Re: Therizinosauria Cladogram

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

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

>   Therizinosauria was coined in 1997 by Maryanska (as I recall, no one
> could find an earlier occurence of this name ... it is listed as "implied"
> by Maleev on the Dinosauricon, a function of taxonomy no longer favorable
> when cladistics is applied).

That note is by _Therizinosauroidea_, not _Therizinosauria_. I may not
include such "implied by" notes in the next version -- haven't decided.

> It was never cladistically defined by her.

No but it was defined in the _Encyclopedia of Dinosaurs_ (ed. Currie &
Padian, 1997) in the chapter "Therizinosauria" by Dale A. Russell. An
excerpt from pages 729-730:

"Therizinosaurs include six described genera (_Alxasaurus_,
_Enigmosaurus_, _Erlikosaurus_, _Nashiungosaurus_ [sic], _Segnosaurus_,
and _Therizinosaurus_) of bipedal theropods ... Therezinosaurs [sic] may
be described as the aforementioned taxa and all others closer to them than
to oviraptorosaurs, ornithomimids, and troodontids."

Could have been a bit better worded, maybe, but it's still a phylogenetic
definition. None exist for Segnosauria.

Filtered through the rules of the draft PhyloCode (in which specifiers
must be species or specimens, stem-based definitions may only have a
single internal specifier, and eponyms should be used as internal
specifiers), this would render:

_Therizinosauria_ = Clade(_Therizinosaurus cheloniformis_ <-- _Oviraptor
philoceratops_, _Ornithomimus velox_, _Troodon formosus_)

Which doesn't seem too bad at all to me.

> Meanwhile, a clade name with the same content was proposed back in 1980,
> Segnosauria.

Not the same -- lacking _Alxasaurus_ (which had not yet been discovered).
(Minor note: Wasn't it proposed as an Infraordo, not [necessarily] a
clade?)

> By content and origin, it is the "proper" name.

It's still available for a definition, but it cannot be synonymized
under the phylogenetic system without one.

It's similar to the _Mononykinae_/Parvicursorinae issue. Parvicursorinae
has precedence by naming (and in this case by ICZN rules), but it was
never explicitly defined. _Mononykinae_ was explicitly defined.
Traditionalists should use Subfamilia Parvicursorinae for some group
including _Parvicursor remotus_. Cladists, OTOH, should use _Mononykinae_
for Clade(_Mononykus olecranus _ + _Shuvuuia deserti_ + _Parvicursor
remotus_).

> Appropriateness of the use of a single taxon in all segnosaur suprageneric
> taxa as specifier is a bad reason to favor one name over another when
> clear precedence is available.

It's just icing on the cake.

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