Dating dinosaurs wiki

Dinosaurs are a diverse group of reptiles [note 1] of the clade Dinosauria. They first appeared during the Triassic period, between and Reverse genetic engineering [4] and the fossil record both demonstrate that birds are modern feathered dinosaurs , [5] having evolved from earlier theropods during the late Jurassic Period. This article deals primarily with non-avian dinosaurs. Dinosaurs are a varied group of animals from taxonomic , morphological and ecological standpoints.

Dino Crisis 3

Dinosaurs are a diverse group of reptiles [note 1] of the clade Dinosauria. They first appeared during the Triassic period, between and Reverse genetic engineering [4] and the fossil record both demonstrate that birds are modern feathered dinosaurs , [5] having evolved from earlier theropods during the late Jurassic Period. This article deals primarily with non-avian dinosaurs. Dinosaurs are a varied group of animals from taxonomic , morphological and ecological standpoints.

Birds, at over 10, living species, [8] are the most diverse group of vertebrates besides perciform fish. Most research conducted since the s , however, has indicated that all dinosaurs were active animals with elevated metabolisms and numerous adaptations for social interaction. Some were herbivorous, others carnivorous. Evidence suggests that egg-laying and nest-building are additional traits shared by all dinosaurs, avian and non-avian alike.

While dinosaurs were ancestrally bipedal , many extinct groups included quadrupedal species, and some were able to shift between these stances. Elaborate display structures such as horns or crests are common to all dinosaur groups, and some extinct groups developed skeletal modifications such as bony armor and spines. While the dinosaurs' modern-day surviving avian lineage birds are generally small due to the constraints of flight, many prehistoric dinosaurs non-avian and avian were large-bodied—the largest sauropod dinosaurs are estimated to have reached lengths of Still, the idea that non-avian dinosaurs were uniformly gigantic is a misconception based in part on preservation bias, as large, sturdy bones are more likely to last until they are fossilized.

Many dinosaurs were quite small: Since the first dinosaur fossils were recognized in the early 19th century, mounted fossil dinosaur skeletons have been major attractions at museums around the world, and dinosaurs have become an enduring part of world culture. The large sizes of some dinosaur groups, as well as their seemingly monstrous and fantastic nature, have ensured dinosaurs' regular appearance in best-selling books and films, such as Jurassic Park. Persistent public enthusiasm for the animals has resulted in significant funding for dinosaur science, and new discoveries are regularly covered by the media.

The taxon 'Dinosauria' was formally named in by paleontologist Sir Richard Owen , who used it to refer to the "distinct tribe or sub-order of Saurian Reptiles" that were then being recognized in England and around the world. Other prehistoric animals, including pterosaurs , mosasaurs , ichthyosaurs , plesiosaurs , and Dimetrodon , while often popularly conceived of as dinosaurs, are not taxonomically classified as dinosaurs.

The other groups mentioned are, like dinosaurs and pterosaurs, members of Sauropsida the reptile and bird clade , except Dimetrodon which is a synapsid. Under phylogenetic nomenclature , dinosaurs are usually defined as the group consisting of the most recent common ancestor MRCA of Triceratops and Neornithes , and all its descendants.

Birds are now recognized as being the sole surviving lineage of theropod dinosaurs. In traditional taxonomy, birds were considered a separate class that had evolved from dinosaurs, a distinct superorder. However, a majority of contemporary paleontologists concerned with dinosaurs reject the traditional style of classification in favor of phylogenetic taxonomy; this approach requires that, for a group to be natural, all descendants of members of the group must be included in the group as well.

Birds are thus considered to be dinosaurs and dinosaurs are, therefore, not extinct. Research by Matthew Baron, David B. Norman, and Paul M. Barrett in suggested a radical revision of dinosaurian systematics. Phylogenetic analysis by Baron et al. They resurrected the clade Ornithoscelida to refer to the group containing Ornithischia and Theropoda. Dinosauria itself was re-defined as the last common ancestor of Triceratops horridus , Passer domesticus , Diplodocus carnegii , and all of its descendants, to ensure that sauropods and kin remain included as dinosaurs.

