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Giant theropods: News reports do not equal Science!!!



Geeze, what a way to start the week... :-S

Okay, here are the various scoops:
In almost every single case mentioned, the specimens in question have NOT
been described in details, the precise landmarks used to take the
measurements are NOT available, and so we cannot trust them yet.  Horner
says one of the new specimens he collected last summer (which has not been
described and likely will not be described in detail for years!) is 10%
bigger than Sue, but the particular bone and measurement used to make this
calculation are not avialable.  I suspect Jack is probably right, but let's
wait and see, shall we?  Same goes for the newer specimens of _Spinosaurus_
and the new Currie & Coria carcharodontosaurid.

Rigby's rex:
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAaaaaaaaaaaaaaaaaaaaaaaarrrrrrrrrrrrrrrrrrrrg
ggggggggggggggggggggggggggggggggggghhhhhhhhhhhhhhhhhhhhhhh!!!
(But Tom, tell them what you really feel... :-).
For general information, see the many previous posts on the list.  At
present, there is  nothing else new in the literature.  According to the
Notre Dame article Rigby claims that the tail structure is different from
_T. rex_.  I am quite interested in this, but highly skeptical, as THE
ACTUAL TAIL OF _TYRANNOSAURUS REX_ HAS NEVER BEEN DESCRIBED IN DETAIL IN THE
LITERATURE and THE AMNH MOUNT (from which almost all other _T. rex_ tails
are based) IS DEMONSTRABLY WRONG!!  Haruumph!!  Okay, maybe Rigby has gone
to the FMNH to compare it to Sue, or has made a long and detailed study
comparing it to the real specimens of other tyrannosaurids in collections of
various museums around the world (not the mounts, but the real specimens).
Could be.  I am not willing to bet on it. As for the pubes, let's hear
exactly how it differs from all other known _T. rex_ pubes (not just
different from ONE other, but ALL others).

As for the Minden Monster: 150% bigger than _Allosaurus fragilis_.  Okay,
but WHICH _Allosaurus fragilis_?  The best described specimen (on display at
the Smithsonian) is not a very big individual: there are plenty at least
half again as large.  And yet it is the Smithsonian specimen against which
most other taxa are measured (e.g., _Deltadromeus_ and _Afrovenator_, when
both of those were first published).  Percentage comparisons of this sort
are not useful unless accompanied by some actual measurement (femoral length
in cm, for instance).

Okay, so where do we stand in terms of giant theropods?  As Josh Smith has
pointed out, sample size is very important (and extremely limited) in this
situation, and we really don't have anything like a reasonable sample size
for any of these.

At present, _Giganotosaurus_ seems to be clearly larger than _Tyrannosaurus
rex_.  In absolute terms the two specimens of _Giganotosaurus_ are
apparently larger than any _Tyrannosaurus rex_ specimens for which actual
measurements are available (for instance, the femoral length of Sue is
something like 1380 mm, that of the type of _Gig._ is 1440 mm, and the
dentary fragment of the second is 61 cm from the anteriormost point to the
15th tooth position: comparison with the type indicates that this is 8%
larger from the same homologous positions.

_Carcharodontosaurus_ is smaller than _Giganotosaurus_, and seems to be no
larger than the largest specimens of _T. rex_.

_Spinosaurus_ is huge: the specimens described by Stromer were well within
the top end of the size range of _T. rex_ as currently known, and the
rumored 8 ft long skull (which I have seen pictures of, but I cannot
honestly say its dimensions without some reliable sources...) indicates that
it got larger than any known _T. rex_ OR _Giganotosaurus_.

_Acrocanthosaurus_ was very large, but not as big as the biggest _T. rex_.
Estimated femoral length of NCSM 14345 is 1280 mm and of SMU 74646 is 1090
mm.  The giant Morrison allosaurid (_Allosaurus maximus_ or _Saurophaganax
maximus_ or _Epantarius amplexus_ or whatever you want to call it) has a
femur measuring 1135 mm.

Hope this proves useful.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796