The Cedar Mountain Formation is the name given to a distinctive sedimentary geologic formation in eastern Utah , spanning most of the early and mid- Cretaceous . The formation was named for Cedar Mountain in northern Emery County, Utah , where William Lee Stokes first studied the exposures in 1944.
41-663: Cedarosaurus (meaning "Cedar lizard" - named after the Cedar Mountain Formation , in which it was discovered) was a nasal-crested macronarian dinosaur genus from the Early Cretaceous Period ( Valanginian ). It was a sauropod which lived in what is now Utah . The fossils were discovered in 1996 in eastern Utah within the rocks of the Yellow Cat Member of the Cedar Mountain Formation. It
82-517: A middle dinosaur assemblage between the older and younger ones is controversial because the evidence mostly depends on a single specimen of the ornithopod Tenontosaurus from high in the Ruby Ranch Member and the sauropod Astrodon from low in the Ruby Ranch. Regardless, the upper and lower dinosaur assemblages in the Cedar Mountain Formation document the separation of North America and Europe,
123-451: A ridge inside the depression. In most sauropods the fossae would form pneumatic openings leading to the interior of the centrum, rather than just being a depression. Less well-developed, but similar fossae are known from Cedarosaurus itself. In 2010, Gregory S. Paul estimated the maximum length up to 15 meters (49 ft) and mass up to 10 metric tons (11 short tons). In 2001 Frank Sanders , Kim Manley , and Kenneth Carpenter published
164-415: A study on 115 gastroliths discovered in association with a Cedarosaurus specimen. The stones were identified as gastroliths on the basis of their tight spatial distribution, partial matrix support, and an edge-on orientation indicative of their being deposited while the carcass still had soft tissue. Their high surface reflectance values are consistent with other known dinosaur gastroliths. Nearly all of
205-458: A tiny fraction is exposed and accessible to geologists and paleontologists . Over 75% is still buried under the prairie to the east, and much of its western paleogeographic extent was eroded during exhumation of the Rocky Mountains . It was named after Morrison, Colorado , where some of the first fossils in the formation were discovered by Arthur Lakes in 1877. That same year, it became
246-532: Is composed of non-marine sediments, that is, sediments deposited in rivers, lakes and on flood plains. Based on various fossils and radiometric dates , the Cedar Mountain Formation was deposited during the last half of the Early Cretaceous Epoch, about 127 - 98 million years ago (mya). It has lithography similar to the Burro Canyon Formation in the region. Dinosaur fossils occur throughout
287-628: Is considered to be at the top of the Morrison Formation or at the base of the Cedar Mountain Formation; most geologists and paleontologists consider it part of the Cedar Mountain Formation. In ascending order the remaining members are the Yellow Cat Member, Poison Strip Sandstone, Ruby Ranch Member, and the Mussentuchit Member. Each of these members are named after a geographic area where they were first studied. The Cedar Mountain Formation
328-749: Is light gray, greenish gray, or red. Most of the fossils occur in the green siltstone beds and lower sandstones, relics of the rivers and floodplains of the Jurassic period. It is centered in Wyoming and Colorado , with outcrops in Montana , North Dakota , South Dakota , Nebraska , Kansas , the panhandles of Oklahoma and Texas , New Mexico , Arizona , Utah , and Idaho . Equivalent rocks under different names are found in Canada. It covers an area of 1.5 million square kilometers (600,000 square miles), although only
369-463: Is more gracile in Cedarosaurus . Its middle tail vertebrae's neural spines are angled anteriorly when the vertebrae are aligned. These vertebrae resemble those of Gondwanatitan , Venenosaurus , and Aeolosaurus . The related Venenosaurus had unusual lateral fossae, which looked like deep depressions in the outside walls of the vertebral centra. Some fossae are divided into two chambers by
410-527: Is proving to contain one of the world's richest and most diverse Early Cretaceous dinosaur faunas. The discoveries to date have revealed that the origin of some of the later Cretaceous dinosaurs may lie in Cedar Mountain, but further work is needed to understand the timing and effects the changing position of the North American Plate had on dinosaurian evolution. Also needed is a better understanding of
