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138-480: Originally preserved in 1915 to protect its famous Dinosaur Quarry, the monument was greatly expanded in 1938 to include its wealth of natural history. The park's wild landscapes, topography, geology, paleontology, and history make it a unique resource for both science and recreation. The park contains over 800 paleontological sites and has fossils of dinosaurs including Allosaurus , Deinonychus , Abydosaurus , and various sauropods . The Abydosaurus consists of

276-624: A gazetteer compiled by Chang Qu  ( 常璩 ) during the Western Jin Dynasty (265–316), reported the discovery of dragon bones at Wucheng in Sichuan Province. Villagers in central China have long unearthed fossilized "dragon bones" for use in traditional medicines . In Europe , dinosaur fossils were generally believed to be the remains of giants and other biblical creatures. Scholarly descriptions of what would now be recognized as dinosaur bones first appeared in

414-523: A sacrum composed of three or more fused vertebrae (three are found in some other archosaurs, but only two are found in Herrerasaurus ); and a perforate acetabulum , or hip socket, with a hole at the center of its inside surface (closed in Saturnalia tupiniquim , for example). Another difficulty of determining distinctly dinosaurian features is that early dinosaurs and other archosaurs from

552-421: A "pillar-erect" configuration of the hip joint, where instead of having a projection from the femur insert on a socket on the hip, the upper pelvic bone was rotated to form an overhanging shelf. Dinosaur fossils have been known for millennia, although their true nature was not recognized. The Chinese considered them to be dragon bones and documented them as such. For example, Huayang Guo Zhi  ( 華陽國志 ),

690-717: A compromise that eliminated Echo Park Dam and authorized the rest of the project. The Colorado River Storage Project Act became law on April 11, 1956. It stated, "that no dam or reservoir constructed under the authorization of the Act shall be within any National Park or Monument." Places on the list of National Register of Historic Places include: The Dinosaur National Monument sits on a vast area of desert land in Northwestern Colorado and Northeastern Utah. Typical of high deserts, summer temperatures can be exceedingly hot, while winter temperatures can be very cold. Snowfall

828-488: A controversial taxon that was recently confirmed to exist after archived photos were uncovered. Bruhathkayosaurus was a titanosaur and would have most likely weighed more than even Marrapunisaurus . Recent size estimates in 2023 have placed this sauropod reaching lengths of up to 44 m (144 ft) long and a colossal weight range of around 110 000 – 170 000  kg ( 240 000 – 370 000  lb), if these upper estimates up true, Bruhathkayosaurus would have rivaled

966-448: A corresponding inwardly facing distinct head on the femur. Their erect posture enabled early dinosaurs to breathe easily while moving, which likely permitted stamina and activity levels that surpassed those of "sprawling" reptiles . Erect limbs probably also helped support the evolution of large size by reducing bending stresses on limbs. Some non-dinosaurian archosaurs, including rauisuchians , also had erect limbs but achieved this by

1104-652: A dinosaur. In it he described and named a sauropod tooth , " Rutellum impicatum ", that had been found in Caswell, near Witney , Oxfordshire. Between 1815 and 1824, the Rev William Buckland , the first Reader of Geology at the University of Oxford, collected more fossilized bones of Megalosaurus and became the first person to describe a non-avian dinosaur in a scientific journal . The second non-avian dinosaur genus to be identified, Iguanodon ,

1242-536: A diverse group of reptiles of the clade Dinosauria . They first appeared during the Triassic period , between 243 and 233.23  million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is a subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 mya and their dominance continued throughout

1380-537: A femur of Tyrannosaurus preserved soft, flexible tissue within, including blood vessels , bone matrix , and connective tissue (bone fibers) that had retained their microscopic structure. This discovery suggested that original soft tissues could be preserved over geological time, with multiple mechanisms having been proposed. Later, in 2009, Schweitzer and colleagues reported that a Brachylophosaurus femur preserved similar microstructures, and immunohistochemical techniques (based on antibody binding) demonstrated

1518-422: 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

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1656-595: A larger deposit of oil shale in the Green River formation. The Equity Oil Company currently has 17 wells in declining production of oil near Ashley Field and is looking to inject carbon dioxide into the Weber reservoir to increase the rate of oil flow through their pipelines. At the time of its discovery (2005), the Green River Formation was said to have the world's largest fossil fuel deposits in

1794-486: 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. Early saurischians—"lizard-hipped", from the Greek sauros ( σαῦρος ) meaning "lizard" and ischion ( ἰσχίον ) meaning "hip joint"—retained

1932-649: A nearly complete skull, the lower jaw, and first four neck vertebrae. The specimen was found at the base of the Mussentuchit Member of the Cedar Mountain Formation and is the holotype for the description. Paleontologist Earl Douglass of the Carnegie Museum discovered eight vertebra of an Apatosaurus on August 17, 1909, which became the first dinosaur skeleton discovered and excavated at the new Carnegie Quarry. The area around

2070-583: A now lost partial vertebral neural arch described in 1878. Extrapolating from the illustration of this bone, the animal may have been 58 meters (190 ft) long and weighed 122 400  kg ( 269 800  lb). However, recent research have placed Amphicoelias from the long, gracile diplodocid to the shorter but much stockier rebbachisaurid. Now renamed as Maraapunisaurus , this sauropod now stands as much as 40 meters (130 ft) long and weigh as much as 120 000  kg ( 260 000  lb). Another contender of this title includes Bruhathkayosaurus ,

2208-613: A panic caused by the Meeker Massacre in Colorado. Most of the land in the valley of the river today is owned and controlled by the federal government. Private holdings are largely limited to bottoms. Until the 1940s, the valley's economy was based largely on ranching. Tourism has emerged as the dominant industry in the region in the last several decades. A proposed nuclear power plant, the Blue Castle Project ,

2346-433: A period of time, with estimates ranging from 5–10 million years to 21 million years. 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 pseudosuchians , such as aetosaurs , ornithosuchids and rauisuchians, which were more successful than

2484-663: A potential food source, radiated in the Late Triassic. 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. The general homogeneity of dinosaurian faunas continued into the Middle and Late Jurassic, where most localities had predators consisting of ceratosaurians , megalosauroids , and allosauroids , and herbivores consisting of stegosaurian ornithischians and large sauropods. Examples of this include

