Deinocheirus
Name:
Deinocheirus
(Terrible hand).
Phonetic: Die-noe-ky-rus.
Named By: Osm�lska & Roniewicz - 1970.
Classification: Chordata, Reptilia, Dinosauria,
Theropoda, Ornithomimosauria, Deinocheiridae.
Species: D. mirificus
(type).
Diet: Uncertain.
Size: Estimated between 10 to possibly up to 11
meters long.
Known locations: Mongolia, Nemegt Formation.
Time period: Late Campanian/Early Maastrichtian of
the Cretaceous.
Fossil representation: Iniitally known from a pair
of arms with shoulder
girdle and a few ribs and vertebrae, now two individuals represented by
partial postcranial remains including a skull are now known.
In
1965 on July 9th the Polish paleobiologist Zofia Kielan-Jaworowska
made what would become marked as one of the most fascinating dinosaur
discoveries of all time. During a joint Polish-Mongolian expedition
into the Gobi desert of �mn�govi Province, Mongolia, she found the
partial remains of a then unknown dinosaur, including a complete pair
of forearms with some partially preserved vertebrae and ribs. What
made everyone stop and pay attention to this find was that these arms
measured about 2.4 meters long, and since these arms were formed
in such a way that they seemed to come from a theropod dinosaur, they
were the largest dinosaur arms of their kind. Eventually in 1970
these arms were described as the basis for a new dinosaur genus which
was named Deinocheirus, which translates to
English as ‘terrible
hand’, a clear reference to the large size of the hands and claws.
After
this Deinocheirus became an established part of
dinosaur popularity,
with near mandatory inclusion in all dinosaur books along with other
big names such as Tyrannosaurus,
Diplodocus,
Stegosaurus
and
Triceratops.
However in these books the arms were always portrayed as
a mystery with statements like ‘no one knows what kind of dinosaur
Deinocheirus was’, and these statements
persisted into the early
days of the internet and into the early twenty-first century.
Palaeontologists
knew that the arms of Deinocheirus were those of a
theropod dinosaur,
dinosaurs of the saurischian (lizard hipped) evolutionary line
that had well developed rear legs to support bipedal (two legged)
locomotion. The large arms were seen as a reflection of a large body
size, but they did not match up to the known forms of other large
theropod types. A 2006 study by Barsbold and Kobayashi however
came to a new conclusion; that the arms of Kobayashi show several
characteristics that are akin with the ornithomimosaurs.
This
study raised a few eyebrows, the ornithomimosaurs were theropods,
but genera of this group averaged between two and four meters long,
with the largest individual genus Gallimimus
being up to eight meters
long. Even Gallimimus however did not have arms
anywhere near as
large those of Deinocheirus, which in turn would
mean that
Deinocheirus would have had to have been the largest
known
ornithomimosaur and comparable to some of the largest theropods.
Then
in 2013, forty-eight years after the first fossils were found in
the Gobi desert, two new individuals (discovered in 2006 and
2009) of Deinocheirus were formally presented to
the scientific
community, and it was confirmed, Deinocheirus
was the largest
ornithomimosaur. Neither of these individuals was complete, but
between them it was possible to get an idea of the complete skeleton.
Not only was this the first time that palaeontologists could get a
complete idea of what Deinocheirus actually looked
like, but the
larger of this two individuals actually had arms that were larger than
those of the holotype.
What
soured this discovery however is the theft of the skull and feet of
these specimens by thieves who stole them so that they could be sold on
the fossil black market. Evidently someone or some people were aware
of the significance of this find and decided to act to support their
own finances as opposed for the good of science. Fortunately at least
some of these missing fossils were later found by Francois Eskulie and
donated to the Royal Beligian Institute of Natural Sciences. These
fossils have now been repatriated to Mongolia with a formal ceremony
held on the 1st May, 2014.
Go to pages --> Shantungosaurus, Tarbosaurus, Beishanlong, Therizinosaurus, Gigantoraptor.
What
we know about Deinocheirus now is that for lack of
a better word it was
weird. For a start Deinocheirus grew
significantly larger than most
other ornithomimosaurs, though late cretaceous Asian ornithomimosaurs
such as Gallimimus and
Beishanlong are both known to have grown up to
eight meters long, and these two are also significantly larger than
most others. Other types of dinosaurs also seem to have grown
unusually large, such as the hadrosaur
Shantungosaurus
and the
oviraptosaur
Gigantoraptor.
Around 2006 when the second
individual of Deinocheirus was found estimates of
around ten meters
long began to be circulated, but after the 2013 presentation a
larger specimen was credited as being as much as eleven meters long.
Whereas
Deinocheirus had been famous for the large arms,
it is now known that
Deinocheirus actually had growths rising up from
their backs which may
have formed either a heavily built sail or indeed a fatty hump. Once
again the same theories regarding the formations of back growths are
circulating and this time in reference to Deinocheirus,
with the
two most common being thermoregulation and fat storage for surviving
droughts and times of little food availability. Another is display
for interspecies recognition and even signalling members to the
opposite sex with a well formed hump indicating a healthy and well fed
individual. What is known is that at the time of this discovery,
Deinocheirus was the only ornithomimosaur known to
have had a growth
on its back, something that still stands at the time of writing.
