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DINOSAURS

The main evidence on which knowledge of dinosaurs is based is that of their preserved bones and teeth. It is from the skeletons that the overall shape and posture of dinosaurs can be accurately determined.

From the proportions of the bones and muscle scars it is possible to reconstruct the muscles of dinosaurs and work out the type of movements that were possible.

The construction of the limbs and limb girdles is evidence of posture, but fossil footprints provide proof of the exact way the dinosaurs strode the earth. The evidence of trackways confirms that their gait was basically mammalian and even allows to calculate the speed at which individuals were moving.

There are presently more than 800 species of dinosaurs which have been discovered.

THE ORIGIN OF DINOSAURS

The ancestry of the dinosaurs can be traced back to small lizard-like reptiles inhabiting the extensive tropical Carboniferous coal swamps of about 300 million years ago and feeding on the abundant insect life.

During the Upper Carboniferous, two major evolutionary lineages began: the lepidosaurs led to the lizards and snakes, and the archosaurs include the crocodiles and dinosaurs.

By the beginning of the Triassic period, some 225 million years ago, the archosaurs entered an ecological niche that had never been occupied before.

The emergence of the archosaurs from water heralded the beginning of the Age of Dinosaurs.

The first dinosaurs were bipedal flesh-eaters and their invasion of the land was responsible for the collapse of the Age of the Paramammals. The beginning of the Age of Dinosaurs also witnessed the origin of the mammals which 140 million years later were to replace the dinosaurs as masters of the Earth.

DINOSAUR EGG

One of the more surprising discoveries in the realm of dinosaurs is that of nurseries. Parent dinosaurs constructed nest mounds of mud 5 feet high and 10 feet across, and excavated at the summit to place the eggs.

In one such depression were found the skeletal remains of 11 young hadrosaurs up to 3 feet in length and all with worn teeth.

This means that after hatching the young stayed together living in an open invitation to any passing predator. The only explanation for such an occurrence is that the site must have been under the protection of the adults.

Presumably the young would have followed the parent while feeding and at night would have been protected by the proximity of the adults somewhat in the manner of ostriches, although it is difficult to imagine a 3 ton adult actually sitting on the nest.

DINOSAUR EXTINCTION

One of the greatest mysteries surrounding the dinosaurs is their sudden disappearance. Measured in geological time, this event could have taken place over 500,000 years.

Careful consideration of all the evidence from both biology and geology paints a complex picture. Synthetic theories, although less exciting than cataclysmic theories, can account for more facts.

By the end of the Cretaceous period, there is clear evidence from carbon and oxygen isotope studies that there was a marked increase in global temperature. From the microscopic study of the structure of dinosaur eggshells, it is evident that they were suffering from some kind of stress. This may have been heat stress which would have adversely affected their reproductive cycle.

The geographical changes from subtropical forest to open woodland encouraged the increase in mammal numbers. Evidence shows a gradual ecological replacement of the dinosaurs by the mammals. Competition for food left the oversized dinosaurs at a disadvantage against their smaller competitors.

The combination of climatic changes and mammalian competition in the changing conditions seems to be the most acceptable theory to account for the extinction of the dinosaurs.

WHERE THINGS GO WHEN THEY DIE

Every animal or plant that dies on earth could be fossilized, but it has to die in the right place. If its body is eaten, or rots away, or is broken up by the sea, it is lost forever. But if it is buried quickly by mud or sand, there is a good chance that it will be fossilized.

The most likely place for quick burial is in the sea where sediments are collecting all the time. That is why most fossils are found in marine sediments. It also explains why shells, sea urchins, and corals are common fossils while land animals like birds, monkeys, dinosaurs and insects are much rarer.

Fortunately, there are other places whee fossils can form. Lakes, ponds, lagoons and estuaries often contain remains of plants, fishes and small animals. Natural tar pits sometimes contain perfect fossils, and mammoths have been found in the frozen earth of the Arctic, with even the hair and skin preserved.

This exhibit will examine a few of the millions of fossils which have been unearthed and what they tell us about the universe and the history of our own planet.

DINOSAUR MYTHS

Dinosaurs are probably not the slow clumsy creatures they were once made out to be. In fact, the carnivores, the meat-eating dinosaurs, were probably very fast which is what enabled them to catch their meals.

Another myth about dinosaurs such as being big and stupid is also probably mistaken. Though some of them, like Stegosaurus who measured 19 feet in length, weighed 2 tons and had a brain the size of a walnut, had very little brains, most of them had larger more proportionate brains.

Dinosaurs probably lived in herds. Traces of stampedes of almost 200 dinosaurs indicate that the herbivorous varieties would graze together until they were disturbed by hungry carnivores.

Another fact which supports the herd theory is the evidence of group nesting. Nests indicate that the dinosaurs sat as close as possible together on their nests leaving only enough room to squeeze through between them. Of course, because of their size this means a large distance by our standards but barely enough for them.