By Jason Palmer
Science and technology reporter, BBC News
A metre-long section of the fossil shows the size of the hadrosaur's scales
A remarkably well-preserved fossil of a dinosaur has been analysed by scientists writing in the journal Proceedings of the Royal Society B.
They describe how the fossil's soft tissues were spared from decay by fine sediments that formed a mineral cast.
Tests have shown that the fossil still holds cell-like structures - but their constituent proteins have decayed.
The team says the cellular structure of the dinosaur's skin was similar to that of dinosaurs' modern-day descendants.
A member of the duck-billed hadrosaur family, the fossil was found in North Dakota in the US and has been nicknamed "Dakota".
Phil Manning of the University of Manchester and his collaborators have been employing a number of techniques to tease out as much information as they can from the fossil.
They believe that the dinosaur fell into a watery grave, with little oxygen present to speed along the decay process. Meanwhile, very fine sediments reacted with the soft tissues of the animal, forming a kind of cement.
As a result, the 66 million-year-old fossil still retains some of the organic matter of the original dinosaur, mixed in with the minerals.
The team found that although the proteins that made up the hadrosaur's skin had degraded, the amino acid building blocks that once made up the proteins were still present.
"We're looking at the altered products of proteins from the skin of this animal, locked within the three dimensional mineralised skin," Dr Manning told BBC News.
"You're looking at cell-like structures; you slice through this and you're looking at the cell structure of dinosaur skin. That is absolutely gobsmacking."
A study of the cell structures show that, like modern-day crocodiles and birds, the skin was made up of two layers: a surface epidermis against a deeper dermis layer made up of dense connective tissue.
Although that finding is what might have been expected based on the presumed lineage of the modern animals, Dr Manning said it is "clean science".
"If you've got a hypothesis and you can't test it, it remains a hypothesis. Now we've had an exceptionally preserved dinosaur which has allowed us to ask that question and answer it for the first time," he said.
Microprobe studies showed tendon structure, preserved with silicon
Studies of the skin from across the fossil show that the skin was thinner toward the flanks, between the tail and the hips, where other hadrosaur fossils have shown bite marks. Dr Manning said that region may have been the dinosaur's "Achilles heel".
"If you understand the distribution of these structures in the skin of a prey animal, you can understand something about predator-prey interactions, and it might explain some of the hadrosaur fossils we see with these bite marks," he said.
Derek Briggs, a palaeontologist at Yale University and an expert in exceptionally preserved fossils, praised the work, saying that the important step was elucidating the mechanism by which such fossils could be preserved.
"One can't be certain, but I suspect that in many cases these kinds of skin impressions have gone unnoticed and people have gone after the skeleton, which is of course what you'd expect to be preserved," he told BBC News.
"This kind of discovery just demonstrates very clearly that soft tissue does survive, that the processes involved are unusual but not absolutely extraordinary - so there's no reason why this kind of material won't be discovered again."
Dr Manning said that studies on Dakota were continuing apace on a fossil he described as a pleasure to work with.
"Whereas most of us have to deal with disjointed sentences and occasional fractured words to reconstruct the volumes of the fossil record, you've got a whole chapter lying there and you can flick through the pages at your leisure," he said.