Qianzhousaurus
Name:
Qianzhousaurus
(Ganzhou lizard).
Phonetic: Ke-an-su-sor-us.
Named By: J. Lu, L. Yi, and S. L.
Brusatte, L., Yang, H. Li, & L. Chen - 2014.
Classification: Chordata, Reptilia, Dinosauria,
Saurichia, Theropoda, Tyrannosauroidea, Tyrannosaurinae,
Alioramini.
Species: Q. sinensis (type).
Diet: Carnivore.
Size: Holotype skull roughly about 95
centimetres long. Total body size uncertain due to lack of remains,
but holotype individual roughly estimated to be about 6.3-7 meters
in length.
Known locations: China - Nanxiong Formation.
Time period: Maastrichtian of the Cretaceous.
Fossil representation: Almost complete skull with
left lower jaw. Nine cervical (neck) and first 3 dorsal
(back) vertebrae also known. Additional post cranial remains
attributed.
Qianzhousaurus
is a genus of medium sized tyrannosaurid
dinosaur that lived in China
during the late Cretaceous, and at the time of its description,
unlike any other tyrannosaur previously seen. Some Asian tyrannosaur
genera such as Alioramus
have been noted for having gracile builds and
proportionately slightly longer snouts than their larger cousins such
as Tarbosaurus
and Tyrannosaurus.
In Qianzhousaurus however the snout
is particularly long, so long in fact that Qianzhousaurus
quickly
assumed the nickname of ‘Pinocchio rex’.
Why
Qianzhousaurus developed such a specialised skull is
perhaps simply a
case of predatory specialisation. With Zhuchengtyrannus
and the
aforementioned Tarbosaurus Asia already had more
than one genus of
large tyrannosaur hunting on it and both of these genera display the
robust, shorter and deeper snouts more commonly associated with
tyrannosaurs. These skulls were evolved to house huge jaw closing
muscles as well as amplify the effects of them so that the larger
tyrannosaurs had crushing bites that could kill larger tougher prey
animals such as large hadrosaurs,
ceratopsians
and perhaps even
ankylosaurs.
Their specialisation however was of no practical benefit
for killing the smaller dinosaurs that if they could catch, they
would not need such a powerful bite force to kill. This meant that
there was a gap in the ecosystem, and this is where genera like
Qianzhousaurus came in.
As already stated Qianzhousaurus had a very long snout for a tyrannosaur, but the skull was also not very deep, and this all reduced space for the jaw closing muscles. By extension this meant that because the jaw closing muscles could not be as large, Qianzhousaurus would have nothing near the bite force of larger genera such as Tarbosaurus. This idea is also backed up by the teeth of Qianzhousaurus which were also proportionately smaller and not as deep rooted as the teeth of larger genera, which means that they were not being put under the same kinds of stress. However, just because the bite was weaker than a large tyrannosaur, it does not mean it was an evolutionary design weakness.
While
reconstructions of Qianzhousaurus are still
sketchy, we know by the
overall form of the known fossil remains that Qianzhousaurus
was also
lightly built, meaning that while Qianzhousaurus
were not as strong
as their larger relatives, they were faster and more agile than
them. This meant that they could more easily track down and hunt the
faster prey dinosaurs such as smaller ornithopods, ornithomimids
and
oviraptosaurs,
most of which would have been too fast for a large
tyrannosaur to bother with. Most predators ambush their prey,
bursting out from a hidden location to sprint after a prey animal,
and while Qianzhousaurus was faster than a large
tyrannosaur, it
would have still had to struggle to keep up with a medium sized
ornithomimid for any length of time. This is where a long snout comes
into play, Qianzhousaurus would not have to
overtake a prey animal,
just come close enough to reach it with is jaws. Overall in terms
of niche, tyrannosaurs like Qianzhousaurus would
have fallen in
between smaller predatory dinosaurs such as dromaeosaurs
and
troodonts,
and their larger tyrannosaur relatives.
Other
dinosaurs that Qianzhousaurus may have come into
contact with include
oviraptorids
like Banji,
Ganzhousaurus,
Nankangia,
Huanansaurus
and Jiangxisaurus,
therizinosaurs
like Nanshiungosaurus,
and the
sauropod
Gannansaurus.
Further reading
- A new clade of Asian Late Cretaceous long-snouted tyannosaurids.
- Nature Communications 1-10. - J. Lu, L. Yi, and S.
L. Brusatte, L., Yang, H. Li, & L. Chen -
2014.
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