Cedar Mountain Formation
Encyclopedia
The Cedar Mountain Formation is the name given to distinctive sedimentary rocks in eastern Utah that occur between the underlying Morrison Formation
and overlying Naturita Formation
(sometimes incorrectly 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 the Early Cretaceous
, about 127 - 98 million years ago (mya).
Dinosaur
s 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 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 formation was named for Cedar Mountain in northern Emery County, Utah, where William Lee Stokes first studied the exposures in 1944. 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 is considered to be at the top of the Morrison Formation or at the base of the Cedar Mountain Formation; most geologists and paleontologist 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.
. Typically, 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.
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 prior to 1990, serious research did not begin until that year. Since then, several organizations have conducted field work collecting dinosaurs, chiefly the Oklahoma Museum of Natural History, the Denver Museum of Nature & Science, the 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 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 iguanodon
tid 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 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. For example, the primitive ankylosaurid Cedarpelta
is related to Gobisaurus
and Shamosaurus
from Mongolia, but is more primitive than either because it has teeth in the premaxilla. The upper assemblage also has a tyrannosaurid, 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 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.
Some of the gastroliths examined in a 2001 study of Cedarosaurus
gastroliths couldn't be tested for reflectance due to a confounding metallic coating, which may have been hematite
. The metallic coating "probably originated from the iron
rich mudstone
" surround the fossils.
The various vertebrates are listed by member in the list below.
Non-vertebrate fossils are more widely distributed in the Cedar Mountain Formation. These include the distinctive reproductive structures of fresh water algae that are called charophytes. Charophytes are so distinctive that they are used to correlate strata of similar age, and thus were used to show that the Yellow Cat Member was time equivalent to Barremian age strata in England. Ostracod
s, small crustaceans with clam-like shells, also occur in fresh water deposits, along with “finger-clams” or chonchostracans. Pollen have been found in the Mussentuchit Member and are important for reconstructing the environment. In a few places, large petrified logs are known, especially from the Poison Strip. These conifer logs are over a meter in diameter and indicate the presence of trees over 30 m (100 feet). The distinct wood of the tree fern Tempskya is occasional found as well.
Data from Carpenter (2006), Cifelli et al. (1999), Kirkland and Madsen (2007), and The Paleobiology Database.
Morrison Formation
The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is 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 is light grey, greenish...
and overlying Naturita Formation
Naturita Formation
The Naturita Formation was named by Robert G. Young for Cretaceous sedimentary rocks exposed near Naturita, Colorado. The formation lies between the Cedar Mountain Formation and Mancos Shale, thus occupies the position for sedimentary strata that have historically been called the Dakota Formation...
(sometimes incorrectly called the Dakota Formation
Dakota Formation
The Dakota Formation is a geologic formation composed of sedimentary rocks deposited on the western side of the Late Cretaceous Western Interior Seaway. F.B. Meek and F.V. Hayden named it for exposures along the Missouri River near Dakota City, Nebraska...
). 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
Radiometric dating
Radiometric dating is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates...
, the Cedar Mountain Formation was deposited during the last half of the Early Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
, about 127 - 98 million years ago (mya).
Dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s 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 the replacement of older, European-like dinosaurs with younger, Asian-like dinosaurs as the North American Continental Plate
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...
drifted westward. A middle dinosaur assemblage may be present, but the fossil record is not clear.
The formation was named for Cedar Mountain in northern Emery County, Utah, where William Lee Stokes first studied the exposures in 1944. 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 is considered to be at the top of the Morrison Formation or at the base of the Cedar Mountain Formation; most geologists and paleontologist 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.
Stratigraphy
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 148.1 ± 0.5 Ma . or lower TithonianTithonian
In the geologic timescale the Tithonian is the latest age of the Late Jurassic epoch or the uppermost stage of the Upper Jurassic series. It spans the time between 150.8 ± 4 Ma and 145.5 ± 4 Ma...
. Typically, the Jurassic-Cretaceous boundary in western North America is marked by an unconformity
Unconformity
An unconformity is a buried erosion surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe...
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.
