ORNITHOMIMID THERIZINOSAURS

["Matthew Troutman" <m_troutman@hotmail.com>]

<<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.>>

Actually, I think that Pete decided that therizinosaurs are 
bullatosaurian ornithomimid relatives, a position that I hold to, as 
well as Sereno, but not oviraptorosaurs.  Currently, in the published 
material (I'm sure there are still pros who disagree) the widely 
accepted placement for therizinosaurs lies near or within the 
Oviraptorosauria (Oviraptoroidea of Jamie Headden).  The most recent, 
thorough analysis of this idea was Sues' 1997 _JVP_ 17:4 description of 
_Chirostenotes_.  However, I think that the analysis was very flawed 
because of its poor coding, retention of function-related characters, 
and characters that are found in few members of a taxon.  (The analysis 
also found Dromaeosauridae and Troodontidae sister-groups, something 
that I think makes the cladogram suspect).  Sues also said that 
therizinosaurs and oviraptorosaurs share many features of the palate 
(Elzanowski in press) most notably the shift of the ectopterygoid 
lateral to the palatine.  Plus, the medial elongation of the 
ectopterygoid and the short quadrate ramus of the pterygoid.  Until 
Elzanowski's work is published (the characters given by Sues sound like 
they are related to function, much like the similiarities between the 
quadrate of oviraptorids and birds, and the "neognathus" palate of 
hesperornithiforms) , I still stick by the position that therizinosaurs 
are ornithomimid relatives based mainly on the braincase features (the 
inflated parabasiphenoid for one). 

Matt Troutman

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