Dinosaur
Saurischians\nSaurischians (from the Greek Saurischia meaning "lizard hip") include all the Theropods, bipedal carnivores such as the tyrannosaurs, and sauropods in the dinosaur classification. (brief further characterization is needed here). For more detail, see Saurischia.Ornithischians\nThe other great dinosaurian clade is the Ornithischia (or Predentata). For more details on these dinosaurs, please refer to Ornithischia.Warm-blooded dinosaurs\nThere has been a constant and vigorous debate over the method of regulation of temperature of dinosaurian blood, a debate first popularized by Robert T. Bakker. Since the first discovery of dinosaurs, the idea that they were ectothermic creatures was considered most likely. This would have meant that the animals were mostly slow, dormant organisms, comparable to modern reptiles that need the sun to heat their bodies. However, new evidence of dinosaurs in chilly temperate climates and scientific analysis of the blood-vessel structures within dinosaur bone have opened the possibility that some dinosaurs were endothermic, regulating their body temperature by internal biological methods. Skeletal structures suggest active lifestyles for theropods and other creatures. This means that an endothermic cardiovascular system would have been more suitable for dinosaurs. This doesn't mean all dinosaurs were endothermic, though. The debate still continues to this day (although many paleontologists would agree that endothermic systems are more likely now).Feathered dinosaurs\nFeathered dinosaurs were found at the end of the 20th century, Most of these specimens were local to China, an island continent in the Cretaceous, and were theropods. These animals include Sinosauropteryx, Protarchaeopteryx, Caudipteryx and Confuciusornis, all coming from northern China's Yixian formation. The dromaeosauridae also exhibited feathers as was shown by a remarkable subadult Sinornithosaurus ( see picture). This small " raptor" was also found in the Liaoning Province of the China.\nBecause feathers are often associated with birds, feathered dinosaurs are often touted as the missing link between birds and dinosaurs. However,the association of multiple skeletal features also shared by the two groups is the more important link for paleontologists.
Speculation on dinosaur behavior\nThe behavior of non-avian dinosaurs will always be a mystery simply because none exist today. The only evidence paleontologists have to go on are fossil tracks, skeletons locked in battle (Velociraptor and Protoceratops), and fossilized nests. All the evidence varies, depicting several different behaviors. Herbivores may have been much more social, migrating in huge herds much like modern day mammals (i.e. African species). This could have been a successful predator warning system, depending on the predator. The carnivorous dinosaurs possibly exhibited social characteristics as well, like wolves and large cats. Families may have traveled together for a very long time in order to maximize survivability. But all of this is speculation, and a more accurate description is likely distant in the future. Considering the success of dinosaurs, as the dominant creatures for millions of years, some type of social order seems likely to have been present.Extinction\nThe extinction of the dinosaurs is one of the most intriguing problems in paleontology. Only since the 1980s has the nature of this extinction become apparent. The theory first proposed by Walter Alvarez linked the extinction event at the end of the Cretaceous period to a meteorite impact about 65.5 million years ago, based on a sudden change in Iridium levels in fossilized layers. The bulk of the evidence now indicates that a 10-kilometer-wide bolide hit the Yucatan Peninsula 65 million years ago, creating the 170-km wide Chicxulub crater, and caused the extinction. Scientists are still disputing whether dinosaurs were in steady decline or still thriving before the meteor struck. Although the speed of extinction cannot be deduced from the fossil record alone, the latest models suggest the extinction was extremely rapid. It appears to have been caused by heat caused by the meteorite impact and the matter ejected from the crater re-entering the atmosphere around the world. Other theories link the extinction with increased volcanic activity, decreasing oxygen level in the atmosphere and dropping temperatures. The survivors of this mass extinction appear to have been two things: small animals hiding underground and/or aquatic creatures relatively safe underwater. Neither of this applies to dinosaurs, most of whom were probably incinerated in the heat blast. Other groups as well as the dinosaurs, including ammonites, mosasaurs, plesiosaurs, pterosaurs, herbivorous turtles and crocodiles, most kinds of bird, and many groups of mammals, became extinct.Classification of dinosaurs\nDinosaurs are divided into two major orders, the Saurischia and the