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Therizinosaur systematics (was Re: Dinosaur Web Pages' Re-Opening)



George wrote (many times... this is why Mickey wanted us all to wait before
responding):

<< The lower jaw of _Erlicosaurus-[...]
>The two mandibles are completely different.[...]
        And the teeth in them.  So what does te jaw say about the
relationship with prosaropods?

<< >(4) Segnosaurs (= therizinosaurs) are not theropods.
         Therizinosaurs (= segnosaurs). >>
>Segnosauria as a higher-order taxon has priority over "Therizinosauria" or
>any of its incarnations.
        I am not aware of Segnosauria having been defined, at least not
phylogenetically. Therizinosauroidea is defined as = { + _Alxasaurus_, +
_Therizinosauridae_ }, and takes priority over undefined taxa.

>In my analysis, the characters of the feet outweighed the characters of the
>manus, so the manus is homoplastic. No a priori here.
        So now the manus isn't so different?
        I would then call into question your a priori weighting of these
characters, and whatever the rest of your analysis consists of.  Your
dataset?  Your methods? It sounds to me like there has been some manual
cladistics going on here...

It's not just "my" Phytodinosauria; it's Bakker's Phytodinosauria, as well as
the slightly earlier Michael Cooper's Ornithischiformes.
        Bakker's Phytodinosauria did not stand up to "Gauthier's" Saurischia.

>And--just note also how >similar< the rest of the segnosaur skeleton is to
>that of ornithomimids and _Mononykus_. Why, the feet are virtually identical,
        In case anybody out there thinks George is responding to something I
said, note that I never claimed that therizinosaurs shared a more recent
common ancestor with the taxa George mentions above than with any other
major coelurosaur group.

>differing only in such minor features as toe count,
        In many analyses, this is a reversal.

>metatarsal conformation,
        Therizinosaurs show the shortening of MT II of most coelurosaurs,
and their metatarsus is not all that different from that of some
oviraptorsaurs, barring the extra toe.

>and tarsal count!
        Oh, do tell?  I cannot recall any tarsals data...

>As are the pelves,
        As I pointed out, they share several pelvic characters with
oviraptorsaurs.

>the forelimbs,
        Again, oviraptorsaurs.

>Indeed, we might characterize a "dinosaur cladist" as an individual
>who cannot distinguish a segnosaur from an ornithomimid.
        We might then define a "hand cladist" as someone who can't tell a
theropod from a prosauropod.

        "But like a poor marksman, you keep missing the target..."
+--------------------------------------------------------------------------+
| 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             |
+--------------------------------------------------------------------------+