A restoration of the Hell Creek Formation's giant oviraptorosaur, Anzu.
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Art by Mark Klingler/Carnegie Museum of Natural History.
A restoration of the Hell Creek Formation's giant oviraptorosaur, Anzu.

Mysterious Dinosaur Anzu Debuts

Of all western North America’s fossiliferous lands, the Hell Creek Formation is among the richest boneyards. The 68-66 million year old exposures that stretch from Wyoming through Montana and the Dakotas have yielded countless dinosaurs, including the Cretaceous celebrities Edmontosaurus, Triceratops, and Tyrannosaurus. So much has been found that the chances of finding new, large dinosaurs are relatively slim, and many paleontologists have shifted their focus to investigating the biology of the formation’s abundant dinosaurs. Yet the Hell Creek isn’t totally tapped out yet. A bizarre dinosaur announced just this week shows that the famous formation still holds secrets.

Described by paleontologists Matt Lamanna, Hans-Dieter Sues, Emma Schachner, and Tyler Lyson in PLoS One, the new dinosaur is officially named Anzu wyliei. Journalists have had more fun crowing the creature’s nickname. Anzu was the “Chicken from Hell” – an eleven-foot-long Cretaceous weirdo with a toothless beak, a flashy crest, and elongated arms tipped with nasty-looking claws, all wrapped up in a coat of prehistoric plumage.

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A reconstruction of Anzu with postcranial bones (figured in gray on the skeleton). Image from Lamanna et al., 2014.

In the tangled branches of the dinosaur family tree, Anzu was an oviraptorosaur. These superficially bird-like, omnivorous dinosaurs have been found at other Cretaceous sites in North America and Asia, but to find a giant form hiding in the Hell Creek Formation was a surprise. That’s why paleontologists and dinosaur fans spent a decade and a half anxiously waiting for this dinosaur to be published.

The first two partial skeletons of Anzu were discovered in 1999 by Fred Nuss and Robert Detrich as they searched for fossils on a private South Dakota ranch. The two specimens weren’t buried together – the skeletons rested about 330 feet apart with the second individual in a rock layer about 11 feet below the first – but, once prepped by the commercial outfit Triebold Paleontology, it was clear that both represented the same dinosaur. Word was getting out about the amazing oviraptorosaur when Scott Haire found another partial skeleton on a private ranch in North Dakota that went to a growing research collection in the town of Marmarth.

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Anzu at the Carnegie Museum of Natural History. Photo by Brian Switek.

Reconstructions of the dinosaur’s skeleton only generated more buzz. Not only did the Carnegie Museum of Natural History in Pittsburgh acquire the first two skeletons, but they also put up a mount of Anzu made by Triebold when they reopened their renovated dinosaur halls in 2008. That mount became the basis for other, scrappier oviraptorosaurs discovered in western North America. The Natural History Museum of Utah’s mount of Hagryphus – an earlier oviraptorosaur as yet known from less material – has casts of some Anzu bones to help fill out the skeleton.

Anzu is no longer the dinosaur who must not be named. That alone is enough cause for celebration. Even better is that in the space of 15 years, Anzu has gone from being invisible to an exceptionally well-represented dinosaur. In addition to the three specimens already collected, a Burpee Museum of Natural History crew uncovered what’s likely a fourth Anzu skeleton. Anzu is well on its way to becoming a Hell Creek star.

But most important of all is the lesson Anzu teaches about what’s yet to be discovered. If such a superlative feathery weirdo could remain hidden for so long, who knows what’s still out there awaiting discovery?

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Lamanna, M., Sues, H-D., Schachner, E., Lyson, T. 2014. A new large-bodied oviraptorosaurian theropod dinosaur from the Latest Cretaceous of western North America. PLoS ONE. 9, 3: e92022. doi:10.1371/journal.pone.0092022