2622-681: A presentation about fossil reptiles to the British Association for the Advancement of Science in 1841, but reports of the time show that Owen did not mention the word "dinosaur", nor recognize dinosaurs as a distinct group of reptiles in his address. He introduced the Dinosauria only in the revised text version of his talk published in April 1842. With the backing of Prince Albert , the husband of Queen Victoria , Owen established

2760-599: A review paper by Paul Sereno in 1998, were accompanied by increases in the number of published phylogenetic trees for dinosaurs. Dinosaur fossils are not limited to bones, but also include imprints or mineralized remains of skin coverings, organs, and other tissues. Of these, skin coverings based on keratin proteins are most easily preserved because of their cross-linked , hydrophobic molecular structure. Fossils of keratin-based skin coverings or bony skin coverings are known from most major groups of dinosaurs. Dinosaur fossils with scaly skin impressions have been found since

2898-418: A road to the quarry, removal of overburden covering the bone-bearing strata, and building of a small, temporary museum. World War II interrupted work, but this was resumed in 1951 with the building of a small metal building over the east portion of the quarry to test whether bone was abundant enough to warrant a larger, more permanent building. This more permanent building was erected in the mid-1950s as part of

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3036-549: A series of studies that likewise argued for active lifestyles in dinosaurs based on anatomical and ecological evidence (see § Physiology ), which were subsequently summarized in his 1986 book The Dinosaur Heresies . New revelations were supported by an increase in dinosaur discoveries. Major new dinosaur discoveries have been made by paleontologists working in previously unexplored regions, including India, South America, Madagascar, Antarctica, and most significantly China. Across theropods, sauropodomorphs, and ornithischians,

3174-603: 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 either are 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 Infratemporal fenestrae (openings in

3312-490: A universally agreed-upon list of their distinguishing features, nearly all dinosaurs discovered so far share certain modifications to the ancestral archosaurian skeleton, or are clearly 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

3450-468: 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

3588-460: A wintering ground for American trappers in the next decades, with trading posts established at the mouth of the White near Whiterocks, Utah , and Browns Park . The Upper Green River Rendezvous Site near Pinedale, Wyoming was a popular location for annual mountain man rendezvous during the 1820s and 1830s, with as many as 450 to 500 trappers attending during its heyday in the 1830s. The region

3726-430: Is 39.7 meters (130 ft) long. There were larger dinosaurs, but knowledge of them is based entirely on a small number of fragmentary fossils. Most of the largest herbivorous specimens on record were discovered in the 1970s or later, and include the massive Argentinosaurus , which may have weighed 80 000 to 100 000 kilograms (88 to 110 short tons) and reached lengths of 30 to 40 meters (98 to 131 ft); some of

3864-710: Is a synapsid ). None of them had the erect hind limb posture characteristic of true dinosaurs. Dinosaurs were the dominant terrestrial vertebrates of the Mesozoic Era , especially the Jurassic and Cretaceous periods. 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. Dinosaurs have always been recognized as an extremely varied group: over 900 non-avian dinosaur genera have been confidently identified (2018) with 1124 species (2016). Estimates put

4002-470: Is an inexact art, and reconstructing the muscles and other organs of the living animal is, at best, a process of educated guesswork. The tallest and heaviest dinosaur known from good skeletons is Giraffatitan brancai (previously classified as a species of Brachiosaurus ). Its remains were discovered in Tanzania between 1907 and 1912. Bones from several similar-sized individuals were incorporated into

4140-755: Is based in part on preservation bias , as large, sturdy bones are more likely to last until they are fossilized. Many dinosaurs were quite small, some measuring about 50 centimeters (20 inches) in length. The first dinosaur fossils were recognized in the early 19th century, with the name "dinosaur" (meaning "terrible lizard") being coined by Sir Richard Owen in 1842 to refer to these "great fossil lizards". Since then, mounted fossil dinosaur skeletons have been major attractions at museums worldwide, and dinosaurs have become an enduring part of popular culture . The large sizes of some dinosaurs, as well as their seemingly monstrous and fantastic nature, have ensured their regular appearance in best-selling books and films, such as

4278-466: Is between 1 and 10 metric tons (1.1 and 11.0 short tons). This contrasts sharply with the average size of Cenozoic mammals, estimated by the National Museum of Natural History as about 2 to 5 kg (4.4 to 11.0 lb). 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

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4416-493: Is common, but the snow melts rapidly in the arid and sunny climates of these states. Rainfall is very low, and the evaporation rate classifies the area as desert, even though the rainfall exceeds 10 inches. The "Wall of Bones" located within the Dinosaur Quarry building in the park consists of a steeply tilted (67° from horizontal) rock layer which contains thousands of dinosaur fossils . The preserved section

4554-621: Is derived from a variety of fossil and non-fossil records, including fossilized bones, feces , trackways , gastroliths , feathers , impressions of skin, internal organs and other soft tissues . Many fields of study contribute to our understanding of dinosaurs, including physics (especially biomechanics ), chemistry , biology , and the Earth sciences (of which paleontology is a sub-discipline). Two topics of particular interest and study have been dinosaur size and behavior. Current evidence suggests that dinosaur average size varied through

4692-804: Is in western Wyoming, in northern Sublette County , on the western side of the Continental Divide in the Wind River Range and the Bridger–Teton National Forest . It flows south through Sublette County and western Wyoming in an area known as the Upper Green River Valley, then southwest and is joined by the Big Sandy River in western Sweetwater County . At the town of La Barge, it flows into Fontenelle Reservoir , formed by Fontenelle Dam. Below

4830-650: Is joined by the Duchesne River , and three miles (5 km) farther downstream by the White River . Ten miles farther downstream, it is joined by the Willow River . South of the plateau, it is joined by Nine Mile Creek , then enters the Roan Cliffs where it flows south through the back-to-back Desolation and Gray canyons, with a combined length of 120 mi (192 km). In Gray Canyon, it

4968-585: Is joined by the Price River . South of the canyon, it passes the town of Green River, Utah and is joined by the San Rafael River in southern Emery County . In eastern Wayne County it meanders through Canyonlands National Park , where it joins Colorado. The Flaming Gorge Dam in Utah is a significant regional source of water for irrigation and mining, as well as for hydroelectric power. Begun in

5106-557: Is navigable by small craft throughout its course and by large motorboats upstream to Flaming Gorge Dam. Near the areas where the Oregon Trail crosses the river, it is 400 to 500 feet (120 to 150 m) wide and averages about 20 feet (6.1 m) deep at normal flow. Archaeological evidence indicates that the tributary canyons and sheltered areas in the river valley were home to the Fremont Culture , which flourished from

