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Re: Anything new on Deinocheirus



Larry Akins
>I'm just wondering are there any other Therizinosaurs other than 
>Therizinosaurus, and possibly Deinocheirus?

OK, here we go:
1) To my knowledge, at present no further material of _Deinocheirus_ has
been described. It's just a pectoral girdle and forelimb taxon at this point.

2) _Deinocheirus mirificus_ has been placed in the Ornithomimisauria (or
whatever was passing for it at the time) by several authors. Metacarpal I is
similar in length to MC II, a character state seen in ornithomimids (and
not, as previously believed, in _Compsognathus_, see the new
_Sinosauropteryx paper). As pointed out by Norman in _The Dinosauria_, other
authors have enumerated several points where the taxon does not conform to
the ornithomimid mold. However, most of these differences appear
plesiomorphic or autapomorphic.

3) At first (very cursory) glance, I can see no reason to suggest that
_Deinocheirus_ is a therizinosauroid. Certainly, large size, large arms
whathaveyou, is a poor basis for any sort of taxonomic assignment or
phylogenetic evaluation. If anyone can come up with better characters, they
would be of great interest.
        Y'know, in the old days, they'd just call it a megalosaur and move
on to more important matters. You could also see a movie for a quarter...
Everybody: "Mister we could use a man like Herbert Hoover again/... Those
were the daaaaaaays")

4) Therizinosauroidea was defined by Russel and Dong (1993) [ as = {+
_Alxasaurus_, + _Therizinosauridae} for whatever that's worth] based on
their _Alxasaurus_ material. They made a very convincing case for the
inclusion of "segnosaurs" in Therizinosauridae. I do not have their paper
immediately handy, but I think Therizinosauroidea was believed to include:
        _Alxasaurus_
        _"Chilantaisaurus" zheziangensis_
        _Enigmosaurus_
        _Erlicosaurus_
        _Nanshiungusaurus_
        _Segnosaurus_
        _Therizinosaurus_

        Recent work by Holtz (SVP 1996?) suggested that _Microvenator_ was
more closely related to therizinosaursoids than to oviraptorsaurs. Were a
stem-based Segnosauria to be defined [minimal definition = {+ _Segnosaurus_,
- _Oviraptor_}], this might make it a "segnosaur", but not a therizinosauroid.

        Wagner

P.S. For all you Phylogenetic Taxonomy fans out there who think I am a bit
too radical in suggesting multiple anchor taxa (at least exclusive anchors
for stem-based taxa), check out Seus' (1997) half-PT, half Linnean
definition of Caenagnathidae!
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    Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
        "Why does the universe hate me?" - G'Kar