Dinosaur

the dinosaurs are animal Vertébrés having reigned on the terrestrial ecosystems lasting more than 160 million years. They appeared on Ground at the end of the Trias, approximately 230 million years ago. The Pangée not being yet fragmented with Sorted, the dinosaurs could colonize all the continents with dry foot. At the end of the Cretaceous , approximately 65 million years ago, a catastrophe caused the extinction of the dinosaurs and put an end to their reign on the terrestrial Faune. A group of dinosaurs however survived this catastrophe; indeed, the taxinomists regard the birds of today as the descendants of the théropodes.

Description

Definitions

The Taxon of the Dinosauria was introduced by the English paleontologist Richard Owen in 1842 to gather a “tribe or sub-order distinct from Sauropsidés”. The term derives from the Greek δεινός ( deinos : “formidable, terrible”) and of σαύρα ( will know : “lizard” or “reptile”). Owen chose this name by reference to the fear which could inspire their size, their teeth and their claws often impressive. Indeed, a great number of dinosaurs could be of a considerable size (more than fifteen meters length), which was worth an unquestionable success to them. However, these animals could also have very a small size (a few centimetres). The specific epithet of certain dinosaurs corresponds in the name of the people who discovered them.

The recent discoveries made more difficult the clear distinction between various dinosaurs however the found fossil skeletons seem almost all to have common points with those of Archosauriens. The posterior dinosaurs have slightly modified characteristics.

The Synapomorphie S of the dinosaurs include for example an oval peak on the Humérus, a cranium Diapside.

Cut

While being based on the discovered fossils, it is certain that the dinosauriens were a group of large animals although their intermediate size varied for the periods of Sorted, Jurassic and Cretaceous. According to the paleontologist Bill Erickson, the median weight oscillates between 500 kg and 5 tons; a recent study on 63 kinds of dinosaurs gave an average weight of 850 kg (comparable with that of a Grizzly) and a median weight of almost two tons, is as much as a Girafe. In comparison, the average weight of the mammals is of 863 grams, that is to say that of a large rodent. Smallest of the dinosaurs discovered was larger than two thirds of the current mammals. The majority of the dinosaurs was larger than 98  % of the existing mammals.

Larger and smaller dinosaurs

Only a small fraction of the dead animals become fossils, and only some specimens discovered are complete fossils, and the impressions of skins and soft fabrics are rare. The rebuilding of a skeleton of a species by comparing the size and the morphology of the bones with those of another better known similar species is an inaccurate art, and to make the recombining of the muscles and other bodies of a specimen is scientifically difficult. One will be thus never really certain size of largest and smaller dinosaurs.

Among the dinosaurs, the Sauropode S were gigantic, largest were a Order of magnitude more massive than all the animals having gone since on the Earth. Prehistoric mammals like the Indricotherium and the Colombian Mammouth were dwarves compared with the sauropodes. Only a handle of contemporary aquatic animals approach them or exceed them in the face, the such Blue whale, which weighs 190 tons and reaches 33,50 meters length.

Largest and heavier dinosaur known starting from complete skeletons where almost is the Brachiosaurus brancai (also known like Giraffatitan ). It was 12 m high, 22,5 m length, and would have weighed between 30 and 60 tons (for memory a elephant of savanna of Africa, the largest terrestrial animal of the world, weighs on average 7,7 tons). The longest dinosaur resulting from a complete fossil is the Diplodocus which made 27 m (Pittsburgh, Carnegie Natural History Museum, 1907).

There were larger dinosaurs but the known data are based on some fragmentary fossils. The majority are Herbivore S discovered in the years 1970 or after, among which enormous the Argentinosaurus , which could have weighed between 80 and 100 tons; longest of all, the Supersaurus of 40 meters; and largest, the Sauroposeidon of 18 meters, which could have reached a window on the 6th floor.

A dinosaur even larger, the Amphicoelias fragillimus , known only of some vertebrae discovered in 1878, could have reached 58 meter length and a weight of 120 tons. Heaviest could have been the known not very and still discussed Bruhathkayosaurus , which could have reached from 175 to 220 tons.

