In 1965, paleontologists unearthed a ghastly pair of eight-foot, claw-tipped dinosaur arms – and little else. Since then, researchers have been searching for the rest of Deinocheirus mirificus (Latin for "unusual, horrible hands"). Now, a team working in Mongolia has found it.

Photo Credit: Jordi Payà via flickr | CC BY-SA 2.0

In the latest issue of Nature, a team led by Yuong-Nam Lee, director of the Geological Museum in Daejeon, South Korea, describes the two nearly-complete specimens of a dinosaur whose arms have puzzled paleontologists for nearly fifty years. [Photo Credit: Eduard Solà via Wikimedia Commons]

Some had hypothesized that Deinocheirus used its arms to ensnare live prey, but stomach contents recovered by Lee and his colleagues suggest this dinosaur ate plants and fish. In their publication, the team pegs Deinocheirus as the largest-known member of the ornithomimosaurs, a group of "ostrich-like" theropods that includes such dinosaurs as Gallimimus, of they're-flocking-this-way fame:

But while paleontologists believe most ornithomimosuars to have been swift, svelte, and agile like Gallimimus, they use very different words to describe Deinocheirus.

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"Deinocheirus was much weirder than anyone could have imagined," University of Edinburgh paleontologist Stephen Brusatte told National Geographic's Ed Yong, "a colossal, slow-moving, horse-headed, hump-backed dinosaur that looks like something out of a bad sci-fi movie."

Above: The two newly described Deinocheirus specimens, and a composite reconstruction, via Lee et al.

Someone more considerate of Deinocheirus' feelings might describe the dinosaur by the numbers. At thirty-six feet long and twelve-thousand pounds, Deinocheirus was certainly quite large, and its relatively stubby legs would suggest it took its time getting around. Along its back ran a prominent sail. Its face was elongated, and tapered to a toothless, duck-like beak:

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Above: An artist's reconstruction of Deinocheirus, courtesy Yuong-Nam Lee/Kigam

Lee's team suspects that Deinocheirus' large, hoofed feet would have kept it from sinking into its boggy habitat, where it would have plodded, according to brash experts, "goofily," from place to place. As paleontologist and evolutionary biomechanist John Hutchinson told the BBC, "People were really wondering what the rest of this animal looked like... Now we know, and it's just so freaking weird – we never would have expected this animal to look so bizarre."

Read the full scientific study in the latest issue of Nature.

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