It stood 11.5-feet tall and tipped the scales at perhaps 500 pounds, with the body of a raptor, the head of a chicken and the crest of a cassowary; it sported big sharp claws and, probably, feathers. That’s the picture emerging from three fossil skeletons that paleontologists say represent a dinosaur species new to science: Anzu wyliei, or the “chicken from hell,” as they have nicknamed it. The fossils, which were discovered in North and South Dakota, date to around 66 million years ago--near the end of the dinosaurs’ reign.

The skeletons, described in a paper published today in PLOS ONE, cast new light on a mysterious clade of dinosaurs known as the oviraptorosaurs, which are known mainly from specimens found in China and Mongolia. According to Matthew Lamanna of the Carnegie Museum of Natural History in Pittsburgh and his co-authors, the new species reveals “the first comprehensive picture of the skeletal structure” of the so-called caenagnathid lineage of oviraptorosaurs.

Exactly how these peculiar dinosaurs, with their toothless, beak-covered jaws, long legs and big feet made a living is unclear. Scientists have variously proposed that the caenagnathids were specialized waders, fleet-footed runners and skilled tree climbers. Some contend that the beasts specialized in eating eggs, others suggest that they ate mostly plants and still others argue that the creatures fed on small aquatic invertebrates.

Anzu brings fresh evidence to bear on the matter. The remains came from mudstones in the fossil-rich Hell Creek Formation that suggest these dinosaurs lived in a floodplain habitat, rather than a drier environment. Lamanna and his colleagues note that fossilized trackways in Wyoming that look to have been left by theropod dinosaurs similar to Anzu also hint that caenagnathids hung out by the water’s edge and may have waded. Large-bodied caenagnathids like Anzu seem unlikely to have spent much of their adult life in the trees, they add. As for what these dinosaurs ate, the team observes that their jaw morphology would have allowed them to process a wide range of foods. “In sum, in our view, Anzu and other derived caenagnathids may well have been ecological generalists that fed upon vegetation, small animals, and perhaps even eggs on the humid coastal plains of western North America at the end of the Age of Dinosaurs,” the authors conclude.