- The Buckhorn Conglomerate is considered the lowermost member of the Cedar Mountain Formation in the region of the San Raphael Swell by Stokes. It is named for exposures near Buckhorn Reservoir near Cedar Mountain. Its position immediately below the Ruby Ranch Member suggests that it may be equivalent to the channel sandstones in the Yellow Cat Member and the Poison Strip Sandstone farther to the east. This idea is strengthened by the similar composition of the gravels in these members, but a direct correlation has not yet been established.
- The Yellow Cat Member is named for exposures near the Yellow Cat mining area north of Arches National ParkArches National ParkArches National Park is a U.S. National Park in eastern Utah. It is known for preserving over 2000 natural sandstone arches, including the world-famous Delicate Arch, in addition to a variety of unique geological resources and formations....
. It is limited to the eastern portions of the formation and is thickest near Arches National Monument. The member is composed of drab greyish mudstoneMudstoneMudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...
s and some lenses of sandstoneSandstoneSandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
. The mudstones were deposited on flood plains, and show evidence of ancient soil development called paleosols. The mudstones originated as flood deposits from river channels that are marked by the sandstone lenses. A recent radiometric date of 126 ± 2.5 Ma places Yellow Cat Member in the BarremianBarremianThe Barremian is an age in the geologic timescale between 130.0 ± 1.5 Ma and 125.0 ± 1.0 Ma). It is a subdivision of the Early Cretaceous epoch...
,
- The Poison Strip Sandstone was named for prominent, cliff-forming sandstones in the Poison Strip uranium district north of Arches National Monument. It is actually a series of sandstones that were deposited in river channels, and lesser amounts of mudstones and limestones that were deposited on the flood plain and small ponds. The Poison Strip Sandstone may represent a meandering river complex. Based on the position of the Poison Strip between the Yellow Cat and Ruby Ranch members, it probably was latest Barremian to earliest AptianAptianThe Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...
.- Volunteers from the Denver Museum of Natural History discovered Tony's Bone Bed in 19981998 in paleontology-Amphibians:A. C. Henrici. 1998. A new pipoid anuran from the Late Jurassic Morrison Formation at Dinosaur National Monument, Utah. Journal of Vertebrate Paleontology 18:321-332-Dinosaurs:...
in the Poison Strip Member. Prior to that, Posion Strip dinosaurs were only known from possible SauropeltaSauropeltaSauropelta is a genus of nodosaurid dinosaur that existed in the Early Cretaceous Period of North America. One species has been named although others may have existed. Anatomically, Sauropelta is one of the most well-understood nodosaurids, with fossilized remains recovered in the U.S. states of...
and isolated theropod and sauropod bones. Tony's bone bed is 3.75 m below the top of the poison strip. Quality of the bones are "highly variable." Ends of bones may have been damaged by scavenging. Some of the bones may have been trampled. Some of the vertebrae preserve "delicate lamina". None of the bones were articulated so the was probably not buried quickly after death. Tony's Bonebed probably accumulated over time when the water in the river channel was low during the dry seasonDry seasonThe dry season is a term commonly used when describing the weather in the tropics. The weather in the tropics is dominated by the tropical rain belt, which oscillates from the northern to the southern tropics over the course of the year...
. CarbonateCarbonateIn chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
growths appear on bones in the quarry from which Venenosaurus was extracted.
- Volunteers from the Denver Museum of Natural History discovered Tony's Bone Bed in 1998
- The Ruby Ranch Member is the most widespread and distinctive member of the Cedar Mountain. It was named for exposures on the Ruby Ranch located southeast of Green River, Utah. The member is composed of maroon mudstones with irregular spheres of carbonate nodules. The nodules formed in ancient soils that developed in the mud deposited on the flood plain in a strongly seasonal, semiarid climate. Evaporation of groundwater during the dry season concentrated calcium carbonate and other minerals in the upper parts of the soil horizon. Radiometric dates place the upper portions of the Ruby Ranch in the late Aptian. Exhumed river channelExhumed river channelAn exhumed river channel is a ridge of sandstone that remains when the softer flood plain mudstone is eroded away. The process begins with the deposition of sand within a river channel and mud on the adjacent floodplain. Eventually the channel is abandoned and over time becomes buried by flood...
s in the Ruby Ranch indicate that stream flow during the Aptian was towards the northeast, the direction of the encrouching Western Interior Seaway.
