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Re: ADV: Re: Classification: A Definition



On Tue, May 22, 2007 at 11:19:24PM +0100, Mike Taylor scripsit:
> Graydon writes:
[snippage; I ask what the harm is in defining "Brachiosaurus" as "FMNH P
25017"]
>  > > I see where you're coming from, but do you really want to take
>  > > away the ability of field-workers in Utah to say "we've found a
>  > > new Brachiosaurus specimen"?
>  > 
>  > Well, in practise, isn't what they're really saying much closer to
>  > "we've found something, and based on the parts of it that are
>  > sticking out of the rocks and various not-too-severely-weathered
>  > indicators and the general cut of its jib, we think it's least
>  > dissimilar to Brachiosaurus"?
> 
> Ye-es.

And considering various "boy was our initial guess off the mark" things
that happen -- Sue the Tyrannosaur's evidence of face-biting, say --
it's not going to do any harm to get into the habit of saying "we think
it's like a Brachiosaurus, but ask us again when we've got the bones
prepared".

>  > If your hypothetical Utah field-workers get their specimen out of
>  > the ground, prepared, and coded, they have a testable affinity to
>  > Brachiosaurus, provided there is some sort of consensus about
>  > "doesn't code differently enough".
>  > 
>  > And you must admit achieving that consensus would provide *years*
>  > of entertainment for all concerned [...]
> 
> :-)

Well, yeah, but also probably a worthy exercise -- the effort to produce
testable, sharable cladograms has certainly done more good than harm,
and as computer power increases/becomes less expensive, there are more
and better statistical methods to apply.  (Some of which would be
presently almost practical for the number of specimens available in a
"we think this is all the same unit of selection" specimen group, even
if not practical for a big "neosauropoda" tree.)

>  > [...] especially as the named specimen groups hit fifteen or fifty
>  > individual specimens and some enterprising soul took more capable
>  > mathematics and measuring devices to the group to see how well it
>  > held up.
> 
> Well, isn't that pretty much what Kathy Forster did with
> _Triceratops_?  I've not read this paper, but IIRC, she used
> morphometric clumping to show that the Triceratops specimens fell
> neatly out into two species, rather than the four, ten or one that had
> been previously suggested.

That's my recollection as well.

In a case like that, under the proposed "name = specimen list" scheme,
you'd see a paper designating two names, each with attached specimen
lists.  Presumably there would be rules for name priority, and maybe
even the same ones, because the thing that would change in that scheme
is what gets a name, rather how names are conserved.

> Wow.  Just imagine having enough specimens to do that kind of thing!

As a general trend, over time, people do find more. :)

Eventually, measurement gets better, too.  It's by no means
inconceivable that, soon enough, it will be possible to stuff all the
bones of a sauropod skeleton through a measuring device able to model
the whole bone -- inside and out -- on a sub-millimetre grid, and to
give the resulting bone-models to a computer to do statistics on.

Given that, it's not impossible for half a femur to become diagnostic.

-- Graydon