Using one of the above definitions, dinosaurs can be generally described as archosaurs with hind limbs held erect beneath the body. Other groups of animals were restricted in size and niches; mammals, for example, rarely exceeded the size of a domestic cat, and were generally rodent-sized carnivores of small prey. In , the estimated number of dinosaur species that existed in the Mesozoic era was estimated to be 1,—2, While dinosaurs were ancestrally bipedal as are all modern birds , some prehistoric species were quadrupeds, and others, such as Anchisaurus and Iguanodon , could walk just as easily on two or four legs.

Cranial modifications like horns and crests are common dinosaurian traits, and some extinct species had bony armor. Although known for large size, many Mesozoic dinosaurs were human-sized or smaller, and modern birds are generally small in size. Dinosaurs today inhabit every continent, and fossils show that they had achieved global distribution by at least the early Jurassic period. While recent discoveries have made it more difficult to present a universally agreed-upon list of dinosaurs' distinguishing features, nearly all dinosaurs discovered so far share certain modifications to the ancestral archosaurian skeleton, or are clear descendants of older dinosaurs showing these modifications.

Although some later groups of dinosaurs featured further modified versions of these traits, they are considered typical for Dinosauria; the earliest dinosaurs had them and passed them on to their descendants. Such modifications, originating in the most recent common ancestor of a certain taxonomic group, are called the synapomorphies of such a group. A detailed assessment of archosaur interrelations by Sterling Nesbitt [34] confirmed or found the following twelve unambiguous synapomorphies, some previously known:.

Nesbitt found a number of further potential synapomorphies, and discounted a number of synapomorphies previously suggested. Some of these are also present in silesaurids , which Nesbitt recovered as a sister group to Dinosauria, including a large anterior trochanter, metatarsals II and IV of subequal length, reduced contact between ischium and pubis, the presence of a cnemial crest on the tibia and of an ascending process on the astragalus, and many others.

A variety of other skeletal features are shared by dinosaurs. However, because they are either common to other groups of archosaurs or were not present in all early dinosaurs, these features are not considered to be synapomorphies. For example, as diapsids , dinosaurs ancestrally had two pairs of temporal fenestrae openings in the skull behind the eyes , and as members of the diapsid group Archosauria, had additional openings in the snout and lower jaw.

These include an elongated scapula , or shoulder blade; a sacrum composed of three or more fused vertebrae three are found in some other archosaurs, but only two are found in Herrerasaurus ; [19] and a perforate acetabulum , or hip socket, with a hole at the center of its inside surface closed in Saturnalia , for example.

Dinosaurs stand with their hind limbs erect in a manner similar to most modern mammals , but distinct from most other reptiles, whose limbs sprawl out to either side. Dinosaurs may have appeared as early as million years ago, as evidenced by remains of the genus Nyasasaurus from that period, though known fossils of these animals are too fragmentary to tell if they are dinosaurs or very close dinosaurian relatives.

When dinosaurs appeared, they were not the dominant terrestrial animals. The terrestrial habitats were occupied by various types of archosauromorphs and therapsids , like cynodonts and rhynchosaurs. Their main competitors were the pseudosuchia , such as aetosaurs , ornithosuchids and rauisuchians , which were more successful than the dinosaurs.

Rhynchosaurs and dicynodonts survived at least in some areas at least as late as early-mid Norian and late Norian or earliest Rhaetian , respectively, [50] [51] and the exact date of their extinction is uncertain. These losses left behind a land fauna of crocodylomorphs , dinosaurs, mammals , pterosaurians , and turtles. Dinosaur evolution after the Triassic follows changes in vegetation and the location of continents. In the late Triassic and early Jurassic, the continents were connected as the single landmass Pangaea , and there was a worldwide dinosaur fauna mostly composed of coelophysoid carnivores and early sauropodomorph herbivores.

Early sauropodomorphs did not have sophisticated mechanisms for processing food in the mouth, and so must have employed other means of breaking down food farther along the digestive tract. Dinosaurs in China show some differences, with specialized sinraptorid theropods and unusual, long-necked sauropods like Mamenchisaurus.

