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Date: Tue, 21 Sep 2004 15:06:49 -0700 (PDT)
From: [unknown]
To: dinosaur@usc.edu, phylocode@ouvaxa.cats.ohiou.edu
Cc: mightyodinn@yahoo.com
Subject: Re: Lumping Spinosauridae Redux
Mike Keesey (mightyodinn@yahoo.com) wrote: <At what time? Sorry, I still don't follow.> I was hoping my allusion to crowns would have simplified this. I me= ant, "all valid type species considered at the time the clade name is defi= ned 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= hing in some circumstances and ... a species can be considered a clade, comprised of internal specifiers (as a stem including the type specim= en), or a crown, or a node (of all individuals), or even a stem-defined no= de (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= ryonyx_.> 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= utely 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. = I think that's what you're missing.> I think I get that. The species are defined on specimens, and the g= enera are defined on their type species. If one treats this as a continuum,= and every named genus as a clade, then all further internal bifurcations = or lineages are also clades. One may also assume that if a genus is defi= ned by a species that is defined by a specimen, then the genus can be tho= ught to be essentially tied to the specimen, and the species is an interme= diate "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= ype specimens of species that are defined by mutually excluding one anoth= er, and thus as species defined by mutually excluding one another. Their definitions as offered do NOT permit synonymy at the "genus" level, s= o *Suchomimus* will never be a synonym of *Baryonyx.* Cheers, =3D=3D=3D=3D=3D 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) =09=09 _______________________________ Do you Yahoo!? Declare Yourself - Register online to vote today! http://vote.yahoo.com