Largest Carnivore was the Spinosaurus , which reached a size from 16 to 18 meters and weighed 9 tons. Other large carnivores included the Giganotosaurus , Mapusaurus , Tyrannosaurus rex and Carcharodontosaurus . Without including the contemporary birds like the hummingbirds, the smallest dinosaurs had the size of a Corbeau or a Poulet. The théropodes Microraptor and Parvicursor made less 60cm length.

Behavior

The interpretation of the behavior of the dinosaurs is generally based on the provision of the discovered fossils, them habitat, simulations by computer of their Biomécanique S, and the comparisons with current animals located in same the ecological Niche. Like such, the current comprehension of the behavior of the dinosaurs rests on speculations, of which some will remain probably discussed during still a long time. However, there is a consensus on the fact that certain currents which are common in the crocodiles and the birds (the species closest to the dinosaurs) are also current in the dinosaurs.

Herds

The first obviousness of Troupeau X of dinosaurs was discovered in 1878 in Belgium with Bernissart. 31 Iguanodon S seemed to have perished together after being fallen in a deep and flooded Doline. In spite of the discovery that these skeletons resulted from the three distinct events, other sites of massive deaths were discovered. Those, with many fossil traces suggested that the herds where the Horde S were common in many species. The tracks of the hundreds, even of thousands of herbivores, indicated that the dinosaurs with duck nozzle could move in large herds, the such Bison or the Springbok. Traces of Sauropode S made it possible to see that these animals travelled in groups made up of several different species, and others kept the young people in the middle of the herd in order to protect them, according to the traces in Davenport Ranch with the Texas.

Nests

The discovery in 1978 per Horner Jack of the Nest of the Maiasaura (" dinosaur good mère") with the Montana showed that the parental care lasted well after the blossoming at the Ornithopode S. There is as evidence as other dinosaurs of the Crétacé as the sauropode Saltasaurus (overdraft in 1997 in Patagonie) had similar behaviors, and than these animals gathered in immense colonies nidificatrices like those of the Manchot S. the Oviraptor of Mongolia was discovered (1993) in a position of Couvaison like that of the Poule, which means that it was covered with a layer of insulating feathers which kept egg with the heat. Fossil tracks also confirmed the maternal behavior among the sauropodes and the ornithopodes of the island of Skye. Nests and eggs were found for the majority of the independent groups of dinosaurs, and it appears probable that the dinosaurs communicated with their small in a way similar to the birds and the current crocodiles.

Coupling and communication

The peaks of certain dinosaurs, like the Marginocephalia NS, the Théropode S and the Hadrosauridae be, could have been too fragile for an active defense and thus would be probably used for the sexual parades or at ends of intimidation, although there exists little of elements on the territorialism and the coupling of the dinosaurs. The nature of the communications between dinosaurs remains also enigmatic, but recent discoveries suggest that the peak digs lambeosaurines could have functioned like a Caisse of resonance used for a large variety of Vocalisation S.

Drive out

From the behavioral point of view, one of the fossils most important of dinosaur was discovered in the Gobi Desert in 1971. It included a Velociraptor attacking a Protoceratops , proving physically that the dinosaurs attacked themselves and ate themselves between them. Although the Cannibalisme among the Théropode S is not a surprise, it was confirmed by traces of teeth on a fossil of Madagascar in 2003.

Displacement

Based on the existing fossil evidence, there were no species of digger dinosaur and few climbing dinosaurs. Since the expansion of the mammals to the Cénozoïque saw the appearance of many species digger and climbing, the lack of evidence for similar species of dinosaurs is somewhat surprising.

A good comprehension of how the dinosaurs moved is the key of the models of behaviors of the species. The Biomécanique in particular provided many elements such as for example the determination the speed of race of the dinosaurs according to the study of the forces exerted by their muscles and gravity on the structure of their skeleton, knowledge if the diplodocide S could create a Supersonic bang by sweeping the air with their tail in the shape of whip, to determine if the giant théropodes were to slow down when they coursaient their preys to avoid wounds mortals, and if the sauropodes could float.

