > bit.  Our best knowledge to date is that birds are dinosaurs, and whether 
> > or not other dinosaurs had feathers or not is irrelevant.
> 
>      We've haven't been arguing about the phylogenetic relationships of 
> dinosaurs and birds.  We've been tallking about whether birds derived  
> enough in regard to physiology, metabolism, and lifestyle to warrent being 
> called something different.  When you get right down to it, its a totally 
> subjective argument and theres probably not much more we can do with it. 

But do you see where I'm coming from?  The way I see it, birds *can't* be 
"derived enough" to "warrant being called something different", just as 
neither I nor any of my descendants can ever not be a mammal and a 
primate.  A bird can't change itself enough to erase who its ancestors 
were, or what its closest relatives are.  

In my book, the purpose of 
taxonomy is to illustrate what is related to what.  You can't do that if 
you go around ripping groups out of their proper places in the tree of 
life and pretending that they've become something else.  

It's less extreme but similar to saying that there are two divisions of 
life on earth:  Me and Not Me.  It's obvious that I'm just one of 
the six or so billion human beings on this planet, and also quite 
obvious that I am a hominid, an anthropoid, a primate, an archontan, a 
mammal, a therapsid, a theropsid, an amniote, a tetrapod, etc.

If you don't like the sound of "birds are dinosaurs," pick another name.  
I came up with the class Ornithopsida.  Then you can say, "Birds are 
ornithopsids, as are many extinct animals called 'dinosaurs' in 
colloquial parlance."  The usefulness of the bird/non-avian dinosaur (or 
ornithopsid) dichotomy, however, seems to me only very slightly less 
un-useful than the opposition between Me and Not Me.

In fact, I've come up with several amniote class names, all monophyletic, 
their names based on the Greek name for their living representatives:

Class Theropsida (mammals, non-mammalian therapsids, pelycosaurs)
Class Mesosauria (it had to be that way, based on the position of the 
   mesosaurs in the family tree of the Amniota)
Class Chelonopsida (turtles, procolophons, pareiasaurs, and other anapsids)
Diapsida
   (basal members)
   Class Sauropsida (lizards, snakes, plesiosaurs and kin, ?ichthyosaurs)
 Archosauromorpha
   (basal members)  
   Class Crocodylopsida (crocs, "thecodonts" closer to crocs than birds)
   Class Ornithopsida (pterosaurs, lagosuchians, dinosaurs)

This system is consistent, and it is concise.  Anyone is free to use it.

> LN Jeff
> 

Nick Pharris
Pacific Lutheran University
Tacoma, WA 98447
(206)535-8204
PharriNJ@PLU.edu

"If you can't convince them, confuse them." -- Harry S. Truman