- The Mussentuchit Member is the uppermost member of the Cedar Mountain Formation. It was named for exposures along Mussentuchit Wash southwest of the San Rafael Swell. It is predominantly composed of grey mudstones high in organic carbon from fossil plant material, as well as volcanic ash. The mudstones were originally deposited on a broad coastal plain with a high water table or with abundant rainfall. Thus, carbonate nodules are rare. A radiometric date of 98.37 ± 0.07 Ma places the upper part of the member in the Lower CenomanianCenomanianThe Cenomanian is, in the ICS' geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series. An age is a unit of geochronology: it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding...
, while lower portions of the member have been dated to 104.46 ± 0.95 Ma, in the AlbianAlbianThe Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous epoch/series. Its approximate time range is 112.0 ± 1.0 Ma to 99.6 ± 0.9 Ma...
stage.
- Although not part of the Cedar Mountain Formation, the Naturita FormationNaturita FormationThe Naturita Formation was named by Robert G. Young for Cretaceous sedimentary rocks exposed near Naturita, Colorado. The formation lies between the Cedar Mountain Formation and Mancos Shale, thus occupies the position for sedimentary strata that have historically been called the Dakota Formation...
immediately overlies the Cedar Mountain and marks the encroaching Western Interior SeawayWestern Interior SeawayThe Western Interior Seaway, also called the Cretaceous Seaway, the Niobraran Sea, and the North American Inland Sea, was a huge inland sea that split the continent of North America into two halves, Laramidia and Appalachia, during most of the mid- and late-Cretaceous Period...
. 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 or its equivalent. The name Dakota FormationDakota FormationThe Dakota Formation is a geologic formation composed of sedimentary rocks deposited on the western side of the Late Cretaceous Western Interior Seaway. F.B. Meek and F.V. Hayden named it for exposures along the Missouri River near Dakota City, Nebraska...
has been improperly used for these strata.
Dinosaurs
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
Gastonia
Gastonia may refer to:Places:*Gastonia, North Carolina, United StatesIn biology:*Gastonia , a genus in the ivy or ginseng family*Gastonia , a genus of ankylosaur...
and a yet unnamed iguanodon
Iguanodon
Iguanodon is a genus of ornithopod dinosaur that lived roughly halfway between the first of the swift bipedal hypsilophodontids and the ornithopods' culmination in the duck-billed dinosaurs...
tid 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 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. For example, the primitive ankylosaurid Cedarpelta
Cedarpelta
Cedarpelta is an extinct genus of basal ankylosaurid ankylosaur, based on material recovered from the Lower Cretaceous of North America. The skull lacks extensive cranial ornamentation, a trait which has been interpreted as plesiomorphic for ankylosaurs....
is related to Gobisaurus
Gobisaurus
Gobisaurus is an extinct genus of basal ankylosaurid ankylosaur from the Upper Cretaceous Ulansuhai Formation of China. The holotype consists of a skull and as yet undescribed postcranial remains. It was first named by Matthew K. Vickaryous, Anthony P. Russell, Philip J...
and Shamosaurus
Shamosaurus
Shamosaurus is an extinct genus of basal ankylosaurid ankylosaur from Early Cretaceous deposits of Höövör, Mongolia. Shamosaurus is known from the holotype PIN N 3779/2 complete skull and jaw and the paratypes include partial skeleton remains and an armor. It was collected from the...
from Mongolia, but is more primitive than either because it has teeth in the premaxilla. The upper assemblage also has a tyrannosaurid, 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
Tenontosaurus
Tenontosaurus is a genus of medium- to large-sized ornithopod dinosaur. The genus is known from the late Aptian to Albian ages of the middle Cretaceous period sediments of western North America, dating between 115 to 108 million years ago...
from high in the Ruby Ranch Member and the sauropod Astrodon
Astrodon
Astrodon was a genus of large herbivorous sauropod dinosaur, related to Brachiosaurus, that lived in what is now the eastern United States during the Early Cretaceous period. Its fossils have been found in the Arundel Formation, which has been dated through palynomorphs to the Aptian-Albian...
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.
