DINOSAURS

COMPUTER PROJECT WORK

Dinosaurs are a diverse group of animals of the clade Dinosauria. They first appeared during the Triassic period, approximately 230 million years ago, and were the dominant terrestrial vertebrates for 135 million years, from the beginning of the Jurassic (about 201 million years ago) until the end of the Cretaceous (66 million years ago), when the Cretaceous–Paleogene extinction event led to the extinction of most dinosaur groups at the close of the Mesozoic Era. The fossil record indicates that birds evolved from theropod dinosaurs during the Jurassic Period and, consequently, they are considered a subgroup of dinosaurs by many paleontologists.[1] Some birds survived the extinction event that occurred 66 million years ago, and their descendants continue the dinosaur lineage to the present day.[2]Dinosaurs are a varied group of animals from taxonomic, morphological and ecological standpoints. Birds, at over 9,000 living species, are the most diverse group of vertebrates besides perciform fish.[3] Using fossil evidence, paleontologists have identified over 500 distinct genera[4] and more than 1,000 different species of non-avian dinosaurs.[5] Dinosaurs are represented on every continent by both extant species and fossil remains.[6] Some are herbivorous, others carnivorous. 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. Evidence suggests that egg laying and nest building are additional traits shared by all dinosaurs.

INTRODUCTION

CLASSIFICATION OF DINOSAURS

Triceratops is a genus of herbivorous ceratopsid dinosaur that lived during the late Maastrichtian stage of the Late Cretaceous Period, around 68 to 65.5 million years ago (Mya) in what is now North America. It was one of the last non-avian dinosaur genera to appear before the Cretaceous–Paleogene extinction event.[1] The term Triceratops, which literally means "three-horned face", is derived from the Greek τρί- (tri-) meaning "three", κέρας (kéras) meaning "horn", and ψ (ops) meaning "face".[2][3]ὤBearing a large bony frill and three horns on its large four-legged body, and conjuring similarities with the modern rhinoceros, Triceratops is one of the most recognizable of all dinosaurs and the best known ceratopsid. It shared the landscape with and was preyed upon by the fearsome Tyrannosaurus,[4] though it is less certain that the two did battle in the manner often depicted in traditional museum displays and popular images.The exact placement of the Triceratops genus within the ceratopsid group has been debated by paleontologists. Two species, T. horridus and T. prorsus, are considered valid although many other species have been named. Recent research suggests that the contemporaneous Torosaurus, a ceratopsid long regarded as a separate genus, represents Triceratops in its mature form,[5][6] though this is disputed.[7]Triceratops has been documented by numerous remains collected since the genus was first described in 1889, including at least one complete individual skeleton.[8] Paleontologist John Scannella observed: "It is hard to walk out into the Hell Creek Formation and not stumble upon a Triceratops weathering out of a hillside." Forty-seven complete or partial skulls were discovered in just that area during the decade 2000–2010. Specimens representing life stages from hatchling to adult have been found.

TRICERATOPS

Apatosaurus also known by the popular but scientifically redundant synonym Brontosaurus, is a genus of sauropod dinosaur that lived from about 154 to 150 million years ago, during the Jurassic Period Kimmeridgian and early Tithonian ages).[1] It was one of the largest land animals known to have ever existed, with an average length of 23 m (75 ft) and a mass of at least 16 metric tons (18 short tons).[2] Fossils of these animals have been found in Nine Mile Quarry and Bone Cabin Quarry in Wyoming and at sites in Colorado, Oklahoma and Utah, present in stratigraphic zones 2-6.[3]The cervical vertebrae were less elongated and more heavily constructed than those of Diplodocus and the bones of the leg were much stockier (despite being longer), implying a more robust animal. The tail was held above the ground during normal locomotion. Like most sauropods, Apatosaurus had only a single large claw on each forelimb, with the first three toes on the hind limb possessing claws.

APATOSAURUS

Saurischia (/1] is one of the two basic divisions of dinosaurs. In 1888, Harry Seeley classified dinosaurs into two orders, based on their hip structure.[2] Saurischians ('lizard-hipped') are distinguished from the ornithischians ('bird-hipped') by retaining the ancestral configuration of bones in the hip.All carnivorous dinosaurs (the theropods) are saurischians, as are one of the two primary lineages of herbivorous dinosaurs, the sauropodomorphs. At the end of the Cretaceous Period, all saurischians except the birds became extinct. This is referred to as the Cretaceous–Paleogene extinction event.