5244-591: Is now at the American Museum of Natural History in New York City, while Marsh's is at the Peabody Museum of Natural History at Yale University . World War II caused a pause in palaeontological research; after the war, research attention was also diverted increasingly to fossil mammals rather than dinosaurs, which were seen as sluggish and cold-blooded. At the end of the 1960s, however,

5382-767: Is now known as Sevier Lake . Later cartographers extended the error, representing the Buenaventura River as flowing into the Pacific Ocean . At least one charted the Buenaventura as draining the Great Salt Lake . Later, Spanish and Mexican explorers adopted the name Rio Verde, meaning "Green River" in Spanish . Exactly when the Spanish started using this name and why is unknown. Explanations of

5520-654: Is often stated 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 Era. Terror birds and bathornithids occupied carnivorous guilds alongside predatory mammals, and ratites are still fairly successful as midsized herbivores; eogruiids similarly lasted from the Eocene to Pliocene , becoming extinct only very recently after over 20 million years of co-existence with many mammal groups. Dinosaurs belong to

5658-719: Is only a portion of what was originally present when Douglass made his discovery as seen on the map above. When work ceased in 1922, a portion of the quarry was left for future development. This work began as part of President Franklin Roosevelt's Civil Works Administration, which provided employment during the Depression under the Transient Relief Service and later under the Works Progress Administration. This work included constructing

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5796-497: Is set to begin construction near Green River in 2023. The plant will use 53,500 acre-feet (66,000,000 m ) of water annually from the Green River once both reactors are commissioned. The La Barge oil field was discovered in 1924. Oil was produced from Tertiary sandstones ( Wasatch Formation and Green River Formation ), within an anticline 600 to 1200 feet deep. The Big Piney -La Barge complex has produced gas since 1956 and oil since 1960. Cumulative production by 1976

5934-535: The Jurassic Park franchise. Persistent public enthusiasm for the animals has resulted in significant funding for dinosaur science, and new discoveries are regularly covered by the media. Under phylogenetic nomenclature , dinosaurs are usually defined as the group consisting of the most recent common ancestor (MRCA) of Triceratops and modern birds (Neornithes), and all its descendants. It has also been suggested that Dinosauria be defined with respect to

6072-437: The blue whale and Perucetus colossus as one of the largest animals to have ever existed. The largest carnivorous dinosaur was Spinosaurus , reaching a length of 12.6 to 18 meters (41 to 59 ft) and weighing 7 to 20.9 metric tons (7.7 to 23.0 short tons). Other large carnivorous theropods included Giganotosaurus , Carcharodontosaurus , and Tyrannosaurus . Therizinosaurus and Deinocheirus were among

6210-695: The Anisian epoch of the Triassic, approximately 243 million years ago, which is the age of Nyasasaurus from the Manda Formation of Tanzania. However, its known fossils are too fragmentary to identify it as a dinosaur or only a close relative. The referral of the Manda Formation to the Anisian is also uncertain. Regardless, dinosaurs existed alongside non-dinosaurian ornithodirans for

6348-941: The Canyon of the Lodore (otherwise known as the Gates of Lodore) and is joined by the Yampa River at Steamboat Rock . It turns westward back into Utah along the southern edge of the Uintas in Whirlpool Canyon . In Utah, it meanders southwest across the Yampa Plateau and through the Uintah and Ouray Indian Reservation and the Ouray National Wildlife Refuge . Two miles south of Ouray, Utah , it

6486-462: The Carnian pluvial event . Dinosaur evolution after the Triassic followed 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. Gymnosperm plants (particularly conifers ),

6624-637: The Ischigualasto and Santa Maria Formations of Argentina and Brazil, and the Pebbly Arkose Formation of Zimbabwe. The Ischigualasto Formation ( radiometrically dated at 231–230 million years old ) has produced the early saurischian Eoraptor , originally considered a member of the Herrerasauridae but now considered to be an early sauropodomorph, along with the herrerasaurids Herrerasaurus and Sanjuansaurus , and

6762-773: The Jurassic and Cretaceous periods. The fossil record shows that birds are feathered dinosaurs , having evolved from earlier theropods during the Late Jurassic epoch , and are the only dinosaur lineage known to have survived the Cretaceous–Paleogene extinction event approximately 66 mya. Dinosaurs can therefore be divided into avian dinosaurs —birds—and the extinct non-avian dinosaurs , which are all dinosaurs other than birds. Dinosaurs are varied from taxonomic , morphological and ecological standpoints. Birds, at over 11,000 living species , are among

6900-491: The Late Triassic epoch are often poorly known and were similar in many ways; these animals have sometimes been misidentified in the literature. 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. This posture is due to the development of a laterally facing recess in the pelvis (usually an open socket) and

7038-657: The Morrison Formation of North America and Tendaguru Beds of Tanzania. Dinosaurs in China show some differences, with specialized metriacanthosaurid theropods and unusual, long-necked sauropods like Mamenchisaurus . Ankylosaurians and ornithopods were also becoming more common, but primitive sauropodomorphs had become extinct. Conifers and pteridophytes were the most common plants. Sauropods, like earlier sauropodomorphs, were not oral processors, but ornithischians were evolving various means of dealing with food in

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7176-497: The Natural History Museum, London , to display the national collection of dinosaur fossils and other biological and geological exhibits. In 1858, William Parker Foulke discovered the first known American dinosaur, in marl pits in the small town of Haddonfield, New Jersey . (Although fossils had been found before, their nature had not been correctly discerned.) The creature was named Hadrosaurus foulkii . It

7314-529: The Oregon , California , and Mormon emigration trails. Nearly all primary emigration routes had to cross the Green River. The main trail crossed near where the Big Sandy River joins the Green River in Wyoming. The river is too big and much too deep to ford at any time of the year and is the largest, most dangerous river crossed by the Oregon Trail. For that reason, ferries were commonly run on this stretch of

7452-621: The Pietraroja Plattenkalk of Italy. It preserves portions of the intestines, colon, liver, muscles, and windpipe. Concurrently, a line of work led by Mary Higby Schweitzer , Jack Horner , and colleagues reported various occurrences of preserved soft tissues and proteins within dinosaur bone fossils. Various mineralized structures that likely represented red blood cells and collagen fibres had been found by Schweitzer and others in tyrannosaurid bones as early as 1991. However, in 2005, Schweitzer and colleagues reported that

