In 1825, English country doctor Gideon Mantell published an outlandish claim: giant repiles had once roamed the rolling Sussex countryside. It was based on the discovery of some fossil teeth the resembled those of an iguana but were 20 times bigger. Mantell imagined the creature must have been at least 18 metres long and named it Iguanadon. 

For two centuries scientists had to use lots of imagination to put flesh on the teeth and bones of Iguanadon and other dinosaurs. But in 2000 another doctor made an equally remarkable discovery. While fossil hunting on a vast cattle ranch in Montana, Dan Stephenson became the first human being to gaze upon a seven-metre, 75-million-year-old duck-billed hadrosaur mummy. Stephenson was not gazing on bones. This dinosaur's skin, muscles and internal organs had been preserved. Leonardo, as he was named, made it into the Guinness book of records as the most perfectly preserved dinosaur mummy ever found. 

There was only one problem. Revealing the secrets of this mummy would require something far more sophisticated than tinkering with bones.

Enter NASA. Using X-ray machines thousands of times more powerful than those used in hospitals, the NASA team performed an autopsy without making a single cut.

It was just the beginning: the dinosaur mummy had many secrets to reveal.  

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In Mantell's time, palaeontologists had to imagine dinosaurs from a few fossilised teeth or bones. To fill the gaps, they let their imaginations run a little wild. In 1830, English geologist Henry De la Beche painted Duria Antiquior (Ancient Dorset), above, based on fossils found in the seaside town of Lyme Regis on the southern England coast. 

Over the years, as more fossils were found, artists refined their drawings. Still it seemed the best they could ever do was to make educated guesses about what dinosaurs realled looked like. 

Leonardo changes all that. Based on the smooth texture of the skin on his stomach, the pattern on his legs, and the shape and position of his muscles, scientist-artist Julius Csotonyi was able to paint one of the most accurate pictures of a dinosaur has ever seen, below. 

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Leonardo's well-preserved stomach revealed secrets about the world he inhabited. NASA researchers identified the remains of ancient plants. More than 400 different species were identified including ferns and magnolias, cycads and conifers. In 2008 Dennis Braman, Karen Chin and their collleagues published these results in the journal Palaios

Csotonyi used this new information to Leonardo's world to life, below. Every plant used in this image was found in his gut. The painting also shows a pair of dome-headed two-metre dinosaurs called Stegoceras that were fairly common on the coastal plain where Leonardo lived. 

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Why was Leonardo turned into a mummy? One theory is that shortly after dying, Leonardo's body was caught in a flood and rapidly covered in sand. The surging floodwaters carried tannins and aldehydes leached from fallen conifer trees. These natural antibacterials protected Leonardo from decay, preserving him as a mummy.

We can imagine Leonardo's last day. His X-ray revealed a fracture to his ribs. Already injured, the dinosaur must have strugg;ed to escape rising floodwaters as a hurricane raced from the area now known as the Gulf of Mexico up the shallow sea that divided east and west America at the time. Unable to fight his way to higher ground, Leonardo drowned, eventually washing up on a sand bar, below. (Csotonyi won Scientific American's Lazendorf aware for this portrait).

Palaeontologists suspect hurricanes like these caused mass deaths and explain why so many dinosaur skeletons remain in the sandstone rocks of Cretaceous Montana today. There were simply too few animals left to consume all the carcasses, so their bones were left to fossilise or, in a rare combination of circumstances, become mummified, only to be rediscovered by an inquisitive species of modern primate tens of millions of years later. 

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