Scientists on Monday announced the discovery of what appears to be the world's most intact dinosaur mummy: a 67-million-year-old plant-eater that contains fossilized bones and skin tissue, and possibly muscle and organs.

Preserved by a natural fluke of time and chemistry, the four-ton mummified hadrosaur, a duck-billed herbivore common to North America, could reshape the understanding of dinosaurs and their habitat, its finders say.

"There is no doubt about it that this dinosaur is a very, very significant find," said Tyler Lyson, a graduate student in geology at Yale University who discovered the dinosaur in North Dakota.

"To say we are excited would be an understatement," said Phil Manning, a paleontologist at England's University of Manchester who is leading the examination. "When I first saw it in the field, (I thought) 'Shiiiit, that's a really well preserved dinosaur.' It has the potential to be a top-10 dinosaur, globally."

After excavating the dinosaur, scientists encased it and the surrounding soil in plaster. It was hauled to Boeing's giant CT scanner near Los Angeles.

Photo: National Geographic ChannelNicknamed Dakota, the hadrosaur is one of only five naturally preserved dinosaur mummies ever discovered. Unlike previous dinosaur mummies, which typically involve skin impressions pressed into bones, Dakota's entire skin envelope appears to remain largely intact.

"The skin has been mineralized," said Manning. "It is an actual three-dimensional structure, backfilled with sediment."

The fidelity of the envelope, he said, raises the possibility that Dakota could contain other soft-tissue remnants, including muscles and organs.

Then-16-year-old Lyson was fossil-hunting in 1999 in the Hell Creek Formation badlands of North Dakota when he first spotted the dinosaur's bone-like protrusion from a hill. In 2004, after Lyson returned to begin excavating the fossil and discovered skin remnants, a friend studying at the University of Manchester alerted Manning, who had the experience and resources to organize a more cautious excavation.

Only after the body and a chunk of the hillside was moved to a lab did the scientists realize the extent of the discovery. "On vast areas of the tail and body," Manning said, "there was what looked to be a three-dimensional skin envelope, in the same way as a sock around your foot – which did not make any sense at all."

Manning brought on dozens of scientists and engineers – in disciplines ranging from computer science to organic chemistry and physics – to investigate every aspect of the find using state-of-the-art tools.

"Up until Phil showed me this dinosaur," said Roy Wogelius, a geochemist from the University of Manchester studying the soil surrounding Dakota, "I had no interest in dinosaurs. As soon as I saw this specimen, I was fascinated."

In North Dakota, the researchers used Light Detection and Ranging equipment (LiDAR) to develop a three-dimensional topographical map of the area where Dakota died. Manning speculated that the dinosaur collapsed in a riverbed during the late Cretaceous Period and was rapidly buried in mineral-rich wet sand, preventing bacteria from devouring all of its tissue. "There was active-enough chemistry in the sediments that the decay process didn't occur as quickly as the mineralization process," he said. "It was a perfect chemical soup."

The CT scan showed that the hadrosaur's vertebrae, which museums commonly stack together, are actually spaced a centimeter apart. That means we may have been underestimating the size of many dinosaurs.

Image: National Geographic ChannelAfter examining the dinosaur at a local lab, the scientists encased it and the remaining surrounding soil in plaster and hauled it by truck to a Boeing research center in Canoga Park, California, north of Los Angeles. There, Boeing volunteered the world's largest computerized tomography, or CT, scanner, originally built by NASA to scan space shuttle parts for flaws. At 8,000 pounds, the fossil became the largest object ever scanned at high resolution. The researchers are using the data to survey the body's interior before chipping away further on the fossil. "The CT scan is like a roadmap," said Manning. "It will help us recover the rest of the animal more easily and efficiently."

The first significant findings from the dinosaur, currently under review at a major scientific journal, will describe the unique chemical balance that preserved the fossil. The body, meanwhile, remains on the Boeing scanner, as Manning and his colleagues sift through terabytes of data. So far, they have determined that the hadrosaur's hindquarters are 25 percent larger than previously thought for the species, meaning that it could run up to 28 mph – faster than previously estimated. They have also discovered that the specimen's vertebrae, which museums commonly stack together, are actually spaced 10 millimeters apart. The result, Manning said, implies that scientists may have been underestimating the size of hadrosaurs and other dinosaurs.

The National Geographic Channel, which helped fund the research, will recount the saga of Dakota's discovery in a documentary, Dino Autopsy, Sunday, Dec. 9, at 9 p.m. EST. Manning is also publishing a book, Grave Secrets of Dinosaurs, describing the fossil and its history. Although there are a lot of scientists involved in the project, Lyson and Manning have not yet allowed experts outside the project to assess the mummified dinosaur.

But the scientific findings from the specimen may take decades to exhaust. "I'm 40 years old now," Manning said. "If I live till 80 I think I'll still be at the tip of the iceberg."