7590-504: The Quarry Visitor Center was closed due to structural problems that since 1958 had plagued the building because it was built on unstable clay. The decision was made to build a new facility elsewhere in the monument to house the visitor center and administrative functions, making it easier to resolve the structural problems of the quarry building while still retaining a portion of the historic Mission 66 era exhibit hall. It

7728-708: The United States and displayed in Pittsburgh 's Carnegie Museum of Natural History in 1907. The longest dinosaur known from good fossil material is Patagotitan : the skeleton mount in the American Museum of Natural History in New York is 37 meters (121 ft) long. The Museo Municipal Carmen Funes in Plaza Huincul , Argentina, has an Argentinosaurus reconstructed skeleton mount that

7866-427: The largest and smallest dinosaurs to have ever existed. This is because only a tiny percentage of animals were ever fossilized and most of these remain buried in the earth. Few non-avian dinosaur specimens that are recovered are complete skeletons, and impressions of skin and other soft tissues are rare. Rebuilding a complete skeleton by comparing the size and morphology of bones to those of similar, better-known species

8004-534: The "lizard-hipped" dinosaurs—birds evolved from earlier dinosaurs with "lizard hips". The following is a simplified classification of dinosaur groups based on their evolutionary relationships, and those of the main dinosaur groups Theropoda, Sauropodomorpha and Ornithischia, compiled by Justin Tweet. Further details and other hypotheses of classification may be found on individual articles. Timeline of major dinosaur groups per Holtz (2007) . Knowledge about dinosaurs

8142-483: The 1950s and finished in 1963, it was highly controversial and opposed by conservationists. Originally, a dam was to be built in Whirlpool Canyon, but the conservationist movement traded the Flaming Gorge Dam for halting that proposal. The Green is a large, deep, powerful river. It ranges from 100 to 300 feet (30 to 100 m) wide in the upper course and from 300 to 1,500 feet (91 to 457 m) wide in its lower course, and from 3 to 50 feet (0.91 to 15.24 m) in depth. It

8280-677: The 1970s , however, has indicated that dinosaurs were active animals with elevated metabolisms and numerous adaptations for social interaction. Some were herbivorous , others carnivorous . Evidence suggests that all dinosaurs were egg-laying , and that nest -building was a trait shared by many dinosaurs, both avian and non-avian. 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

8418-409: The 19th century. Samuel Beckles discovered a sauropod forelimb with preserved skin in 1852 that was incorrectly attributed to a crocodile; it was correctly attributed by Marsh in 1888 and subject to further study by Reginald Hooley in 1917. Among ornithischians, in 1884 Jacob Wortman found skin impressions on the first known specimen of Edmontosaurus annectens , which were largely destroyed during

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8556-418: The 7th century to the 13th century. The Fremont were semi-nomadic people who lived in pithouses and are best known for the rock art on canyon walls and in sheltered overhangs. In later centuries, the river basin was home to the Shoshone and Ute peoples, both nomadic hunters. The Shoshone inhabited the river valley north of the Uinta Mountains , whereas the Utes lived to the south. The current reservation of

8694-419: The Colorado River began at its confluence with the Green River. Above the confluence, Colorado was called the Grand River. In 1921, U.S. Representative Edward T. Taylor of Colorado petitioned the Congressional Committee on Interstate and Foreign Commerce to rename the Grand River as the Colorado River. On July 25, 1921, the name change was made official in House Joint Resolution 460 of the 66th Congress , over

8832-401: The English paleontologist Sir Richard Owen coined the term "dinosaur", using it to refer to the "distinct tribe or sub-order of Saurian Reptiles" that were then being recognized in England and around the world. The term is derived from Ancient Greek δεινός (deinos)  'terrible, potent or fearfully great' and σαῦρος (sauros)  'lizard or reptile'. Though

8970-688: The Fremont culture is unclear. Recent theories suggest that the Fremont's lifestyle may have changed due to drought or other climate factors, dwindling natural resources, or the influence of other neighboring cultures. They left evidence of their presence in the form of petroglyphs and pictographs of human and animal figures, and abstract designs. Human figures typically have trapezoidal bodies and elaborate decorations that suggest headdresses , earrings, necklaces, or shields. The animal figures include bighorn sheep, birds, snakes, and lizards. Purely abstract or geometric designs, such as circles, spirals, and various combinations of lines, are common. Many designs in

9108-529: The Greek ornitheios (ὀρνίθειος) meaning "of a bird" and ischion (ἰσχίον) meaning "hip joint"—had a pelvis that superficially resembled a bird's pelvis: the pubic bone was oriented caudally (rear-pointing). Unlike birds, the ornithischian pubis also usually had an additional forward-pointing process. Ornithischia includes a variety of species that were primarily herbivores. Despite the terms "bird hip" (Ornithischia) and "lizard hip" (Saurischia), birds are not part of Ornithischia. Birds instead belong to Saurischia,

9246-422: The Green and Yampa Rivers. They argued that if a national monument was not safe from development, how could any wildland be kept intact? On the other side of the argument were powerful members of Congress from western states, who were committed to the project in order to secure water rights, obtain cheap hydroelectric power and develop reservoirs as tourist destinations. After much debate, Congress settled on

9384-443: 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 dental batteries , taken to its extreme in hadrosaurids. Some sauropods also evolved tooth batteries, best exemplified by

9522-734: The MRCA of Megalosaurus and Iguanodon , because these were two of the three genera cited by Richard Owen when he recognized the Dinosauria. Both definitions cover the same known genera: Dinosauria = Ornithischia + Saurischia . This includes major groups such as ankylosaurians (armored herbivorous quadrupeds), stegosaurians (plated herbivorous quadrupeds), ceratopsians (bipedal or quadrupedal herbivores with neck frills ), pachycephalosaurians (bipedal herbivores with thick skulls), ornithopods (bipedal or quadrupedal herbivores including " duck-bills "), theropods (mostly bipedal carnivores and birds), and sauropodomorphs (mostly large herbivorous quadrupeds with long necks and tails). Birds are

9660-401: The Middle to Late Triassic epochs, roughly 20 million years after the devastating Permian–Triassic extinction event wiped out an estimated 96% of all marine species and 70% of terrestrial vertebrate species approximately 252 million years ago. The oldest dinosaur fossils known from substantial remains date to the Carnian epoch of the Triassic period and have been found primarily in