In
general the diets of ornithomimosaurs are unknown except for a few
genera such as Pelecanimimus
where we can get a fairly good idea from
fossil evidence. Other ornithomimosaurs have been interpreted as
being herbivores, predators of small vertebrates like primitive
mammals, lizards and snakes, to omnivores that ate both plants and
flesh to even egg thieves that raided unguarded nests. When only the
arms of Deinocheirus were known, the large claws
on the ends of the
fingers were interpreted by many to be for rending the flesh of any
dinosaur that had been unfortunate to have been caught by them,
however we now know that large claws are not always killing weapons.
The
wider understanding of
therizinosaurs gathered during the latter half
of the twentieth and early twenty-first centuries is proof that some
large clawed theropods were herbivores. This observation coupled with
a large concentration of smooth rounded stones discovered near what
would have been the digestive area of one of the Deinocheirus
specimens, indicating that they may be gastroliths, has been taken
as evidence that supports a more herbivorous lifestyle, with the
large claws possibly being used to hook around and pull down branches.
However, the herbivorous diet theory may not be the only
possibility.
With
the recovery of the stolen skull, we also know that Deinocheirus
had
a ‘spoonbill’, upper and lower jaws that widened out to form a
rounded spoon-shape. This begs the question, was Deinocheirus
similar to modern spoonbill birds that are known to snatch out
invertebrates and small fish from water systems. Here the widened
bill increases the catch area making it easy to snatch prey from the
water. A comparison to the spinosaurs
could also be in order. Some
genera of spinosaur
such as Ichthyovenator
and of course Spinosaurus
itself are known to have had growths on their backs as well as
well-developed and long arms and claws, both features that can now be
seen in Deinocheirus. In addition, the possible
gastroliths of
Deinocheirus could have just as easily have been
used to strip off the
scales from fish making them easier to digest. It may be that
Deinocheirus waited for seasonal rains to swell
rivers and water
systems which then brought in a greater amount and variety of fish,
which they then gorged themselves upon in times of plenty to build up
there fat reserves stored in a hump, which they then relied upon to
see them through the remainder of the year in leaner times. If true
then Deinocheirus may have been in a
comparative evolutionary
niche as the spinosaurs that were common in earlier in the Cretaceous.
Finally one should consider that as a saurischian theropod,
Deinocheirus as an ornithomimosaur would have
been descended from
predatory ancestors and even some earlier ornithomimids such as
Pelecanimimus are perceived to have been more
predatory in their
dietary needs. This is only speculation however, it remains to be
seen to just what other surprises Deinocheirus may
have in for us.
As
one of the larger dinosaurs in its environment Deinocheirus
probably
only had to worry about other large theropod dinosaurs when fully
grown, as late Cretaceous Asia seems to have been dominated by
large tyrannosaurs
such as Tarbosaurus
and Zhuchengtyrannus.
Tarbosaurus in particular may have been a
particular threat given that
a least one of the ribs discovered at the fossil site of the original
arms shows tooth marks that were likely caused by a tyrannosaur, with
Tarbosaurus also being known from that
approximate location. If
this was active predation or more imply a case of scavenging however is
simply impossible to say. Aside from tyrannosaurs, Deinocheirus
likely came into contact with other types of dinosaurs such as
hadrosaurs, ceratopsians,
dromaeosaurs,
oviraptorids,
therizinosaurs, pachycephalosaurs
as well as the occasional
titanosaur,
all while early birds and pterosaurs
flew on overhead.
Further reading
- Third (1965) Polish-Mongolian Palaeontological Expedition to
the Gobi Desert and western Mongolia. - Bulletin de l'Acad�mie
Polonaise des Sciences, C1. II 14 (4): 249–252. -
Zofia Kielan-Jaworowska - 1966.
- Giant claws of enigmatic Mesozoic reptiles. - Paleontological
Journal, 1970(1): 117-125. - A. K. Rozdestvensky -
1970.
- Ornithomimids from the Nemegt Formation of Mongolia. - Journal
of the Paleontological Society of Korea, 22(1): 195-207. -
Y. Kobayashi & R. Barsbold - 2010.
- Hip heights of the gigantic theropod dinosaurs Deinocheirus
mirificus and Therizinosaurus cheloniformis,
and implications for
museum mounting and paleoecology. Bulletin of the Gunma Museum of
Natural History, 14: 1-10. - P. Senter & H. J.
Robins - 2010.
- Tyrannosaur feeding traces on Deinocheirus
(Theropoda:?Ornithomimosauria) remains from the Nemegt Formation
(Late Cretaceous), Mongolia. - Cretaceous Research - Phil
R. bell, Philip J. Currie & Young-Nam Lee - 2012.
- New specimens of Deinocheirus mirificus from the
Late Cretaceous of
Mongolia. - Society of Vertebrate Paleontology Abstracts of Papers:
161. - Y. N. Lee, R. Barsbold, P. J. Currie, Y. Kobayashi & H.
J. Lee - 2013.
- Resolving the long-standing enigmas of a giant ornithomimosaur
Deinocheirus mirificus. - Nature. 515 (7526):
257–260. - Y. N. Lee, R.
Barsbold, P. J. Currie, Y. Kobayashi, H. J. Lee - 2014.
- First insights into the bone microstructure of Deinocheirus
mirificus. - 13th Annual Meeting of the European Association of
Vertebrate Palaeontologists: 25. - M. Kundr�t & Y. N. Lee -
2015.
- Histological analysis of the gastralia of Deinocheirus
mirificus from
the Nemegt Formation of Mongolia. - 6th Annual Meeting Canadian Society
of Vertebrate Palaeontology Ottawa, Ontario. Ottawa. p. 46. - B. Roy,
M. J Ryan, P. J. Currie, E. B. Koppelhus & K. Tsogtbaatar -
2018.
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