Dinosaur
From Wikipedia, the free encyclopedia.
| Dinosauria Status Extinct | ||||||||||||||||||||||
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Saurischia Order Sauropodomorpha Order Theropoda Order Ornithischia | ||||||||||||||||||||||
The formal name Dinosauria was first proposed by the English scientist Richard Owen in 1842. The term is a combination of the Greek words deinos ("terrible" or "fearfully great" or "formidable") and sauros ("lizard" or "reptile").
Dinosaurs varied greatly in size. The smallest known species were about the size of a chicken, but most were much larger. The biggest dinosaurs were the Sauropoda; the species Argentinosaurus currently holds the record for the largest land animals ever to live, and were second in size only to certain species of whale. However, the extraordinarily massive femur of a brachiosaur, titled Ultrasaurus, suggests an animal that could have weighed as much as 130 tons, drwarfing the competition.
Saurischians
Saurischians (from the Greek Saurischia meaning "lizard hip") include all the Therapods, bipedal carnivores such as the tyrannosaurs, and sauropods in the dinosaur classification. (brief further characterization is needed here). For more detail, see Saurischia.
Ornithiscians
Many other types of reptiles lived at the same time as the dinosaurs. Some of these are commonly, but incorrectly, thought of as dinosaurs: these include plesiosaurs (which are not closely related to the dinosaurs), and Pterosaurs, which developed separately from reptile ancestors in the late Triassic.
Warm-blooded dinosaurs
There has been a constant debate over dinosaurian blood. Since the beginning of the dinosaur discovery, the idea of ectothermic creatures was ideal. This would mean that the animals were mostly slow, dormant biologicals that needed the Sun to heat their bodies. They would be comparitive to modern reptiles, such as snakes. New evidence and scientific breakthroughs have opened the possibility that dinosaurs were endothermic, however. Skeletal structures suggest active lifestyles of 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 (albeit many paleontologists would agree that endothermic systems are more likely now).
Feathered dinosaurs
Feathered dinosaurs have been found. Most of these specimens are local to China, and are theropods. A few of these animals are Sinosauropteryx, Protarchaeopteryx, Caudipteryx and Confuciusornis, all coming from northern China's Yixian formation. It is believed that Confuciusornis was the only one that could truly fly. There is speculation that the dromaeosauridae may have exhibited feathers as well. It is commonly believed that feathered dinosaurs could be the missing link between birds and dinosaurs.
Surmises about dinosaur behavior
The behavior of 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 dinosaurs were successfully the dominating creatures for millions of years, some type of social order would have been present.
Extinction
The 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 extinction appears to have been rapid, following a period of decreased dinosaur biodiversity, and besides the dinosaurs, other groups, including ammonites, mosasaurs, plesiosaurs, pterosaurs, herbivorous turtles and crocodiles, most kinds of bird, and many groups of mammals, became extinct. The bulk of the evidence now indicates that this extinction event is linked to a bolide impact 65 million years ago, a theory first proposed by Walter Alvarez. The survivors of this mass extinction appear to have been two things that dinosaurs in general were not: small and/or aquatic.
Classification of dinosaurs
Dinosaurs are divided into two major orders, the Saurischia and the Ornithischia, on the basis of hip structure.
- Saurischia
- Theropoda
- Ceratosauria (e.g. Coelophysis, Procompsognathus, Dilophosaurus, Abelisaurus)
- Spinosauridae (e.g. Spinosaurus)
- Allosauridae (e.g. Allosaurus)
- Coelurosauria
- Tyrannosauridae (e.g. Tyrannosaurus, Albertosaurus)
- Ornithomimidae (e.g. Ornithomimus, Struthiomimus, Gallimimus)
- Oviraptoridae (e.g. Oviraptor)
- Therizinosauridae (e.g. Therizinosaurus, Segnosaurus)
- Troodontidae (e.g. Troodon)
- Dromaeosauridae (e.g. Deinonychus, Utahraptor, Velociraptor)
- Aves (birds)
- Sauropodomorpha
- Plateosauridae (e.g. Plateosaurus)
- Sauropoda
- Diplodocidae (e.g. Apatosaurus, Diplodocus, ?Mamenchisaurus?)
- Brachiosauridae (e.g. Brachiosaurus)
- Titanosauridae (e.g. Titanosaurus, Saltasaurus)
- Theropoda
- Ornithischia
- Thyreophora
- Stegosauria (e.g. Stegosaurus)
- Ankylosauria (e.g. Ankylosaurus, Euplocephalus, Nodosaurus, Scolosaurus)
- Neornithischia
- Ornithopoda (e.g. Anatosaurus, Parasaurolophus, Hypsilophodon, Iguanodon)
- Pachycephalosauria (e.g. Pachycephalosaurus)
- Ceratopia (e.g. Psittacosaurus, Protoceratops, Triceratops)
- Thyreophora
External links
- Family tree of dinosaurs
- Another family tree of dinosaurs
- Dinosauria On-Line Dinosaur Omnipedia
- Royal Tyrrell Museum of Palaeontology, with 35 complete skeletons and more than 110,000 specimens
- BBC Dinosaur site, with a huge amount of accurate and comprehensible information and pictures
Other Meanings
Dinosaur is sometimes used as a derogatory term to describe 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'. Considering that dinosaurs were actually highly successful life forms for some 150 million years, this term could be seen as quite ironic. It is even more ironic when one considers that birds are most probably direct descendants of dinosaurs, which implies that not only the dinosaurs aren't extinct (in the sense of, say, trilobites), but also that their modern descendants are themselves a highly successful group that have been able to colonize almost every habitat on the planet.
Dinosaurs was also a sitcom television series from Jim Henson Productions.