Metabolism

A French study on the isotopic composition in Oxygen of the teeth and bone of 80  dinosaurs of the Cretaceous (Théropode S, Sauropode S, Ornithopode S and Cératopsien S) coming from layers of North America, of Europe, of Africa and Asia, showed that those were to be Homéotherme S. the ¹⁸O/¹⁶O report/ratio - which depends on the Température intern of the live animal - is identical to that of the Mammifère S and Oiseau X, homéothermes, and differs clearly from that of the current reptiles, Ectotherme S, and of the Chélonien S and Crocodilien S fossils of the Cretaceous. The presence of structures of Havers (microchannels surrounded by a concentric layer of bone within the skeletons) in the fossilized bones would be also an element in favor character endothermic. Another team, of Florida, estimated that the temperature was proportional to the mass and growth rate, going from 25 °C for the small dinosaurs up to 41 °C for largest. They applied a numerical model , making it possible to consider the temperature body according to the size and of growth rate, with eight species, of the Psittacosaure ( Psittacosaurus mongoliensis , 12 kg) to the Apatosaure ( Apatosaurus excelsus , 26.000 kg). According to this team, the internal temperature of Sauroposeidon proteles , heaviest of the known dinosaurs (60 tons), was to reach 48 °C. This model would thus tend to prove that the large dinosaurs were heated by “inertial homeothermy”.

The crisis cretaceous-tertiary sector (crisis K-T) or “the extinction of the dinosaurs”

See also: Extinction of the Cretaceous

The disappearance of the dinosaurs gave rise to many theories, unquestionable eccentric like the destruction of the dinosaurs by Extraterrestre S, and others more probable and scientifically testable. It is advisable however to note that the extinction of the dinosaurs is a semantic problem: the dinosaurs are not extinct since there remains Oiseau X.

On the other hand, there was well a crisis at the end of the Crétacé, there are 65 My. Although the latter has have impact average on Biodiversity in general (if one compares it with crisis permo - Sorted ic or even with that of Ordovicien) and that it especially decimated marine organizations the such Foraminifère S and not of the terrestrial organizations whose relative extinction is much raised, it became very famous because of on-mediatization relating to the dinosaurs.

The comparison of the rate of extinction taxon by taxon watch that some of the contemporary clades of the dinosaurs were very affected (the such Plésiosaure S and the Ptérosaure S) and others much less (Crocodilien S and Chélonien S for example). Even if this crisis actually caused the extinction of the majority of tax dinosauriens living at the end with the cretaceous, with many tax died out front, not because the dinosaurs were in a prédictible decline but by the simple fact of the continuous extinction of species during geological times.

The most probable causes having induced crisis K-T are:

• the fall of a Meteorite several tens kilometers in diameter causing a major catastrophe which, by the means of remains due to the collision, plunged the Earth in the darkness and the cold during several years, thus preventing photosynthesis, which induced a massive impoverishment in plants and especially in plankton and led to the extinction of many species dependant on these resources whatever their trophic level. This theory, nowadays very argued (Crater of Chicxulub in Mexico gone back to - 65 My), in particular makes it possible to explain to a certain extent differential survivals of tax;

• eruptions at the end of the cretaceous of a Supervolcan (Trapps of Deccan, in India) for one rather short period on the level of geological times, causing a planetary cataclysm by modifying the climate and preventing photosynthesis while plunging the Earth in the darkness by the means of clouds of ashes. This theory is as argued as the preceding theory, inter alia by the dating of - 65 My of the trapps of Deccan, whose surface is equivalent to several times France, and by results on the fall of the luminosity on the surface of the Earth at the time of the recent eruption of the Pinatubo (April 1991) to the Filipino . This theory recuts that of the meteoric collision partly;
• very important marine regressions at the end of the cretaceous changing the conformation and the extent of the littoral and benthic mediums while inducing an important climate change. This theory is it also based on solid evidence and it is known now that a very great marine regression took place with the higher cretaceous.

These three theories are based on facts and crisis K-T could be the consequence of the quasi-simultaneity of these three events. The divergent opinion with regard to the relative importance of each one of them.

Current representatives of the dinosaurs

The first fossil of Bird, the Archæopteryx, of the Jurassic superior, was discovered in Bavaria in the years 1860. Its great resemblance to certain small biped carnivorous dinosaurs, like the Compsognathus, immediately revealed the theory according to which the birds went down from a species belonging to this group of dinosaurs, the Cœlurosauriens.

During one century, the theory remained is very discussed, even rejected. Indeed, the birds have Clavicule S, when the cœlurosauriens did not have any.

In the years 1970, however, Cœlurosauriens equipped with clavicles were discovered, and the theory dinosaurienne on the origin of the birds is become again dominant.

