June 14 (Xinhua) -- Chinese archaeologists have discovered a the remains of
gigantic bird-like dinosaur in the Gobi Desert in north China's Inner Mongolia
Autonomous Region, which could overturn theories that dinosaurs became generally
smaller as they evolved into birds.
Chinese archaeologists have discovered a
the remains of gigantic bird-like dinosaur in the Gobi Desert in north
China's Inner Mongolia Autonomous Region, which could overturn theories
that dinosaurs became generally smaller as they evolved into birds.(Xinhua
The animal, named gigantoraptor erlianensis, is
believed to have been about eight meters in length, weighed 1,400 kg, and stood
up to five meters high.
Chinese archaeologists said that despite its enormous
size, gigantoraptor erlianensis belonged to the oviraptorosauria, a group of
smaller, feathered animals.
In light of its size, the researchers performed two
different tests to confirm that it belonged to the oviraptorosaur family.
"The analyses strongly supported the oviraptorosaur affinity of
gigantoraptor erlianensis and suggested this new dinosaur was in an intermediate
position in oviraptorosaurian evolution," Xu Xing, a researcher with
the Institute of Vertebrate Paleontology and Paleon anthropology with the
Chinese Academy of Sciences.
Chinese archaeologists believe gigantoraptor
erlianensis was an anomaly in the evolution of dinosaurs to birds and its
discovery complicates the evolutionary pattern.
Xu said they had no direct evidence that
gigantoraptor erlianensis was feathered like its close relatives, but based on
its close relationship to other feathered species such as caudipteryx and
protarchaeopteryx, gigantoraptor erlianensis probably had feathers on its arms
and tail at least.
The largest known feathered animal so far is the
500-kg Stirton's thunder bird (dromornis stirtoni), which lived in Australia
eight to six million years ago. Gigantoraptor erlianensis was about three times
as heavy as dromornis stirtoni.
"Discovering such a big featured animal is beyond our
imagination. It's like seeing a mouse as big as a pig," Xu said.
Researchers found that gigantoraptor erlianensis
possessed many features unknown in other dinosaurs, such as highly specialized
caudal vertebrae and the bizarre humerus, suggesting that morphological
diversity among the dinosaurs is higher than previously known.
Xu said normally when dinosaurs become so large, they
had proportionally stouter limbs and shorter lower legs than their smaller
relatives. However, gigantoraptor erlianensis has much more slender limbs and
longer lower legs than similarly-sized theropods, suggesting that it might have
been adapted for running.
Early archaeological study has shown that in their
evolution into birds, dinosaurs become smaller in size and within each dinosaur
group smaller species are normally more bird-like than their larger relatives.
But Chinese archaeologists said gigantoraptor
erlianensis is more bird-like than its small relatives in many features such as
a longer arm and a more bird-like leg.
"This suggests that there are different underlying
mechanisms along the line to birds in theropod evolution," Xu said.
Chinese researchers also found that the
one-and-half-ton gigantoraptor erlianensis had no teeth, but was beaked
Gigantoraptor's diet remains unknown, but it shows
both herbivorous features (such as small head and long neck) and carnivorous
features (such as sharp claws).
Other oviraptorosaurs are believed to have been
plant-eaters, egg-eaters, mollusc-eaters, and meat-eaters according to various
Researchers deducted that the animal probably died in
its 11th year based on the growth lines preserved in the fibular bone.
They also inferred that the animal reached maturity
within seven years and was still relatively young at the time of death.
The bird-like dinosaur fossil was discovered in 2005
at Erlian Basin, known for its dinosaur fossils and other vertebrate fossils.
The dissertation on gigantoraptor erlianensis will be published
in Nature on June 14.