Dinosaurs – mighty creatures
The word “dinosaur” is derived from two Greek words, meaning “terrible lizard.” The dinosaurs arose during the interval of geologic time known as the Mesozoic (middle life) era, often called the “golden age of reptiles” or “the age of dinosaurs.”
Species of dinosaurs ranged from chicken-sized creatures to colossal, herbivorous animals known as “sauropods”.
Dinosaurs were remarkable and impressive animals. Some species of dinosaurs were large predators, others were immense herbivores, and still others were smaller predators, herbivores, or scavengers. Most, if not all, dinosaurs laid eggs. Some dinosaurs built large nests to keep their babies together. Large dinosaurs might have lived almost 100 years.
Dinosaurs lived for about 160 million years and were the dominant terrestrial animals on Earth throughout the Jurassic and Cretaceous periods—a span of over 100 million years. The dinosaurs were the ancient cousins of today’s crocodiles, snakes, and lizards.
One of the most popular theories about the death of the dinosaurs is that the world just grew too cold for them. Indeed, for large, coldblooded creatures, even a few nights of cold could spell death.
Some scientists think that when new kinds of plants began to grow on Earth, dinosaurs couldn’t eat them. It’s also possible that disease killed dinosaurs by the millions.
Many scientists believe that dinosaurs died because an asteroid struck the Earth about 65 million years ago. The dust raised by the impact would have blocked out sunlight for months, so that plants stopped growing and the temperature dropped.
However, some scientists believe that acid rain killed the prehistoric dinosaurs. Many scientists think that the dinosaurs had started to die off millions of years before the end of the Cretaceous Period. And even more amazing, fossils have been found in the United States and southern China that might show dinosaurs lived long after they were supposed to have disappeared!
Fossilized dinosaur bones have been discovered on all continents. Discoveries of fossils in the Arctic and in Antarctica suggest that the climate was much warmer.
A find of dinosaur eggs in an Argentinian desert in1998 is one of the largest collections ever discovered.
At least 1,000 types of dinosaur are known. Paleontologists (scientists who study fossils) discover new types almost every year.