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52-628: The formation in Utah and western Colorado overlies the Cedar Mountain and Burro Canyon Formations, and underlies the Mancos Shale formation, thus occupying a similar position of sedimentary strata that have widely been called Dakota Formation in Iowa, Kansas and Nebraska. The use of the name "Dakota" in western states was the result of early geological mapping by F.V. Hayden beginning in

104-544: 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 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

156-501: A brachiosaurid sauropod , the bothremyid turtle Paiutemys . and fossil mammals Cedar Mountain Formation 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

208-528: A classification, though sources have differed on what its rank should be. Most who still employ the use of ranks have retained its traditional ranking of suborder, though some have reduced to the level of infraorder. In clade -based phylogenetic taxonomy , Ceratopsia is officially defined in the PhyloCode as "the largest clade containing Ceratops montanus and Triceratops horridus , but not Pachycephalosaurus wyomingensis . Under this definition,

260-750: A detailed review of the history of the problem, Carpenter argued 1) that during their deposition, the Dakota Formation and the Naturita Formation were separated by the Western Interior Cretaceous Seaway, 2) stream depositing the Dakota and Naturita Formations were flowing towards each other on opposite sides of the Seaway, but the formations did not connect one side of the seaway to the other, and 3) sediments of

312-429: A dinosaur, but noted that even though the fossil lacked a skull, it was different from any type of dinosaur then known. He named the new species Agathaumas sylvestris , meaning "marvellous forest-dweller". Soon after, Cope named two more dinosaurs that would eventually come to be recognized as ceratopsids: Polyonax and Monoclonius . Monoclonius was notable for the number of disassociated remains found, including

364-589: A forward-oriented pubis . Marsh considered the group distinct enough to warrant its own suborder within Ornithischia. The name is derived from the Greek κέρας / kéras meaning 'horn' and ὄψῐς / ópsis meaning 'appearance, view' and by extension 'face'. As early as the 1960s, it was noted that the name Ceratopsia is actually incorrect linguistically and that it should be Ceratopia . However, this spelling, while technically correct, has been used only rarely in

416-433: A fossil horn. The frill bone was interpreted as a part of the breastbone. In 1888 and 1889, Othniel Charles Marsh described the first well preserved horned dinosaurs, Ceratops and Triceratops . In 1890 Marsh classified them together in the family Ceratopsidae and the order Ceratopsia. This prompted Cope to reexamine his own specimens and to realize that Triceratops , Monoclonius , and Agathaumas all represented

468-610: A middle section of mostly thin, but locally thick coal beds; and an upper section that is gray-orange to light brown, moderately erosion resistant, locally fossiliferous sandstone that is interbedded with light-olive-gray shale. Locally, a channel conglomerate is present at the base. Where missing, a lag of conglomerate may be present indicating winnowing of sediments, which occurred by advancing Cretaceous seas. In other places, deposition of Naturita sediments did not occur, and these areas may have been quiet lagoons because oyster shells are often present in great abundance. The lower portion of

520-666: A mostly North American group of mostly small bodied and quadrupedal ceratopsians. Another subset of neoceratopsians is called Coronosauria , which is "the smallest clade containing Protoceratops andrewsi and Triceratops horridus ". Coronosaurs show the first development of the neck frill and the fusion of the first several neck vertebrae to support the increasingly heavy head. Within Coronosauria, two groups are generally recognized. One group can be called Protoceratopsidae and includes Protoceratops and its closest relatives, all Asian. The other group, Ceratopsoidea , includes

572-421: A single group of similar dinosaurs, which he named Agathaumidae in 1891. Cope redescribed Monoclonius as a horned dinosaur, with a large nasal horn and two smaller horns over the eyes, and a large frill . Ceratopsia was coined by Othniel Charles Marsh in 1890 to include dinosaurs possessing certain characteristic features, including horns, a rostral bone , teeth with two roots , fused neck vertebrae , and

