Message 2004-10-0147: Re: Lumping Spinosauridae Redux

Tue, 21 Sep 2004 15:06:49 -0700 (PDT)

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Date: Tue, 21 Sep 2004 15:06:49 -0700 (PDT)
From: [unknown]
Subject: Re: Lumping Spinosauridae Redux

Mike Keesey ( wrote:

<At what time? Sorry, I still don't follow.>

  I was hoping my allusion to crowns would have simplified this. I me=
"all valid type species considered at the time the clade name is defi=
and described..."

  ... but then it follows who considered valid what....

<No, _Suchomimus_ would be a clade and _walkeri_ a species. Different
types of taxa.>

  As described below and elsewhere, these mean essentially the same t=
in some circumstances and ... a species can be considered a clade,
comprised of internal specifiers (as a stem including the type specim=
or a crown, or a node (of all individuals), or even a stem-defined no=
(all individuals of the given type that share a relationship that doe=
s not
include, say, the type of another species).

<If _Suchomimus_ =3D genus(_tenerensis_), _Baryonyx_ =3D genus(_walke=
ri_), and
_tenerensis_ =3D _walkeri_, then it follows that _Suchomimus_ =3D _Ba=

  This would only be true, in my opinion, if one could determine that
*tenerensis* =3D *walkeri,* which I contend is not likely to be absol=
provable. Whatever their synapomorphies, their differences may be
considered "specifically" separatable, given one worker or another.

<But the provisional definitions rests on species, not on specimens. =
think that's what you're missing.>

  I think I get that. The species are defined on specimens, and the g=
are defined on their type species. If one treats this as a continuum,=
every named genus as a clade, then all further internal bifurcations =
lineages are also clades. One may also assume that if a genus is defi=
by a species that is defined by a specimen, then the genus can be tho=
to be essentially tied to the specimen, and the species is an interme=
"clade" or organism, or category. If a "genus" clade can be anchored =
on a
species, and it is found that the specimens of two relatively close
species would be sister-taxa (or synonyms), they are each still the t=
specimens of species that are defined by mutually excluding one anoth=
and thus as species defined by mutually excluding one another. Their
definitions as offered do NOT permit synonymy at the "genus" level, s=
*Suchomimus* will never be a synonym of *Baryonyx.*


Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to mak=
ing leaps in the face of adversity, that a simple skip is so hard to =
do.  We should all learn to walk soft, walk small, see the world arou=
nd us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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