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Sunday, January 28, 2007

how to name it?
When a new dinosaur is discovered, it can be named in one of the following ways: Dinosaurs can be named after a person. Leallynasaura was named after Leallyn Rich, the daughter of the palaeontologists Tom Rich and Patricia Vickers who found the skull. Some dinosaurs are named after the place where their bones were discovered. Muttaburrasaurus was found near the town of Muttaburra, Australia. Other dinosaurs get their names from a certain physical characteristic. Iguanodon has teeth like an iguana while Dienonychus has a terrible claw. Many dinosaurs names seem long and difficult to pronounce and often contain Greek or Latin words. Many words come from these two languages, and they are recognised by the world-wide scientific community.
What makes a dinosaur a dinosaur?
Despite their great variety, all the dinosaurs - if they are to be regarded as a group - have to share at least a few common characteristics by which that group can be identified. It is now accepted that to be classified as a dinosaur, an animal must have: 1. Lived during the Mesozoic era. 2. An upright posture in which the legs come straight down from the body. 3. Bird-like or lizard-like hips. 4. Extra openings in the skull. 5. Lived and moved on land. Because animals such as the flying pterosaurs, the swimming ichthyosaurs and the sprawling crocodiles may share some of these characteristics, but not all of them, they cannot be considered dinosaurs.
When did the dinosaurs first appear on Earth? The oldest dinosaur types are known from rocks in Argentina and Brazil and are about 230 million years old in the Triassic Period. One of the earliest known primitive dinosaurs was Eoraptor ("dawn hunter") a fast-running, one-metre long carnivore. Because Eoraptor's skeleton shows some advanced skeletal features, older dinosaurs may yet be found. After the evolution of such early types, dinosaurs evolved very quickly, becoming more and more diverse and reaching out into all the ecological niches.
How many types of dinosaurs are known?
Approximately 700 species have been named. However, a recent scientific review suggests that only about half of these are based on fairly complete specimens that can be shown to be unique and separate species. These species are placed in about 300 valid dinosaur genera (Stegosaurus, Diplodocus, etc.), although about 540 have been named. Recent estimates suggest that about 700 to 900 more dinosaur genera may remain to be discovered. Most dinosaur genera presently contain only one species (for example, Deinonychus) but some have more (for example, Iguanodon). Even if all of the roughly 700 published species are valid, their number is still less than one-tenth the number of currently known living bird species, less than one-fifth the number of currently known mammal species, and less than one-third the number of currently known spider species.
Why did dinosaurs become extinct?
The fact that dinosaurs became extinct might suggest they had some "Achilles heel" which led to their downfall. But it seems it was just bad luck and they weren't alone. At the end of the Cretaceous Period all the dinosaur families, together with the pterosaurs and marine reptiles, as well as about 75 percent of all other species on earth went extinct. There are numerous theories for this great extinction, but at present only three are taken seriously: 1. Fossil evidence shows that there was a gradual decline in the abundance and variety of dinosaurs during the last 10 million years of the Cretaceous Period. This may have been because the climate climate became much cooler and drier. 2. In India, huge volcanic eruptions unleashed enormous quantities of lava, volcanic ash and poisonous gas which would have caused widespread climatic change.3. At about the same time a large asteroid struck the Earth forming a 240 kilometre crater in what is now the Yucatan Peninsula in Mexico. This impact would have caused - among other disasters - several extremely cold months or years because of dust in the atmosphere. Evidence between the three theories is balanced and the debate ranges on. It is tempting to suggest that a number of groups already on the wane for ecological reasons were pushed into oblivion by either a final meteorite impact or volcanic activity, so that all three theories play a part in the final extinction event. But until more data is available no positive judgement can be made.
How long could a dinosaur live? Scientists do not know the exact lifespan of dinosaurs, but they estimate that they lived about 75 to 300 years. Animal lifespans relate in part to their body size and in part to their type of metabolism. Their possible maximum age can be estimated from the maximum lifespans of modern reptiles, such as the 66-year lifespan of the common alligator and the impressive lifespan of some tortoises. One specimen of the now-extinct Black Seychelles Tortoise, which was an adult when captured, lived a record 152 years in captivity (1766-1918) and had an accidental death. These estimates, based on lifespans of cold-blooded animals, would be too long if dinosaurs had metabolisms more similar to modern birds and mammals.
Were dinosaurs social animals?
Some dinosaurs were social creatures. Recently discovered trackways indicates that they travelled together. Some may even have migrated because dinosaur fossils have been found above the Arctic Circle, where food supply would have been seasonal. Grouped hadrosaur nest sites have been found which were apparently used by many animals over a number of years, in a similar way to the nesting colonies of some birds. The nests themselves contain both badly crushed eggshells and skeletons of baby dinosaurs with slightly worn teeth. This suggests that some babies stayed in their nests after hatching and were probably fed by their parents.
Did dinosaurs communicate? Dinosaurs probably communicated both vocally and visually. The chambered headcrests on some hadrosaurs and the large nose on Muttaburrasaurus might have been used to amplify grunts or bellows. The huge frill on the back of torosaurus' skull contains two large holes. These would have been covered with stretched skin creating vivid eye-spots when flushed with blood. Defensive posturing, courtship behaviour, and territory fights probably involved both vocal and visual displays. An angry Torosaurus bull shaking his massive head at you, even silently, would have made himself very clearly understood!
Why did they grow so big?
Dinosaurs actually came in all sizes and shapes but certainly many were big and some of the sauropods were absolutely huge. One of the largest was Brachiosaurus - 22 metres long and 14 metres tall. Its weight is disputed, ranging from 35 to 80 tonnes, but either way it was a heavyweight. Recently there have been reports of even bigger sauropods. These are mostly based on rather fragmentary remains, but if scaled up do suggest animals considerably bigger than Brachiosaurus. Ultrasaurus may have been 30m long, Supersaurus up to 40 m long, and Seismosaurus might have been as much as 45m long. The size of these creatures is probably a simple consequence of how they fed. Vegetation is a tough diet for all animals and sauropods were high browsers relying on the particularly tough leaves of conifers. Their teeth were simple and designed for nipping or raking foliage from trees, rather than for chewing. They had stone laden gizzards which they used to grind up the tough leaves, but breaking down the plant cells could only be achieved by using the stomach as a huge fermentation tank. Sauropods had to be big because they had to contain a huge stomach. And being big is a useful adaptation in itself. It gives some protection against predators - unless they too evolve bigger. It also gives more insulation, either to prevent overheating in the sun, or to avoid heat loss when it gets cold.
Were dinosaurs warm-blooded or cold-blooded?
There's still no definite answer whether dinosaurs were warm-blooded or cold-blooded. For many years, scientists thought all dinosaurs were cold-blooded like all reptiles are today. Then, in the 1970s, scientists begin to look at some evidence indicating that dinosaurs may be warm-blooded. This evidence included several things: the way dinosaurs stood straight-legged like mammals, their big rib cages that could have held mammal-like hearts and lungs, and bones that contained channels for quick blood circulation as found in warm-blooded animals' bones. More recent studies, however, suggest that dinosaurs were neither warm-blooded nor cold-blooded, but something in between. Big dinosaurs may not have had much control over their body temperature but probably didn't need to - their huge size would have been very effective in insulating them from temperature fluctuations. Whatever the truth, it is clear that dinosaurs were active, dynamic creatures, and not just overgrown lizards.

from today onwards i will be posting facts and finds relating to dinosaurs . ( my new passion). feel free to ask any questions and i will be there to clarify your every doubts ok ! yours IRVIN

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