In the years 1990, many fossils of dinosaurs with feathers were discovered, in particular in China, and completed to impose this theory. It is not a question of intermediate fossils between dinosaurs and birds, but well of dinosaurs cœlurosauriens with feathers or proto-feathers. The interpretation which is made of these discoveries is that a species of dinosaur cœlurosaurien (even the ancestor of Cœlurosauriens itself) developed the character “plucks” and that among the descendants of this species is inter alia the ancestor common to all the birds. It is it should be noted that in 2005, no fossil intermediate between birds and nonavian dinosaurs (a proto-bird) was discovered.

Certain scientists think that the development of the feathers could be older than the appearance of the cœlurosauriens, but in 2005, no irrefutable discovery consolidates this thesis.

The birds do not go down at all from the flying reptiles, the Ptérosaure S, which are a group (or Clade) cousin of the Dinosaurs, within the broader group of the Archosauriens (Dinosaurs, Crocodiles, Ptérosaures…).

Contemporary reptiles with the dinosaurs

Many reptiles which lived at the same geological periods that the dinosaurs were sometimes confused with the dinosaurs by the cinema or the literature, whereas they are not scientifically classified as tel. most known are:

• the Ptérosaure S (flying reptiles) including the Ptéranodon and the Ptérodactyle;

• the Plésiosaure S, the Pliosaure S, the Mosasaure S and the Ichthyosaure S (marine reptiles).

History of their study

One knows fossils of dinosaurs since millenia, without their true nature being included/understood. For the Chinese they was bones of dragons, for Europeans of the remainders of the biblical Géants and other creatures killed by the Déluge. Georges Cuvier described a marine lizard Mosasaure (contemporary of the dinosaurs, but which was not one) as of 1808. The first identified and baptized species were the Iguanodon, discovered in 1822 by the English geologist Gideon Mantell, which noticed similarities between its fossils and the bones of the contemporary Iguane. The first scientific article on the dinosaurs was published two years afterwards, it was published by the reverend William Buckland, professor of geology to the Université of Oxford, and related to Megalosaurus bucklandii , whose fossil had been discovered close to Oxford. The study of these “large fossil lizards” was the interest object great in the European and American scientific circles, and the English paleontologist Richard Owen invented the term “dinosaur” in 1842. He noticed that the remainders previously found ( Iguanodon , Megalosaurus and Hylaeosaurus ) were many joint, and decided to create a new taxonomic group. With the assistance of the prince Albert of Saxony-Cobourg-Gotha, husband of the queen Victoria, it created the Muséum of natural history of London, in South Kensington (Natural History Museum), to expose the national collection of fossils of dinosaurs, thus some other objects of botanical and geological interest.

In 1858 the first fossil of American dinosaur was discovered, in Marnière S close to the small town of Haddonfield, in the New Jersey (it is not the first fossil of dinosaur found in America, but the first identified like such). The animal was named Hadrosaurus foulkii , of the name of the city and its discoverer: William Parker Foulke. This discovery was very important because it was about the first almost complete skeleton discovered, and he highlighted undoubtedly possible that the animal was biped. Hitherto the majority of the scientists believed that the dinosaurs walked to four legs like the lizards. This discovery marked the beginning of a hunting with the fossils of dinosaurs with the United States. The fight baited between Edward Drinker Cope and Othniel Charles Marsh was known under the name of “war of the bones” ( Bone Wars ). Their quarrel lasted almost 30 years, and finishes in 1879 when Cope died after having spent all her fortune in this search. Marsh left victorious, grace especially to the financial aid of the Geological Organization of the United States (United States Geological Survey). The collection of Cope is today with the natural history museum of natural history of New York, that of Marsh to the natural history museum of natural history of Peabody, with the Université Yale.

Since, the search for fossils extended to all surface from the sphere, including in the Antarctic, where a Nodosaurid ankylosaurus was discovered in 1986, on the island of Ross. It is however in 1994 that a dinosaur really living the Antarctic, Cryolophosaurus ellioti , was described in a scientific newspaper. The particularly interesting zones are today South America, and especially the Argentine, and the China, whose basement revealed many skeletons preserved very well.

