[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

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



On Thu, 8 Feb 1996 Dinogeorge@aol.com wrote:

> In a message dated 96-02-08 21:37:19 EST, pharrinj@PLU.edu (Nicholas J.
> Pharris) writes:
> 
> >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.  
> 
> When a paraphyletic taxon is created, this acknowledges that at least one
> descendant group includes organisms morphologically or in some other
> significant way very different  from the parent group. Nobody is saying that
> the excised group is _unrelated_ to the parent group...just that the group is
> significantly different.

Difference doesn't matter to me.  What matters to me (and, I imagine, to 
many other taxonomists in various fields) is relationships.  I know from 
personal experience that many young potential scientists take their first 
phylogenetic lessons from phylogeny.  They want to know what's related to 
what, not what some scientist thinks is "different enough to merit a 
different name".  Phylogeny should, if AT ALL possible, be easily 
reconstructible from taxonomy.

> >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.  
> 
> This is not the only purpose of taxonomy. We also group similar organisms as
> a form of shorthand when discussing their common features and properties.

It is just as important to discuss the common features and properties of 
birds as a whole and their closest dinosaurian relatives (theropods, 
tetanurans, coelurosaurs, maniraptorans).

> Nobody's ripping the groups out of their proper places in the tree of life!
> Systematists just put boxes of various kinds and names around the branches,
> is all. The branches remain intact. Sometimes it makes sense to name the
> branches, other times it makes sense to name different portions of the tree.

I'm sorry, but I fail to see where it is useful to put one branch around 
practically the whole tree and put another around a small (in terms of 
morphological disparity) branch buried in the middle of the tree.

Dinosaurs were a big, variegated bush, only one branch of which has 
happened to survive to this day.  It doesn't become a different bush 
simply by virtue of that fact.

I repeat:  It makes no sense and is of no use to classify _Deinonychus_, 
_Triceratops_, and _Apatosaurus_ in one group and exclude the birds, when 
_Deinonychus_ is far more like any given bird than it is like 
_Apatosaurus_ or _Triceratops_.

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