Ankylosaurs
New genus and species of iguanodont present in the Ruby Ranch and Yellow Cat members. Indeterminate neoceratopsian present in the Mussentuchit Member. Indeterminate pachycephalosaurid present in the Mussentuchit Member.| Ankylosaurs reported from the Cedar Mountain Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Member | Material | Notes | Images |
Animantarx Animantarx Animantarx is a genus of nodosaurid ankylosaurian dinosaur from the Upper Cretaceous of western North America. Like other nodosaurs, it would have been a slow-moving quadrupedal herbivore covered in heavy armor scutes, but without a tail club... |
Animantarx ramaljonesi |
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"Partial skull [and] skeleton." |
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Cedarpelta Cedarpelta Cedarpelta is an extinct genus of basal ankylosaurid ankylosaur, based on material recovered from the Lower Cretaceous of North America. The skull lacks extensive cranial ornamentation, a trait which has been interpreted as plesiomorphic for ankylosaurs.... |
Cedarpelta bilbeyhallorum |
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"Skull [and] postcranium." |
Cedarpelta bilbeyhallorum was not from the Ruby Ranch Member as initially described. |
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Gastonia Gastonia (dinosaur) Gastonia is a genus of nodosaurid dinosaur from the Early Cretaceous of North America, around 125 million years ago. Closely related to Polacanthus, it has a sacral shield and large shoulder spikes. It is also the first polacanthine dinosaur to have been mounted for display at the Denver Museum of... |
Gastonia burgei |
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"[Two] skulls, [two] partial skulls, [and four] or [five] partial skeletons." |
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New species |
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Peloroplites Peloroplites Peloroplites is a genus of nodosaurid armored dinosaur from Lower Cretaceous rocks of Utah... |
Peloroplites cedrimontanus |
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Sauropelta Sauropelta Sauropelta is a genus of nodosaurid dinosaur that existed in the Early Cretaceous Period of North America. One species has been named although others may have existed. Anatomically, Sauropelta is one of the most well-understood nodosaurids, with fossilized remains recovered in the U.S. states of... |
Unnamed |
"Skull and partial skeleton, isolated sacrum." |
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Marginocephalians
Indeterminate neoceratopsian present in the Mussentuchit Member. Indeterminate pachycephalosaurid present in the Mussentuchit Member.Ornithopods
New genus and species of iguanodont present in the Ruby Ranch and Yellow Cat members. Indeterminate neoceratopsian present in the Mussentuchit Member. Indeterminate pachycephalosaurid present in the Mussentuchit Member.| Ornithopods reported from the Cedar Mountain Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Member | Material | Notes | Images |
Cedrorestes Cedrorestes Cedrorestes is a genus of iguanodontian dinosaur from the Early Cretaceous of Utah... |
Cedrorestes crichtoni |
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 |
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Eolambia Eolambia Eolambia is a genus of herbivorous iguanodontian dinosaur from the mid-Cretaceous Period of the USA.In 1992 Carole Jones and her husband Ramal Jones near Castle Dale in Emery County, Utah, on the San Rafael Swell Anticline discovered a fossil site which would be named the Carol Quarry in her honour... |
Eolambia caroljonesa |
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Hippodraco Hippodraco Hippodraco is a genus of herbivorous iguanodontian dinosaur. It is a basal iguanodontian which lived during the Lower Cretaceous period in what is now Utah, USA... |
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Iguanocolossus |
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Iguanodon Iguanodon Iguanodon is a genus of ornithopod dinosaur that lived roughly halfway between the first of the swift bipedal hypsilophodontids and the ornithopods' culmination in the duck-billed dinosaurs... |
I. ottingeri |
"Teeth." |
Dubious. |
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Planicoxa Planicoxa Planicoxa is a genus of advanced iguanodontian dinosaur from the Early Cretaceous of North America. It is known from the partial skeletons of several individual specimens. Its fossils were discovered in Utah and South Dakota, United States.... |
Planicoxa venenica |
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"Associated postcranium." |
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Tenontosaurus Tenontosaurus Tenontosaurus is a genus of medium- to large-sized ornithopod dinosaur. The genus is known from the late Aptian to Albian ages of the middle Cretaceous period sediments of western North America, dating between 115 to 108 million years ago... |
Tenontosaurus sp. |
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Zephyrosaurus Zephyrosaurus Zephyrosaurus is a genus of hypsilophodont ornithopod dinosaur. It is based on a partial skull and postcranial fragments discovered in the Aptian-Albian-age Lower Cretaceous Cloverly Formation of Carbon County, Montana... |
cf. Zephyrosaurus sp. |
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Sauropods
New titanosaurid genus and species present in the Yellow Cat Member. Indeterminate brachiosaurid remains present in the Mussentuchit Member.Some of the gastroliths examined in a 2001 study of Cedarosaurus
Cedarosaurus
Cedarosaurus was a nasal-crested macronarian dinosaur genus from the Early Cretaceous Period . It was a sauropod which lived in what is now Utah...
