Huge reptiles called Dinosaurs lived on earth about 180 million years ago. They flourished and ruled the earth for more than 120,000,000 years. But today we can’t see even a single one of them, because all of them died out about 60 million years ago.
Why such strong and flourishing creatures should suddenly
disappear completely, is a question that still puzzles scientists today.
The most probable explanation is the climate of the earth changed too much
about 60 million years ago for the dinosaurs to continue living.
The earth on which the dinosaurs lived was much warmer, with
swamps and shallow seas rich in plant matter. The plant-eating dinosaurs
scooped up this plant matter for their living, while the flesh-eating ones
lived by killing these plant-eating ones.
Then the earth grew colder and drier. New kinds of vegetation
began to appear on earth. The dinosaurs probably could not live on this plant
matter and the changed climate. The plant-eating dinosaurs began to die, and
their disappearance was followed by the meat-eating dinosaurs.
The huge-sized reptiles called lived on earth millions of years ago. But all of them were not as big as some dinosaurs of the biggest ones. Dinosaurs existed in a great variety of sizes. Most were 25 to 30 feet long and weighed from five to ten tons. Some were much smaller (about the size of a rhinoceros) and a few early varieties were as small as a chicken!
Tyrannosaurus stood up to 20 feet tall and weighed about 8
tons. These were meat-eaters. Another variety, the Brontosaurus, was 65 feet
long and weighed 35 tons. The more slender ones called Diplodocus grew 85 feet
long but weighed less than 25 tons.
The real big ones of the dinosaur family were the Brachiosaurus, which were long-necked creatures and weighed more than 50 tons. They stood higher than the three-storey building of today!