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Re: Classification: A Definition



On Tue, May 22, 2007 at 07:13:30PM +0200, Andreas Johansson scripsit:
> On 5/22/07, Graydon <oak@uniserve.com> wrote:
> >On Fri, May 18, 2007 at 10:53:56PM +0100, Mike Taylor scripsit:
> >> Species or genus -- doesn't matter which, we need one of them.
> >
> >Why?
> >
> >We need a label that people can remember and say for a specimen or a
> >group of specimens.  We don't need to attach a meaning beyond "this
> >non-empty list of specimens" to the label, though.  I think it could be
> >argued that in paleontology one *should not* go beyond that, because
> >there isn't enough information to do it.
> 
> When you say a list, do you mean a literal list, or a potential one? I
> mean, it may be possible and worthwhile to list every brachiosaur
> specimen, perhaps every dinosaur one, but it certainly won't when we
> get to fossil bivalves or diatoms.

Both, actually.

For dinosaurs, or any other rare and potentially detailed fossils, it
makes sense to code up your new specimen, go look at the literature, and
either say "this codes indistinguishably from <name> (and comes from a
stratigraphically comparable horizon, etc.) so it's a <name>, and
belongs in <name>'s specimen group", or "this doesn't code like anything
with an existing name, so we're calling it <new name>, formally cited as
<new name>, <publication>, <specimen number>".

So that gives a literal list, but I don't think an *obligation* of a
literal list; there shouldn't be any reason you can't publish on your
caudal series and say "codes with <name>, but we don't think that's
grounds to make it part of <name>'s list or to give it a name".

For common/numerous fossils  -- bivalves, diatoms, pollen, leaves, etc.
-- that doesn't make sense, but it's still important to be able to tell
them apart. (Especially if they're used as index fossils!)

In that case, you would do your analysis, and presumably publish
something of the form "these specimens code indistinguishably from
<name> and this is not surprising" (which doesn't extend <name>'s formal
specimen list), "these specimens code indistinguishably from <name> and
that's surprising, so we add them to <name>'s formal specimen list (or
declare serious convergence)", or "these specimens don't code with
anything named, so we will call them <new name>, cite, etc."

There's always the "we can't code this meaningfully" case, too, where
the conclusion is "this isn't a useful specimen", rather than reference
to a specimen group.

This sort of scheme assumes that there's some quantified way of telling
the fossils of interest apart, and that might not always be true, but in
those cases I don't think any scheme is going to work very well.

-- Graydon