What Is A Dinosaur Reading Passage
What Is A Dinosaur Reading Passage
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Even if the name dinosaur is derived from the Greek for “terrible lizard”, dinosaurs were not, actually, lizards at all. Like lizards, dinosaurs are included in the class Reptilia or reptiles, one of the five main categories of vertebrates, animals with backbones. But, at the next level of categorisation, within reptiles, noteworthy differences in the skeletal anatomy of lizards and dinosaurs have led analysts to place these classes of animals into two different superorders: Lepidosauria, or lepidosaurs, and Archosauria, or archosaurs.
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Sorted as lepidosaurs are lizards and snakes and their primordial forebears. Included among the archosaurs, or “ruling reptiles ', are primordial and modern crocodiles and the now-abolished conodonts, pterosaurs and dinosaurs. Pre Historians believe that both dinosaurs and crocodiles evolved in the later years of the Triassic period(c.248-208 million years ago) from creatures called pseudosuchia, the conodonts (crocodilian-line archosaurs). Lizards, snakes and different kinds of conodont are believed to have evolved earlier in the Triassic period from reptiles called Eosuchians.
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The primary skeletal variance between dinosaurs and other archosaurs is in the bones of the skull, pelvis and limbs. Dinosaur skulls are found in a great variety of shapes and sizes, reflecting the different eating habits and lifestyles of a large, diverse group of animals that dominated life on Earth for a remarkable 165 million years. However, unlike the skulls of any other known animal, the skulls of dinosaurs had two long bones called vomers. These bones expanded on either side of the head, from the front of the muzzle to the level of the holes on the skull called the antorbital fenestra, located in front of the dinosaur’s orbits or eye sockets.
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All dinosaurs, even if large or small, four-footed or two-footed, fleet-footed or slow-moving, shared an ordinary body plan. Spotting of this plan makes it possible to evolve dinosaurs from any other kinds of animal, even other archosaurs. Most notably, in dinosaurs, the pelvis and femur had evolved so that the hind limbs were held upright below the body rather than splaying out to the sides like the limbs of a lizard. The femoris of a dinosaur had a sharply in-turned neck and a rounded head, which was inserted into a fully open socket or hip socket. A pseudo defect of the acetabular cartilage crest helped avert disruption of the femoris. The position of the knee joint, lined up beneath the socket, made it feasible for the whole hind limb to sway backwards and forwards. This distinctive amalgam of characteristics gave dinosaurs what is called a “fully improved gait”. The progress of this highly organised method of walking also evolved in mammals, but amid reptiles, it only happened in dinosaurs.
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For the motive of further categorisation, dinosaurs are split into orders: Saurischia(reptile-hipped), or saurischian dinosaurs, and Ornithischia(bird-hipped), or ornithischian dinosaurs. This separation is made on the basis of their pelvic anatomy. All dinosaurs had a pelvic girdle with each side full of three bones: the pubis(pelvic bone), ilium(iliac bone) and ischium(V-shaped bone). But, the inclination of these bones follows one of two designs. In saurischian dinosaurs, as well as known as lizard-hipped dinosaurs, the pubis(pelvic bone)points forward, as is normal in most types of reptiles. By difference, in ornithischian, or bird-hipped, dinosaurs, the pubis points backwards towards the rear of the animal, which is as well as true of birds.
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Of the sequence of dinosaurs, the Saurischia was the biggest and the first to evolve. It is split into two suborders: Theropod, or theropods, and Sauropodomorpha, or sauropodomorphs. The theropods, or “beast feet”, were two-footed, predacious carnivores. They varied in size from the mighty Tyrannosaurus rex, 12m long, 5.6m tall and weighing an assessed 6.4 tonnes, to the smallest called dinosaur, Compsognathus, a mere 1.4m long and assessed 3kg in weight when fully grown. The sauropodomorphs, or “lizard feet forms”, included both two-footed and four-footed dinosaurs. Some sauropodomorphs were carnivorous or omnivorous, but later types were usually herbivorous. They included some of the biggest and best-known of all dinosaurs, such as Diplodocus, a huge four-footed with an elephant-like body, a long, bong tail and neck that gave it a total length of 27m, and a tiny head.
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Bird-hipped dinosaurs were two-footed or four-footed herbivores; they are now normally divided into three suborders: Ornithopoda, Thyreophora and Marginocephalia. The Ornithopoda, or “bird feet '', both large and small, could walk or run on their long back legs, poising their body by holding their tails stiffly off the ground behind them. An instance is an iguanodon, up to 9m long, 5m tall and weighing 4.5 tonnes. The thyreophora, or “shield bearers'', also known as armoured dinosaurs, were four-footed with rows of preservative bony prongs, studs or plates along their backs and tails. They contained stegosaurus (stegosaurus longispinus), 9m long and weighing 2 tonnes.
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The marginocephalians, or “margined heads”, were two-footed or four-footed bird-hipped with a deep thin ruffle or narrow shelf at the back of the skull. An instance is a three-horned dinosaur, rhinoceros-like dinosaur, 9m long, weighing 5.4 tonnes and possessing a prominent neck ruffle and three large horns.
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