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Re: Classification: A Definition



----- Original Message ----- From: "Mike Taylor" <mike@indexdata.com>
Sent: Wednesday, May 16, 2007 7:35 PM


No, no, _alpha_ taxonomy, the naming of species and genera.  Those we
will never get rid of.  Above that level I am broadly in agreement
that the ranks do more harm than good -- which should not particularly
suprising given that most of what little there is of my publishing
record is on rank-free phylogenetic nomenclature.

Well, this "species and genera" thing is much more complicated. For Mesozoic dinosaurs, as you have often mentioned, species and genera are almost always the same; if we'd give a genus name to every species and then suddenly decided to stop using species names, almost nothing would change (and this is something the PhyloCode allows). But we only need to go to extant mammals or frogs (not even to insects) to find genera with tons of subgenera, kilotons of species groups, and megatons of species, so to say. There, genera are large clades that are far from alpha-taxonomy.


I happen to think that species names are nonsense in fossil-poor extinct clades. Most species concepts (maybe all except the most boring morphological ones) require population biology. If we have a single specimen, or two or three, we can't even pretend approximating any kind of population biology. Talking about *Mantellisaurus* is useful, talking about *Mantellisaurus atherfieldensis* is nice to Atherfield but otherwise completely useless. Most Mesozoic dinosaur genera are LITUs; if we stop calling them genera and stop pretending we can apply any useful species concept to them, we don't lose anything.

For neontology, species are in most cases useful (as long as people are explicit about which species concept they use...), even though to varying degrees. Accordingly, the PhyloCode will not abolish species. (It will, however, allow you to name clades without naming or recognizing any species in them.) Neontological genera, on the other hand, are clades like any other; their only function as genera is in Linnaean binominals.

The buckets would still be arbitrary, dependent to a ludicrously
unstable degree on the taxon selection.  Throw another basal sauropod
in there and Neosauropoda is suddenly eleven nodes down from the root
instead of ten, and the hypothetical chapter-headings scheme in which
we use the level-ten nodes suddenly leaves with no Neosauropoda
chapter but with an unexciting
Node-uniting-Lourinhasaurus-with-Neosauroda chapter.  Picking an
arbitrary level is also a horrible way to go -- which is why
_Dinosauria_ 2nd ed. does what everyone sane would have expected it
to do, and uses chapter headings based on the "well-known" clades.

... but as soon as you've nominated some clades as more well-known
than others, you've done taxonomy.  We may as well admit it to
ourselves.  It's certainly true that PN requires us to do much _less_
taxonomy than previously, but it doesn't eliminate it.

Hm... well. The differences are that such a book doesn't expect that anyone should follow its selection of which clades are important enough to get a separate chapter, and that it doesn't pretend that the clades -- or paraphyletic groups -- treated in each chapter are somehow on some same level or otherwise comparable.


BTW, there is a book whose table of contents is a tree. It's a German neontological book about vertebrate diversity and anatomy.

> > I truly don't know.  It certainly is awfully hard to resist them
> > tempatation to write things like "... and so representatives of at
> > least four sauropod families are known from the Wealden".  And
> > changing that to "at least four clades" only makes things worse.

No, it doesn't make things any worse than they already are (as you mentioned earlier in the same post). It only makes them more visible. It takes the disinformation away.


> "Representatives of the sauropod clades <clade name> <cited
> definer> <date>, .... are known from the Wealden" strikes me as
> much more useful.  Even the angiosperm worker knows what they've
> got and where to look up the definitions.

That works. It gets cumbersome pretty quickly, though.

Why? Chances are you wouldn't have stopped at "at least four sauropod families are known from the Wealden" but have listed them in the same sentence. So, in sum, PN saves space. :-)