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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 meant,
"all valid type species considered at the time the clade name is defined
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 thing
in some circumstances and ... a species can be considered a clade,
comprised of internal specifiers (as a stem including the type specimen),
or a crown, or a node (of all individuals), or even a stem-defined node
(all individuals of the given type that share a relationship that does not
include, say, the type of another species).

<If _Suchomimus_ = genus(_tenerensis_), _Baryonyx_ = genus(_walkeri_), and
_tenerensis_ = _walkeri_, then it follows that _Suchomimus_ = _Baryonyx_.>

  This would only be true, in my opinion, if one could determine that
*tenerensis* = *walkeri,* which I contend is not likely to be absolutely
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 genera
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 defined
by a species that is defined by a specimen, then the genus can be thought
to be essentially tied to the specimen, and the species is an intermediate
"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 type
specimens of species that are defined by mutually excluding one another,
and thus as species defined by mutually excluding one another. Their
definitions as offered do NOT permit synonymy at the "genus" level, so
*Suchomimus* will never be a synonym of *Baryonyx.*

  Cheers,

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making 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 around us rather than zoom by it.

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


                
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