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

Metriacanthosauridae revisited

        Several weeks ago we had a to do on this list about the taxonomy of
the Sinraptoridae, specifically, does Paul's Metriacanthosaurinae have
priority.  Having leafed through _Dinosaurs from China_ a few times, I
think I can safely say that I doubt Paul's referral of Yangchuanosaurus as
"Szechuanosaurus" to Metriacanthosaurus.
        Although it is true that Yangchuanosaurus' ischium is more
backswept than is illustrated in _The Dinosauria_, and the iliac blades of
Y. houyanshanenis [sic?], Y. magnus (and this really *does* look like an
adult Y. houyanshanensis!), and "S". campi all are somewhat more angular
than they are illustrated as in that volume, I really cannot see the same
shape as Metriacanthosaurus.  Metriacanthosaurus does not appear to have an
ischial boot, although that area may be broken off, and the pubic boot
(identified with a "?" in _The Dinosauria_) is more like Gasosaurus than
like any allosauroid.  Although it too is broken off, it does at least
appear to have a rostal portion, which "Szechuanosaurus" lacks.  I am going
to assume that the femoral similarities cited (but not elaborated upon) by
Paul are symplesiomorphic (er... primitive).
        My latest cladogram has Metriacanthosaurus as a basal spinosauroid,
although personally I think it's on crack.  I do not believe that there is
sufficient evidence at this point to refer Metriacanthosaurus to any group,
there is no evidence to support the subsumation of Sinraptoridae into
Metriacanthosauridae, and there is no evidence to support synonymizing
Yangchuanosaurus and Metriacanthosaurus, nor for referring the
"Szechuanosaurus" specimen (Paul makes a good case for not including it in
Szechuanosaurus...) to that genus.  You could make an argument, I suppose,
for synonymizing Szechuanosaurus and Yangchuanosaurus, since Szech's ilium
(the only difference which leaps out at me) looks a lot like Y. magnus'
(possibly indicating that it is a mature specimen of a smaller species).
        This makes a Paul-style taxonomy look like:
                        Yangchuanosaurus houyanshanensis
                        Yangchuanosaurus sp.
                        Sinraptor ? (I still haven't got the CJES yet!)


P.S.  The Shanshanosaurus pictures in _Dinosaurs from China_ do indeed look
alot like Aublysondon, especially Lehman and Carpenter's new specimen.  The
only difference I can tell off hand is that Shanshan's pubic boot is shaped
like the nosegear of an x-wing fighter (ventral surface of the rostral
projection angled antero-dorsally to form a flange above the level of the
boot), while Aublysodon cf. A. mirandus (Lehman and Carpenter, 1990) has a
more T. rex-like boot.