Palaeontologists have made important breakthroughs in understanding how dinosaurs behaved, what they resembled and how they managed to cope with the physical strain of being the biggest animals to have lived on land - until their extinction 65 million years ago.
Knowledge of dinosaurs has exploded over the past five years, underlined this week by the discovery of the first dinosaur species to be found on two continents, and calculations showing that the long-necked Diplodocus grazed like a cow rather than like a giraffe, with its head held high, as depicted in the film Jurassic Park.
Only a few years ago, suggestions on how dinosaurs raised their young, caught their prey or controlled their internal physiology would have been pure speculation. But finds such as the huge breeding ground on an ancient floodplain in Patagonia, Argentina, are revolutionising study of a dinosaur's way of life. The largest meat- eating dinosaur may have been found at the site this week, according to Rodolfo Coria, an Argentine palaeontologist.
Thousands of eggs litter the once muddy landscape. When researchers opened the fossilised eggs they found perfectly preserved embryos and the first glimpse of a baby dinosaur's scaly skin - which looks remarkably like that of a modern-day lizard.
Other scientists hope that preserved pigments in the skin may reveal the colour of a dinosaur for the first time.
A clutch of eggs found in the Gobi Desert in Mongolia has shown that female dinosaurs brooded like birds. A sudden sandstorm engulfed an Oviraptor while she was on her nest, preserving her position for posterity. It was one of the most powerful pieces of evidence to show that dinosaurs took care of their young, unlike most present-day reptiles. It also showed that Oviraptor - which means egg- stealer - had been maligned when it was named 70 years ago after its discovery near a nesting site.
The link between dinosaurs and birds has also been confirmed with a dramatic discovery of perfectly preserved feathered dinosaurs at Sihetun, in the Liaoning province, north-west China. "We've been dead lucky," said Angela Milner, a dinosaur palaeontologist at the Natural History Museum in London. "It was one of those rare cases when very fine silt preserves things beautifully."
One of the most dramatic finds to emerge from Sihetun was of a small therapod dinosaur, called Sinosauropteryx prima, which was the first dinosaur to be found with feathered wings, suggesting that some dinosaurs at least did not die out but live on today as birds. One specimen had a pair of eggs ready for laying. Another had the bony remains of a small lizard in its stomach.
The internal organs of another finely preserved dinosaur, called Scipionyx, which was found in Italy and lived 110 million years ago, revealed it had a primitive diaphragm, enabling it to boost its oxygen supply to fuel bursts of activity.
Cold-blooded animals in a warm climate can move quickly, said Nicholas Geist, a palaeontologist from Oregon State University. "If you add in the lung capacity that we're finding for meat-eating dinosaurs, what you have is a turbo-charged reptile," he said.
The mystery of whether dinosaurs were cold-blooded like reptiles or warm-blooded like mammals may be solved with studies of the growth rings of dinosaur bones. American scientists investigating the bones of Deinosuchus, a giant crocodile-like dinosaur, found they went through a rapid growth spurt early in life, indicating a warm-blooded physiology.
"We know enough to know there was a huge range in physiological types. Some of the small meat-eaters were probably not much removed from being warm-blooded, but the big vegetarians were probably cold-blooded," Dr Milner said.
It may be that dinosaurs had an internal switch, which could allow them to change from one type of physiology to another - the growth rings of Deinosuchus indicate it became cold blooded in later life. "No other animals show this," she said.
Footprints left behind have also helped scientists to understand how dinosaurs walked and how they socialised in herds. Even fossilised dung has been used to reveal some of the mysteries of Tyrannosaurus rex. The loaf-shaped "coprolites" contained crushed bones, showing that the world's biggest terrestrial carnivore chewed its prey before swallowing.
"This is a piece of fossilised behaviour," said Peter Andrews, a coprolite expert at the Natural History Museum. "This tells us they were using their teeth literally to crush. They did not just tear off big chunks and swallow them whole."
The Egg Mother
When a fossilised Oviraptor, which lived about 80 million years ago, was found brooding on a clutch of eggs, scientists had the strongest evidence to date that dinosaurs cared for their young
Fine details of a dinosaur's internal organs emerged with the discovery of a 113 million-year-old Scipionyx hatchling, suggesting that its blood was turbo-charged with a rich oxygen supply
One of the most dramatic dinosaur finds, in north-west China, revealed the first feathered dinosaurs, such as Sinosauropteryx prima, making the link with modern-day birds
Insights into Tyrannosaurus rex, the biggest carnivore to walk on land, came from the find of a loaf-sized piece of dung containing crunched bones of prey, showing it chewed its food before swallowing
How It all began
A breeding site in Patagonia in Argentina, littered with thousands of dinosaur eggs, revealed stunning details of developing embryos and the first glimpse of a baby dinosaur's scaly skinReuse content