Dinosaur Teacher Guide to Dinosaurs

Did you know that the word dinosaur comes from a Greek word which means terribly powerful and wondrous lizard? We've all seen these gigantic lizards in movies and cartoons, played with boney horned reptile action figures, and read about them in comic books. These pre-historic creatures have big teeth, are enormous in size with long necks and tails and look as though they want to pick you up and devour you. Some may wonder if dinosaurs are something man dreamed up or if they are actually something real. Well the answer to that is definitely yes. Dinosaurs are real although they are not big lizards. Evidence of their existence can be found throughout history that scientists have used to gain important information about these now extinct creatures.

The first dinosaurs were thought to roam the earth about 230 million years ago and continued to be a major part of the world, on every continent, for 165 million years. That's a long time! Through the study of fossils and bones, scientists have identified over 500 different groups and more than 1,000 different species of dinosaurs. It's hard to imagine that only 10% of the dinosaur population has been found and studied. It will take years to gather important facts in order for future generations to gain critical knowledge of these mysterious giants.

There are two major groups of known dinosaurs. They are the Saurischia and the Ornithischia. Saurischia dinosaurs were more lizard-like and Ornithischia dinosaurs were bird-like. These two main groups contain seven popular groups which if you are a dinosaur lover, you may have heard of. They are Theropods, Sauropodomorphs, Ornithopods, Stegosaurs, Ankylosaurs, Pachycephalosaurs and Ceratopsians. Each type differs in their look and size, their mobility and their eating habits.

The dinosaurs that were shown to be bird-like in appearance and able to fly such as the Pterodactyl, scientists believe are descendents of the birds we enjoy in our world today. Those that wandered the earth on foot were able to change body postures, going from standing on four feet (quadrupedal) to standing upright on two (bipedal). Some were solely meat eaters (carnivorous) and others ate only plants (herbivorous). And although the Diplodocus dinosaur was the largest creature to ever roam the earth, most were the size of humans or smaller.

No matter the type of dinosaur, there were some characteristics that they all had in common. These include jaw muscles that opened widely onto the top of the skull, a ridge of strong muscles from the shoulder to the elbow area and strongly built boney hips, knees and ankles. Dinosaurs were not slow or lazy as some think. They could run at very fast speeds. They reproduced by laying eggs with hard shells in nests. Fossils show that they may have incubated their eggs by sitting on their nests. The nests were guarded by the parent to protect the eggs from predators. Once the babies outgrew the eggs and hatched, they did not leave the nest right away. Instinct told them when it was time to leave home. Many times they stayed together in groups but others liked the freedom of living alone.

Of those studied, scientists found BIG results. The longest dinosaur measuring about 100 feet in length was the Seismosaurus or the Diplodocus. The tallest dinosaur was thought to be about 40 feet tall and the Brachiosaurus or the Paralititan took the honor. The dinosaur that weighed the most, about 80 tons, was the Argentinosaurus. Those were big! You may wonder why dinosaurs got so big. Well the clearest answer is that it was their defense to mean and hungry predators. They could protect themselves from harm. They also had indeterminate growth. This simply means that as long as they were healthy and had food, they could continue to grow. Since they were egg layers, they did not need to use up their energy or strength by nursing their babies. Their energy was devoted to growing and grow they did!

By the end of the Cretaceous Period, nearly all living dinosaurs had gone extinct. These immense and wonderful lizard and bird figures were gone! As scientists study why this could have happened, they come to realize there is no set answer. Perhaps climate change could have been responsible. (The world was a warmer place when the dinosaurs lived.) Or maybe they became extinct due to volcanoes and a lowering of the level of the seas causing the continents to shift. Many believe it was because an asteroid hit the earth. Another theory is that dinosaurs went into extinction because of predators eating the eggs. Perhaps we'll never know the exact cause. But it's a sure thing. Dinosaurs definitely left their footprints behind and have a unique way of capturing our imaginations.

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