Cedar Mountain Formation
Stratigraphic range: middle Berriasian-earliest Cenomanian
~140–98.37 Ma

PreЄ

Type section of the Cedar Mountain Formation

Type| Geological formation
Sub-units| See text
Underlies| Naturita Formation
Overlies| Morrison Formation
Thickness| Varies, some sections over 1000 metres
Lithology
Primary| Conglomerate, sandstone, mudstone
Location
Coordinates|  [ ⚑ ] : 39°15′00″N 110°49′26″W﻿ / ﻿39.250°N 110.824°W﻿ / 39.250; -110.824
Paleocoordinates|  [ ⚑ ] 40°12′N 69°00′W﻿ / ﻿40.2°N 69.0°W﻿ / 40.2; -69.0
Region| Utah
Country| United States
Type section
Named for| Cedar Mountain
Named by| William Stokes
Year defined| 1944

Cedar Mountain Formation (the United States)

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Cedar Mountain Formation (Utah)

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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.[1]

## Contents

* 1 Geology
* 1.1 Stratigraphy
* 1.1.1 Formation members
* 2 Fossil content
* 2.1 Dinosaurs
* 2.1.1 Ankylosaurs
* 2.1.2 Neornithischians
* 2.1.3 Sauropods
* 2.1.4 Theropods
* 2.2 Other vertebrate fossils
* 2.2.1 Other reptiles
* 2.2.1.1 Crurotarsans
* 2.2.1.2 Lepidosaurs
* 2.2.1.3 Turtles
* 2.2.2 Amphibians
* 2.2.3 Fish
* 2.2.3.1 Bony fish
* 2.2.3.2 Cartilaginous fish
* 2.2.4 Mammaliaformes
* 3 See also
* 4 References
* 4.1 Bibliography and further reading
* 5 Further reading
* 6 External links

## Geology

The drab-colored lower portion of the Cedar Mountain Formation, overlying the brighter Morrison Formation.

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 Early Cretaceous Epoch, about 140 - 94 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 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.

### 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 135.10 ± 0.30 Ma[2] 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.[3] This boundary between the Morrison and Cedar Mountain is commonly marked by a horizon of carbonate nodules[4][5] 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 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.[6]

#### Formation members

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[7] or four[8] 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 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.

Type section of the Buckhorn Conglomerate western side of Cedar Mountain, Emery County, Utah.

* The Buckhorn Conglomerate is considered the lowermost member of the Cedar Mountain Formation in the region of the San Raphael Swell by Stokes.[4] 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 Park. It is limited to the eastern portions of the formation and is thickest near Arches National Monument. The member is composed of drab greyish mudstones and some lenses of sandstone. 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. Formerly considered Barremian, the latest chemostratigraphic and geochronological studies conclude that the Yellow Member is older, with deposition occurring Berriasian–Valanginian stages.[2]
* 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.[9] Based on the position of the Poison Strip between the Yellow Cat and Ruby Ranch members, it probably was latest Barremian to earliest Aptian. Carbonate growths appear on bones in the quarry from which Venenosaurus was extracted.[10]
* This image shows the Cedar Mountain Formation near its type section at Buckhorn Reservoir, Utah. The formation is capped by a very thin bed of Naturita Formation. The Cedar Mountain Formation is an Early Cretaceous fluvial formation, that was deposited in the foreland basin of the Sevier Mountains just before it was flooded by the ocean to form the Western Interior Seaway.The Poison Strip Sandstone was the source of Tony's Bone Bed, a significant concentration of dinosaur bones. Before it was discovered, only possible Sauropelta remains and the isolated bones of sauropods and theropods had been recovered from the Poison Strip member.[11] Volunteers from the Denver Museum of Natural History discovered Tony's Bone Bed in 1998, 3.75m below the top of the member.[12] The quality of the preserved remains in Tony's Bone Bed are "highly variable". The condition of many of its fossils suggest the deposit accumulated gradually. Many of the bones seem to have been trampled before burial, and some of the ends of bones are missing and were likely removed by scavengers. None of the bones were preserved articulated with each other. All of this suggests a significant period of time between the deaths of the animals and their final entombment. Tony's Bonebed probably accumulated over time when the water in the river channel was low during the dry season.[13]

* 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 channels in the Ruby Ranch indicate that stream flow during the Aptian was towards the northeast, the direction of the encroaching 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 Cenomanian, while lower portions of the member have been dated to 104.46 ± 0.95 Ma, in the Albian stage.[14]

## Fossil content

Fauna of Yellow Cat Member from the Cedar Mountain Formation

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 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.