Saurischians are distinguished from ornithischians by their three-pronged pelvic structure, with the pubis pointed forward. The ornithischians' pelvis is arranged with the pubis rotated backward, parallel with the ischium, often also with a forward-pointing process, giving a four-pronged structure.The saurischian hip structure led Seeley to name them "lizard-hipped" dinosaurs because they retained the ancestral hip anatomy also found in modern lizards. However, as later study revealed, this "bird-hipped" arrangement actually evolved twice independently in dinosaurs, first in the ornithischians and then in the lineage of saurischians including true birds (Avialae). In this example of convergent evolution, birds developed hips oriented similar to the earlier ornithischian hip anatomy, in both cases possibly as an adaptation to a herbivorous or omnivorous diet

SAURISCHIA

Tawa was estimated to have been 2 m (6.5 ft) long, almost 2.5 feet at the hips. Other estimates suggest that Tawa weighed 40 kilograms (88 pounds) at most.[4] The holotype, a juvenile individual, cataloged GR 241, consists of a mostly complete but disarticulated skull, forelimbs, the pectoral girdle, a partial vertebral column, hindlimbs, the pelvic girdle, ribs, and gastralia. The determination was made that this specimen is a juvenile based on the presence of an open braincase and unfused neurocentral sutures.[3] An isolated femur GR 244 suggests that adults were at least 30% larger than the juvenile holotype. Tawa preserves characters that can be associated with different dinosaur taxa. It's skull morphology resembles that of coelophysoids and the illium approximates that of a herrerasaurid. Like the coelophysoids, Tawa has a kink in its upper jaws, between the maxilla and the premaxilla. With respect to limb proportion, the femur is very long compared to the tibia. A neck vertebrae adaptation in Tawa supports the hypothesis that cervical air sacs predate the origin of the taxon Neotheropoda and may be ancestral for Saurischians, and also links the dinosaurs with the evolution of birds. Compared to earlier dinosaurs like Herrerasaurus and Eoraptor, Tawa had a relatively slender build.

Tawa (pron.:"Ta-WAH"; named after the Hopi word for the Puebloan sun god) is a genus of theropod dinosaur from the Late Triassic period.[1] The discovery of Tawa alongside the relatives of Coelophysis and Herrerasaurus supports the hypothesis that the earliest dinosaurs arose in Gondwana during the Late Triassic period in what is now South America, and radiated around the globe from there.[2] The specific name honours Ruth Hall, founder of the Ghost Ranch Museum of Paleontology.[3]

TAWA

Tyrannosaurus meaning "tyrant lizard", meaning "tyrant," and sauros meaning "lizard"[1]) is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex (rex meaning "king" in Latin), commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, at the time an island continent termed Laramidia, with a much wider range than other tyrannosaurids. Fossils are found in a variety of rock formations dating to the Maastrichtian age of the upper Cretaceous Period, 67 to 65.5 million years ago.[2] It was among the last non-avian dinosaurs to exist before the Cretaceous–Paleogene extinction event.Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to the large and powerful hindlimbs, Tyrannosaurus forelimbs were small, though unusually powerful for their size, and bore two clawed digits. Although other theropods rivaled or exceeded Tyrannosaurus rex in size, it was the largest known tyrannosaurid and one of the largest known land predators, the most complete specimen measuring up to 12.3 m (40 ft) in length,[3] up to 4 metres (13 ft) tall at the hips,[4] and up to 6.8 metric tons (7.5 short tons) in weight.[5] By far the largest carnivore in its environment, Tyrannosaurus rex may have been an apex predator, preying upon hadrosaurs, ceratopsians, and possibly sauropods.[6] although some experts have suggested it was primarily a scavenger. The debate over Tyrannosaurus as apex predator or scavenger is among the longest running in paleontology.More than 30 specimens of Tyrannosaurus rex have been identified, some of which are nearly complete skeletons. Soft tissue and proteins have been reported in at least one of these specimens. The abundance of fossil material has allowed significant research into many aspects of its biology, including life history and biomechanics..

TYRANNOSAURUS

The origin of birds has historically been a contentious topic within evolutionary biology. However, most researchers now support the view that birds are a group of theropod dinosaurs that evolved during the Mesozoic Era.A close relationship between birds and dinosaurs was first proposed in the nineteenth century after the discovery of the primitive bird Archaeopteryx in Germany. Birds share many unique skeletal features with dinosaurs.[1] Moreover, fossils of more than twenty species of dinosaur have been collected with preserved feathers. There are even very small dinosaurs, such as Microraptor and Anchiornis, which have long, vaned, arm and leg feathers forming wings. The Jurassic basal avialan Pedopenna also shows these long foot feathers. Witmer (2009) has concluded that this evidence is sufficient to demonstrate that avian evolution went through a four-winged stage.[2]Fossil evidence also demonstrates that birds and dinosaurs shared features such as hollow, pneumatized bones, gastroliths in the digestive system, nest-building and brooding behaviors. The ground-breaking discovery of fossilized Tyrannosaurus rex soft tissue allowed a molecular comparison of cellular anatomy and protein sequencing of collagen tissue, both of which demonstrated that T. rex and birds are more closely related to each other than either is to the alligator.[3] A second molecular study robustly supported the relationship of birds to dinosaurs, though it did not place birds within Theropoda, as expected. This study utilized eight additional collagen sequences extracted from a femur of Brachylophosaurus Only a few scientists still debate the dinosaurian origin of birds, suggesting descent from other types of archosaurian reptiles

DINOSAURUS BIRDS

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