The History Of Dinosaurs Essays - Saurischia, Tyrannosaurus

The History of Dinosaurs The dinosaurs were reptiles that appeared about 230 million years ago. It's believed that they had scaly skin and some ate plants and others ate meat. Scientists don't know whether or not the dinosaurs were cold blooded, but they think the smaller ones were warm blooded, and the large ones were cold-blooded. In this report you'll learn about the earliest dinosaurs, the kinds of dinosaurs, and how the dinosaurs died. There are two main groups of the earliest dinosaurs: Thesaurischian, and the ornithischian First I'll tell you about the Saurischian. The Saurischian were the first main group of dinosaurs. The Saurischian had lizard like hip joints. In this group there is the Theropoda. These weird dinosaurs were meat eaters that walked on their hind legs. Also there was the Sauropoda. The Sauropoda were the plant eating dinosaurs that walked on all four legs. The second main kind of dinosaurs were the Ornithischian, which had bird like hip joints. There is only one group belonging to this group and that is the ornithopoda. The Ornithopoda were plant-eating dinosaurs that walked on two legs. There were also the armored and horned dinosaurs, which were also plant eaters. There were many, many different kinds of dinosaurs. Some of them are the Brachiosaurus, the Stegosaurus, the Triceratops, the Tyrannosaurus, and the Zizhongosaurus. All of the dinosaurs are in one of two major groups. Plant eaters or meat eaters. Some plant eaters are the Saltasaurus, the Kritosaurus, and the Datousaurus. Some Meat eaters are the Chilantaisaurus, the Poekilopleuron, and probably the most terrifying one of all, the Tyrannosaurus. During the Carboniferous Period (360 to 286 million years ago), dense tropical forests were concentrated along the equator. Decaying vegetation, compressed by overlying deposits of sand and mud, was gradually converted into coal. Coal deposits of Illinios, the Appalachians, Britain and Germany were originally formed in a continuous band which was dispersed when the continents drifted apart. The Mesozoic Era lasted from 245 until 65 million years ago. In the sea, marine communities began to assume a modern composition of molluscs and other invertebrates. On land, dinosaurs dominated faunas, and the first flowering plants appeared. At the beginning of the Mesozoic, all of the earth's continents were joined as the supercontinent Pangea. Some dinosaurs can swim and some can fly. The ones that swim have large, flat arms, or flippers, that help them through the water. The ones that fly usually have two legs and huge wings that can have a 30 foot wingspan! There are many theories about how the dinosaurs died. The most populaur one is that the weather became cooler, and the dinosaurs had no feathers or fur to protect them against the changing weather. Others are like a star exploded, but then how could some other speacies have lived. Another one is that an astioriod hit the earth and made the land dark for three, or so , years. So only the animals that could live on nuts or rotten plants could live. They also think that they have the rock. The dinosaurs came to rise in the earlier part of the Triassic period, and ecologically dominated our planet until the late cretaceous. Dinosaurs evolved from reptiles, and birds evolved from the dinosaurs (to clear up an erroneous myth circulating out there, the dinosaurs did not evolve into birds. The birds came from the dinosaurs). Dinosaurs have been divided into two main groups: Saurischians, or "lizard-hipped" dinosaurs, and Ornithchians, or "bird-hipped" dinosaurs Saurischians, in my opinion, are the better of the two groups. They include all dinosaurian predators and the sauropods, or animals such as Apatosaurus and other very large animals. The ornithchians essentially include everyone else; Triceratops, Stegosaurus, Ankylosaurus, and all of the other herbivores. The saurischians are divided further into the theropods (animals that walked on two feet), and the sauropods, as mentioned above. Further information about these animals can be found in my two dinosaur databases, below. By now, most people are beginning to believe that dinosaurs were warm-blooded. Others believe that the dinosaurs were cold-blooded, and then there is the "muddy middle", or those who believe that the dinosaurs were some of both. This is known as the endo-ecto question, which asks whether the dinosaurs were endotherms (warm-blooded) or ectotherms