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624-635: Is traditional for ceratopsian genus names to end in " -ceratops ", although this is not always the case. One of the first named genera was Ceratops itself, which lent its name to the group, although it is considered a nomen dubium today as its fossil remains have no distinguishing characteristics that are not also found in other ceratopsians. Early members of the ceratopsian group, such as Psittacosaurus , were small bipedal animals. Later members, including ceratopsids like Centrosaurus and Triceratops , became very large quadrupeds and developed elaborate facial horns and frills extending over

676-599: The Cretaceous Period , although ancestral forms lived earlier, in the Jurassic . The earliest known ceratopsian, Yinlong downsi , lived between 161.2 and 155.7 million years ago. The last ceratopsian species, Triceratops prorsus , became extinct during the Cretaceous–Paleogene extinction event , 66 million years ago . Triceratops is by far the best-known ceratopsian to the general public. It

728-563: 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 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

780-608: The epoccipital bones . The name is a misnomer, as they are not associated with the occipital bone . Epoccipitals begin as separate bones that fuse during the animal's growth to either the squamosal or parietal bones that make up the base of the frill. These bones were ornamental instead of functional, and may have helped differentiate species . Epoccipitals probably were present in all known ceratopsids. They appear to have been broadly different between short-frilled ceratopsids ( centrosaurines ) and long-frilled ceratopsids ( chasmosaurines ), being elliptical with constricted bases in

832-399: The skull . On the tip of a ceratopsian upper jaw is the rostral bone, an edentulous (toothless) ossification, unique to ceratopsians. Othniel Charles Marsh recognized and named this bone, which acts as a mirror image of the predentary bone on the lower jaw. This ossification evolved to morphologically aid the chewing of plant matter. Along with the predentary bone, which forms the tip of

884-644: 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 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

936-527: The 1850. For convenience, he maintained the same terminology developed during the early mapping along the Missouri River as he began mapping farther west in the 1860s even while acknowledging "There are very few points of resemblance between these beds and those which form the Dakota group, as seen in Kansas and Nebraska. All the evidence therefore that I have had to guide me in regard to these beds along

988-508: 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 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

1040-644: 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 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

1092-678: The Dakota Formation on the east side of the Seaway were derived from the North American Craton, whereas sediments of the Naturita Formation were derived from the Sevier uplift along the Nevada-Utah border. Thus, the two formations were derived independent of each other. The formation is described as having a lower section that is dark-brown to black, carbonaceous claystone, gray shale, and siltstone, and some beds of gray-orange to white coarse-grained sandstone which may form ledges;

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1144-683: The Dakota/Naturita Formation sequence and fossil pollen species in Utah were correlated with the Ludvigson and Witzke report on the Dakota at the Nebraska type location. Radiometric dates and fossil invertebrates show that the Naturita Formation becomes progressively younger southwards and westwards across Utah, thus recording the advancing Western Interior Seaway. A low diversity flora assemblage has been described from Utah consisting of horsetails, ferns and angiosperms. Many of

1196-587: 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 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

1248-579: 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

1300-421: The Mussentuchit Member. Possible indeterminate hesperornithiformes present in the Mussentuchit Member. cf. Acrocanthosaurus Ceratopsian Ceratopsia or Ceratopia ( / ˌ s ɛr ə ˈ t ɒ p s i ə / or / ˌ s ɛr ə ˈ t oʊ p i ə / ; Greek : "horned faces") is a group of herbivorous , beaked dinosaurs that thrived in what are now North America , Europe , and Asia , during

1352-559: The Naturita Formation represents river channel and floodplain deposits, whereas the upper part represent a complex of estuarine, lagoonal, and swamp environments of a coastal plain. Ludvigson and Witzke, correlated the Dakota Formation in Iowa with the "Dakota" along the Colorado Front Range based on palynostratigraphy and recognized those palynostratigraphic sequences throughout the Western Interior. In 2012,

1404-819: 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 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

1456-969: 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 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

1508-413: The analysis of Eric M. Morschhauser and colleagues in 2019 , along with all previously published diagnostic species excluding the incomplete juvenile Archaeoceratops yujingziensis and the problematic genera Bainoceratops , Lamaceratops , Platyceratops and Gobiceratops that are very closely related to and potentially synonymous with Bagaceratops . While there were many unresolved areas of

