Anzu lived 68 million to 66 million years ago, roaming the Earth at the same time as Tyrannosaurus rex, not long before dinosaurs went extinct.
A cast of the new skeleton is on display at the Carnegie Museum of Natural History in Pittsburgh. Assembled from three fossils found separately on the Hell Creek Formation in North and South Dakota, it's the most complete example ever discovered of a mysterious group of birdlike dinosaurs called caenagnathidae.
Though dozens of related species have been found in China and Mongolia, caenagnathids have been "one of the least understood of all major dinosaur groups," according to the Carnegie Museum.
Scientists have long believed they lived in North America because the continents were often connected during the Mesozoic Era, but fossil evidence has been disappointingly scarce until now.
"After nearly a century of searching, we paleontologists finally have the fossils to show what these creatures looked like from virtually head to toe," lead study author Matthew Lamanna of the Carnegie Museum said in a statement. "And in almost every way, they're even weirder than we imagined."
But despite its birdlike features, Anzu wasn't a direct avian ancestor.
"This animal is not the closest dinosaur to birds," Schachner said. "It's one branch in the tree close to the bird branch. It has a lot of notable features that are very similar to birds, but they might be secondary."
Though the examples announced Wednesday weren't found with fossilized feathers, close relatives were.
"Unless he's really unusual, this one would have had feathers," Schachner said.
They could have been used to regulate its body temperature, incubate eggs, or display in the competition for a mate.
The earliest-discovered Anzu cousin was found in 1924 on a nest of fossilized eggs. It was dubbed oviraptor, or egg thief, though later evidence showed the creature was most likely sitting on its own nest rather than snatching a meal.
The biggest example unearthed so far is the 1.5-ton Gigantoraptor, whose lineage has also become clearer, thanks to Wednesday's discovery. Scientists now know it was more closely related to caenagnathids like Anzu, and the oviraptor is a more distant cousin.
Schachner got involved with the project as a graduate student at the University of Pennsylvania 10 years ago, when she helped excavate six bones from the neck, forelimbs and shoulder on a North Dakota dig with Tyler Lyson, a postdoctoral fellow at the Smithsonian Institution's National Museum of Natural History.
When they presented their find at a conference, Lamanna approached them to say the Carnegie had just paid $1 million to private collectors for an almost-complete skeleton of the same animal.
"He said, 'Please don't name it before us,' " she said.
Instead, the scientists teamed up to study and classify the animal. They were joined by expert Hans-Dieter Sues, also from the National Museum of Natural History. Lengthened by distance and busy schedules, the study process continued as Schachner came to Utah in 2010 to work on the evolution of lizard breathing.
The first part of the formal name, Anzu, comes from a birdlike demon in Mesopotamian mythology, and the second, wyliei, is after a dinosaur-loving boy named Wylie, grandson of a Carnegie trustee.
The work was "really exciting," Schachner said in a statement. "Naming a dinosaur is one of those things I've wanted to be involved in since I was a kid."
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