Conifers and pteridophytes were the most common plants. Sauropods, like the earlier prosauropods, were not oral processors, but ornithischians were evolving various means of dealing with food in the mouth, including potential cheek -like organs to keep food in the mouth, and jaw motions to grind food. By the early Cretaceous and the ongoing breakup of Pangaea, dinosaurs were becoming strongly differentiated by landmass.

The earliest part of this time saw the spread of ankylosaurians, iguanodontians , and brachiosaurids through Europe, North America, and northern Africa. These were later supplemented or replaced in Africa by large spinosaurid and carcharodontosaurid theropods, and rebbachisaurid and titanosaurian sauropods, also found in South America. In Asia, maniraptoran coelurosaurians like dromaeosaurids , troodontids , and oviraptorosaurians became the common theropods, and ankylosaurids and early ceratopsians like Psittacosaurus became important herbivores.

Meanwhile, Australia was home to a fauna of basal ankylosaurians, hypsilophodonts , and iguanodontians. A major change in the early Cretaceous, which would be amplified in the late Cretaceous, was the evolution of flowering plants. At the same time, several groups of dinosaurian herbivores evolved more sophisticated ways to orally process food.

Ceratopsians developed a method of slicing with teeth stacked on each other in batteries, and iguanodontians refined a method of grinding with tooth batteries , taken to its extreme in hadrosaurids. There were three general dinosaur faunas in the late Cretaceous. In the northern continents of North America and Asia, the major theropods were tyrannosaurids and various types of smaller maniraptoran theropods, with a predominantly ornithischian herbivore assemblage of hadrosaurids, ceratopsians, ankylosaurids, and pachycephalosaurians.

In the southern continents that had made up the now-splitting Gondwana , abelisaurids were the common theropods, and titanosaurian sauropods the common herbivores. Finally, in Europe, dromaeosaurids, rhabdodontid iguanodontians, nodosaurid ankylosaurians, and titanosaurian sauropods were prevalent. Theropods were also radiating as herbivores or omnivores , with therizinosaurians and ornithomimosaurians becoming common. The Cretaceous—Paleogene extinction event , which occurred approximately 66 million years ago at the end of the Cretaceous period, caused the extinction of all dinosaur groups except for the neornithine birds.

Some other diapsid groups, such as crocodilians, sebecosuchians , turtles , lizards , snakes , sphenodontians , and choristoderans , also survived the event. The surviving lineages of neornithine birds, including the ancestors of modern ratites , ducks and chickens , and a variety of waterbirds , diversified rapidly at the beginning of the Paleogene period, entering ecological niches left vacant by the extinction of Mesozoic dinosaur groups such as the arboreal enantiornithines , aquatic hesperornithines , and even the larger terrestrial theropods in the form of Gastornis , eogruiids , bathornithids , ratites , geranoidids , mihirungs , and " terror birds ".

It is often cited that mammals out-competed the neornithines for dominance of most terrestrial niches but many of these groups co-existed with rich mammalian faunas for most of the Cenozoic. Dinosaurs belong to a group known as archosaurs , which also includes modern crocodilians. Within the archosaur group, dinosaurs are differentiated most noticeably by their gait.

Dinosaur legs extend directly beneath the body, whereas the legs of lizards and crocodilians sprawl out to either side. Collectively, dinosaurs as a clade are divided into two primary branches, Saurischia and Ornithischia. Saurischia includes those taxa sharing a more recent common ancestor with birds than with Ornithischia , while Ornithischia includes all taxa sharing a more recent common ancestor with Triceratops than with Saurischia.

Anatomically, these two groups can be distinguished most noticeably by their pelvic structure. Saurischia includes the theropods exclusively bipedal and with a wide variety of diets and sauropodomorphs long-necked herbivores which include advanced, quadrupedal groups. Unlike birds, the ornithischian pubis also usually had an additional forward-pointing process.

