[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Spinosaurus



Dinogeorge wrote:
>I would keep them in different genera but agree that they belong in the same
>family (Sinraptoridae, as far as I'm concerned, along with _Sinraptor_,
>Piatnitzkysaurus_, _Metriacanthosaurus_, and _Yangchuanosaurus_, among

        _Piatnitzkysaurus_ does not share several derived characters with
your "sinraptors" in general, including the loss of the ischial lamella and
the presence of an obturator process (not illustrated for yangchuan, but I
find myself wondering about the illustrations of this animal's pelvis more
and more...).  Piatz has a melange of features, some of which may be
unrecognized symplesiomorphies for the Tetanurae (IMHO), which have lead
people to believe that it is an abelisaur (Currie?  Pharris?), an
allosaur/carnosaur (Molnar et al.), and even a megalosaur (moi).  I
currently favor Holtz's 1996 analysis (mostly because it is backed by data,
but also because it makes some sense) that this animal is a basal tetanuran.
Perhaps it belongs to an as-yet unidentified early radiation.
        Metria could certainly be a sinraptor, or it could be a half-dozen
other things.  As I posted earler this year, Paul's (PDW) statement about
the similarity of the ilia of metria and yangchuan does not appear to hold
up on examination of photographs of both genera.  Incidentally, I have yet
to see an illustration of the pelves of these animals which agrees with the
photos.  In any case, it shows a hip form very similar to _Stokesosaurus_,
which has been claimed to be a tyrannosaur, based (IMHO) on the relatively
weak evidence of a braincase (I believe) referred based on size.
        As an aside, let's stop suspecting things are tyrannosaurs basd on
that darned ascending process on the ilium.  This feature has been
illustrated for _Tyrannosaurus_, _Piatnitzkysaurus_, and even
_Megalosaurus_.  It seems to be a widely distributed character.  IMHO, it
may mark the division between fore and aft segments of illac musculature.

>others; _B._ and _A._ were the most-derived-known members). The centra of

        There is a good body of published evidence that suggests that
_Acrocanthosaurus_ forms a clade with _Giganotosaurus_ and
_Carcharodontosaurus_, as George is no doubt aware.  Currie is rumored to
believe that acro is not closely related to these others, but no one has
said whether he has suggested that they do not form a monophyletic group or
not (since he seems to use traditional taxonomy, I cannot be sure if he is
referring to morphological distance or phylogeny).
        In any case, I should like to hear your reasons for this referral.

Tim Williams wrote:
>_M._'s ilium has a rather
>unusual shape for a sinraptorid.  (And wouldn't this also give the
>name Metriacanthosauridae priority over Sinraptoridae??).

        Yes, but the real question is not whether the ilium looks different,
it is whether the ilium looks more similar to some other animal.  The answer
to this is _Stokesosaurus_, IMHO (gettin' a lot of MHO today...).  Now you
just have to figure out where *that* genus fits in, or whether there are
other characters which preclude a close relationship.

>I'd also
>put _Szechuanosaurus_ (_S. campi_, not _S. zigongensis_) and probably
>also _Marshosaurus_ (which has a very sinraptorid-like maxilla) in the
>Sinraptoridae.

        Almost certainly "S." campi!
        Marsho?  Doesn't it have an abelisaur-like premax?  Also, this
taxon's pelvis is very interesting...

        Wagner
+--------------------------------------------------------------------------+
| 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             |
+--------------------------------------------------------------------------+