1560-469: The exposures in 1944. The formation occurs between the underlying Morrison Formation and overlying Naturita Formation (sometimes formerly called the Dakota Formation ). It 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

1612-481: The family Ceratopsidae and closely related animals like Zuniceratops . This clade is defined as "the largest clade containing Ceratops montanus and Triceratops horridus , but not Protoceratops andrewsi ". Ceratopsidae itself includes Triceratops and all the large North American ceratopsians and is further divided into the subfamilies Centrosaurinae and Chasmosaurinae . All previously published neoceratopsian phylogenetic analyses were incorporated into

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1664-533: The first evidence of ceratopsid horns and frills. Several Monoclonius fossils were found by Cope, assisted by Charles Hazelius Sternberg , in summer 1876 near the Judith River in Chouteau County , Montana. Since the ceratopsians had not been recognised yet as a distinctive group, Cope was uncertain about much of the fossil material, not recognizing the nasal horn core, nor the brow horns, as part of

1716-487: 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 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

1768-404: The former group, and triangular with wide bases in the latter group. Within these broad definitions, different species would have somewhat different shapes and numbers. In centrosaurines especially, like Centrosaurus , Pachyrhinosaurus , and Styracosaurus , these bones become long and spike- or hook-like. A well-known example is the coarse sawtooth fringe of broad triangular epoccipitals on

1820-615: The frill of Triceratops . When regarding the ossification's morphogenetic traits, it can be described as dermal. The term epoccipital was coined by paleontologist Othniel Charles Marsh in 1889. The first ceratopsian remains known to science were discovered during the U.S. Geological and Geographical Survey of the Territories led by the American geologist F.V. Hayden . Teeth discovered during an 1855 expedition to Montana were first assigned to hadrosaurids and included within

1872-404: The genus Trachodon . It was not until the early 20th century that some of these were recognized as ceratopsian teeth. During another of Hayden's expeditions in 1872, Fielding Bradford Meek found several giant bones protruding from a hillside in southwestern Wyoming . He alerted paleontologist Edward Drinker Cope , who led a dig to recover the partial skeleton. Cope recognized the remains as

1924-402: The identifications are dated and a new study may increase the diversity. Equisetum Asplenium Coniopteris Hausmannia Gleichenia Matonidium Astralopteris Cladophlebis Ilex Magnolia Ficus Eucalyptus Platanus Salix Fossi vertebrates include dinosaur bone fragments of ceratopsians , a possible primitive tyrannosaurid , nodosaurid ankylosaurs ,

1976-560: 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 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

2028-462: The lower jaw in all ornithischians , the rostral forms a superficially parrot -like beak. Also, the jugal bones below the eye are prominent, flaring out sideways to make the skull appear somewhat triangular when viewed from above. This triangular appearance is accentuated in later ceratopsians by the rearwards extension of the parietal and squamosal bones of the skull roof, to form the neck frill. The neck frills of ceratopsids are surrounded by

2080-799: The margin of the mountain ranges has been their position." (p. 114). Despite this doubt by Hayden, the name Dakota Formation became entrenched in many western states, but has been renamed as the Lakota Formation in South Dakota, the Cloverly Formation in Wyoming and Montana (in part), and the South Platte Formation in eastern Colorado, but not on the northern half of the Colorado Plateau where

2132-484: The members of Chaoyangosauridae and Psittacosaurus are excluded from Neoceratopsia, while all more derived ceratopsians are part of this clade. A slightly less inclusive group is Euceratopsia , named and defined by Daniel Madzia and colleagues in 2021 as "the smallest clade containing Leptoceratops gracilis , Protoceratops andrewsi , and Triceratops horridus ". This clade includes the family Leptoceratopsidae and all more derived ceratopsians. Leptoceratopsids are

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2184-664: The most basal known ceratopsians are the family Chaoyangsauridae and the well known genus Psittacosaurus , from the Early Cretaceous Period, all of which were discovered in northern China or Mongolia . The rostral bone and flared jugals are already present in all of these forms, indicating that even earlier ceratopsians remain to be discovered. The clade Neoceratopsia is defined as "the largest clade containing "the largest clade containing Triceratops horridus , but not Chaoyangsaurus youngi and Psittacosaurus mongoliensis ". By this definition, only

