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Re: Lumping Spinosauridae Redux



> Date: Fri, 17 Sep 2004 22:38:47 -0700 (PDT)
> From: "Jaime A. Headden" <qilongia@yahoo.com>
>
> If *tenerensis* and *walkeri* are sister groups, as seems to be
> supported by virtually everyone who's worked on the fossils, then
> why does *Suchomimus* have to be lost? Does the nature of the name
> *Suchomimus* mean something else than *tenerensis* or can we treat
> *Suchomimus tenerensis* as the WHOLE name for the single animal from
> the Tenéré, and not have to worry about generic separation and the
> meaning of species versus genera?

_Uh_-oh.

Can open.  Worms everywhere.

> Any discussion?

Here's my take on this.  To define any kind of higher group, in these
enlightened days, we need at least two specifiers: either two ingroups
(for a node) or an ingroup and an outgroup (for a stem).  (Here I am
ignoring apomorphy-based clades, and quite right, too.)  The magic of
the "genus" (and the "species", which is arguably no less illusory for
fossil animals) is that you're allowed to define it on only one
specifier.  (Actually, you don't have to define it at all, but if you
do, you only need one specifier.)  For example:

* Species _Baryonyx walkeri_ = specimen BMNH R9951 and all other
  individuals that are pretty damned similar to it.

* Genus _Baryonyx_ = specimen BMNH R9951 and all other individuals
  that are quite similar to it but not necessarily _that_ similar.

* Clade Baryonychinae = (_Baryonyx_ > _Spinosaurus_)

Given these definitions, you can find morphological evidence that the
type of _Suchomimus tenerensis_ belongs in Baryonychinae, but how
could you possibly have "evidence" that it either does or doesn't fit
into _Baryonyx_ or _Baryonyx walkeri_?

This is all very terrible from a mathematical precision perspective,
but it does turn out to be terribly convenient.

        "It's pretty much whatever a good taxonomist says it is."
                -- John Ostrom's definition of "species".

Or a maybe even more apposite quotation:

        "I don't have any solution but I certainly admire the problem."
                -- Ashleigh Brilliant.

In what will have to stand in the place of a conclusion, systematics
may be science, but taxonomy remains an art.  Good luck reaching a
coherent position on this.  Even better luck in trying to get anyone
to agree with you :-)

 _/|_    _______________________________________________________________
/o ) \/  Mike Taylor  <mike@indexdata.com>  http://www.miketaylor.org.uk
)_v__/\  Remember that "ministry" means "service": if what you do in
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