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It has been a wonderful season for dinosaur enthusiasts. New discoveries as far apart as China, South Africa and Spain have put some meaningful flesh on the fossilised bones of the biggest-ever beasts to walk the land. With each new discovery, dinosaurs are becoming a little less mysterious than they once seemed.
Chinese scientists have led the way with a series of stunning finds, such as the discovery of a giant bird-like creature that walked on two legs, weighed more than a ton and was armed with dagger-like claws and a bone-crushingly large beak.
Twice as tall as a man, Gigantoraptor was the stuff of nightmares. Its fearsome head and parrot-like beak sat on a muscular, elongated neck. Its body was also covered in feathers, underscoring the growing realisation that modern birds are almost certainly the living descendants of dinosaurs.
The announcement of Gigantoraptor's discovery in the Gobi desert of inner Mongolia came just a day after another team of researchers said that they had identified the remains of a new species of mini-dinosaur found in South Africa. It turned out that the creature was related to two of the lumbering vegetarians of the dinosaur world - Stegosaurus and Triceratops - which are famous for their armour-plated skins and horny protective ruffs.
Only this time, the bones of Eocursor parvus, or "little dawn runner", indicated it was far sleeker and smaller than its massive cousins. In fact it grew no bigger than a fox say the scientists, who had finally got round to analysing the fossils 12 years after they were unearthed at a site in South Africa's Orange Free State.
It is not the first time dinosaurs - creatures synonymous with giants - have turned out to have their pygmy variations. Last year, for instance, scientists revealed that fossils excavated from a quarry in Germany belonged to a member of the sauropod dinosaurs, which are famous for specimens growing up to 45m long and weighing as much as 80 tons. Only this time the sauropod dinosaur weighed less than a ton and stopped growing at 6m.
Size difference is just one of the many features to emerge from the latest discoveries of dinosaur fossils. With the sophisticated tools of the modern laboratory, scientists can glean far more about the life and behaviour of what may otherwise seem like a pile of old bones.
Two recent studies, for example, have shed light on how dinosaurs moved, even though this aspect of behaviour is not directly preserved when a dinosaur's remains become fixed in stone. The findings demonstrate how far scientists have come in their ability to study this bizarre group of animals that ruled the land for more than 160 million years before finally becoming extinct about 65 million years ago.
Loic Costeur, of the University of Nantes, was studying the sandstone deposits at a well-known dinosaur site at La Virgen del Campo in the Cameros Basin of northern Spain when he spotted a trackway of scratch marks. It turned out they were made by the hind limbs of a bipedal dinosaur as it swam against a strong current.
Dinosaur tracks preserved in stone are well documented, but this was the first time experts had found an underwater trackway made by a true-swimming dinosaur. It moved by paddling its hind legs a bit like a modern duck, Dr Costeur said.
"The trackway is quite amazing. It cannot have been made by a walking dinosaur because the scratch marks are quite delicate, with long grooves made in the sediment indicating a large, swimming animal," he said.
"They are so delicate that they could only be made by an animal whose body was supported by water. There were also ripple marks in the sandstone, indicating that the water was up to 3m deep," he added.
Conventional studies of the fossilised remains of dinosaurs, whether bones, skin, eggs or tracks, can yield only so much about the true nature of these creatures. Computers, medical scanners and other modern analytical tools have allowed scientists to go much further into dinosaur behaviour.
John Hutchinson, of the Royal Veterinary College, University of London, has carried out a detailed mathematical study of how Tyrannosaurus rex, the greatest of all land carnivores, managed to move at speed. He concluded from biomechanical calculations of its bone structure - which he fed into a series of computer models - that T rex would have been front heavy and could manage no more than a "leisurely jog" at a top speed of 24km/h. Unlike modern carnivores, T rex would have only been able to turn slowly on two legs if it had chased, rather than scavenged, its prey.
But, as lumbering as it was, T rex was still an agile hunter according to an analysis of its skull using a medical brain scanner. The dinosaur had a relatively sophisticated inner ear - the organ of balance and poise - compared to diplodocus, a large and lumbering herbivorous dinosaur. And although T rex's brain was small, it had a relatively large olfactory centre, giving it a good sense of smell.
"What we see in T rex is very different to diplodocus. We see an inner ear, the organ of balance, that is associated with a much smaller, more agile animal. T rex is a gigantic animal and we might have expected its inner ear to be more like that of diplodocus," said Professor Lawrence Witner, of the Ohio University College of Osteopathic Medicine.
"This may show that T rex had a heightened sense of equilibrium and balance and was able to employ relatively rapid turning movements of its eyes and its head," Professor Witner said.
Fossilised bones can also tell scientists how the biggest dinosaurs managed to grow so big - they did not just grow continually throughout life, but experienced an adolescent growth spurt. A study of T rex at Florida State University analysed the creature's bones and found that its growth rings indicated that it grew much faster in its younger years than later in life.
Whether T rex cared for its young is still an open question, but there is convincing evidence that at least some species of dinosaur did not abandon their eggs once they were laid, as modern reptiles do.
The first convincing piece of evidence for parental care among the dinosaurs came out in 2004 with the discovery of fossils showing that an adult dinosaur was apparently protecting a clutch of its young when they were all engulfed by a mudslide more than 100 million years ago.
The Chinese scientists who made the discovery said that the find indicated a degree of parental care that went beyond simply protecting a nest of eggs. The young psittacosaurus dinosaurs - a brood of 34 in total - were several months old and, although physically capable of fending for themselves, they still seemed to need their mother.
Opinions on whether dinosaurs cared for their young had to be revised when it emerged that a dinosaur called oviraptor - named the "egg stealer" after it was found near a clutch of eggs - was not in fact attempting to eat them but was instead guarding them.
Oviraptors, which lived between 80 million and 120 million years ago, had a toothless beak and walked on two legs. They could grow up to 3.9m long and their forelimbs were armed with sharp, powerful claws. One fossilised oviraptor, unearthed at a site in southern China, revealed that it was about to lay two eggs. Birds lay one egg at a time, whereas reptiles lay dozens at a sitting. Oviraptor, therefore, showed it was somewhere in between.
"This supports the theory that oviraptor-like dinosaurs retained two functional oviducts, like crocodiles, but had reduced the number of eggs ovulated to one per oviduct, as in birds," said the scientists when their study was published in 2005 in the journal Nature.
It was further evidence that dinosaurs and birds were linked. But even stronger links were established, again by scientists in China, with the discovery that some small, meat-eating dinosaurs grew feathers.
Why they had feathers is still open for debate. One suggestion is that they were used initially as thermal insulation, suggesting that these creatures were active and warm-blooded. Only later in their evolution were feathers used aerodynamically, for flight.
Four years ago, Chinese scientists stunned the world with the announcement they had found a feathered dinosaur with four wings. Microraptor gui may not have been a direct ancestor of modern birds, but it must be one of their more exotic relatives.
The question of powered flight with feathered wings centred on a debate over whether powered flight had resulted from the ground up, or from the trees down. One idea was that insect-chasing dinosaurs with insulating feathers began jumping up into the air from the ground and thereby learnt to fly.
The other was that small, feathered dinosaurs took to the trees and learnt to glide from branch to branch, before engaging in powered flight. Either way, the evidence seemed to be in favour of a transition from a small, feathered dinosaur that dined on meat to the earliest common ancestor of all modern birds.
Whether the extinction of the dinosaurs was the result of a giant asteroid collision or the serial eruption of a network of supervolcanoes - or both - their genes at least have lived on in the rich variety of feathered creatures around today. So the next time you spy a blackbird on the lawn, think about where its ancestors came from 65 million years ago.
- Independent
