A once-in-a-lifetime find in 2000 by Museum of Northern Arizona paleontologists led to the discovery of the most complete therizinosaur skeleton ever found. See the newest and strangest dinosaur in all of North America at MNA's stunning new major exhibit THERIZINOSAUR—Mystery of the Sickle-Claw Dinosaur, opening Sunday, September 16, 2007 and running through March 29, 2009.
On display are real 93-million-year-old bones excavated near Big Water, in the desert landscape of southern Utah. A freestanding skeleton, cast from the original bones of the 13-foot-tall, one-ton, sickle-clawed, and feathered dinosaur, is the first mounted interpretation of this long-lost animal's stance and posture.
All dinosaurs lived on land, but this one was found in a location that was the bottom of the Cretaceous Western Interior Seaway, an ancient sea that covered the middle of North America. The initial discovery, a single toe bone, led to the recovery of the nearly complete skeleton. But how did the whole animal get buried in a seafloor, 60 miles from shore?
The dinosaur's identity was a mystery well into the excavation. "We weren't thinking ‘therizinosaur' at first, because at that time they were known only from Asia," said Dr. David D. Gillette, exhibit curator and MNA's Colbert Chair of Vertebrate Paleontology. "From that first toe bone, we thought maybe we had a big ‘raptor' (an agile, hunting dinosaur). But when we found peculiar bones of the massive hips, we knew we had a sickle-claw dinosaur. They were like nothing we'd ever seen."
Most dinosaurs in this mysterious family are known only from partial skeletons. And the lifestyle of these lumbering, pot-bellied, sickle-clawed forms has been debated for decades; MNA's skeleton fills in some major gaps in what is known about therizinosaur anatomy and habits.
"In the past two decades, new studies have regrouped therizinosaurs with carnivorous (meat-eating) dinosaurs," noted Gillette, "but there are many questions. Was this animal truly carnivorous as indicated by its shared ancestry with forms like Tyrannosaurus rex? How did it use its three slashing sickles on each hand? Did this small-headed predator actually prey on plants?"
