‘Ostrich’ dinosaur a real monster “The reality of this thing turns out to be even crazier than what people were dreaming up.”

Creature weighed 14,000 pounds, had 8-foot arms

What had arms nearly 8 feet long, looked like a giant ostrich and lived in Mongolia?

That riddle has baffled scientists since 1965, when a Polish researcher unearthed a pair of dinosaur arms in the Gobi Desert. Some experts thought the arms belonged to a fearsome carnivorous dinosaur, while others argued for an oversized sloth-like creature.

Now the mystery has been solved, and the truth is even weirder than anyone had envisioned. It’s a beast called Deniocheirus that lived 70 million years ago and belonged to an ostrich-like family of dinosaurs.

At 14,000 pounds, it was 10 times heavier than its next-biggest relatives. When it walked on its hind legs, as it usually did, it stood 16 feet high, taller than an elephant.

Scientists report in Nature that the long-armed dino had lanky ostrich-like back legs, a toothless bill, an enormous hump on its back and probably a fan of long feathers on the end of its tail. It ate plants and fish, making it perhaps the biggest omnivorous dinosaur. It’s like nothing seen before, and it raises a host of new questions, such as why it was so big and why it resorted to a diet normally reserved for smaller creatures.

“For the last half-century, people have been going out to the Gobi Desert trying to find the rest of this animal,” says Stephen Brusatte, a University of Edinburgh paleontologist who is not connected to the new study. “Thankfully, the reality of this thing turns out to be even crazier than what people were dreaming up.”

“None of us suspected it looked like a duck-billed ostrich-camel,” says paleontologist Thomas Holtz of the University of Maryland, who wasn’t a part of the research team either.

The sleuthing to discover the dinosaur’s true identity is itself worthy of a detective yarn. In 2006, scientists digging in the Gobi found a strange, partial skeleton, its hands and skull stripped by poachers. In 2009, they found a very similar fossil. It too was mutilated by poachers, but they’d left behind a telltale arm.

That arm told the researchers that the 2006 and 2009 dinosaurs were Deinocheirus mirificus, or “unusual horrible hand,” the species known only from an enormous pair of arms dug up some 45 years earlier.

“I was totally stunned and thrilled,” study co-author Yuoung-Nam Lee of the Korea Institute of Geoscience and Mineral Resources said via email. “I had found what I had always been looking for in the Gobi.”

In a stroke of luck, a colleague told the scientists about a Deinocheirus skeleton in the European laboratory of a private fossil dealer.

The researchers quickly realized those bones were a perfect match to the skeleton they’d unearthed in 2009.