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Re: Deinocheirus



        Lord almighty, not *another* _Deinocheirus_ posting...
At 11:51 PM 1/29/98 -0800, Jaime Headden wrote:
>>>The scapula and coracoid point at the [oviraptorosaurs], [...]

>In that the scapula is anteriorly flanged, both dorsally and ventrally. 
>This is true, also, of ornithomimosaurs.
        If you are referring to the acromial process and the flange for the
glenoid, these appear to be both minimally present in _Deinonychus_,
_Megalosaurus_, _Allosaurus_, and possibly several other tetanurans outside
the groups you mention. Therefore, in absence of a comprehensive analysis,
this is a synapomorphy of a larger group, and cannot be used to unite these
taxa.

>The scapulocora- coid is pentagonal in general shape,
        This is certainly a peculiar way to phrase this. The distinctive
shape of the plesiomorphic avethropod coracoid, with its short posterior
process superimposed on a roughly lunate shape, might indeed look
pentagonal. However, this is plesiomorphic, occuring as it does in
_Allosaurus_, most basal coeulrosaurs, and even perhaps (based on photos of
a mount where the bones may be reconstructed) in _Piatnitzkysaurus_.

>with a sharp dorsal sutural prominence;
        Without better illustrations at my disposal, I am unable to address
this. It may constitute a genuine derived condition. On the other hand, it
appears to be true of _Compsognathus_, and so may represent an ancestral
character state.

>the glenoid joint is also processed post- and pre- in both groups. The
        This appears to be true of other tetanurans as well, including
_Megalosaurus_, _Allosaurus_, _Deinonychus_, etc., and thus is likely an
ancestral character state.
 
>coracoid deeply juts down like a finger on all three forms, giving an 
>interesting synapomorphy that no other theropod enjoys.
        Hmm? If you are referring to the posterior process of the coracoid,
this is a synapomorphy of Avertheropoda (last time I checked), and exists in
numerous other theropods (apparently including birds). Indeed, from the
illustration in Lessem's _Dinosaur Encyclopedia_, this process is not all
that well developed in _Deinocheirus_, although this may be due to the
perspective of the drawing. Apart from the condition in _Struthiomimus_, the
ornithomimid coracoid seems rather typical for a maniraptorform theropod.

>Now, sister-taxa characters are the scapulocoracoid (above) forelimb 
>structure,
        Hmm... equivocal, IMHO.

>femur,
        You're doing it again... "Point[ing] out a few characters without
describing them too far (or not at all)"

>and pelvis (degrees from *Gallimimus*).
        Huh?        

>Metriacanthosauridae ~
>*Metriacanthosaurus* + *Yangchuanosaurus*, their common ancestor, and 
>all descendants thereof, minus sister group Allosauridae.

        Word to the wise: nevernevernever add more than one inclusive anchor
taxon (anchor taxon: the taxa you use to define the group, eg. yang, metria
and Allosauridae (and by commutation, its anchors _Allosaurus_ and
_Acrocanthosaurus_), in this case) in a stem-based definition. You are
assuming that the tree topology you currently see will hold up to continued
research. If it does not, your taxon could end up meaningless or paraphyletic.
        Recall: Allosauridae = { +_Allosaurus_, +_Acrocanthosaurus_}
        By your definition, if the tree topology read (_Metriacanthosaurus_,
(_Acrocanthosaurus_, (_Allosaurus_, _Yangchuanosaurus_)))), what would your
taxon be? You have the clade containing all four, MINUS the clade formed by
anchor taxa allos and acrocanth. What does this mean? Are your included taxa
just yang. and metria. (paraphyletic)? Are all four included (despite your
definition)? Is the taxon just ignored as invalid? How do you resolve this?
        If you're making a stem-based taxon, IMHO you should use only one,
generic-level inclusive anchor (the taxon included in the taxon you're
defining), and do not use node-based taxa as anchors in the definition. For
node-based taxa, do not specify exclusive anchors (non-included taxa, eg:
"more closely related to inclusive anchor than to exclusive anchor").

>The pelvis of Yang and Metria are very similar,
        As I have written to this list many times, others have noted that
the pelvis of _Yangchuanosaurus shangyounensis_ was probably incorrectly
restored, and more properly looks like that of _Y. magnus_. Further, the
remainder of the pelvis is not all that similar. Thus, Gregory Paul's
original basis for proposing a close relationship between metria and yangy
is moot.
        As I have also written to this list, the outline of the ilium of
_Metriacanthosaurus_ is similar to that of _Neovenator_, perhaps suggesting
that the former taxon is an allosaurid.

>and Sin is more divergent, except for characters of the vertebrae, skull,
and >ischium;
        IMHO: the differences among sinraptorids (sensu the folks who coined
it, i.e. yangy and _Sinraptor_) may be ontogenetic.

>The supposed metriacanthosaur from China is considered very 
>similar to Metria, 
        You mean "_Szechuanosaurus_"? I believe Paul considered it so, on
the basis that it is similar to _Yangchuanosaurus_, which he felt was
similar to _Metriacanthosaurus_. A somewhat weak basis, in light of recent
evidence.

>I based my assumption of Paul's taxon because PDW is considered a 
>"paper" and viable reference for such work, is an officially recognized 
>work, and therefore valid.
        I love the book, but unfortunately it is 10 years out of date. A lot
has happened, and while it is a testament to PDW that it is still a valuable
work, some of the ideas you are concerned with have changed, or may change
soon. Just so you know...

>Metriacanthosauridae holds priority, but as 
>you said, is based on slim-pickin's [...] Metriacanthosauridae is valid.
        I would say it has no claim on anything, at this point.

>Curve of the humerus compared between *Deinocheirus* and *Harpy- mimus* 
>(in the strongest curve I've seen in the Ornithomimosauria) and 
>*Oviraptor* are all similar, and even close to *Anserimimus*;
     Perhaps, but in the gross features and shape of the humeri are different.

>shortened ulna compared to humerus,
        Interesting...

>and metacarpals very strong,
        In oviraptorsaurs? Maybe in _Ingenia_... How do you define "strong"?

>the claws similarly curved and "knobbed."
        Actually, the manual claws of ornithomimids and therizinosaurs are
rather derived with respect to other theropods.

[I wrote]
>>"long arms"). However, allometry, changes in proportions during 
>>ontogeny due to differential growth, can really mess with ratios. 
        Yes Dickie, there are other types of allometry, but I'm trying to
keep it simple here...
[back to the main programme]

>Even comparing the arms to 
>therizinosaurs, we come to the same conclusion in length, so one can 
>safely assume that, if my ratios are not exact, they are pretty close to 
>the truth and very useful as estimates.
        Perhaps, but I wouldn't go around trying to use them to prove
anything. See Holtz 1994b on hindlimb ratios in the arctometatarsaliam pes.

        Wagner
----------------------------------------------------------------------------
    Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
     "If I were landing thrusters, which button would I be?" - L. Molari