gastroliths couldn't be tested for reflectance due to a confounding metallic coating, which may have been hematite
Hematite
Hematite, also spelled as haematite, is the mineral form of iron oxide , one of several iron oxides. Hematite crystallizes in the rhombohedral system, and it has the same crystal structure as ilmenite and corundum...
. The metallic coating "probably originated from the iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
rich mudstone
Mudstone
Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...
" surround the fossils.
| Sauropods reported from the Cedar Mountain Formation | ||||||
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| Genus | Species | Location | Member | Material | Notes | Images |
Abydosaurus |
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 |
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cf. Astrodon Astrodon Astrodon was a genus of large herbivorous sauropod dinosaur, related to Brachiosaurus, that lived in what is now the eastern United States during the Early Cretaceous period. Its fossils have been found in the Arundel Formation, which has been dated through palynomorphs to the Aptian-Albian... |
Indeterminate |
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Cedarosaurus Cedarosaurus Cedarosaurus was a nasal-crested macronarian dinosaur genus from the Early Cretaceous Period . It was a sauropod which lived in what is now Utah... |
Cedarosaurus weiskopfae |
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"Postcranial skeleton." |
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Venenosaurus Venenosaurus Venenosaurus named after the Poison Strip Member of the Cedar Mountain Formation in Utah, where the fossils were discovered by a Denver Museum of Natural History volunteer Tony DiCroce in 1998. Venenosaurus dicrocei was first described as a new species in 2001 by Virginia Tidwell, Kenneth... |
Venenosaurus dicrocei |
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"Partial postcranial skeleton." |
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Brontomerus Brontomerus Brontomerus is a genus of camarasauromorph sauropod which lived during the early Cretaceous . It was named in 2011 and the type species is Brontomerus mcintoshi... |
Brontomerus mcintoshi |
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Theropods
Indeterminate dromaeosaurine present in the Mussentuchit Member. Indeterminate velociraptorine remains present in the Mussentuchit Member. Possible indeterminate tyrannosaurid 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 the Mussentuchit Member. Possible indeterminate hesperornithiformes present in the Mussentuchit Member. Possible new allosaurid species present in the Ruby Ranch Member.| Theropods reported from the Cedar Mountain Formation | ||||||
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| Genus | Species | Location | Member | Material | Notes | Images |
cf. Acrocanthosaurus Acrocanthosaurus Acrocanthosaurus is a genus of theropod dinosaur that existed in what is now North America during the Aptian and early Albian stages of the Early Cretaceous. Like most dinosaur genera, Acrocanthosaurus contains only a single species, A. atokensis. Its fossil remains are found mainly in the U.S... |
Indeterminate |
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Deinonychus Deinonychus Deinonychus was a genus of carnivorous dromaeosaurid dinosaur. There is one described species, Deinonychus antirrhopus. This 3.4 meter long dinosaur lived during the early Cretaceous Period, about 115–108 million years ago . Fossils have been recovered from the U.S... |
Indeterminate |
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Falcarius Falcarius Falcarius is a genus of therizinosaurian dinosaur found in east-central Utah, United States. Its name is derived from the word sickle , which scientists have used to describe its unwieldy clawed hands... |
Falcarius utahensis |
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Geminiraptor Geminiraptor Geminiraptor is a genus of troodontid dinosaur. Geminiraptor lived during the lower Cretaceous period in what is now Utah, USA. It is known from CEUM 7319, a maxilla recovered from the lower Yellow Cat Member of the Cedar Mountain Formation, dating to at least the early Barremian stage... |
Geminiraptor suarezarum |