Ornithischia, on the basis of hip structure. SUPERORDER DINOSAURIA\n* Order Saurischia\n** ?Herrerasauridae\n** Theropoda\n*** Incertae sedis: Dilophosaurus, ?Saltopus\n*** Coelophysoidea (e.g. Coelophysis, "Syntarsus", Procompsognathus)\n*** Ceratosauria (e.g. Ceratosaurus)\n**** Abelisauridae (e.g. Abelisaurus, Indosuchus, Noasaurus, Carnotaurus, Majungatholus)\n*** Tetanurae (e.g., Piatnitskysaurus)\n**** Spinosauroidea (e.g. Spinosaurus, Megalosaurus, Baryonyx)\n**** Carnosauria (e.g. Xuanhanosaurus, Acrocanthosaurus)\n***** Sinraptoridae (e.g. Metricanthosaurus, Sinraptor)\n***** Allosauridae (e.g. Allosaurus)\n****** ? Carcharodontosaurinae (e.g. Carcharodontosaurus, Giganotosaurus)\n**** Coelurosauria (e.g. Coelurus, Ornitholestes, Compsognathus, Sinosauropteryx)\n***** Tyrannosauroidea (e.g. Aviatyrannis, Dryptosaurus)\n****** Tyrannosauridae (e.g. Tyrannosaurus, Albertosaurus, Tarbosaurus, Gorgosaurus, Daspletosaurus)\n***** Ornithomimosauria (e.g. Ornithomimus, Struthiomimus, Gallimimus, Deinocheirus)\n***** Alvarezsauridae (e.g. Mononykus, Shuvuuia)\n***** Segnosauria (e.g. Segnosaurus)\n****** Therizinosauridae (e.g. Therizinosaurus)\n***** Oviraptorosauria (e.g. Caudipteryx)\n****** Oviraptoridae (e.g. Oviraptor, Khaan)\n***** Deinonychosauria (e.g. Variraptor, Microraptor, Sinornithosaurus)\n****** Troodontidae (e.g. Troodon (=Stenonychosaurus), Saurornithoides)\n****** Dromaeosauridae (e.g. Utahraptor)\n******* Dromaeosaurinae (e.g. Dromaeosaurus)\n******* Velociraptorinae (e.g. Deinonychus, Velociraptor Saurornitholestes)\n***** Aves (birds)\n** Sauropodomorpha\n*** Prosauropoda\n**** Plateosauridae (e.g. Plateosaurus)\n*** Sauropoda\n**** ? Anchisauridae\n**** ? Melanorosauridae\n**** Cetiosauridae\n**** Euhelopodidae (e.g. Mamenchisaurus)\n**** Neosauropoda\n***** Camarasauridae (e.g. Camarasaurus)\n***** Diplodocidae (e.g. Apatosaurus, Diplodocus, Supersaurus (="Ultrasaurus"))\n***** Brachiosauridae (e.g. Brachiosaurus)\n***** Titanosauridae (e.g. Titanosaurus, Paralititan, Saltasaurus)\n* Order Ornithischia\n** Lesothosaurus\n** Genasauria\n*** Thyreophora (sturdy armored ornithischians)\n**** Stegosauria (thyreophores with elongated skulls and plated armor, e.g. Stegosaurus)\n**** Ankylosauria (thyreophores with squatter skulls and a virtual hoshposh of armory on their backs, veritable dinosaurian tanks, e.g. Euoplocephalus, Gastonia, Edmontonia)\n*** Cerapoda\n**** Ornithopoda (sophisticated chewers, ranging from lithe nippers like Hypsilophodon to gigantic grazers like Iguanodon, Hadrosaurus, Edmontosaurus and Lambeosaurus )\n**** Neornithopoda\n***** Heterodontosauridae (little herbivores with nasty teeth)\n***** Marginocephalia\n****** Pachycephalosauria (hard-headed marginocephalians)\n****** Ceratopia (curious-looking browsers with a variety of head shapes, mostly employing horns and frills of various sizes and shapes)Dinosaurs in cultureEven though dinosaurs were highly successful life forms for some 150 million years, dinosaur is sometimes used as a derogatory term to describe people and things that are perceived as being out of date or no longer in touch with the spirit of the times, and therefore ought to be extinct. An example was the manner in which the punk movement described the "progressive" bands that preceded them as "dinosaur groups". Decentralized social movements often describe centralized governments or corporations as dinosaurs. Dinosaurs have long captured the public mind, and children are especially fascinated with them. This is evidenced by the many dinosaurs in fictional works. Notable examples include the Arthur Conan Doyle book The Lost World and the Michael Crichton book Jurassic Park. Dinosaurs are also a frequent topic of television documentaries and popular, nonfiction books. Dinosaurs are a common theme in the popular Bill Watterson comic strip Calvin and Hobbes. See also List of fictional dinosaurs.Trivia\nThere has been much speculation about the availibility of technology to bring dinosaurs back to life. The idea proposed in Michael Crichton's book Jurassic Park, using blood in fossilized mosquitos that have been suspended in sap since the dinosaur times, and then filling in the gap with aspects of frog genes to create the DNA of a dinosaur is probably impossible. Scientists however, are still unsure about whether or not we could bring these extinct animals back to life.External links\n*Family tree of dinosaurs\n*Another family tree of dinosaurs\n*Dinosauria On-Line Dinosaur Omnipedia\n*Royal Tyrrell Museum of Palaeontology, with 35 complete skeletons and more than 110,000 specimens\n*BBC Dinosaur site, with a huge amount of accurate and comprehensible information and pictures\n*The Dinosauricon - a good source for any dinosaur information. Includes a complete cladogram.\n*A Fiery Death for Dinosaurs? by Amit Asaravala\nCategory:Dinosaurs \n\n\n\n\n\n\n\n\n\n\nsimple:Dinosaur\n\n |
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