This color-illustrated encyclopedia of dinosaurs introduces over 50 types of dinosaurs. Clearly written and easy to understand text introduces us to the most important of these amazing rulers of our planet Earth which suddenly disappeared about 65 million years ago.The first animals we can recognize as dinosaurs lived about 225 million years ago. To begin with dinosaurs were small animals about a meter long, running on their hind legs. Early dinosaurs were among the first animals to evolve legs for supporting great weight or moving fast to catch prey or escape enemies. It may well have given them an advantage over other animals around.The ruled our planet hundreds millions years but died out in just a few million years. By 65 million years ago they were extinct. At about this time the climate became much cooler and plant-life changed. For animals adapted to warm conditions, like dinosaurs, life became difficult. Some scientist think a sudden climatic change killed them off. This could have happened when a giant meteorite hit the Earth and threw up dust, blocking out sunlight.