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Nedcolbertia Nedcolbertia Nedcolbertia is a genus of dinosaur from the Early Cretaceous Period. It was a coelurosaur which lived in North America during the Barremian. Kirkland, Britt, Madsen and Burge in 1995 reported its discovery in the basal Cedar Mountain Formation in Utah. The type species, N... |
Nedcolbertia justinhofmanni |
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"Partial skeletons of [three] individuals." |
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cf. Richardoestesia |
Indeterminate |
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Utahraptor Utahraptor Utahraptor is a genus of theropod dinosaurs, including the largest known members of the family Dromaeosauridae. Fossil specimens date to the upper Barremian stage of the early Cretaceous period... |
Utahraptor ostrommaysorum |
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"Skull and postcranial fragments." |
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Indeterminate |
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Other Fossils
Besides dinosaurs, the Cedar Mountain Formation has produced a wealth of small fossils (a.k.a. microfossils), mostly teeth from a variety of vertebrates. Most of these specimens have been found in the Mussentuchit Member where they are collected by washing the rock through fine window screen. The teeth and other small fossils are picked from the residue.- Fish include primitive fresh or brackish water sharks (e.g., Hybodus) and rays (c.f., Ischyrhiza), the lung fish (Ceratodus) and several bony fishes known from vertebrae. Lung fish are able to breathe air when pond water become poorly oxygenated, such as during the dry season.
- Amphibians include both salamanders (e.g. Albanerpeton) and frogs, but neither is common.
- Reptiles are more abundant and better studied. These include aquatic turtles (Glyptops, Naomichelys), at least one type of snake (Coniophis), and several different lizards, including teiids (Bicuspidon), possible skinkSkinkSkinks are lizards belonging to the family Scincidae. Together with several other lizard families, including Lacertidae , they comprise the superfamily or infraorder Scincomorpha...
s and some extinct families (e.g., Paramacellodidae). Crocodiles are also present but their remains are fragmentary. They include Bernissartia, an unnamed atoposaurid, and unnamed pholidosaurid. At least one fragment of a large pterosaur is known from the base of the Mussentuchut Member. Unfortunately, it is too incomplete to identify to family or genus. - Bird remains are very fragmentary because of their delicate structure. At least one aquatic bird is known. Based on the diversity of birds from the Early Cretaceous of China, other birds were probably present in Utah at this time as well.
- Mammals are the most thoroughly studied thanks to the work of Jeffrey Eaton and Richard Cifelli. They include triconodonts (e.g., Astroconodon), which have the molar cusps arranged in a single row; symmetrodonts (e.g., Spalacolestes; Spalacotheridium), characterized by molars having three cusps arranged in a triangle; multituberculates (e.g., Janumys; Cedaromys; Paxacimexomys), with their multiple rows of cusps on the molars; one of the earliest marsupials (Kokopellia), and several unnamed tribotheres, characterized by molars having three cusps that are typically asymmetrically arranged.
The various vertebrates are listed by member in the list below.
Non-vertebrate fossils are more widely distributed in the Cedar Mountain Formation. These include the distinctive reproductive structures of fresh water algae that are called charophytes. Charophytes are so distinctive that they are used to correlate strata of similar age, and thus were used to show that the Yellow Cat Member was time equivalent to Barremian age strata in England. Ostracod
Ostracod
Ostracoda is a class of the Crustacea, sometimes known as the seed shrimp because of their appearance. Some 65,000 species have been identified, grouped into several orders....
s, small crustaceans with clam-like shells, also occur in fresh water deposits, along with “finger-clams” or chonchostracans. Pollen have been found in the Mussentuchit Member and are important for reconstructing the environment. In a few places, large petrified logs are known, especially from the Poison Strip. These conifer logs are over a meter in diameter and indicate the presence of trees over 30 m (100 feet). The distinct wood of the tree fern Tempskya is occasional found as well.
Data from Carpenter (2006), Cifelli et al. (1999), Kirkland and Madsen (2007), and The Paleobiology Database.
