Re: Therizinosauria Cladogram

["T. Mike Keesey" <tmk@dinosauricon.com>]

On Fri, 11 Jan 2002, Jaime A. Headden wrote:

>   While true that one could argue that because the ICZN does not govern
> suprafamilial taxa, Segnosauria and Therizinosauria (which was used at
> part of the title and in vernacular in Maryanska, 1997, _the Complete
> Dinosaur_ as well as by Barsbold, 1997, _Encyclopedia of Dinosaurs_, but
> again) cannot truly be considered synonyms.

Which Barsbold chapter?

> In the suprafamiliar convention, taxa can be synonyms by content.

Not under the phylogenetic system. They must be defined before synonymy
(be it homodefinitional or heterodefinitional) can be determined.

> Therizinosauria Maryanska, 1997 has the same included content as
> conventional usage of Segnosauria,

As pointed out before, Segnosauria never explicitly included _Alxasaurus_,
TMK. Not to mention _Beipiaosaurus_, etc. (Of course, it never had a
chance to....) Even *if* it did, that's no guarantee that it is synonymous
with Clade(_Therizinosaurus_ <-- _Oviraptor_, _Ornithomimus_, _Troodon_).

> sensu Osmolska and Barsbold, 1990, and thus may be considered synonyms of
> one another. However, they can be defined separately. One can define
> Segnosauria as the stem, as was suggested before,

Once *could*, but since _Therizinosauria_ has already been used for
that, it would become a heterodefnitional synonym.

> and Therizinosauria as the node *Beipiaosaurus* + *Therizinosaurus*.

You could define Segnosauria as Clade(_Segnosaurus galbinensis_ +
_Beipiaosaurus_), if it were deemed useful to name that clade.

> However, the general usuage of Therizinosauria has been to supplant
> Segnosauria. In this case, Segnosauria is the senior name available
> for the group, both by history, eponym,

But not by definition! And definition is the only way to ascertain
synonymy under the phylogenetic system.

> and content

Not strictly speaking.

_____________________________________________________________________________
T. MICHAEL KEESEY
 The Dinosauricon        <http://dinosauricon.com>
  BloodySteak             <http://www.bloodysteak.com>
   personal                <keesey@bigfoot.com> --> <tmk@dinosauricon.com>
    Dinosauricon-related    <dinosaur@dinosauricon.com>
     AOL Instant Messenger   <Ric Blayze>
      ICQ                     <77314901>
       Yahoo! Messenger        <Mighty Odinn>