DINOSAURS OF THE
I am writing this paper on the Jurassic Period. I will be talking about the different periods of dinosaurs. What dinosaur life was like during the Jurassic Period. I will also be going more in depth with several dinosaurs that lived during the early, middle, and late Jurassic Period. The history of the Jurassic Period in North America as well as Mexico also caught my interest. The three ages of Dinosaurs were in the Triassic, Jurassic, and Cretaceous periods. First I would like to explain all 3 periods before getting into the Jurassic period more specifically. The start of the Triassic period followed the Permian Extinction, an event of unknown cause that wiped out over two-thirds of land-dwelling vertebrates and 95 percent of ocean-dwelling species. It was during the late Triassic period that the mammal-like reptiles evolved into the first mammals. During the Triassic period, all of the earth's continents were joined together into a vast landmass called Pangaea. There were as yet no polar ice caps, and the climate was hot and dry, punctuated by violent monsoons. Except for insects, the skies of the early Triassic period were relatively quiet. The Triassic period wasn't nearly as lush and green as the later Jurassic and Cretaceous periods, but it did see an explosion of various land-dwelling plants, including cycads, ferns, and Gingko-like trees. Part of the reason there were no enormous dinosaurs during the Triassic (along the lines of Brachiosaurus) is that there simply wasn’t enough vegetation to nourish them! During the Jurassic period, relatives of the small, quadrupedal, plant-eating prosauropods of the Triassic period gradually evolved into gigantic sauropods like Brachiosaurus and Diplodocus. This period also saw the rise of medium- to large-sized theropod dinosaurs like Allosaurus and Megalosaurus, which helps explain the evolution of the earliest ankylosaurs (armored herbivorous dinosaurs). The Jurassic period was also the heyday of the stegosaurs, typified by Stegosaurus. The climate was hot and humid, with steady rainfall, ideal conditions for the explosive spread of lush, green plants. By the end of the Jurassic period, the skies were filled with relatively advanced pterosaurs like Pterodactylus, Pteranodon and Dimorphodon. Prehistoric birds had yet to fully evolve, leaving the skies firmly under the sway of these avian reptiles (with the exception of some prehistoric insects). During the early Cretaceous period, the inexorable breakup of the Pangaean supercontinent continued, with the first outlines of modern North and South America, Europe, Asia and Africa taking shape. Conditions were as hot and muggy as in the Jurassic, with the added twist of rising sea levels and the spread of endless swamps. It was during the Cretaceous period that dinosaurs really came into their own. Thousands of genera roamed the slowly separating continents, including raptors and tyrannosaurs. The main innovation of the Cretaceous period was the evolution of flowering plants, which spread across the separating continents, along with thick forests and other kinds of dense, matted vegetation; this is also when grass first started to appear on the scene. At the end of the Cretaceous period, 65 million years ago, a meteor impact on the Yucatan Peninsula raised huge clouds of dust, blotting out the sun and causing most of this vegetation to die out. The herbivorous dinosaurs that fed on the plants died, as did the carnivorous dinosaurs that fed on the herbivorous dinosaurs. There are four dinosaurs I would like to talk about during the Early Jurassic period and they are Ammosaurus, Crylophosaurus, Dilophosaurus, and Podokesaurus. Ammosaurus Dinosaur lived during the early Jurassic period, around 180 million years ago. It was a herbivore and could walk on both four or two feet, the latter undoubtably allowing it to reach higher branches. It had large claws on its hands to...
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