451-421: The Cedarosaurus gastroliths were found within a .06 m volume of space in the gut region of the skeleton. The total mass of the gastroliths themselves was 7 kilograms (15 lb). Most were less than 10 millilitres (0.35 imp fl oz; 0.34 US fl oz) in volume. The least massive clast was 0.1 grams (0.0035 oz) and the most was 715 grams (25.2 oz), with most of them being toward
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#1732899126317492-589: The Bullington Member, which has been discarded entirely. Though many of the Morrison Formation fossils are fragmentary, they are sufficient to provide a good picture of the flora and fauna in the Morrison Basin during the Kimmeridgian. Overall, the climate was dry, similar to a savanna but, since there were no angiosperms ( grasses , flowers , and some trees ), the flora was quite different. Conifers ,
533-565: The Lower Yellow Cat and Ruby Ranch Members. Indeterminate dromaeosaurine present in the Mussentuchit Member. Indeterminate deinonychosaurian remains present in the Mussentuchit member. Indeterminate velociraptorine remains present in the Mussentuchit Member. Indeterminate troodontid remains present in the Mussentuchit Member. Indeterminate therizinosaurid remains present in the Mussentuchit Member. Indeterminate dromaeosaurine remains present in
574-535: The Morrison and Cedar Mountain is commonly marked by a horizon of carbonate nodules or by highly polished pebbles that are allegedly gastroliths. Although not part of the Cedar Mountain Formation, the Naturita Formation immediately overlies the Cedar Mountain and marks the encroaching Western Interior Seaway . The Naturita is not uniformly distributed and was eroded away in places by the advancing Seaway so that
615-498: The Mussentuchit Member. Possible indeterminate hesperornithiformes present in the Mussentuchit Member. cf. Acrocanthosaurus Morrison Formation The Morrison Formation is a distinctive sequence of Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone , sandstone , siltstone , and limestone and
656-750: The Oklahoma Museum of Natural History, the Denver Museum of Nature & Science, Utah State University-Eastern (formerly College of Eastern Utah), the Utah Geological Survey, Brigham Young University, and Dinosaur National Monument staff. This research indicates that at least two, possibly three dinosaur assemblages are contained within the formation. The oldest of these assemblages is from the Yellow Cat, Poison Strip and basal Ruby Ranch members. The small, Ornitholestes -like theropod Nedcolbertia and
697-650: The Rocky Mountains started pushing up to the west. The deposits from their east-facing drainage basins , carried by streams and rivers from the Elko Highlands (along the borders of present-day Nevada and Utah) and deposited in swampy lowlands, lakes, river channels and floodplains , became the Morrison Formation. In the north, the Sundance Sea , an extension of the Arctic Ocean , stretched through Canada down to
738-459: The United States. Coal is found in the Morrison Formation of Montana, which means that the northern part of the formation, along the shores of the sea, was wet and swampy, with more vegetation. Aeolian , or wind-deposited sandstones, are found in the southwestern part, which indicates it was much more arid—a desert , with sand dunes . The Morrison Formation is subdivided into several members,
779-548: The brachiosaurid sauropod Cedarosaurus may be considered as relics, with their closest relatives in the Morrison Formation. In contrast, the polacanthid ankylosaur Gastonia and a yet unnamed iguanodontid are similar to related forms from the Lower Cretaceous of southern England. These dinosaurs show that the connection between North America and Europe still existed during the Barremian. All of this changes, however, with
820-471: The center of the Bone Wars , a fossil-collecting rivalry between early paleontologists Othniel Charles Marsh and Edward Drinker Cope . In Colorado, New Mexico, and Utah, the Morrison Formation was a major source of uranium ore. According to radiometric dating , the Morrison Formation dates from 156.3 ± 2 million years old ( Ma ) at its base, to 146.8 ± 1 million years old at
861-453: The chert clasts actually contained fossils. Since some of the most irregular gastroliths are also the largest, it is unlikely that they were ingested by accident. Cedarosaurus may have found irregular clasts to be attractive potential gastroliths or was not selective about shape. The clasts were generally of dull coloration, suggesting that color was not a major factor for the sauropod's decision making. The high surface area to volume ratio of
