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Tyrannotaxonomy [was Re: Nomenclature]



T. Mike Keesey wrote:
>Tyrannosauroidea being tyrannosaurids plus a few
>possible relatives (_Itemirus_, _Siamotyrannus_, _Stokesosaurus_, and
>others have been proposed).
        Although I realize that this is not phrased as a definition, I feel
the need to point out that we should all be very wary of including some of
these poorly known taxa in definitions.
        While many people far more knowledgable than I consider the
braincase to be very helpful in phylogenetic reconstruction, especially
given its purported "conservative" nature, we should be very wary of any
conclusions drawn from only a braincase. Thus passeth _Itemerus_.
        I understand the reasoning behind the assignment of braincases to
_Stokesosaurus_, and I will not argue the point at this time. However, we
should be aware that the type material of that genus is *not* the braincase,
and the "tyrannosaurish" characters of the type material are by no means
certain. 
        As for _Siamotyrannus_, my personal opinion is that the thing
couldn't look more "kindatyrannosaur" (but what do I know?). Still,
including such animals in a definition might not be all that good. After
all, it could really just be a giant ur-bullatosaur, who knows? Still, of
the three options given, this is the animal I feel by far the most confident
assigning to a clade of animals more closely related to "t-saurs" than any
other coelurosaur group.
        Which brings me to my point. The best means of tackling an "ordinal"
"tyrannosauresque" taxon is a stem-based definition, with _Troodon_
(=_Stenonychosaurus_), _Ornithomimus_, _Oviraptor_ and _Deinonychus_ as
exclusive outgroups. This avoid the difficulty of having to sort out who we
might want to include.
----------------------------------------------------------
(Dino)George Olshevsky wrote:
>I created the group Tyrannosauria in my 1995 article for Gakken for
>(essentially--since I didn't define it cladistically) all coelurians more
>closely related to _Tyrannosaurus_ than to bullatosaurs.
        Excellent... except that it isn't wise to use a node-based taxon as
an exclusive anchor. What happens if the correct topology is
(_Ornithomimius_, (_Tyrannosaurus_, _Troodon_))? Unpleasantness abounds.

>This would encompass such groups and genera as shanshanosaurines, [...]
>and perhaps even _Stokesosaurus_ and _Compsognathus_ 
        Applause for your caution on the former, confusion on the latter.
Knowing you, George, I hardly think the latter suggestion is based only upon
the putative presence of two digits in the manus of that taxon. However, if
this is the case, you may wish to review the big Nature (or was it
Science...) _Sinosauropteryx_ paper, in which they suggest that mcI of
_Compsognathus_ is in fact missing, and pxI-1 has been misinterpreted as a
metcarpal. Thus, compies would have a regular three-digit manus (as
evidenced by the Chinese (and the Italian?) taxon).
----------------------------------------------------------
Tim Williams wrote:
>_Shanshanosaurus_, I've heard, could just be a juvenile _Tarbosaurus_ 
>- the original reconstruction needs a little work.
        I'll say, at least for the one in The Dinosauria... it only takes a
beer for it to start looking like a spinosaur. On the other hand, it takes a
beer to look at a spinosaur anyway...

>_Tonouchisaurus_ - has this thing been described?
        And what the heck is it? Have I had my head in hadrosaurs for too long?

        Wagner
----------------------------------------------------------------------------
    Jonathan R. Wagner, Dept. of Geosciences, TTU, Lubbock, TX 79409-1053
"Only those whose life is short can... believe that love is forever"-Lorien