Ornithischia includes a variety of species which were primarily herbivores. The following is a simplified classification of dinosaur groups based on their evolutionary relationships, and organized based on the list of Mesozoic dinosaur species provided by Holtz Knowledge about dinosaurs is derived from a variety of fossil and non-fossil records, including fossilized bones , feces , trackways , gastroliths , feathers , impressions of skin, internal organs and soft tissues.

Current evidence suggests that dinosaur average size varied through the Triassic, early Jurassic, late Jurassic and Cretaceous periods. The sauropods were the largest and heaviest dinosaurs. For much of the dinosaur era, the smallest sauropods were larger than anything else in their habitat, and the largest were an order of magnitude more massive than anything else that has since walked the Earth.

Giant prehistoric mammals such as Paraceratherium the largest land mammal ever were dwarfed by the giant sauropods, and only modern whales approach or surpass them in size. Large animals are more efficient at digestion than small animals, because food spends more time in their digestive systems. This also permits them to subsist on food with lower nutritive value than smaller animals. Sauropod remains are mostly found in rock formations interpreted as dry or seasonally dry, and the ability to eat large quantities of low-nutrient browse would have been advantageous in such environments.

Scientists will probably never be certain of the largest and smallest dinosaurs to have ever existed. This is because only a tiny percentage of animals ever fossilize, and most of these remain buried in the earth. Few of the specimens that are recovered are complete skeletons, and impressions of skin and other soft tissues are rare.

A fossil is any preserved remains, impression, or trace of any once-living thing from a past The development of radiometric dating techniques in the early 20th century allowed . has been the discovery of soft tissue in dinosaur fossils, including blood vessels, and the isolation of proteins and evidence for DNA fragments. Dinosaurs evolved within a single lineage of archosaurs Ma (million years ago) from . Dinosaurs used in creating these charts are (in date order): Eo Eoraptor; Prosauropods Ri Riojasaurus, Pl Plateosaurus, Yu Yunnanosaurus, Ms .

Dino Crisis 3 is an action-adventure game released exclusively for the Xbox. It is the fourth game in release order, and the final console game in the series. Like the previous iterations of the Dino Crisis series, gameplay revolves around fighting dinosaurs. The action takes place in outer space, on a starship, the Ozymandias.

It is diagnosed by many features including loss of the postfrontal on the skull and an elongate deltopectoral crest on the humerus.

It begins. The most precious moment. The result of incalculable actions and reactions, trials and errors, genetic mutations and unknowable combinations, chaos

Why Did the Dinosaurs Die Out?

Jurassic World: The game was officially released worldwide on May 24, , Dinosaurs have returned to rule the Earth. They have fled Jurassic World on the unstable island of Isla Nublar … and they're roaming free in your cities and neighborhoods. As a brand-new member of the Dinosaur Protection Group DPG , your mission is to save dinosaurs from a second extinction. Explore your surrounding area to find your favorite dinosaurs — including new breeds that are more awe-inspiring and terrifying than ever before.

Downloadable content

A fossil from Classical Latin fossilis ; literally, "obtained by digging" [1] is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons , stone imprints of animals or microbes , objects preserved in amber, hair, petrified wood , oil, coal, and DNA remnants. The totality of fossils is known as the fossil record. Paleontology is the study of fossils: The development of radiometric dating techniques in the early 20th century allowed scientists to quantitatively measure the absolute ages of rocks and the fossils they host. There are many processes that lead to fossilization, including permineralization , casts and molds, authigenic mineralization , replacement and recrystallization, adpression, carbonization , and bioimmuration. A fossil normally preserves only a portion of the deceased organism, usually that portion that was partially mineralized during life, such as the bones and teeth of vertebrates , or the chitinous or calcareous exoskeletons of invertebrates. Fossils may also consist of the marks left behind by the organism while it was alive, such as animal tracks or feces coprolites. These types of fossil are called trace fossils or ichnofossils , as opposed to body fossils.

The Cretaceous-Tertiary extinction event, or the K-T event, is the name given to the die-off of the dinosaurs and other species that took place some


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