Scientists now think these dinosaurs were more muscular than previously thought

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Skin, muscle, tendons and other tissue that rarely survive fossilisation have all been preserved in the specimen unearthed in North Dakota, US.

The 67 million-year-old dinosaur is one of the duck-billed hadrosaur group.

The preservation allowed scientists to estimate that it was more muscular than thought, perhaps giving it the ability to outrun predators like T. rex.

The researchers propose that the dinosaur's rump was 25% larger than had previously been thought. This probably meant more muscle mass and therefore greater acceleration, giving it a greater chance of evading meat-eating dinosaurs in hot pursuit.

Depth and structure

While it has been dubbed a dinosaur "mummy", the dinosaur is actually fossilised into stone.

But unlike the collections of bones found in many museums, this hadrosaur came complete with fossilised skin, ligaments, tendons and possibly some internal organs, according to researchers.

"It's unbelievable when you look at it for the first time," said palaeontologist Phillip Manning from the University of Manchester, UK.

The scales are still visible on the fossilised skin

Dr Manning said there was a pattern of banding to the larger and smaller scales on the skin.

Because it has been fossilised researchers do not know the colour of the skin. But looking at it in monochrome shows a striped pattern. He noted that in modern reptiles, such a pattern is often associated with transitions between different skin colours.

The fossil was found in 1999 and is now nicknamed Dakota. It is being analysed in the world's largest CT scanner, operated by the Boeing corporation.

The machine usually is used for space shuttle engines and other large objects. Researchers hope the technology will help them learn more about the fossilised insides of the creature.

The reptile had no chest cavity, suggesting it had been partially eaten by predators before being "mummified" in unusual conditions: acidic, waterlogged sediments collected around the dinosaur, triggering the rapid deposit of minerals and trapping organic molecules before they decayed.