• Dispute creationnist

According to the creationnists, the extinction of the dinosaurs and their fossils would go back only to a few thousands of years. This assumption is based in particular on the recent discovery of soft fabrics, in relatively good state of conservation. The interpretation given by the scientists who made this discovery does not have however anything to see since these " tissus" , in fact of the mineral-bearing collagen traces, were found safe from a gangue of sandstone gone back to 68 My which allows the dispersion of the Enzyme S persons in charge of the decomposition of fabrics generally observed with the other fossils.

Classification of the dinosaurs

Yet not such a long time ago, one classified in the dinosaurs: the ichthyosaures, the pliosaures, the plésiosaures (3 groups of watery reptiles) and the ptérosaures (flying reptiles) which, today, are regarded as evolutionary lines independent of the dinosaurs among the reptiles having lived with the Mesozoic one. The dinosaurs were a group of extremely various animals; according to a study of 2006,527 kinds of dinosaurs were described with certainty, and more than 1.844 kinds are still to classify ^, . Some of them were herbivorous, other carnivores. Certain dinosaurs were biped, others were quadrupeds and certain, such Ammosaurus and Iguanodon, could go as well on two or four legs.

The dinosaurs are named in a precise way according to their kind and their species. Often, this name of species is given according to the name of the place of its discovery like Saltasaurus , the dinosaur of the Salta river in Argentine, according to an anatomical characteristic like the Triceratops , vis-a-vis three horns, or according to the name of a paléontolongue known like Othnielia for Othniel Charles Marsh. With the rise of paleontology, the names of species are internationalized. The Greek and Latin roots are replaced sometimes by Chinese, Mongolian or African roots like Nqwebasaurus coming from the Xhosa a language of South Africa.

Summary table

On the basis of the international Code of zoological nomenclature, one can recognize from 630 to 650 species of dinosaurs. A little more half of these species are represented only by one specimen (often incomplete) and less than 20 percent of the species are known by more than five specimens. This general table provides bonds between the independent groups of dinosaurs. One will find on the right some kind S illustrating the orders and the families represented.

|- | |- | colspan=" 2" | |- | rowspan=" 2" | Sauropodomorphe S | |- | |- | rowspan=" 6" | Ornithischien S | rowspan=" 3" align=center| Thyréophore S | align=right | |- | align=right | |- | align=right | |- | rowspan=" 2" align=center| Marginocéphale S | |- | align=right | |- | colspan=" 2" | |}

Sub-order of the Théropode S

• super-family of the Ornithomimosaures
• family of the Ornithomimidés
• super-family of the Droméosaures
• family of the Droméosauridés
• family of the Thérizinosauridés
• super-family of the carnosaures
• family of the Allosauridés
• family of the Tyrannosauridés
• family of the Spinosauridés

Sub-order of the Sauropodomorphe S

• super-family of the Prosauropode S
• family of the Anchisauridé S
• family of the Thécodontosauridé S
• family of the Platéosauridé S
• family of the Mélanorosauridé S
• family of the Yunnanosauridé S
• super-family of the Sauropode S
• family of the Cétiosauridé S
• family of the Brachiosauridé S
• family of the Camarasauridé S
• family of the Diplodocidé S
• family of the Titanosauridé S
• family of the Agustinidé S
• family of the Astrodontidé S
• family of Rebbachisauridé S
• family of the Dicraéosauridé S

Sub-order of the Ornithopode S (iguanodontoïdés)

• family of the Fabrosauridé S
• family of the Hétérodontosauridé S
• family of the Hypsilophodontidé S
• family of the Iguanodontidé S
• family of the Rhabdodontidé S
• family of the Hadrosauridé S
• subfamily of the Hadrosauriné S
• subfamily of the Lambéosauriné S

Sub-order of the Thyréophore S

• super-family of the Stégosaurien S
• family of the stegosauridés
• super-family of the Ankylosaurien S
• family of the Scélidosauridé S
• family of the Nodosauridé S
• family of the Ankylosauridé S

Sub-order of the Marginocéphale S

• super-family of the Psittacosaure S
• family of the Psittacosauridé S
• super-family of the Cératopsien S
• family of the Protocératopsidé S
• family of the Cératopsidé to long flange
• family of the Cératopsidé to short flange
• super-family of the Pachycéphalosaure S
• family of the Pachycéphalosauridé S