Dinosaur (Encyclopedia of Science)
Dinosaurs are a group of now-extinct, terrestrial reptiles in the order Dinosauria. They lived during the Mesozoic Era, from about 225 million years ago to 66 million years ago. Species of dinosaurs ranged from chicken-sized creatures such as the 2-pound (1-kilogram) predator Compsognathus to colossal, herbivorous animals known as sauropods weighing more than 80 tons (72 metric tons). The sauropods were larger than any terrestrial animals that lived before or since.
Some dinosaurs were enormous, awesomely fierce predators, while others were mild-mannered plant eaters. The word dinosaur is derived from two Greek words meaning "terrible lizard." The name comes from the fact that the remains of the earliest dinosaurs discovered were very large and showed they had a lizardlike appearance.
Biology of the dinosaurs
The dinosaurs shared some common physical characteristics, such as the presence of two openings on opposite sides of their skulls and 25 vertebrae. However, the dinosaurs also differed from each other in many important ways. They displayed an enormous range of forms and functions, and they filled a wide array of ecological niches. Some of the dinosaurs were, in fact, quite bizarre in their shape and, undoubtedly, their behavior.
Most species of dinosaurs had a long tail and long neck, but this was not the...
(The entire section is 2336 words.)
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