Introduction to Dinosaurs
Introduction to Dinosaurs
The Mesozoic Era
The Mesozoic Era was between 250 and 65 million years ago and is split into three periods, known as the Triassic, the Jurassic and the Cretaceous.
Triassic Period (250 – 200 million years ago)
During the Triassic Period there were no continents only one single landmass called Pangaea. It was covered by large deserts, as the climate was exceptionally dry and hot. There would have been no polar ice caps. The plant and animal life would have been very similar, and mainly consisted of those that thrive in hot climates such as cacti and reptiles, whose kidneys are excellent at conserving water and skin is less porous than mammal skin, so perspire less in extreme heat. Before the Triassic Period, the dominant land reptiles were archosaurs (ruling lizards) and therapsids (mammal-like reptiles). These reptiles evolved into the first dinosaurs. But for over twenty million years after the first dinosaurs appeared the most fearsome reptiles were crocodiles. Towards the end of the Triassic period, a series of volcanic eruptions and earthquakes split Pangaea slowly into two smaller land masses, divided by what is known today as the Atlantic Ocean. This affected the climate and vegetation that could survive, which in turn influenced the dinosaurs’ evolution.
Jurassic Period (200 – 145 million years ago)
When Pangaea split into two it created two continents. The southern most continent was called Gondwana and the northern most continent was called Laurasia. However, similarities in the fossils found during the Jurassic period suggest there were probably land bridges between these two land masses. The new ocean would have caused an increase in rainfall. But the climate would have still been warmer than it is now, due to high amounts of carbon dioxide in the atmosphere. The discovery of fossil fuels, indicate plants such as ferns and forests of tall conifer trees grew over vast areas. The changes in the environment and climate caused many large land animals to become extinct – but dinosaurs survived. They evolved into a wide variety of different forms and increased in numbers. The bountiful plant supply encouraged the emergence of enormous herbivore sauropods, such as the Brachiosaurus and Diplodocus. These were the largest animals ever to walk the Earth. By the end of the Jurassic period their herds would have dominated the landscape.
Cretaceous Period (145 – 65 million years ago)
The word Cretaceous comes from the Latin word ‘creta’ meaning chalk. This is because during the Cretaceous period, the sea levels rose and fell, causing single-celled algae to repeatedly flourish and die. Their skeletons would sink to the seabed, forming chalk. The seas separated the land into some of the continents we know today, although they are in different positions. Europe was made up of lots of small islands. The separation of the land masses saw a boost in evolution. Dinosaurs evolved independently in different regions of the world, becoming more diverse. Other groups of organisms also diversified. The first snakes evolved, as well as the first flowering plants. Various insect groups evolved, including bees, which helped to increase the spread of these flowering plants. Mammals evolved into ground dwellers, tree climbers and predators capable of killing small dinosaurs.