Scientists said on Wednesday two almost complete skeletons of the
bizarre 70-million-year-old creature, Deinocheirus mirificus (meaning
"unusual horrible hand"), show it boasted a combination of unorthodox
traits, including the famous arms, never before seen in a single
dinosaur.
At 36-feet-long and 6.4 tons, it was the largest known
member of a group of bird-like dinosaurs called ornithomimosaurs
("ostrich mimics"), the researchers said.
Its back was topped with
long spines that supported a sail-like structure whose function remains
enigmatic. It had fused tail vertebrae to support tail feathers.
Thriving
in an river region, it was an omnivore, eating fish and plants with a
beaked, toothless snout that flared out to the sides like the
herbivorous duckbilled dinosaurs. It had broad feet with toes ending in
squared-off hooves that may have helped it stand on wet ground.
Deinocheirus
had wide hips and moved slowly but was capable of defending itself
thanks to its sheer size and its three ripping claws on each hand. It
was virtually as big as the apex predator in the neighborhood,
Tyrannosaurus rex's cousin Tarbosaurus.
Scientists
had speculated for decades about Deinocheirus. It was accurately
recognized as a type of theropod, the dinosaur branch that includes
giants like T. rex but also the lineage that evolved into birds - but
what type?
"Deinocheirus has remained one the most mysterious
dinosaurs in the world. We found almost (complete) skeletons of
Deinocheirus and know now how it looked, how big it was and what it
ate," said paleontologist Yuong-Nam Lee, director of Geological
Museum at the Korea Institute of Geoscience and Mineral Resources
in Daejeon, South Korea.
University
of Maryland paleontologist Thomas Holtz, who wrote a commentary
accompanying the study in the journal Nature, said no one could have
predicted its astonishing array of attributes.
"I've literally waited my whole life to see Deinocheirus finally unveiled," Holtz said.
Some
bad luck almost prevented the unveiling. The two new skeletons were
found in 2006 and 2009 at Gobi sites in Mongolia. Both suspiciously were
missing their heads and other key parts. The scientists realized those
had been poached by illegal fossil collectors, with parts sold off to
private collectors.
The missing parts from the 2009 excavation
ended up with a collector in Germany but fortuitously were seen by
Belgian paleontologist Pascal Godefroit, who recognized what they were
and informed Lee and other scientists.
Lee said the researchers
persuaded the collector to donate the fossils because of their
importance to science. The fossils were returned to Mongolia in May. But
Lee said the 2006 fossils remain missing.
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