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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_.
Pacific Lutheran University
Tacoma, WA 98447
"If you can't convince them, confuse them." -- Harry S Truman