### Dinosaurs

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 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 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 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 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.[15]

Data from Carpenter (2006),[15] Cifelli et al. (1999),[16] Kirkland and Madsen (2007), and The Paleobiology Database.

#### Ankylosaurs

Ankylosaurs reported from the Cedar Mountain Formation

Genus  | Species  | Location  | Member  | Material  | Notes  | Images
Animantarx | A. ramaljonesi |  |

* Mussentuchit Member

| A partial skull and right mandible, cervical vertebrae, dorsal vertebrae, ribs, scapulacoracoids, fragment of sternal plate, humerus, left ilium with ischium, and femur.[17] |  |
Cedarpelta[18] | C. bilbeyhallorum[18] |  |

* Mussentuchit Member[18]

| [Two] skulls, cervical vertebrae, dorsal vertebrae, synsacrum, caudal vertebrae, humeri, ulna, ischium, partial right ischium, fragments of the right ilium, cervical ribs, metacarpals, phalanges, unguals, coracoid, femur, tibia, and osteoderms.[19] | Cedarpelta was not from the Ruby Ranch Member as initially described.[18] |
Gastonia | G. burgei |  |

* Upper Yellow Cat Member

| A skull, maxillary tooth, ischium, caudal vertebrae, scapulocoracoid, scapula, ilium, femurs, ulna, humerus, tibia, anterior dorsal vertebra, caudal spines, shoulder spines, caudal plates, osteoderms, and portions of sacral shield.[20] | A polacanthine nodosaurid.
G. lorriemcwhinneyae[20] |  |

* Poison Strip Member

| A skull roof, braincase, partial cranium, quadrate, cervical vertebrae, dorsal vertebrae, dorsal rib, synsacrum, caudal vertebrae, chevrons, scapulocoracoid, scapulae, coracoid, humerus, ulna, ilia, ischium, ischia, pubis, femur, fibula, tibia, and osteoderms.[20] | A polacanthine nodosaurid.  |
Peloroplites | P. cedrimontanus |  |

* Mussentuchit Member

| A partial skull, cervical vertebrae, dorsal vertebrae, synsacrum, caudal vertebrae, chevron, scapulacoracoids, humeri, radii, ulnae, ilia, pubis, ischium, femora, tibiae, fibula, metacarpals, metatarsal, metapodials, phalanges, unguals, osteoderms, and fragments.[18] | A polacanthine nodosaurid.  |
cf. Sauropelta | Indeterminate  |  |

* Poison Strip Member

| Caudal vertebrae, dorsal vertebrae, ribs, and osteoderms.  | cf. Sauropelta sp. may, instead, represent a large polacanthine.

#### Neornithischians

A large sail-backed iguanodont represented by large vertebrae and fragmentary remains from the Upper Yellow Cat Member.[21]

Neornithischians reported from the Cedar Mountain Formation

Genus  | Species  | Location  | Member  | Material  | Notes  | Images
Cedrorestes | C. crichtoni |  |

* Upper Yellow Cat Member

| Fragments of ribs, fused sacrum, ilium, preacetabular process of an ilium, tibia, metatarsal, and ossified tendons.  | A basal styracostern ornithopod.  |  |

Eolambia

E. caroljonesa

|  |

* Mussentuchit Member

| Predentaries, dentaries, surangulars, premaxillae, nasal, maxillae, jugals, postorbitals, quadrates, spuamosal, braincases, frontals, parietal, supraoccipital, opisthotic-exoccipital, prootic, laterosphenoid, parasphenoid-basisphenoid, basioccipital, cervical vertebrae, dorsal vertebrae, caudal vertebrae, cervical ribs, dorsal ribs, sacral vertebrae, chevrons, sternal, scapula, coracoid, humerus, ulna, radius, metacarpals, manual phalanges, ilium, pubis, ischium, femur, tibia, fibula, tarsus, metatarsals, and pedal phalanges.  | A basal hadrosauromorph ornithopod.  | Eolambia
Fona[22] | F. herzogae |  |

* Mussentuchit Member

| