Gorgosaurus
Name: Gorgosaurus
(Fierce lizard)
Phonetic: Gor-go-sore-us.
Named By: Lawrence Lambe - 1914.
Synonyms: Albertosaurus libratus ,
Deinodon
libratus, Gorgosaurus sternbergi, Deinodon sternbergi,
Albertosaurus sternbergi.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Theropoda, Tyrannosauroidea, Tyrannosauridae,
Albertosaurinae.
Species: G. libratus (type).
Type: Carnivore.
Size: 8 to 9 meters long.
Known locations: Canada, Alberta. Possibly the
US state of Montana.
Time period: Campanian of the Cretaceous
Fossil representation: Many specimens of
Gorgosaurus are known making it perhaps the best
represented
tyrannosaurid currently known. Skin impressions have also been found.
Gorgosaurus
had the same basic body plan of all tyrannosaurids with a large head on
an s-shaped neck, small arms and bipedal stance. With around sixty
teeth in its mouth (there is some variance between specimens)
Gorgosaurus shared a common trait with other
tyrannosaurids of its
size, as the larger the tyrannosaurids go the less teeth they have.
A
skin impression of Gorgosaurus discovered by Philip
J. Currie shows
that its skin lacked the large scales as often found in other
dinosaurs, giving it a smooth texture, not unlike the secondarily
featherless skin of birds. This also lends further support to the
theory that the larger dinosaurs did not have feathers on the grounds
that larger bodied animals naturally lost less heat because of the
smaller surface area to body volume ratio.
As
with other tyrannosaurids, Gorgosaurus went
through an initial stage
of slow growth when young before suddenly shooting up to adult size
within the space of a few years. Normally it is found that the femur
is the longest bone in the leg, but some specimens of young
Gorgosaurus show the tibia was the longer of the
two. This
arrangement of longer lower leg bones is seen in many fast running
animals and reinforces the theory that when young, Gorgosaurus
would
have focused its attention upon hunting fast moving prey such as
ornithomimids. When the growth spurt kicked in, the femur would
likely grow to be longer reducing the potential speed of Gorgosaurus,
although the longer stride of bigger legs may have compensated for
this in some part. This would also initiate a shift in hunting
patterns for larger prey such as hadrosaurs that would have been better
able to sustain a large predator. Two hunting patterns at different
life stages would also reduce competition between the adult and
juvenile members of the species.
Gorgosaurus
roamed North America at the same time as another tyrannosaurid,
Daspletosaurus.
Although both are approximately the same size as one
another, Gorgosaurus has a more gracile build to
that of the robust
Daspletosaurus. This has led to speculation that
the two may have
specialised in hunting different types of prey with Gorgosaurus
favouring the swifter dinosaurs such as hadrosaurs.
There
has been a lot of debate as to whether Gorgosaurus
deserves its own
genus on the basis that it is so similar to another member of the
tyrannosaurids,
Albertosaurus.
Being more gracile than other
tyrannosaurids, Both Gorgosaurus and Albertosaurus
appear much alike
and also have adult sizes similar to one another. Those in favour of
keeping these two dinosaurs separate point to subtle differences in the
bones of the two, particularly the skull bones that encase the
brain. Most of those involved though will concede that further study
needs to be done before any decision can be made.
Further reading
- On a new genus and species of carnivorous dinosaur from the Belly
River Formation of Alberta, with a description of the skull of
Stephanosaurus marginatus from the same horizon. -
The Ottawa
Naturalist 28:13-20. - Lawrence Lambe - 1914.
- On the fore-limb of a carnivorous dinosaur from the Belly River
Formation of Alberta, and a new genus of Ceratopsia from the same
horizon, with remarks on the integument of some Cretaceous herbivorous
dinosaurs. - Ottawa Naturalist 27: 129–135. - Lawrence Lambe
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