9798-439: The National Park Service Mission 66 plan. The architectural design was high controversial for its ultra-modern use of glass, steel and concrete ramp that spiraled around a cylindrical office tower. The building opened at the dedication ceremony on June 1, 1958. The design had two levels and abundant natural light so that visitors could watch technicians remove the hard rock to reveal the excavated fossil bones in-situ. In July 2006,

9936-574: The Native Americans). A map of 1847 redirects the course of the Rafael to the north and labels it as Green River. It would be some time before the true confluence of the Green and Colorado Rivers would be known. The Old Spanish Trail from New Mexico to California crossed the river just above the present-day town of Green River, Utah. In the early 19th century, the upper river in Wyoming

10074-524: The Triassic, Early Jurassic, Late Jurassic and Cretaceous. Predatory theropod dinosaurs, which occupied most terrestrial carnivore niches during the Mesozoic, most often fall into the 100-to-1,000 kg (220-to-2,200 lb) category when sorted by estimated weight into categories based on order of magnitude , whereas recent predatory carnivoran mammals peak in the 10-to-100 kg (22-to-220 lb) category. The mode of Mesozoic dinosaur body masses

10212-595: The United States, known as dinosaur mania. Dinosaur mania was exemplified by the fierce rivalry between Edward Drinker Cope and Othniel Charles Marsh , both of whom raced to be the first to find new dinosaurs in what came to be known as the Bone Wars . This fight between the two scientists lasted for over 30 years, ending in 1897 when Cope died after spending his entire fortune on the dinosaur hunt. Many valuable dinosaur specimens were damaged or destroyed due to

10350-721: The Utes is in the Uintah Basin . The Shoshone called the river the Seeds-kee-dee-Agie , meaning "Prairie Hen River." In 1776, the Spanish friars Silvestre Vélez de Escalante and Francisco Atanasio Domínguez crossed the river near present-day Jensen, naming it the Rio de San Buenaventura . The map-maker of the expedition, Captain Bernardo Miera y Pacheco , erroneously indicated that the river flowed southwest to what

10488-886: The area of what is now Dinosaur National Monument before the 14th century, with archaeological evidence dating from c. 200 to c. 1300. Archaeologists first studied and named the Fremont culture along the Fremont River in south-central Utah and have since traced it through much of the Green and Colorado River drainages. The Fremont did not build large permanent dwellings; instead, they lived in small bands within natural shelters, such as rock overhangs or shallow caves, or small villages. They consumed plant foods, such as pine nuts , berries, and cactus fruits, as well as wild game, including mule deer , bighorn sheep , smaller mammals, and birds. They also grew corn, beans, and squash, sometimes using irrigation techniques. The fate of

10626-673: The best-known genera are remarkable for their 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 the Early Jurassic epoch at latest. Modern birds inhabit most available habitats, from terrestrial to marine, and there is evidence that some non-avian dinosaurs (such as Microraptor ) could fly or at least glide, and others, such as spinosaurids , had semiaquatic habits. While recent discoveries have made it more difficult to present

10764-455: The body . Other prehistoric animals, including pterosaurs , mosasaurs , ichthyosaurs , plesiosaurs , and Dimetrodon , while often popularly conceived of as dinosaurs, are not taxonomically classified as dinosaurs. Pterosaurs are distantly related to dinosaurs, being members of the clade Ornithodira . The other groups mentioned are, like dinosaurs and pterosaurs, members of Sauropsida (the reptile and bird clade), except Dimetrodon (which

10902-429: The bone as the lower extremity of the femur of a large animal, and recognized that it was too large to belong to any known species. He therefore concluded it to be the femur of a huge human, perhaps a Titan or another type of giant featured in legends. Edward Lhuyd , a friend of Sir Isaac Newton , published Lithophylacii Britannici ichnographia (1699), the first scientific treatment of what would now be recognized as

11040-462: The canyons, geographic features, and rapids along the river. For example, "we sweep around another great bend to the left, making a circuit of nine miles, and come back to a point within 600 feet of the beginning of the bend. In the two circuits, we describe almost in figure 8. The men call it a `bowknot' of a river; so we name it Bowknot Bend ." (Powell, 1869) From the 1840s through the 1860s, hundreds of thousands of emigrants made their way west along

11178-475: 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. The stegosaurians appear to have gone extinct at some point in the late Early Cretaceous or early Late Cretaceous . A major change in the Early Cretaceous, which would be amplified in

11316-608: The dam, it flows through open sage-covered rolling prairie where it is crossed by the Oregon , California and Mormon emigration trails, and then further south past the town of Green River, Wyoming and into the Flaming Gorge Reservoir in southwestern Wyoming, formed by the Flaming Gorge Dam in northeastern Utah. Before the reservoir's creation, the Blacks Fork joined the Green River south of

11454-536: The dinosaur beds as Dinosaur National Monument in 1915. The monument boundaries were expanded in 1938 from the original 80 acres (0.13 sq mi; 0.32 km) surrounding the dinosaur quarry in Utah, to 210,844 acres (329 sq mi; 853 km) in Utah and Colorado, encompassing the river canyons of the Green and Yampa . The plans made by the U.S. Bureau of Reclamation on a ten-dam, billion dollar Colorado River Storage Project began to arouse opposition in

11592-731: The dinosaur subgroup Maniraptora , which are coelurosaurs , which are theropods, which are saurischians. Research by Matthew G. Baron, David B. Norman , and Paul M. Barrett in 2017 suggested a radical revision of dinosaurian systematics. Phylogenetic analysis by Baron et al. recovered the Ornithischia as being closer to the Theropoda than the Sauropodomorpha, as opposed to the traditional union of theropods with sauropodomorphs. This would cause sauropods and kin to fall outside traditional dinosaurs, so they re-defined Dinosauria as

11730-427: 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 39.7 meters (130 feet) and heights of 18 m (59 ft) and were the largest land animals of all time. The misconception that non-avian dinosaurs were uniformly gigantic

11868-686: The dinosaurs. Most of these other animals became extinct in the Triassic, in one of two events. First, at about 215 million years ago, a variety of basal archosauromorphs, including the protorosaurs , became extinct. This was followed by the Triassic–Jurassic extinction event (about 201 million years ago), that saw the end of most of the other groups of early archosaurs, like aetosaurs, ornithosuchids, phytosaurs , and rauisuchians. Rhynchosaurs and dicynodonts survived (at least in some areas) at least as late as early –mid Norian and late Norian or earliest Rhaetian stages , respectively, and

