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RE: _Giganoto_ is no speedster (was RE: T rex brooding)




        -----Original Message-----
        From:   Thomas R. Holtz, Jr. [SMTP:th81@umail.umd.edu]
        Sent:   Friday, August 21, 1998 7:38 AM
        To:     qilongia@yahoo.com
        Cc:     dinosaur@usc.edu
        Subject:        _Giganoto_ is no speedster (was RE: T rex brooding)

        At 08:49 PM 8/20/98 -0700, Jamie wrote:

        ><The estimates I have read and/or heard is that the Giganotosaurus
was
        >longer & perhaps heavier than a Tyrannosaurus Rex, but not as tall
or
        >muscular. Does that match the Mount in Philadelphia?>
        >
        >  Longer, perhaps. Longer skull, definately. Taller, perhaps, but
more
        >muscular? Perhaps not. *Tyrannosaurus* definatelty had a stronger,
        >more bulky neck, even thighs and tail, while *Giganotosaurus* was a
        >slender, speedier fellow.

        Speedier?  Not likely!!

        _Gig._ has very robust, short, stocky legs whose proportions track
        allometrically with other typical theropods (most ceratosaurs, basal
        tetanurines, carnosaurs, and most coelurosaurs).

        _Tyrannosaurus_ has long, slender legs whose proportions track with
the
        ornithomimosaurs, troodontids, caenagnathids, etc.  On top of that,
they
        have a certain unusual adaptation of the metatarsus, which some
functional
        morphometric and biomechanical work (me, 1995, JVP 14:480-519) seems
to
        indicate is related to enhanced cursorial ability.

        Also, in _Tyrannosaurus_ (as in coelurosaurs in general), the
caudofemoralis
        probably terminates closer to the pelvis than in more primitive
theropods,
        so the anterior portion of the tail might have been "bulkier" than
in
        _Giganotosaurus_, but the posterior part of the tail would probably
be more
        slender (less muscled).

        [As an aside for artists and others: PLEASE be VERY VERY cautious
when
        restoring proportions of the limbs and tail in _Tyrannosaurus rex_.
The
        AMNH mount and those derived from it (such as the ANSP mount) have
some
        major errors: the legs are from a larger, more robust individual
than the
        rest of the skeleton, the foot is restored far to short and far to
broad
        (and lacking the true structure of tyrannosaurid feet), the tail of
the
        mount still uses _Allosaurus_ based vertebral and chevron "falsies"
(when
        perfectly good examples of real tyrannosaurid caudals and chevron
are to be
        found on the _Gorgosaurus_ models on the wall), etc.]

        >A slash & run attacker, unlike the Super Rex
        >(or at least, I presume not).

        I seriously doubt running is much of an option for _Gig._, relative
to
        tyrannosaurids.  
        On the matter of slashing, however, I agree most whole heartedly, as
I will
        discuss in a lot more detail at SVP this year (the title of my talk
being
        "LARGE THEROPOD COMPARATIVE CRANIAL FUNCTION: A NEW "TWIST" FOR
TYRANNOSAURS").

        Thomas R. Holtz, Jr.
        Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
        Dept. of Geology              Email:th81@umail.umd.edu
        University of Maryland        Phone:301-405-4084
        College Park, MD  20742       Fax:  301-314-9661

        That's pretty much the impression of Giganotosaurus I had from the
articles on this dinosaur.  Just from the physics of the design,
Tyrannosaurus Rex seems been better adapted for running.  Could
Giganotosaurus have been primarily an ambusher of prey?  It also seems that
from the descriptions I have read that the Giganotosaurus skull (while
indeed LONGER than the Tyrannosaurus skull), may not have been as
biomechanically powerful.  Is this correct?

        Dwight