Dinosaurs walked the earth for over 165 million years. They lived during a period of time known as the Mesozoic Era, or Age of Reptiles. At the end of the Cretaceous Period they became extinct. That was 65 million years ago. During this time there was a great deal of volcanic activity and many earthquakes. Many people believe that dinosaurs became extinct because an asteroid hit the earth changing the climate dramatically. It is believed that dinosaurs couldn't adapt to these changes.
The word dinosaur means terrifying lizard. The name was invented by Sir Richard Owen in 1842.
The oldest known dinisaur is Eoraptor, a meat-eater that lived 228 million years ago. Most dinosaurs hatch from eggs, and they could not fly or live in water.
Dinosaurs are classified as reptiles. They are divided into two groups based on the structure of the hip. One group has lizard-like hips and the other group has bird-like hips. Most paleontologists, scientists that study dinosaurs, believe that birds are the only surviving dinosaurs. Therefore, technically speaking, dinosaurs aren't really extinct because their decendents live on. Just think, the smallest bird is actually a dinosaur.
The biggest dinosaurs were over 100 feet long and 50 feet tall. The sauropod was the largest dinosaur. The smallest dinosaurs were the size of a chicken.
Some dinosaurs were carivores, meat-eaters, and some were herbivores, plant eaters. Some walked on two legs, while others walked on all four.Some had horns and spikes, others had thick bumpy skin, and some even had feathers. No one knows the color of dinosaurs, because no one was alive when they walked the earth.
There are currently over 330 described dinosaur species and this number is growing. |
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Subject Index 