Amphibians
Indeterminate anuran remains present in the Mussentuchit Member.| Amphibians of the Cedar Mountain Formation | ||||||
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| Genus | Species | Location | Member | Abundance | Description | Images |
Albanerpeton Albanerpeton Albanerpeton is an extinct genus of salamander-like lissamphibian found in North America and Europe. Members of the genus have a robust head and neck which likely allowed them to actively burrow and they lived in a wide range of environments... |
Albanerpeton cf. A. nexuosus |
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Bony fish
Indeterminate amiiform present in the Yellow Cat and Mussentuchit Members. Indeterminate neopterygion remains present in the Mussentuchit Member. Possible indeterminate pycnodontid remains present in the Mussentuchit Member. Possible indeterminate lepisosteid remains present in the Mussentuchit Member.| Bony Fishes of the Cedar Mountain Formation | ||||||
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| Genus | Species | Location | Member | Abundance | Description | Images |
Semionotus Semionotus Semionotus is an extinct genus of ray-finned fish found throughout Northern Pangaea during the late Triassic, becoming extinct at the start of the Jurassic.-External links:... ? |
Semionotus? sp. |
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Ceratodus Ceratodus Ceratodus was a wide-ranging genus of extinct sarcopterygiian lungfish. Fossil evidence dates back to the Middle Triassic 228 million years ago. A wide range of fossil species from different time periods have been found around the world in places such as the United States, Argentina, England,... |
New species. |
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Ceratodus sp. |
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Cartilaginous fish
A new genus and species of orectolobid present in the Mussentuchit Member.| Cartilaginous Fishes of the Cedar Mountain Formation | ||||||
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| Genus | Species | Location | Member | Abundance | Description | Images |
Hybodus Hybodus Hybodus is an extinct genus of once-common, widespread and long lived sharks, first appearing towards the end of the Permian period, and disappearing at the beginning of the Cretaceous. During the Triassic, Jurassic, and Cretaceous periods the hybodonts were especially successful and could be... |
Hybodus sp. |
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Polyacrodus |
Polyacrodus parvidens |
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Lissodus Lissodus Lissodus is an extinct genus of freshwater shark. It lived from the Early Triassic to the Albian period of the Cretaceous. It was about long and had flat teeth that it used for eating clams.... |
Lissodus spp. |
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Ischyrhiza Ischyrhiza Ischyrhiza is an extinct genus of cartilaginous fish from the Cretaceous and Paleogene belonging to the primitive Batoidea family Sclerorhynchidae.-Sources:* Fossils by David Ward * accessed on 8/21/09... |
Ischyrhiza sp. |
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Pseudohypolophus |
Pseudohypolophus sp. |
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cf. Baibisha |
New species |
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Cretorectolobus |
Indeterminate |
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Mammals
New genus and species of pappotheriid present in the Mussentuchit Member. Indeterminant genus and species of picopsid present in the Mussentuchit Member.| Mammals of the Cedar Mountain Formation | ||||||
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| Genus | Species | Location | Member | Abundance | Description | Images |
Ameribaatar Ameribaatar Ameribaatar is an extinct mammal of the Late Cretaceous. It was a member of the also extinct order of Multituberculata. It lived in North America during the Mesozoic, also known as the "age of the dinosaurs". Whether it belongs to Plagiaulacida, Cimolodonta, or neither, is presently unclear... |
Ameribaatar zofiae |
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Astroconodon |
Astroconodon delicatus |
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Bryceomys Bryceomys Bryceomys is an extinct mammal that lived during the late Cretaceous period and thus shared the world with dinosaurs. It was a member of the also extinct order of Multituberculata... |
Bryceomys intermedius |
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Cedaromys Cedaromys Cedaromys is an extinct mammal which lived during the Upper Cretaceous, at the same time as many dinosaurs. It was a member of the also extinct order of Multituberculata. It's within the suborder of Cimolodonta, and a possible member of the Paracimexomys group.The genus Cedaromys was named by... |
Cedaromys bestia |
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Cedaromys parvus |
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Corviconodon |
Corviconodon utahensis |
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Janumys Janumys Janumys is a genus of extinct mammal of the middle Cretaceous. It was a member of the order of Multituberculata . It lived in North America during the Mesozoic era, also known as the "age of the dinosaurs." It has been previsionally placed within the informal suborder "Plagiaulacida"... |
