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THERIZINOSAUROIDEA



James Close wrote:
 <<Does Segnosauria still reside in Theropoda? and Is feet the only
 qualifier for being a Theropod?>>

The current opinion of most workers is that Segnosauria, or Therizinosauroidea
does fall within the Theropoda.  There are a few quite vocal oponents to this
idea, most noticibly George Olshevsky and Tracy Ford.  To date, no cladistic
analysis has shown that therizinosaurs do NOT fall within Theropoda.

The position of Olshevsky and others is that therizinosaurs are
"transitionals" between prosauropods and ornithischians, ie, the outgroup to
all known ornithischians.  This was first put forth by Greg Paul in 1984.
Since then, Greg has changed his mind, though has not published.

I do not wish to have this become a debate between George, Tracy, Jon
(Wagner), and I.  The arguments are very well summed up and argued out in the
archives.  Any post with the words 'therizinosaur' or 'segnosaur' or anything
of the like is likely to have arguments about this.
 
Jaime Headden wrote in response to James Close' original quarry: 
 <<However, many characters of the skull and postctrania (except the foot) are
 similar to ornithomimosaurs and oviraptorosaurs, a position I've found
 best advocated by Peter Buchholtz. >>

First thing, my last name is spelled Buchholz, no T.  A very common mistake
however, especially among paleo-folk because Emily Buchholtz DOES spell her
name that way.  Jon Wagner still apparently thinks my name is spelled with a T
:-)

But back to what I was saying...  As I have stated previously I believe the
most parsimonious position for therizinosaurs is as the sister group to all
known ornithomimosaurs, but within the Ornithomimosauria sensu stricto.  This
is due to many features of the skull and teeth making them bullatosaurs, and a
few jaw features that link them with ornithomimosaurs.  Again, these arguments
are all summed up best in my previous posts to the list, as well as the posts
of others, and I really am not too keen on rehashing them.

Regarding Jaime's statement:
<<similar to ornithomimosaurs and oviraptorosaurs, a position I've found
 best advocated by Peter Buchholtz.>>

I had previously spoken to Jaime privately about the posibility that perhaps
oviraptors and therizinosaurs were sister groups within the Ornithomimosauria.
There are a lot of weird features of the basal ornithomimosaur that suggest
that perhaps this thing is really a therizinosaur or outside of the Th + Or
clade, or maybe closer to Oviraptors.

This is something that needs A LOT more work, and is only idle speculation on
my part.  Hopefully Harpymimus "there is enough material to write a monograph,
but we decided on a 2 1/2 page paper" okladnikovi will get redescribed and
help sort out some of its features.

Peter Buchholz
Tetanurae@aol.com