12006-489: The early 1950s when it was announced that one of the proposed dams would be at Echo Park , in the middle of Dinosaur National Monument. The controversy assumed major proportions, dominating conservation politics for years. David Brower , executive director of the Sierra Club , and Howard Zahniser of The Wilderness Society led an unprecedented nationwide campaign to preserve the free-flowing rivers and scenic canyons of

12144-585: The early saurischian Alwalkeria , are known from the Upper Maleri and Lower Maleri Formations of India. The Carnian-aged Chañares Formation of Argentina preserves primitive, dinosaur-like ornithodirans such as Lagosuchus and Lagerpeton in Argentina , making it another important site for understanding dinosaur evolution. These ornithodirans support the model of early dinosaurs as small, bipedal predators. Dinosaurs may have appeared as early as

12282-462: The end of the Cretaceous, caused the extinction of all dinosaur groups except for the neornithine birds. Some other diapsid groups, including crocodilians , dyrosaurs , 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

12420-456: The exact date of their extinction is uncertain. These losses left behind a land fauna of crocodylomorphs , dinosaurs, mammals, pterosaurians, and turtles . The first few lines of early dinosaurs diversified through the Carnian and Norian stages of the Triassic, possibly by occupying the niches of the groups that became extinct. Also notably, there was a heightened rate of extinction during

12558-433: The field of dinosaur research experienced a surge in activity that remains ongoing. Several seminal studies led to this activity. First, John Ostrom discovered the bird-like dromaeosaurid theropod Deinonychus and described it in 1969. Its anatomy indicated that it was an active predator that was likely warm-blooded, in marked contrast to the then-prevailing image of dinosaurs. Concurrently, Robert T. Bakker published

12696-543: The form of a solid rock resource called oil shale . There is estimated to be between 500 billion and 1.1 trillion barrels (80 and 175 km ) of potentially recoverable oil in the basin, however; this estimated amount of recoverable oil in the form of kerogen is challenged, and in doubt, as currently there is no economically feasible technology to convert rock into a permeable oil. Kerogen is an uncooked form of hydrocarbon that nature did not convert into actual oil. The cost of converting Green River oil shale into actual oil at

12834-486: The hip structure of their ancestors, with a pubis bone directed cranially , or forward. This basic form was modified by rotating the pubis backward to varying degrees in several groups ( Herrerasaurus , therizinosauroids, dromaeosaurids, and birds ). Saurischia includes the theropods (exclusively bipedal and with a wide variety of diets) and sauropodomorphs (long-necked herbivores which include advanced, quadrupedal groups). By contrast, ornithischians—"bird-hipped", from

12972-432: The last common ancestor of Triceratops horridus , Passer domesticus and Diplodocus carnegii , and all of its descendants, to ensure that sauropods and kin remain included as dinosaurs. They also resurrected the clade Ornithoscelida to refer to the group containing Ornithischia and Theropoda. Using one of the above definitions, dinosaurs can be generally described as archosaurs with hind limbs held erect beneath

13110-627: The late 17th century in England. Part of a bone, now known to have been the femur of a Megalosaurus , was recovered from a limestone quarry at Cornwell near Chipping Norton , Oxfordshire, in 1676. The fragment was sent to Robert Plot , Professor of Chemistry at the University of Oxford and first curator of the Ashmolean Museum , who published a description in his The Natural History of Oxford-shire (1677). He correctly identified

13248-478: The longest were the 33.5-meter (110 ft) long Diplodocus hallorum (formerly Seismosaurus ), the 33-to-34-meter (108 to 112 ft) long Supersaurus , and 37-meter (121 ft) long Patagotitan ; and the tallest, the 18-meter (59 ft) tall Sauroposeidon , which could have reached a sixth-floor window. There were a few dinosaurs that was considered either the heaviest and longest. The most famous one include Amphicoelias fragillimus , known only from

13386-446: The moment would be higher than what it could be sold for. The EROI for oil shale is very low while having a very high destructive environmental impact. The Green River Basin contains the world's largest known deposit of trona ore near Green River, Wyoming. Soda ash mining from trona veins 900 and 1600 feet (300 and 500 m) deep is a major industrial activity in the area, employing over 2000 persons at four mines. The mining operation

13524-561: The monument are accessible for close viewing, along four trails in Utah, one of which is near the visitor center, and a fifth trail in Colorado. The dinosaur fossil beds ( bone beds ) were discovered in 1909 by Earl Douglass , a paleontologist working and collecting for the Carnegie Museum of Natural History . He and his crews excavated thousands of fossils and shipped them back to the museum in Pittsburgh, Pennsylvania for study and display. President Woodrow Wilson proclaimed

13662-479: The most complete theropod specimens, while North American localities have produced the most complete sauropodomorph specimens. Prior to the dinosaur renaissance, dinosaurs were mostly classified using the traditional rank-based system of Linnaean taxonomy . The renaissance was also accompanied by the increasingly widespread application of cladistics , a more objective method of classification based on ancestry and shared traits, which has proved tremendously useful in

13800-495: The most diverse groups of vertebrates. Using fossil evidence, paleontologists have identified over 900 distinct genera and more than 1,000 different species of non-avian dinosaurs. Dinosaurs are represented on every continent by both extant species (birds) and fossil remains. Through the first half of the 20th century, before birds were recognized as dinosaurs, most of the scientific community believed dinosaurs to have been sluggish and cold-blooded . Most research conducted since

13938-509: The most important advantage was dietary. 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

14076-478: 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 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

14214-466: The mouth, including potential cheek -like organs to keep food in the mouth, and jaw motions to grind food. Another notable evolutionary event of the Jurassic was the appearance of true birds, descended from maniraptoran coelurosaurians. By the Early Cretaceous and the ongoing breakup of Pangaea, dinosaurs were becoming strongly differentiated by landmass. The earliest part of this time saw

14352-482: The name "Green" include ideas about the color of the water (though it is usually just as red as that of the Colorado), the color of soapstone along its banks, the color of the vegetation, and the name of a trapper. No explanation can be verified. Wilson Hunt of John Jacob Astor 's Pacific Fur Company called it The Spanish River in 1811. By that time it was clear to the trappers that Miera's map (if they had seen it)

