Austroraptor
Name:
Austroraptor
(Southern thief).
Phonetic: Aw-stro-rap-tor.
Named By: Novas, Pol, Canale, Porfiri
& Calvo - 2008.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Theropoda, Dromaeosauridae, Unenlagiinae.
Species: A. cabazai (type).
Diet: Carnivore.
Size: 5 meters long, skull 80 centimetres
long.
Known locations: Argentina, R�o Negro Province
- Allen Formation.
Time period: Campanian/Maastrichtian of the
Cretaceous.
Fossil representation: Partial skull including
fragmentary post cranial remains of the cervical and dorsal vertebrae,
fore and hind limb.
Although
not as large as the North American Utahraptor,
Austroraptor
is still
the largest dromaeosaurid
currently known from South America. However
to mark Austroraptor down for just this reason
would be doing the genus
a grave injustice as Austroraptor displays many
features that make it
unique among the other members of its group. First are the
proportionately small forearms, limbs that are usually well developed
in other dromaeosaurids so that they can get a better hold on prey as
they use their sickle claws to make a kill. The skull of
Austroraptor is also quite narrow and elongated
which indicates a
lack of developed biting muscles that in turn means a proportionately
weaker bite force. Finally the teeth are not laterally compressed or
serrated like other dromaeosaurids but conical and suited more for
holding prey.
It’s
plausible that Austroraptor may have been a
niche predator that
focused upon just one type of prey. The underdeveloped arms meant
that Austroraptor probably did not leap onto the
sides of large prey,
and as such it possibly hunted smaller animals. The describers of
the genus also compared the conical teeth as being similar to those of
spinosaurids, a group of specialised theropods widely thought to be
fish eaters. Include the weaker bite force into this mix and you have
a predator that is better adapted to small prey despite its larger
size.
It’s
also possible that Austroraptor may have
been more of a
scavenger, using its size to drive off smaller predators from their
kills while using its speed to avoid larger ones, but this does not
support the presence of specialised teeth. Conical teeth like these
are suited for holding small and possibly slippery prey like fish,
not tearing flesh from a carcass. Also just as spinosaurids used the
large claws on their hands to tear apart fish, Austroraptor
may have
used its sickle claws in a similar fashion. Although the sickle claws
are more associated with stabbing rather than slashing, they may well
have still been able to pull apart smaller animals so that the conical
teeth and weaker jaw muscles were not a hindrance.
If
the above is correct then hunting behaviour for Austroraptor
may
involve it using its speed to chase down small animals and using its
claws to stab into their backs. Austroraptor may
have also used its
claws to strike out at fish in shallow water where it could then pick
them out with its specialised teeth holding them firm in its mouth.
On shore it could then use its claws to pull the fish into bite sized
chunks for easier eating.
Further reading
- A bizarre Cretaceous theropod dinosaur from Patagonia and the
evolution of Gondwanan dromaeosaurids. - Proceedings of the Royal
Society B Biological Sciences 276: 1101–1007. - F. E. Novas, D. Pol,
J.I. Canale, J.D. Porfiri & J.O. Calvo - 2009.
- A new specimen of Austroraptor cabazai, Pol,
Canale, Porfiri and
Calvo, 2008 (Dinosauria, Theropoda, Unenlagiidae) from the latest
Cretaceous (Maastrichtian) of R�o Negro, Argentina. - Ameghiniana
49(4):662-667. - P. J. Currie & A. Paulina Carabajal - 2012.
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