Decoding Fossils of Dinosaurs

Topics: Dinosaur, Cretaceous, Tyrannosaurus Pages: 8 (3054 words) Published: October 8, 2006
Dinosaurs lived on earth 65 million years ago. They lived on the earth much before any human being was born. They ruled the earth for over 165 million years, till 65 million years ago. They were huge monsters, even bigger than elephants. The word "dinosaur" was taken from a Greek word which means terrible lizard. But they weren't exactly lizards. Lizards are one type of reptile and dinosaurs are another type. Not all dinosaurs were giants. Some dinosaurs were no bigger than small dogs. The smallest kind was about the size of a chicken. No human being has seen a living dinosaur but, scientists have many ways of learning about them. One important way is by studying fossils. Fossils give scientists a vast amount of information about ancient animal and plant life which have become extinct. They also helped them in finding out how long ago the animal or plant lived. As animals and plants die over the years they get covered up and buried into soil. The soft parts of their bodies rot away leaving behind only the hard parts like bones and teeth. These hard parts lose their original mineral composition or structure. Their remaining parts either get recrystallized or replaced by other minerals such as silica and iron pyrites. This is called a fossil. Recrystallization means exchange of one chemical by another within the skeleton which results in a coarser, perhaps heavier structure. Many fossils consist of original hard parts of the animal as well as minerals taken from the surrounding rocks. This process preserves the fossil's structure but increases its hardness and weight. Plants don't have bones. Only animals have teeth and bones, what happens to plants? Bones and teeth are preserved without much change except that the organic matter in the cavities and tiny spaces in the bone decays, leaving behind the hard, mineral substance of the bone. The spaces left empty by decay get filled with minerals such as lime and silica. Teeth are usually preserved without much change as they are harder than the bones and contain fewer tiny spaces. Aren't some plant fossils only imprints of plants? Jellyfish or other soft bodied animals and plants may be preserved as imprints fossilized over time. However, some of the original leaf substance may be left in the form of a brown or black film of carbon. This process is called carbonization. Other interesting footprints are footprints and trails of certain animals. Dinosaur tracks have been found in various places. Sometimes, footprints and tracks get wiped out by wind and rain. But in some cases the footprints made on soft clay which later dried up and got covered by layers of fresh sediment and was thus preserved and later turned into sedimentary rock. These fossil footprints have supplied a certain amount of information about how dinosaurs walked and about their size. Fossilized dinosaur eggs have also been found. The most famous are the dinosaur eggs found in the Gobi Desert in Central Asia. Some dinosaur fossils have been found in other countries also. Based on these, some species have been identified. Some of them are Indosaurus, Megalosaurus, Dravidosaurus, Titanosaurus and Barapasaurus Tagorei. Scientists have been able to identify 350 species of dinosaurs already. There could be many more. By measuring the age of the rock around a fossil, scientists can tell how old a fossil is. They do this by using several techniques. One such technique is radiocarbon dating which can be used with samples containing remains of living things such as wood. For this they take a small sample of the item to be dated and measure how much of the radioactive isotope, carbon-14, it contains. Isotopes are special forms of an element that have either more or fewer, neutrons than normal atoms of the element. For example, a normal carbon atom contains six neutrons whereas in case of carbon-14 there are eight neutrons instead of the usual six. Do all organisms have carbon-14? Where does it come from? Plants absorb...
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