Segnosaurs vs. Therizinosaurs

["Jaime A. Headden" <qilongia@yahoo.com>]

  In this day and age, though not so prevalent as way back when, it was
fashionable to have your own little name for a group for whatever reason,
even had another applied a name first. Best example, *Griphosaurus*
instead of *Archaeopteryx* because there was no way it could be a bird
(and hence, applying the term "feather" which as we all knew then was a
hoax) was completely erroneous. Of course, we are in a much-enlightened
day and age, but still it is perpetrated that preferrence of names occurs
based on ideals of etymology, derivation, what the eponym _is_, etc., and
articles in the ICZN mandating usage of certain type names for type ranks.
No mind that more than half the scientific populace working on
phylogenetics do not regard ranks as anything more than the most arbitrary
of human constructs and absolutely un-informative. I know my opinion, you
know yours, let's leave it at that.

  However, this is prevalent in the use of the name Therizinosauria for a
group of fossils. Apparently, Russell, 1997 (I had previously cited
Barsbold, 1997, but was wrong, he wrote a separate set of articles for
that volume, so sorry to confuse you -- and yes, i'm still trying to get
past emails sorted out) used the term "therizinosaurs" and did not
explicitly formulate the definition relative to a taxon. The use of
"therizinosaurs" was used for both Therizinosauroidea and, presumably, for
Therizinosauria as well, and both by Russell. Okay, so let's say that the
name Therizinosauria can be "legally" defined by the usage. We have a case
of slapping a definition on a new name, where before one existed. The name
Segnosauridae was dropped to favor Therizinosauridae, but under ICZN
rules, this meant nothing for the use of Segnosauria. It was even
described by Perle & Barsbold (1980, 1983 vide Barsbold, 1983) as an
infraorder. Dismissing the first taxon to favor the second (in Russell's
formulation) is not permittable by convention or "legal" dictate of the
ICZN. In fact, the ICZN has no jurisdiction. The Phylocode will have a
jurisdiction only so far as definition is concerned ... but Segnosauria
has never been defined in a phylogenetic manner.

  However, conspicuous by its absence in Russell, 1997, is the word
"Therizinosauroidea." The statement used to define the group by content is
the same content used to define the node Therizinosauroidea. It does not
include *Beipiaosaurus*. Thus, they can be said to be homodefinitional
synonyms. That is, if the word Therizinosauria had been applied to this
definitions. My feeling is that this may have been a slip of the pen.
*shrug* Who knows.

  So what to do? Well, one can try to synonymize the two as homo-content
taxa, or one can try to define both *properly*. If the definition offered
by Russell applies, the taxon becomes the most inclusive
therizinosaur-only clade. Segnosauria can be formulated differently,
possibly as a node. My previous suggestion has been to use Segnosauria as
the stem, having been named first to exclude the group from other taxa in
the first place, even though it did not include *Therizinosaurus,* and
make Therizinosauria some node-based taxon, inclusive of *Therizinosaurus*
and *Beipiaosaurus*, etc.. Or one could just drop Therizinosauria as a
name without meaning and application, and synonymize it by content with
Therizinosauroidea.

  A reading of the literature shows that the name Therizinosauria was
first used in _The Encyclopedia of Dinosaurs_ was published in August,
1997; I had opportunity to recheck the data, having finally got back to
it. Maryanksa used the term "(therizinosaurs)" in almost the same sense as
did Russell; she also consistently used "segnosaurian" rather than
"segnosaur" and in this it can be shown top be a consistently used term
for the dinosaurs, despite the cropping-up of Therizinosauroidea, synonymy
of Segnosauridae under Therizinosauridae, and the apparently improper
coinage of Therizinosauria by Russell, used without justification.

  Make up your own minds. 

=====
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.

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