The dinosaurs roamed the earth for more than 150 million years. Over this time period, known as the Mesozoic era, the Earth was subject to a lot of change in terms of landscape, climate, flora and fauna. It was a volatile and fertile time, with several natural disasters causing the extinction of many of the world's species, but with enough surviving to evolve into the next wave of life.
The Mesozoic era was a period of history that stretched from 248 to 65 million years ago. It is divided into the three time periods in which the dinosaurs lived: the Triassic, Jurassic and Cretaceous. The term “Mesozoic” means “middle animals." The flora and fauna in the world during this period changed dramatically, with the evolution of dinosaurs, more diverse plants and the first mammals and birds.
The Triassic period (248 to 206 million years ago) began and ended with a massive natural disaster which wiped out around 90 percent of the planet's species. The species that did survive then repopulated the Earth and evolved into completely new creatures. The oceans were packed full of life: mollusks, ammonites and the first corals lived alongside massive Ichthyosaurs and Plesiosaurs. Pterosaurs, a group of flying reptiles, dominated the air and the first large mammals and dinosaurs roamed the earth. One of the first dinosaurs was the Coelophysis, a carnivore which grew up to 9 feet tall and weighed up to 100 pounds.
The dinosaurs survived the natural disaster at the end of the Triassic period and went on to dominate the Jurassic period (208 to 146 million years ago). The supercontinent Pangaea which had dominated the Triassic period was rapidly breaking up, and mountains rising up from the ocean floor pushed sea levels up. This made the previously hot and dry climate fairly humid, and prompted the growth of many more plants and trees such as palms and ferns. The dinosaurs in this period were huge, with the Brachiosaurus standing at 85 feet long, 52 feet tall and weighing 80 tons. These massive herbivores were matched with equally large carnivores, such as Allosaurus. The earliest known bird, Archaeopteryx, also originated from the Jurassic period.
The Cretaceous period stretched from 146 to 65 million years ago, and by the end of this period, the landmasses were in much the same position as they are today. Throughout the period the continents had been moving further apart; this and the increasing expanses of ocean caused the climate to become more moist and cool. New types of dinosaurs evolved as well. Herds of Iguanadon and Triceratops were widespread and Tyrannosaurus Rex terrorized the northern hemisphere while Spinosaurus dominated in the south. Mammals were becoming more common and more species of birds were competing with the flying reptiles for the skies. But, at the end of this period, the dinosaurs were wiped out by another natural disaster and life on Earth was never quite the same again.