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Re: Mongolian dinosaur inspires religion in grad student



At 01:14 AM 9/29/96 -0400, Dinogeorge wrote:

>>         A DISTINCT "LIP" OR EXPANSION OF THE DORSAL MARGIN OF THE
>> ARTICULAR END OF THE MANUAL UNGUALS.
>
>Oh, puh-leeze! You of all people pushing one-character cladistics! And
>especially a trivial character like this!

        The reason it was religious was partially because it reaffirmed my
faith in the ability of cladistic analysis to make testable predictions
about phylogeny.  It did this, with bells on.  Several people have
independantly (and for two (Holtz and Sues) apparently without the
Alxasaurus material) suggested this relationship.  Cladistics?  The fossils
say "yes"!
        But no, I do not say this based on one character.  Right now, I am
convinced that Therizinosauroidea is within the Coelurosauria, and this one
character which it shares with a reasonably established clade,
Oviraptorsauria, solidifies a growing suspicion amongst many workers that
the latter clade includes the therizinosaurs.
        I base all this on many characters, a few of which please find
below.  Please note that this represents work in progress, and a
line-item-style attack of each one will certainly enlighten no one.  I do
welcome constructive comment.

1)  some braincase specifics I have been told about but know not
        the structure of the metatarsus (MT III and IV subequal and
        both longer than I, I code as two characters, I believe Tom
        Holtz codes as one.  Taken together, these are a synapomorphy
        uniting oviraptorsaurs and arctometatarsalians, excepting that
        there seems to be some reversal _within_ some families.)
2)  secondarily quadradactyl structure noted by Russell and Dong
3)  lunate carpal block (which I am assured is present, but which appears
        unfused, why, I am at a loss to say...)
4)  manual proportions (long fingers, long hand)
5)  ungual "lip" mentioned above
6)  loss of predentary teeth (sorry, it *is* a synapomorphy of Oviraptorsauria,
        except, perhaps, alvarezsaurs...)
7)  extreme tooth density (actually, the distribution of this character is
        somewhat odd.  It works if oviraptorsaurs are arctomets, or it
        is convergent, and synapomorphy of some Oviraptorsaurs (Monykus
        and Therizinosaurodea).
8)  ventrally convex dentary (questionable...)
9)  deep preacetabular process of the ilium
10) triangular obturator process of the ischium
11) deep mandibular symphysis (?)
12) (there may be some details concerning the proportions of the ilium...)
13) external nares elongate, horizontal, and positioned back from the snout
14) secondary reduction of the surrangular foramen?

        The preliminary results of analysis including some of these
characters gives a cladeogram something like this:
        (remember to use an equal-spaced font for the full 2D effect!)

                +-Dromaeosaurs    +-Tyrannosauroidea+Ornithomimoidea
        +-------+MANIRAPTORIFORMS |
        |       +-----------------+ARCTOMETATARSALI(=Bullatosauria(?))
        |                         |
--------+COELUROSAURIA            +-Troodontidae
        |
        |       +-Caegnathidae
        +-------+OVIRAPTORSAURIA
                |
                |  +-Elmisauridae
                +--+
                   |  +-Alvarezsauridae
                   +--+
                      +-Therizinosauroidea+Compsognathus

Personally, I believe that this is a little off, and that Dromaeosaurs
belong farther up-clade, but who knows.
        (NOTE:  The Bullatosauria synonomy is a problem.  They can never
*really* represent the same clade, but as presented here, they do...)

        (ALSO NOTE:  these views are my own, and should not be taken as
representing the opinion of any other worker.  They are based on incomplete
research and unpublised data.  If you are caught, I will disavow all
knowledge of this posting....)

        Wagner
+-------------******ONCE AGAIN, NOTE NEW E-MAIL ADRESS******---------------+
| Jonathan R. Wagner                    "You can clade if you want to,     |
| Department of Geosciences              You can leave your friends behind |
| Texas Tech University                  Because your friends don't clade  |
| Lubbock, TX 79409                               and if they don't clade, |
|       *** wagner@ttu.edu ***           Then they're no friends of mine." |
|           Web Page:  http://faraday.clas.virginia.edu/~jrw6f             |
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