The exhibit includes an arrangement of the bones as they were found near Big Water, colorful art illustrations by Victor Leshyk of what the creature may have looked like — including feathers — and videos about the discovery and excavation of the bones.

The first bones of the Utah therizinosaur were found in 1999 by Merle Graffam, a Big Water resident, in an otherworldly gray shale that area residents call "The Moon," said Gillette, who was Utah's state paleontologist from 1988-98.

The bones were very badly fractured and embedded in Tropic shale. The shale was mud when the dinosaur was alive, and over the years, layers of rock accrued and compressed the shale, fracturing the bones. Eventually, erosion stripped away the layers, and bits of the dinosaur were revealed.

But the therizinosaur is a land or shoreline creature. How did it end up far from a shore at the bottom of what was, 93 million years ago, a shallow interior seaway covering the middle of what is today's continent of North America? Was it grabbed by shoreline predators? Did its body float out to sea?

And there are other mysteries: What were its large, dangerous-looking claws for? Feeding? Defense? And did the creature have feathers?

"We suspect all carnivorous dinosaurs had feathers," at least in the early stages of life, Gillette said. When young, they may have needed feathers for thermal regulation, not for flight. The largest may have lost features in adulthood.

Dinosaurs fossils found in China seem to confirm this theory. A therizinosaur found in China is known to have had feathers, and although therizinosaurs are believed to have been plant-eaters, they probably had carnivore ancestors, Gillette said.

When erect, the Big Water therizinosaur would have been 13 feet tall and weighed about a ton.

New horned dinosaurs

The September issue of Survey Notes describes two new Utah horned dinosaurs, or Ceratopsids, from Grand Staircase. They were uncovered in the Wahweap formation, which is just below the Kaiparowits formation where the duckbill was extracted. They lived about 80 million or 81 million years ago.

The two fossils are called the Last Chance skull and the Nipple Butte skull. They were found in 2002 and 2001, respectively.

According to Survey Notes, these creatures are early relatives of the triceratops. The Last Chance skull, discovered and prepared by the survey's DeBlieux, is in especially fine condition, said Kirkland, and will be displayed Oct. 15 in the lobby of the survey's offices on North Temple Street in Salt Lake City.

"It's probably the oldest animal of its kind ever found, and it's certainly the most primitive," Kirkland said.

The skull shows signs of linkage with protoceratops dinosaurs from Asia, he said. Without its long horns, the skull would measure about three feet long. It was so large that, as in the case of the duckbill, "we had to airlift it out," he added.

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