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	Dinosaur - A Short History © 2004 For Our Complete Line Of Dinosaur Products, Click Here
It is hard to believe that a group of animals which lived so long ago could have invaded popular culture as much as the dinosaurs have. This fascinating group of animals has provided the fodder for countless books and movies, and been the subject of innumerable popular exhibits for museums. But what do we really know about the dinosaurs? When did they live? What was the world like when they were alive? This short istory of the dinosaur should help answer some of those questions. Because dinosaurs died many millions of years before humans evolved, no human has ever seen one. So how do we know they even existed? They left the record of their existence in the very ground beneath our feet, in the form of their fossilized remains. Paleontology is the study of fossilized plant and animal remains and this is the science which tells us most of what we have come to know about dinosaurs. The name dinosaur was coined by a nineteenth century anatomist, Sir Richard Owen, who first studied dinosaur fossils in 1842. The name he drew from Greek words, deinos, meaning "terrible" and sauros, meaning "lizard". The name stuck, and we still call this large group of animals by Mr. Owens term.		Fossils are the remains of these animals which have been preserved in rock. Bone, teeth, and shells of long dead animals are preserved by a process called "fossilization". Woody plant material can also be preserved by this process. Geologists studying the development and natural history of the earth have divided the timeline of earths history into long periods called eras. These vast groupings of time include millions of years of earth’s history. These are further divided into smaller units called periods. We are currently living in the Cenozoic Era which started approximately 65 million years ago. The Era immediately preceding the current era is called the Mesozoic Era. This Era lasted about 160 million years, from about 225 million years ago to 65 million years ago. This is the time frame in which the dinosaurs lived. Since humans didn’t begin evolving until about 2.5 million years ago, you can see that dinosaurs died out about 62 million years before our ancestors began to evolve. The world which the dinosaurs knew was quite a bit different than the earth we know today. At the beginning of the Mesozoic Era the continents of the earth were not in the same position that they are today. A process called "continental drift", which has occurred throughout earth's history, is to blame for this. The earth is composed of distinctly different layers. The uppermost layer, where we live, is called the crust. This layer is basically solid rock. It floats upon the next layer, the mantle, which is composed of very hot molten rock. The continental crust floats upon this layer, and is constantly moving. This movement is very slow, occurring over millions of years.

The continents at the beginning of the Mesozoic Era were all grouped together in a single large continent geologists call Pangaea. This "super continent" slowly broke up and drifted apart over millions of years. The day was slightly shorter at this time. As the earth spins on its axis, gravitational influences of both the sun and moon cause its rotation to slow. This is apparent over millions of years. The sun was slightly cooler, then too. This was offset by the higher carbon dioxide levels in the earth’s atmosphere, causing earth’s climate to be somewhat warmer during the whole era than it is today. The first period of the Mesozoic Era is called the Triassic Period. It lasted approximately 45 million years, until about 180 million years ago. The climate was subtropical into regions of what was to become North America as far north as current sites of Montana and New England. The Appalachian Mountains were birthed during this Period as the plates of the crust ground against each other as they slowly drifted north. The Triassic Period is when the first dinosaurs evolved from large crocodile-like animals called archosaurs. Fossil records from about 230 million years ago contain the first evidence of these dinosaurs.

The Triassic Period also saw the beginnings of the first insects-like creatures as well as small rodent-like mammals. Most vegetation was of the evergreen type. Most of the trees were similar to ginkgo and pine. Ferns, mosses and cycad palms also numerous. The flowering plants with which we are familiar were not in existence yet. Much of what is now the Midwest in North America was covered by a shallow sea. The next Period in earth’s history is called the Jurassic Period. This Period lasted until around 135 million years ago, a period of about 45 million years. It is named after the Jura Mountains in Europe which contain many geological deposits from this period. An inland sea still covered much of North America. The climate was still very much warmer than it is today, and the flora of the period, which the great plant eating dinosaurs depended upon for food, still consisted of evergreen trees, tree ferns, scouring rushes, and ferns. The most well known dinosaurs, including the Tyrannosaurus Rex and the brachiosaur, appeared during this period. Small mammals were found on every continent except Australia, which by now had completely broken away from the other main landmass. The last period of the Mesozoic Era is called the Cretaceous Period. It ended with the Dinosaur era, about 65 million years ago. Dinosaurs had become the unquestioned dominant animal group during this period of history, existing in many species and types. Flowering plants evolved during this time, and many of the trees, flowers, and other plants with which we are familiar had their beginnings during this period. The continents as we know them had largely formed by now, but the climate was still warmer than modern times. The Appalachian Mountains, which had largely eroded during the Jurassic Period, saw a period of more uplifting. The Rocky Mountains in the western North American continent began uplifting.

Dinosaurs, as a group, varied considerably. The smallest were only a couple of feet long. The largest grew to over eighty feet. Some, usually the four footed ones, were herbivores, eating only plants. The two legged ones, like the velociraptors and T-Rex, were ferocious carnivores. There were flying dinosaurs, crawling dinosaurs, walking dinosaurs and swimming dinosaurs. They were present on every continent of earth. Scientists don’t know for sure if they were warm blooded, or cold blooded. Evidence suggests that they became more warm blooded through the ages. They do know that most, if not all laid eggs. Typically, they dug nesting cavities into the earth and laid their eggs in them. Fossil evidence suggests that mortality for the small dinosaurs was very high. Their skin was somewhat textured and bare, though some of the smaller ones may have been covered with a fibrous hair or feather like covering. Their eyes were about twice the size of mammals living today. What happened to the dinosaurs? There are two theories in the scientific community, and both have supporting evidence. One group of scientists believes that the dinosaurs became extinct over a long period of time, caused by environmental changes caused by a cooling earth and changing sea levels. Possibly the dinosaurs couldn’t adapt to the changes and died out. Other scientists believe that mass extinction came rather quickly, the result of an asteroid collision with earth. This would have filled the atmosphere with a cloud of dust which blocked sunlight and killed the plants off which the dinosaurs need for food. Most of North and South America would have been devastated by the explosion. A crater has been found in the Yucatan peninsula in Mexico which is about the age of the dinosaur’s extinction. Whatever happened, the dinosaurs are gone, leaving behind their fossils and legend. We are left to speculate about them based upon the fossil remains and what we can guess about their behavior by studying modern animals. There are surely more questions than answers about the history of the dinosaur.