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#1732899126317902-534: The digestive tract. If they were more robust, they could have served as part of a ball-mill system. [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] Cedar Mountain Formation The formation occurs between the underlying Morrison Formation and overlying Naturita Formation (sometimes formerly called the Dakota Formation ). It
943-649: The dominant plants of the time, were to be found with ginkgos , cycads , tree ferns , and horsetail rushes . Much of the fossilized vegetation was riparian , living along the river flood plains. Along the rivers, there were fish , frogs , salamanders , lizards , crocodiles , turtles , pterosaurs , crayfish , clams , and mammaliforms . The dinosaurs were most likely riparian, as well. Hundreds of dinosaur fossils have been discovered, such as Allosaurus , Ceratosaurus , Torvosaurus , Saurophaganax , Camptosaurus , Ornitholestes , several stegosaurs comprising at least two species of Stegosaurus and
984-401: The effects that the changing North American Plate had on the non-dinosaur vertebrates. The Cedar Mountain Formation is one of the last major dinosaur-bearing formations to be studied in the United States. Although sporadic bone fragments were known before 1990, serious research did not begin until that year. Since then, several organizations have conducted fieldwork collecting dinosaurs, chiefly
1025-500: The formation, but their study has only occurred since the early 1990s. The dinosaurs in the lower part of the formation differ from those in the upper part. These two dinosaur assemblages, characterized by distinct dinosaurs, show the replacement of older, European-like dinosaurs with younger, Asian-like dinosaurs as the North American Continental Plate drifted westward. A middle dinosaur assemblage may be present, but
1066-550: The fossil record is not clear. The Cedar Mountain Formation is sandwiched between the Morrison Formation below and the Naturita Formation and Mancos Shale above. The youngest date for Morrison just below the Cedar Mountain Formation is 135.10 ± 0.30 Ma or Berriasian–Valanginian. The Jurassic-Cretaceous boundary in western North America is marked by an unconformity of variable length, and typically signifies 10-49 million years of missing geologic time. This boundary between
1107-570: The large body mass of the sauropods has been interpreted as an adaptation to migration in times of drought. Sauropods that have been discovered include Diplodocus (most famously, the first nearly complete specimen of D. carnegii , which is now exhibited at the Carnegie Museum of Natural History , in Pittsburgh, Pennsylvania), Camarasaurus (the most commonly found sauropod), Brachiosaurus , Apatosaurus , Brontosaurus , Barosaurus ,
1148-445: The largest clasts suggests that the gastroliths may have broken down ingested plant material by grinding or crushing it. The sandstone clasts tended to be fragile and some broke in the process of collection. The sandstone gastroliths may have been rendered fragile after deposition by loss of cement caused by the external chemical environment. If the clasts had been that fragile while the animal was alive, they probably rolled and tumbled in
1189-531: The marine shales of the Mancos Formation lay directly on the Mussentuchit Member or its equivalent. The name Dakota Formation has been improperly used for these strata. Only recently did the 125 m (410 ft) thick formation get subdivided into smaller, distinctive beds called members. There is a debate as to whether there are five members or four depending whether the Buckhorn Conglomerate
1230-563: The occurrence of which are varied across the geographic extent of the Morrison. Members are (in alphabetical order): Other informal or disused designations of the Morrison include the Stockett Bed in Montana, an unofficial sub-unit which contains bituminous coal; the outdated terms Casamero, Chavez, and Prewitt Sandstone for the Brushy Basin, Recapture, and Westwater Canyon, respectively; and
1271-604: The right arm and leg. Iguanacolossus I. fortis Iguanodon I. ottingeri A dubious taxon. Planicoxa P. venenica An ilium, cervical neural arch, dorsal vertebral arches, dorsal centra, dorsal rib fragments, sacral vertebra, caudal centra, humerus, ulna, femora, tibiae, metatarsal, and pedal phalanx Tenontosaurus Various partial specimens. Abydosaurus A. mcintoshi cf. Astrodon Indeterminate Brontomerus B. mcintoshi Cedarosaurus C. weiskopfae Articulated dorsal vertebrae, caudal vertebrae, chevrons, proximal portions of
