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Re: T. efremovi



------NOTE: If you reply to this post, please send a copy to me
directly------

Nice to see citation of some of the more progressive literature on
systematics!

HP Pickering wrote:
> clades are node-, stem-, or apomorphy-based names, with a "specifier"
being a
> taxon utilized in the definition of a clade name and to which that clade
name
> is formally linked. [...] it is premature to recognize a converted
> species name other than bataar, although it is probable other species
thrived
> (stratigraphic positions, geographic locations, etc., need to be
explicated).

Thought I'd clarify something, as far as I might be able to...

As of right now, the draft PhyloCode does not cover the definition or
conversion of species names. In fact, as far as I know, a concrete proposal
regarding exactly *how* species names should be defined has yet to
materialize. I am aware of rumblings from the PhyloCode advisory board
regarding "agreements" to the effect that species names should be explicitly
associated with a diagnosis, but the actual DEFINITION process apparently
has not been worked out. This will probably be hairy, as there are about as
many different takes on what a species is as there are scientists (I mean in
the philosophical sense, not even getting as nitpicky as "species concepts"
of the general literature).

As far as defining species goes, node-, stem-, and apomorphy-based
definitions refer to clades. It would certainly be appropriate to use one or
more of these definitions if you feel that species must be some form of
clade of organisms. If, however, you subscribe to the concept elucidated by
de Quieroz in the paper HP Pickering mentioned, a species is by no means
necessarily monophyletic, and such a definitional format would not be
appropriate.

> On the basis of
 > the existing specimens, Tarbosaurus cannot be separated from
Tyrannosaurus
> (nor, for that matter, should Daspletosaurus be separate from
Tyrannosaurus).
 > Species recognition: these should be considered segments of a
  > population-level lineage

Tyrannosaurus, Tarbosaurus and Daspletosaurus are, of course, genera not
species. Whether or not they can be separated is a matter of personal/
professional opinion, and isn't really something you can test or refute
(unless you have George's famous Generometer [tm]). As long as you accept
"floating point" (to use HP Brochu's apt phrase) definitions/ diagnoses, you
can alter the particulars of these taxa until they remain separate so long
as the type species are believed to be distinct. If we were to, say, define
these genera phylogenetically (and ruin everyone's fun), then we could
determine whether or not they are separate, nested, or not separable (i.e.
synonymous) in the context of a particular phylogeny using their
definitions. I am everyone knows how to do this by now, thanks to the
tireless efforts of HP Holtz.

As for whether these species are actually members of the same LINEAGE...
There are two popular uses of the term "lineage." Many systematists use the
word "lineage" casually to refer to a clade (often with the connotation of a
stem-based definition/  sister-group relationship), e.g. the "mammal
lineage" vs. the "reptile lineage" in amniote phylogeny. This is a quick way
of relating a somewhat verbally cumbersome concept to a diverse audience. De
Quieroz (in his species papers) explicitly uses 'lineage" to refer to a
particular chain of ancestor-descendant individuals (cells, organisms,
species). This is most emphatically not a clade, it amounts to tracing
backward with your pencil from a terminal taxon to the basal node on a
cladogram. The only way species can be members of the same lineage in this
sense is if all of them are either ancestors or descendants of all the
others.

So, if you were using the first meaning of lineage, and you meant to say
that the species included in Daspletosaurus, Tarbosaurus and Tyrannosaurus
form an group exclusive of all other known species, then I think your point
is reasonable. However, if you were using de Quieroz's meaning of lineage,
and you meant that Daspletosaurus torosus, Tarbosaurus efremovi and
Tyrannosaurus rex form an ancestor-descendant series, I suspect that many
listmembers will take exception to this.

Hope this helps,

Wagner