Janumys erebos |
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Jugulator Jugulator -Personnel:*Tim 'Ripper' Owens: Vocals*K.K. Downing: Guitars*Glenn Tipton: Guitars*Ian Hill: Bass*Scott Travis: Drums... |
Jugulator amplissimus |
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Kokopellia |
Kokopellia juddi |
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Possible marsupial. |
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Paracimexomys Paracimexomys Paracimexomys is a genus of extinct mammals in the also extinct Multituberculata order. Paracimexomys lived during the Cretaceous period. The few fossils remains come from North America. Some Romanian fossils were also tentatively assigned to this genus, though that classification now seems... |
Paracimexomys perplexus |
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Paracimexomys robisoni |
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Spalacolestes |
Spalacolestes cretulablatta |
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Spalacolestes inconcinnus |
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Spalacotheridium |
Spalacotheridium noblei |
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Other reptiles
Indeterminate pterosaur remains in the Mussentuchit Member. Indeterminate crocodilian remains present in the Yellow Cat and Ruby Ranch Members. Indeterminate pholidosaurid remains present in the Mussentuchit Member. Indeterminate atoposaurid remains present in the Mussentuchit Member. Indeterminate baenid remains present in the Mussentuchit Member.Crurotarsans
| Crurotarsans of the Cedar Mountain Formation | ||||||
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| Genus | Species | Location | Member | Abundance | Description | Images |
Bernissartia Bernissartia Bernissartia is an extinct genus of crocodyliform that lived in the Early Cretaceous, around 130 million years ago.At only in length, Bernissartia is one of the smallest crocodyliforms that ever lived. It resembled modern species in many respects, and was probably semi-aquatic... |
Bernissartia sp. |
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cf. Dakotasuchus Dakotasuchus Dakotasuchus is a genus of goniopholidid mesoeucrocodylian. Its fossils have been recovered from the Cenomanian-age Upper Cretaceous Dakota Sandstone of Kansas. The type specimen was found in an iron-cemented sandstone concretion near Salina... |
cf. Dakotasuchus sp. |
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Polydectes Deinosuchus Deinosuchus is an extinct genus related to the alligator that lived 73 to 80 Ma , during the late Cretaceous period. The name translates as "terrible crocodile" and is derived from the Greek deinos , "terrible", and soukhos , "crocodile"... |
Polydectes sp. |
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Turned out that it actually came from Deinosuchus. | |||
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Machimosaurus Machimosaurus Machimosaurus is an extinct genus of teleosaurid crocodyliform from the Late Jurassic and Early Cretaceous . The type species, Machimosaurus hugii, was found in France. Other fossils have been found in Austria, England, Germany, Portugal and Switzerland... |
Machimosaurus sp. |
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Lepidosaurs
| Lepidosaurs of the Cedar Mountain Formation | ||||||
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| Genus | Species | Location | Member | Abundance | Description | Images |
Toxolophosaurus Toxolophosaurus Toxolophosaurus was a Sphenodontid from the Early Cretaceous–age Kootenai Formation of Montana.-Discovery:Toxolophosaurus cloudi was found by Olson in 1960 in the Kootenai Formation, 223.75 feet above the base of the Kootenai.-Classification:... |
Toxolophosaurus sp. |
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Harmodontosaurus |
Harmodontosaurus emeryensis |
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Dimekodontosaurus |
Dimekodontosaurus masdeni |
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Dicothodon |
Dicothodon moorensis |
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Bothriagenys |
Bothriagenys mysterion |
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Pseudosaurillus |
Pseudosaurillus sp. |
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Primaderma |
Primaderma nessovi |
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Coniophis |
Coniophis sp. |
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Turtles
| Turtles of the Cedar Mountain Formation | ||||||
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| Genus | Species | Location | Member | Abundance | Description | Images |
Glyptops Glyptops Glyptops is an extinct genus of cryptodire turtle dating from the Late Jurassic and Early Cretaceous periods 155 to 99 m.y.a. Fossils have been found in South Dakota, Wyoming, Colorado, Utah, New Mexico, Oklahoma, and Texas from both the Morrison and Cedar Mountain formations. The type species is G... |
Glyptops sp. |
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Naomichelys |
Naomichelys sp. |
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