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1312-744: The scapulae, coracoids, sternal plates, right humerus, radius and ulna, metacarpal IV, right pubis, partial pubis, proximal portions of ischia, partial femurs, tibia, metatarsals, phalanx, unguals, ribs, and numerous gastroliths. Mierasaurus M. bobyoungi Moabosaurus M. utahensis [Eighteen] braincases, premaxillas, maxillas, dentaries, postorbital, quadrate, cervical vertebrae, dorsal vertebrae, caudal vertebrae, cervical ribs, ribs, sacrum, sternal plate, humerus, ulna and femur. Venenosaurus V. dicrocei Disarticulated caudal vertebrae, scapula, radius, ulna, metacarpals, manus phalanges, pubis, ischium, metatarsals, astragalus, chevrons, and ribs. Indeterminate allosauroid material present in
1353-498: The slightly older Hesperosaurus , and the early ankylosaurs , Mymoorapelta and Gargoyleosaurus , most notably a very broad range of sauropods (the giants of the Mesozoic era). Since at least some of these species are known to have nested in the area ( Camptosaurus embryoes have been discovered), there are indications that it was a good environment for dinosaurs and not just home to migratory, seasonal populations. However,
1394-458: The smaller end of that range. The clasts tended to be close to spherical in shape, although the largest specimens were also the most irregular. The largest gastroliths contributed the most to the total surface area of the set. Some gastroliths were so large and irregularly shaped that they may have been difficult to swallow. The gastroliths were mostly composed of chert , with some sandstone , siltstone , and quartzite clasts also included. Some of
1435-497: The time, the supercontinent of Laurasia had recently split into the continents of North America and Eurasia, although they were still connected by land bridges. North America moved north and was passing through the subtropical regions . The Morrison Basin, which stretched from New Mexico in the south to Alberta and Saskatchewan in the north, was formed during the Nevadan orogeny , a precursor event to later orogenic episodes that created
1476-877: The top, which places it in the earliest Kimmeridgian , and early Tithonian stages of the late Jurassic. This is similar in age to the Solnhofen Limestone Formation in Germany and the Tendaguru Formation in Tanzania . The age and much of the fauna is similar to the Lourinhã Formation in Portugal. Throughout the western United States, it variously overlies the Middle Jurassic Summerville, Sundance , Bell Ranch, Wanakah, and Stump Formations. At
1517-543: The uncommon Haplocanthosaurus and Supersaurus . The very diversity of the sauropods has raised some questions about how they could all co-exist. While their body shapes are very similar (long neck, long tail, huge elephant-like body), they are assumed to have had very different feeding strategies, in order for all to have existed in the same time frame and similar environment. Locations where significant Morrison Formation fossil discoveries have been made include: The Morrison Formation contains uranium deposits, including
1558-410: The upper dinosaur assemblage from the top of the Ruby Ranch and Mussentuchit members. This upper assemblage shows greater similarities with Asian dinosaur assemblages from the same time. The upper assemblage also has a tyrannosauroid , a ceratopsian , and a pachycephalosaur . Although not a dinosaur, the primitive mammal Gobiconodon is known from both Mongolia and the Mussentuchit Member. Evidence for
1599-664: The westward drift of North America, and its connection with Asia 10 to 15 million years later. Data from Carpenter (2006), Cifelli et al. (1999), Kirkland and Madsen (2007), and The Paleobiology Database . A large sail-backed iguanodont represented by large vertebrae and fragmentary remains from the Upper Yellow Cat Member. Cedrorestes C. crichtoni Eolambia E. caroljonesa Hippodraco H. scutodens A nearly complete, disarticulated skull, cervical, dorsal, sacral, and caudal vertebrae, ribs and haemal arches, partial pectoral and pelvic girdles, and
1640-420: Was ascribed to the genus Pleurocoelus , which is now regarded as a junior synonym of Astrodon . However, the shape of the animal's vertebrae and forelimb bones were distinct enough to warrant its classification as a new genus. Cedarosaurus had a more gracile ulna and radius than its relative Venenosaurus . The ratio of the radius' least circumference to its length is .31 in Cedarosaurus . Metatarsal II
1681-584: Was officially named and described by Tidwell, Carpenter and Brooks in 1999. It shows similarities to the brachiosaurid Eucamerotus from the Wessex Formation of southern England, as well as to Brachiosaurus from the Morrison Formation . Cedarosaurus was identified as a brachiosaurid sauropod. Prior to its classification as a new genus, brachiosaurid fossil material from the early and middle Cretaceous Period which had been found in North America