What's so special about a dinosaur named Leonardo?

In spite of its exceptional preservation, Leonardo became a fossil in the usual way. Sediment buried its body, and minerals slowly replaced its tissues. But something about Leonardo's burial was different. Typically, soft tissues like skin, muscle and cartilage decay long before fossilization can take place. In Leonardo's case, something -- perhaps a thick layer of wet sediment -- protected the body from the scavengers and bacteria that break down soft tissue. His skin and internal organs lasted long enough to turn to stone.

This turned Leonardo into one of a handful of mummified dinosaur fossils. At the time of its discovery, Leonardo was one of only four mummified dinosaurs ever found [source: Mayell]. This rarity made studying the fossil without destroying it extremely important.

To do this, researchers relied on one of the same tools doctors use to study human bodies without cutting them -- X-ray imaging. The team used a digital imager to take more than 40 X-rays of Leonardo's head and body. This gave the team a glimpse of what was inside. But to get enough definition of the rock-on-rock organs to really see what went where, the researchers needed a more powerful radiation source than they could use in their building. They took Leonardo to a hangar at Johnson Space Center Ellington Field in Houston, Texas. That's when Leonardo got its $2.5-million insurance policy. At the Ellington Field facility, researchers used highly radioactive isotopes to get a look at the structures deep within Leonardo's body.

All these X-rays have added up to a life-size, 3-D view of Leonardo's organs. Some of the findings are:

Leonardo is so well-preserved that researchers have even figured out what it ate. Inside its digestive system are:

This is a lot of information to come from one fossil, which is why Leonardo has gotten lots of media attention. A Discovery Channel special called "Secrets of the Dinosaur Mummy" documents researchers' work with the fossil. And because of its remarkable state of preservation, Leonardo is recognized in the Guinness Book of World Records as the best preserved dinosaur. But Leonardo isn't just a media event -- it's also a major scientific discovery. Research is ongoing, so Leonardo may yield new information in the future.