Archaeornithomimus
Name:
Archaeornithomimus
(Ancient bird mimic).
Phonetic: Ar-kay-oh-or-mif-oh-mime-us.
Named By: Dale Russel - 1972.
Synonyms: Ornithomimus asiaticus.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Theropoda, Ornithomimidae.
Species: A. asiaticus
(type). A.
bissektensis is still sometimes mentioned, but this
species is not
accepted by all. Refer to main text for details.
Diet: Uncertain, but presumed omnivore.
Size: Around 3.3 meters long.
Known locations: Mongolia, Uzbekistan.
Time period: Late Campanian of the Cretaceous.
Fossil representation: Several individuals but
usually of partial post cranial remains.
In
1972 Dale Russel was undertaking a study of the ornithomimid
dinosaurs which saw some of the focus fall upon Ornithomimus.
After
studying the fossils of this genus he discovered that while some of
them were not attributable to Ornithomimus, but
were of an unknown
ornithomimid dinosaur. However while Russel correctly identified a
new dinosaur, he thought at the time that the fossils dated from the
Cenomanian period of the Cretaceous, making the new genus the oldest
known ornithomimid, hence the name Archaeornithomimus.
Later study
has concluded that Archaeornithomimus actually
dates back to around
seventy million years ago which would actually place it during the late
Campanian stage of the Cretaceous and living at around the same time
period as most other ornithomimds. In terms of the original meaning
the name Archaeornithomimus is now something of a
misnomer, but at
the end of the day if a seventy million year old animal doesn’t qualify
as being ancient then what does?
Two
additionally species have been assigned to Archaeornithomimus,
but
today the validity of both of this species is doubted. A.
affinis
was named from fossils previously attributed to Ornithomimus
affinis by
Dale Russel in 1972. However even before this fossil material had
been placed under Ornithomimus, it had been known
as Dryosaurus
and
even before this, Allosaurus.
In 1990 a study by David Smith
and Peter Galton found that the remains attributed to A.
affinis were
those of another kind of small theropod, and the species fell into
disuse. The third species which is still sometimes recorded is A.
bissektensis and was named from a single femur by Lev Nesov
in 1995
after the Bissekty Formation where it was found. The interesting
thing here is that this actually does date to around the Turonian
period, but other palaeontologists have since doubted its validity.
At the time of writing, only the type species of A.
asiaticus is
accepted as valid.
Like
other ornithomimids, Archaeornithomimus was a
long legged dinosaur
that was built for speed. The tail would have been long and carried
high to serve as a counterbalance to help aid locomotion. The skull
of Archaeornithomimus is so far unknown, but is
expected to be
toothless and formed into a beak like with other dinosaurs of its
group. Unfortunately this also means that Archaeornithomimus
shares
the same controversy about what it ate, as the beak could have been
used for anything from browsing select plant parts to catching insects
and small vertebrates like lizards and mammals.
Because
Archaeornithomimus is known from the Iren Dabasu
Formation, it’s
reasonable to establish that it would have shared its ecosystem with
other dinosaurs such as the tyrannosaur Alectrosaurus,
the
maniraptorian Avimimus,
the huge oviraptorid Gigantoraptor
and even
the dromaeosaurid Velociraptor
amongst others.
Further reading
- On the dinosaurian fauna of the Iren Dabasu Formation. - Bulletin of
the American Museum of Natural History, 67: 23-78. - C. W. Gilmore -
1933.
- Ostrich dinosaurs from the late Cretaceous of western Canada.
Canadian - Journal of Earth Sciences 9:375-402. - D. A. Russel - 1972.
- Osteology of Archaeornithomimus asiaticus (Upper
Cretaceous, Iren
Dabasu Formation, People's Republic of China). - Journal of Vertebrate
Paleontology Vol. 10, No. 2 (Jun. 21, 1990), pp. 255-265. - Peter
Galton & David Smith - 1990.
----------------------------------------------------------------------------
Random favourites
 |
 |
 |
 |