Monday, October 19, 2009

The Age of Dinosaurs

It is widely believed that dinosaurs ruled the earth some 160 million years ago. Is that true??? Had dinosaurs really existed???? Let's examine it now. Dinosaur is the name of a group of prehistoric reptiles. These animals died out millions of years ago, but they have fascinated people ever since they were first described in the early 1800's. The name dinosaur comes from the term Dinosauria, which means terrible lizards. But dinosaurs were not lizards, only distantly related to them, and most were not very terrible.

For many years, people thought that dinosaurs were clumsy, slow-moving, unintelligent creatures that lived much like modern reptiles. However, fossil evidence suggests that some dinosaurs—especially small theropods—were much more active and intelligent than previously thought. In addition, scientists generally agree that small theropods are the closest known relatives to birds. Thus, scientists can learn much about the life of dinosaurs by studying birds and other modern animals that have some similarity to dinosaurs.

While dinosaurs ruled the land during the Mesozoic Era, many kinds of large reptiles inhabited the sea and air. Sea-dwelling reptiles included ichthyosaurs , which resembled dolphins in shape and probably could swim fast. Mosasaurs enormous sea lizards that lived during the late Cretaceous Period, which ended about 65 million years ago. They grew up to 30 feet long. Plesiosaurs had four large flippers and a short tail. Many plesiosaurs also had an extremely long neck.

Flying reptiles called pterosaurs became the first vertebrates to evolve flapping flight, the kind of flight later used by most birds. Each of a pterosaur's wings consisted of a membrane of skin supported by a long finger made of hollow bones. Pterosaurs had no feathers, but hairlike structures probably covered their bodies. Some pterosaurs ranked as the largest flying animals of all time, reaching a wingspan of 40 feet .

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