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Dinosaurs are a species of reptiles and not a specific animal as many people think. They first appeared about 250 million years ago and became extinct 66 million years ago. These animals were divided into the avian and non-avian. Birds are the only existing avian dinosaurs, but all non-avian dinosaurs became extinct. Dinosaurs are the largest animal ever to walk the planet; they were the dominant vertebrates for the entire period they existed. Dinosaurs are classified according to the period they lived.

Triassic Period - 201 to 252 million years ago

During the Triassic period land existed as a single landmass known as Pangaea and most animals and plants exhibited near similar characteristics. A large part of Pangaea was covered by desert and there were no polar ice caps. The hot and dry climate provided suitable conditions for reptiles to thrive, and it was during this period that the dinosaurs began walking the planet. The dinosaurs that existed at the period were known as Triassic dinosaurs, and they include the Coelophysis. As the period ended, earthquakes and volcanic eruptions caused the continent to break into two, and the North Atlantic Ocean was formed.

Jurassic Period - 201 to 145 million years ago

It is evident that mass extinction occurred as the Triassic period ended but the causes elicit hot debates among researchers. Several large animals became extinct, but the dinosaurs survived and evolved into several subspecies. When Pangaea split, it formed Gondwana in the south and Laurasia in the north. Both continents were habitat by dinosaurs. The high amount of CO2 in the atmosphere resulted in the drop in temperature while the formation of the new ocean led to increased rainfall. Plants began growing in areas they never existed providing habitat for animals. The dinosaurs that lived during this period were the largest, and most of them were herbivores. They include Brachiosaurus, Diplodocus, and Apatosaurus.

Cretaceous Period - 66 to 145 million years ago聽

The last of the dinosaurs existed during the Cretaceous period. The land subdivided further into the continents we know today but located in different positions. The dinosaurs evolved independently and created a more diverse species. It was during this period that other living organisms also diversified including snakes, plants, insects, mammals, and even predators.

Why Did Dinosaurs Disappear?

Dinosaurs became extinct during the Cretaceous period. Researchers are uncertain of what exactly caused the mass extinction of dinosaurs. The mystery deepens considering that other large mammals such as elephants, giraffes, and mammoths survived. Other species including crocodiles, frogs, mammals, turtles, snails, and sea creatures also survived. Scientists propose that the extension could have occurred due to the collision of the planet and an extraterrestrial body such as a comet or meteor, or a series of volcanic activities that affected the earth at a global level. The events changed the weather patterns, and the dinosaur鈥檚 large body could not adapt to the change.