14490-768: The now-splitting supercontinent 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. Flowering plants were greatly radiating, with the first grasses appearing by the end of the Cretaceous. Grinding hadrosaurids and shearing ceratopsians became very diverse across North America and Asia. 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

14628-756: The number of named genera began to increase exponentially in the 1990s. As of 2008, over 30 new species of dinosaurs were named each year. At least sauropodomorphs experienced a further increase in the number of named species in the 2010s, with an average of 9.3 new species having been named each year between 2009 and 2020. As a consequence, more sauropodomorphs were named between 1990 and 2020 than in all previous years combined. These new localities also led to improvements in overall specimen quality, with new species being increasingly named not on scrappy fossils but on more complete skeletons, sometimes from multiple individuals. Better specimens also led to new species being invalidated less frequently. Asian localities have produced

14766-602: The objections of representatives from Wyoming and Utah and the United States Geological Survey , which noted that the drainage basin of the Green River was more extensive than that of the Grand River, although the Grand carried a higher volume of water at its confluence with the Green. The Green River is the subject of the song "Green River" by C.W. McCall . The headwaters of the Green River

14904-438: The pair's rough methods: for example, their diggers often used dynamite to unearth bones. Modern paleontologists would find such methods crude and unacceptable, since blasting easily destroys fossil and stratigraphic evidence. Despite their unrefined methods, the contributions of Cope and Marsh to paleontology were vast: Marsh unearthed 86 new species of dinosaur and Cope discovered 56, a total of 142 new species. Cope's collection

15042-408: The presence of proteins such as collagen, elastin , and laminin . Both specimens yielded collagen protein sequences that were viable for molecular phylogenetic analyses , which grouped them with birds as would be expected. The extraction of fragmentary DNA has also been reported for both of these fossils, along with a specimen of Hypacrosaurus . In 2015, Sergio Bertazzo and colleagues reported

15180-458: The preservation of collagen fibres and red blood cells in eight Cretaceous dinosaur specimens that did not show any signs of exceptional preservation, indicating that soft tissue may be preserved more commonly than previously thought. Suggestions that these structures represent bacterial biofilms have been rejected, but cross-contamination remains a possibility that is difficult to detect. Dinosaurs diverged from their archosaur ancestors during

15318-510: The quarry was declared a national monument on October 4, 1915. The International Dark-Sky Association designated Dinosaur National Monument an International Dark Sky Park in April 2019. The rock layer enclosing the fossils is a sandstone and conglomerate bed of alluvial or river bed origin known as the Morrison Formation from the Jurassic Period some 150 million years old. The dinosaurs and other ancient animals were carried by

15456-487: The rebbachisaurid Nigersaurus . 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

15594-511: The river has carved some of the most spectacular canyons in the United States. The Green is slightly smaller than Colorado when the two rivers merge but typically carries a larger load of silt . The average yearly mean flow of the river at Green River, Utah is 6,121 cubic feet (173.3 m ) per second. The status of the Green River as a tributary of the Colorado River came about mainly for political reasons. In earlier nomenclature,

15732-560: The river system which eventually entombed their remains in Utah. The pile of sediments were later buried and lithified into solid rock. The layers of rock were later uplifted and tilted to their present angle by the mountain building forces that formed the Uinta Mountains during the Laramide orogeny . The relentless forces of erosion exposed the layers at the surface to be found by paleontologists. The Fremont people lived in

15870-551: The river, known as the Green River Basin , covers parts of the U.S. states of Wyoming , Utah , and Colorado . The Green River is 730 miles (1,170 km) long, beginning in the Wind River Mountains of Wyoming and flowing through Wyoming and Utah for most of its course, except for a short segment of 40 miles (64 km) in western Colorado. Much of the route traverses the arid Colorado Plateau , where

16008-598: The river. Some popular ferries included the Lombard and Robinson ferries at the main crossing and the Mormon, Mountain Man, and Names Hill ferries where the popular Sublette-Greenwood cutoff crossed the river further upstream. In 1878 the first permanent settlement in the river valley was founded at Vernal by a party of Mormons led by Jeremiah Hatch . The settlement survived a diphtheria epidemic its first winter, as well as

16146-1413: The rocks that produced the Jehol (Early Cretaceous) and Yanliao (Mid-to-Late Jurassic) biotas of northeastern China, from which hundreds of dinosaur specimens bearing impressions of feather-like structures (both closely related to birds and otherwise, see § Origin of birds ) have been described by Xing Xu and colleagues. In living reptiles and mammals, pigment-storing cellular structures known as melanosomes are partially responsible for producing colouration. Both chemical traces of melanin and characteristically shaped melanosomes have been reported from feathers and scales of Jehol and Yanliao dinosaurs, including both theropods and ornithischians. This has enabled multiple full-body reconstructions of dinosaur colouration , such as for Sinosauropteryx and Psittacosaurus by Jakob Vinther and colleagues, and similar techniques have also been extended to dinosaur fossils from other localities. (However, some researchers have also suggested that fossilized melanosomes represent bacterial remains. ) Stomach contents in some Jehol and Yanliao dinosaurs closely related to birds have also provided indirect indications of diet and digestive system anatomy (e.g., crops ). More concrete evidence of internal anatomy has been reported in Scipionyx from

16284-450: The sauropodomorphs Bagualosaurus , Buriolestes , Guaibasaurus , Macrocollum , Nhandumirim , Pampadromaeus , Saturnalia , and Unaysaurus . The Pebbly Arkose Formation, which is of uncertain age but was likely comparable to the other two, has produced the sauropodomorph Mbiresaurus , along with an unnamed herrerasaurid. Less well-preserved remains of the sauropodomorphs Jaklapallisaurus and Nambalia , along with

16422-416: The sauropodomorphs Chromogisaurus , Eodromaeus , and Panphagia . Eoraptor 's likely resemblance to the common ancestor of all dinosaurs suggests that the first dinosaurs would have been small, bipedal predators . The Santa Maria Formation (radiometrically dated to be older, at 233.23 million years old ) has produced the herrerasaurids Gnathovorax and Staurikosaurus , along with

16560-584: The skeleton now mounted and on display at the Museum für Naturkunde in Berlin ; this mount is 12 meters (39 ft) tall and 21.8 to 22.5 meters (72 to 74 ft) long, and would have belonged to an animal that weighed between 30 000 and 60 000  kilograms ( 70 000 and 130 000  lb). The longest complete dinosaur is the 27 meters (89 ft) long Diplodocus , which was discovered in Wyoming in

