Topics: Dinosaur, Jurassic, Cretaceous Pages: 1 (348 words) Published: June 21, 2013
Dinosaurs are the first reptiles appeared during the Jurassic era where the lime stone strata were identified in the Jura Mountains within the European Alps. This was during the Triassic period approximately 230 million years ago and the dominant terrestrial vertebrates for 135 million years from the beginning of the Jurassic and till the end of the cretaceous era. Jurassic means 201 years ago and cretaceous means 66 million years ago. The word dinosaurs means terrible lizard from the Greek language though they are not lizards. Instead they represent a separate group of reptiles which did not exhibit traditionally seen as reptilian. Many pre historic animals are popularly conceived as dinosaurs but are not classified as dinosaurs. Commonly dinosaurs have the basic structures of having crests and horns but some groups developed skeletal changes like spines and bony armors. An extinction event occurred 65 million years ago and that became the end of these creatures. Many pre historic animals are popularly conceived as dinosaurs like pterosaurs mosasaurs, dimetrodon and plesiosaurs but these are not classified as dinosaurs scientifically. Studies show that nearly 500 dinosaurs of non bird’s category has been recognized till now. Total number of dinosaurs in the fossil has been recorded as 1850. We have to discover nearly seventy five of the died out creatures. Another research has predicted that there were 3400 categories of dinosaurs lived but many of them could not been conserved in the record of the fossils. There were 1047 species has been named as different species of dinosaurs. Most of the dinosaurs used their two legs for moving from one place to another place but some pre historic kinds used their four legs for migration. But there are some exceptions like they can use both two legs and four legs for moving. Dinosaurs are well known for its large size. But some dinosaurs were in the size of human beings or even smaller ones. Fossils of dinosaurs are found in...
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