Avimimus
Name: Avimimus
(bird mimic).
Phonetic: A-vee-mi-mus.
Named By: Sergei Kurzanov - 1981.
Classification: Chordata, Reptilia, Dinosauria,
Theropoda, Oviraptorosauria, Oviraptoridae, Elmisaurinae.
Species: A. portentosus (type),
A. nemegtensis.
Diet: Usually thought to be an omnivore or herbivore
though has been suggested to be an insectivore.
Size: 1.5 meters long.
Known locations: Mongolia - Nemegt Formation.
Time period: Campanian/Maastrichtian of the
Cretaceous.
Fossil representation: Numerous specimens.
Avimimus
acquired its name from its bird like characteristics that have led to
some controversy as to how much like a bird it really was. Like in
modern birds the hand bones were fused together, and the presence of
pronounced quill knobs on the lower arm bones confirms that Avimimus
did at least have feathers on this part of its body. The presence of
strongly developed feathers also suggests that Avimimus
possibly had a
lighter feather covering on other parts of its body similar to other
bird like dinosaurs. Sergei Kurzanov considered Avimimus to be
capable of limited flight and even be closer to birds than the classic
transitional fossil Archaeopteryx.
Today
however, palaeontologists
generally agree that Avimimus belongs in the
Elmisaurinae
group of
oviraptorids like Elmisaurus
and Chirostenotes,
and as such probably
could not fly but had feathers for insulation and quite possibly
display.
Like
with other oviraptorid
dinosaurs, the exact diet of Avimimus
has been
impossible to establish with certainty. This is because the mouth of
Avimimus is essentially a toothless beak that could
in theory be used
for a variety of different diets. The premaxillae (front portion of
the upper jaw) of Avimimus however does have a
series of projections
that give it small serrated edge, but again this is not conclusive of
just one dietary preference. While Kurzanov has speculated this could
mean an insectivorous diet it could just as easily be used for cropping
vegetation. Without a confirmed set of stomach contents we may never
know for sure. For a while Avimimus was thought
to have lacked a
developed tail because one was not found with the holotype specimen.
Further discoveries have since confirmed that Avimimus
did indeed have
a tail.
The
legs of Avimimus were long with proportions that
are close to cursorial
birds (birds that spend most or all their time on the ground and run
rather than fly). The leg bones also show prominent muscle scars
revealing that in life the legs of Avimimus would
have been muscular
and suitable for prolonged and fast running. Such legs and high
mobility however may lean Avimimus towards a more
insectivorous diet as
not only would insects supply a large amount of high energy protein to
fuel these muscles, but many cursorial birds of similar size to
Avimimus are known to hunt for insects as well as
small invertebrates.
This would not necessarily mean that Avimimus was
exclusively
insectivorous or even carnivorous, but it may still have relied upon
animal protein to form a good portion of its diet.
Avimimus
seems to have had a large brain for its body size, something which
some researchers consider to mean a greater level of base intelligence
(although the exact level remains variable and controversial because
there are so many factors to consider beyond just total size). The
bones of the skull are also well developed to give increased support
and protection to the brain, beyond a level seen in some other types
of dinosaur.
A
2008 discovery yielded a bone bed of numerous Avimimus
that were all
together at the time of death. The total number of specimens at the
site is still unknown but ten individuals that were subadults as well
as fully grown adults were recovered. The fact that so many
individuals including those of different life stages where found
together has been taken to suggest possible social behaviour where
Avimimus clustered together in what could be loosely
termed
‘flocks’. The possibility of a more highly developed brain may
also infer more complex social interaction between Avimimus
individuals, similar to what can be seen in some groups of birds
today.
Avimimus
is not the only dinosaur whose name translates to ‘bird mimic’ as
that is also the meaning of the name for the dinosaur Ornithomimus.
Further reading
- Reduced cladistic consensus methods and the avian affinities of
Protoavis and Avimimus. - Dyke
& Thorley - 1998.
- New nearly complete skeleton of the bird-like theropod, Avimimus,
from the Upper Cretaceous of the Gobi Desert, Mongolia - Watabe,
Weishampel, Barsbold, Tsogtbaatar & Suzuke - 2000.
- New material of Avimimus portentosus (Theropoda)
from the Iren Debasu
Formation (Upper Cretaceous) of the Erenhot Region of Inner Mongolia. -
M. Ryan, P. Currie & D. Russell - 2001.
- A bonebed of Avimimus sp. (Dinosauria: Theropoda)
from the Late
Cretaceous Nemegt Formation, Gobi Desert: Insights into social behavior
and development in a maniraptoran theropod. - P. Currie, N. Longrich,
M. Ryan, D. Eberth & B. Demchig - 2008.
- The first oviraptorosaur (Dinosauria: Theropoda) bonebed: evidence of
gregarious behaviour in a maniraptoran theropod. - Scientific Reports.
6: 35782. - G. F. Funston, P. J. Currie, D. A. Eberth, M. J. Ryan, T.
Chinzorig, D. Badamgarav & N. R. Longrich - 2016.
- Oviraptorosaur anatomy, diversity and ecology in the Nemegt Basin. -
Palaeogeography, Palaeoclimatology, Palaeoecology. - G. F. Funston, S.
E. Mendonca, P. J. Currie & R. Barsbold - 2018.
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