Giganotosaurus
Name: Giganotosaurus
(Giant southern lizard)
Phonetic: Gee-gah-note-oh-sore-us.
Named By: Rodolfo Coria & Leonardo
Salgado -1995.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Theropoda, Carcharodontosauridae, Giganotosaurinae.
Species: G. carolinii
(type).
Type: Carnivore.
Size: Estimated between 12 and 13 meters
long.
Known locations: Argentina - Candeleros Formation.
Time period: Cenomanian of the Cretaceous.
Fossil representation: The first specimen was almost
three quarters complete, and this included the skull and much of the
post cranial skeleton. A second specimen of just the left dentary has
also been found.
Giganotosaurus
made headlines around the world when it was discovered simply for the
fact that it was a carnivorous dinosaur that was bigger than Tyrannosaurus.
Although the current estimate of Giganotosaurus
has it approaching a
length of thirteen meters, analysis of a dentary from a second
individual suggests that it could grow even bigger.
It’s
is not known exactly how Giganotosaurus grew so
large as to find out
you would need multiple specimens representing different life stages,
and right now these specimens are just not known. Tyrannosaur
remains by contrast are very numerous and consistently show that they
lived the
first few years of their lives growing relatively slowly. After
several years they would suddenly start a rapid rate of growth reaching
almost full size within the space of around ten years, slowing only
when they reached reproductive maturity.
It
must be remembered that Giganotosaurus was not a
member of the
tyrannosaurids but of a separate group of theropods, the
carcharodontosaurids. But for the sake of speculation, if
Giganotosaurus underwent a similar growth cycle,
it would either had
to of been an even more extreme rate of growth, or lived for even
longer than the tyrannosaurids, or maybe even a combination of the
two.
The
fenestrae are proportionately large in the skull of Giganotosaurus,
presumably to reduce the overall weight of its massive skull,
currently the largest amongst the known theropods. Inside the skull
are the usual areas and attachments for powerful biting muscles but
also for a potentially well-developed olfactory region, indicating a
good sense of smell.
The
teeth of Giganotosaurus are flat and serrated to
enable it to easily
slice through the flesh of its prey. These kinds of teeth are
commonly seen in the carcharodontosaurids,
which is why the group is
sometimes called 'shark toothed lizards'. This has led to the
proposed hunting strategy of Giganotosaurus
targeting the large South
American titanosaurs
such as Argentinosaurus.
Whereas some carnivores
could easily crunch through the bones of their prey, the bones of
Argentinosaurus are simply too large. Even a large
theropod would
have trouble just getting its mouth around a femur. So instead,
Giganotosaurus adapted to leave the bones and
concentrate on just the
softer tissue. A series of withering bites could in theory be applied
to the legs and underside by just raking its teeth across the flesh.
Then all Giganotosaurus would have to do is wait
for either blood loss
or infection to finish the job. It's also possible that Giganotosaurus
targeted the leg muscles to try and sever a tendon, cutting the muscle
free from the bone. This would cripple a large titanosaur so that it
had
absolutley no chance of escape.
One
Giganotosaurus probably would not have been able to
tackle a large
individual of Argentinosaurus and may have focused
its attention upon
younger and smaller members. However another dinosaur named
Mapusaurus
was found not too far away from the Giganotosaurus
remains,
and raised eyebrows at the time because not one but seven individuals
were found together. This has led to some speculating that Mapusaurus
could have attacked the larger sauropods as a group,
significantly
increasing their chances of success. It cannot be said if such
behaviour was true for Giganotosaurus, but Mapusaurus
was very
similar to it, and was discovered not too far away. Further
discoveries may yield more clues to the diet and hunting strategy.
Further reading
- A new giant carnivorous dinosaur from the Cretaceous of Patagonia. -
Nature 377: 225-226 - R. Coria & L. Salgado. - 1995.
- New specimen of Giganotosaurus carolinii (Coria
& Salgado,
1995), supports it as the largest theropod ever found - Gaia, 15:
117–122 - J. O. Calvo & R. A. Coria - 1998.
- Braincase of Giganotosaurus carolinii
(Dinosauria: Theropoda) from
the Upper Cretaceous of Argentina. - Journal of Vertebrate
Paleontology, 22(4): 802-811. - R. A. Coria & P. J. Currie -
2002.
- My theropod is bigger than yours...or not: estimating body size from
skull length in theropods - Journal of Vertebrate Paleontology 27 (1):
108–115 - F. Therrien & D. M. Henderson - 2007.
- Cranial endocast of the carcharodontosaurid theropod Giganotosaurus
carolinii Coria & Salgado, 1995 - Neues Jahrbuch fuer
Geologie
& Palaeontologie, Abhandlungen 258(2): 249-256 - A. P.
Carabajal & J.I. Canale - 2010.
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