16698-406: The skull behind the eyes), and as members of the diapsid group Archosauria, had additional openings in the snout and lower jaw. Additionally, several characteristics once thought to be synapomorphies are now known to have appeared before dinosaurs, or were absent in the earliest dinosaurs and independently evolved by different dinosaur groups. These include an elongated scapula , or shoulder blade;

16836-434: The sole surviving dinosaurs. In traditional taxonomy , birds were considered a separate class that had evolved from dinosaurs, a distinct superorder . However, most contemporary paleontologists reject the traditional style of classification based on anatomical similarity, in favor of phylogenetic taxonomy based on deduced ancestry, in which each group is defined as all descendants of a given founding genus. Birds belong to

16974-515: The specimen's excavation. Owen and Hooley subsequently described skin impressions of Hypsilophodon and Iguanodon in 1885 and 1917. Since then, scale impressions have been most frequently found among hadrosaurids, where the impressions are known from nearly the entire body across multiple specimens. Starting from the 1990s, major discoveries of exceptionally preserved fossils in deposits known as conservation Lagerstätten contributed to research on dinosaur soft tissues. Chiefly among these were

17112-538: 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

17250-468: The study of dinosaur systematics and evolution. Cladistic analysis, among other techniques, helps to compensate for an often incomplete and fragmentary fossil record. Reference books summarizing the state of dinosaur research, such as David B. Weishampel and colleagues' The Dinosauria , made knowledge more accessible and spurred further interest in dinosaur research. The release of the first and second editions of The Dinosauria in 1990 and 2004, and of

17388-482: The tallest of the theropods. The largest ornithischian dinosaur was probably the hadrosaurid Shantungosaurus giganteus which measured 16.6 meters (54 ft). The largest individuals may have weighed as much as 16 metric tons (18 short tons). Green River (Colorado River) The Green River , located in the western United States, is the chief tributary of the Colorado River . The watershed of

17526-459: The taxonomic name has often been interpreted as a reference to dinosaurs' teeth, claws, and other fearsome characteristics, Owen intended it also to evoke their size and majesty. Owen recognized that the remains that had been found so far, Iguanodon , Megalosaurus and Hylaeosaurus , shared distinctive features, and so decided to present them as a distinct taxonomic group. As clarified by British geologist and historian Hugh Torrens, Owen had given

17664-849: The total number of dinosaur genera preserved in the fossil record at 1850, nearly 75% still undiscovered, and the number that ever existed (in or out of the fossil record) at 3,400. A 2016 estimate put the number of dinosaur species living in the Mesozoic at 1,543–2,468, compared to the number of modern-day birds (avian dinosaurs) at 10,806 species. Extinct dinosaurs, as well as modern birds, include genera that are herbivorous and others carnivorous, including seed-eaters, fish-eaters, insectivores, and omnivores. While dinosaurs were ancestrally bipedal (as are all modern birds), some evolved into quadrupeds, and others, such as Anchisaurus and Iguanodon , could walk 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

17802-403: The town of Green River, but today the mouth of Blacks Fork is submerged by the reservoir. South of the dam, it is forced to turn sharply eastward by the uplift of the Uinta Mountains , looping around the eastern tip of the range as it travels from Utah into northwestern Colorado and through Browns Park before turning west and then south into Dinosaur National Monument , where it passes through

17940-595: The trappers and American explorers. While it was known that the Green River drained to Colorado, the exact course was not known. Miera's map showed the Colorado River branching into two major streams – the Nabajoo (San Juan) and the Zaguananas. It also showed the Zaguananas branching into four heads, including the Dolores and the Rafael (the latter of which Escalante's journal equates with Colorado per information from

18078-598: Was 65 million bbl of oil and over 1.2 Tcf (trillion cubic feet ) of gas. Production includes the Cretaceous Mesaverde Formation and Frontier Formation . The discovery of petroleum at the Ashley Field after World War II has led to the exploitation of oil and natural gas in the region. The oil at Ashley Field is trapped in Aeolin deposits of "coversands and loess," while there is

18216-457: Was an extremely important find: Hadrosaurus was one of the first nearly complete dinosaur skeletons found ( the first was in 1834, in Maidstone, England ), and it was clearly a bipedal creature. This was a revolutionary discovery as, until that point, most scientists had believed dinosaurs walked on four feet, like other lizards. Foulke's discoveries sparked a wave of interests in dinosaurs in

18354-489: Was 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. There are several proposed advantages for the large size of sauropods, including protection from predation, reduction of energy use, and longevity, but it may be that

18492-622: Was announced in April 2009 that Dinosaur National Monument would receive $ 13.1 million to refurbish and reopen the gallery as part of the Obama administration's $ 750 billion stimulus plan. The Park Service successfully rebuilt the Quarry Exhibit Hall, supporting its weight on 70-foot steel micropile columns that extend to the bedrock below the unstable clay. The Dinosaur Quarry was reopened in Fall 2011. Dinosaur Dinosaurs are

18630-480: Was explored by John C. Fremont on several of his expeditions in the 1840s. Fremont corrected the cartographic error of Miera, establishing firmly that the river did not drain the Great Salt Lake. In 1869, the river was surveyed and mapped by John Wesley Powell as part of the first of his two expeditions to the region. During his two voyages in 1869 and 1871, he and his men gave most of the current names of

18768-616: Was part of the disputed Oregon Country . It was explored by trappers from the North West Company and Hudson's Bay Company , such as Donald Mackenzie who pioneered the area from 1819. In 1825, the American William Ashley and a party of American explorers floated down the river from north of the Uintah Mountains to the mouth of the White River . The valley of the river became increasingly used as

18906-450: Was purportedly discovered in 1822 by Mary Ann Mantell , the wife of English geologist Gideon Mantell , though this is disputed and some historians say Gideon had acquired remains years earlier. Gideon Mantell recognized similarities between his fossils and the bones of modern iguanas and published his findings in 1825. The study of these "great fossil lizards" soon became of great interest to European and American scientists, and in 1842

19044-710: Was wrong, for they had learned from the Native Americans that the Green River drained to the Colorado River and the Gulf of California . When Jedediah Smith reached the lower Colorado in 1826, he first called it the Seedskeedee, as the Green/Colorado River was commonly known among the trappers. By the time of Bonneville's expedition in 1832, the names "Seeds-kee-dee", "Spanish River", "Green River", and even "Colorado River" were used interchangeably by

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