2236-547: The most commonly preserved elements of ceratopsian skeletons and many species are known only from skulls. There is a great deal of variation between and even within ceratopsian species. Complete growth series from embryo to adult are known for Psittacosaurus and Protoceratops , allowing the study of ontogenetic variation in these species. Most restorations of ceratopsians show them with erect hindlimbs but semi-sprawling forelimbs, which suggest that they were not fast movers. But Paul and Christiansen (2000) argued that at least

2288-541: The name "Dakota Formation" continued to be used. In 1960, Young who was investigating uranium ore deposits on the Colorado Plateau for the U.S. Atomic Energy Commission, proposed the name Naturita Formation for the town of Naturita, Colorado . Although he described the general character of the formation, he did not designate a type section until five years later. The proposed name change was ignored by most geologists, probably because Young did not elaborate why he

2340-439: The neck. While these frills might have served to protect the vulnerable neck from predators , they may also have been used for display , thermoregulation , the attachment of large neck and chewing muscles or some combination of the above. Ceratopsians ranged in size from 1 meter (3.3 feet) and 23 kilograms (51 pounds) to over 9 meters (30 feet) and 9,100 kg (20,100 lb). Ceratopsians are easily recognized by features of

2392-476: 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 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

2444-490: 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 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

2496-501: 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, 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

2548-744: 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

2600-480: The scientific literature, and the vast majority of paleontologists continue to use Ceratopsia. As the ICZN does not govern taxa above the level of superfamily , this is unlikely to change. Following Marsh, Ceratopsia has usually been classified as a suborder within the order Ornithischia. While ranked taxonomy has largely fallen out of favor among dinosaur paleontologists, some researchers have continued to employ such

2652-1824: The strict consensus, including all of Leptoceratopsidae, a single most parsimonious tree was found that was most consistent with the relative ages of the taxa included, which is shown below. Psittacosaurus sinensis [REDACTED] Psittacosaurus mongoliensis [REDACTED] Yinlong downsi [REDACTED] Chaoyangsaurus youngi [REDACTED] Hualianceratops wucaiwanensis [REDACTED] Xuanhuaceratops niei Stenopelix valdensis [REDACTED] Liaoceratops yanzigouensis [REDACTED] Archaeoceratops oshimai [REDACTED] Aquilops americanus [REDACTED] Auroraceratops rugosus [REDACTED] Graciliceratops mongoliensis [REDACTED] Asiaceratops salsopaludalis Mosaiceratops azumai [REDACTED] Yamaceratops dorngobiensis [REDACTED] Helioceratops brachygnathus [REDACTED] Leptoceratops gracilis [REDACTED] Ischioceratops zhuchengensis [REDACTED] Prenoceratops pieganensis [REDACTED] Udanoceratops tchizhovi [REDACTED] Zhuchengceratops inexpectus [REDACTED] Koreaceratops hwaseongensis [REDACTED] Montanoceratops cerorhynchus [REDACTED] Cerasinops hodgskissi [REDACTED] Gryphoceratops morrisoni Unescoceratops kopelhusae Bagaceratops rozhdestvenskyi [REDACTED] Magnirostris dodsoni Protoceratops hellenikorhinus [REDACTED] Protoceratops andrewsi [REDACTED] Ajkaceratops kozmai [REDACTED] Zuniceratops christopheri [REDACTED] Turanoceratops tardabilis [REDACTED] Diabloceratops eatoni [REDACTED] Ceratopsidae [REDACTED] Unlike almost all other dinosaur groups, skulls are

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2704-475: Was proposing a name change. Years later, Witzke and Ludvigson independently noted a problem with the use of the name "Dakota Formation" in western states, writing "Usage of the term 'Dakota' for western-derived sedimentary sequences in the Rocky Mountain area is discouraged.". This, too was largely ignored until Carpenter made a detailed case for accepting "Naturita Formation" on the Colorado Plateau. After

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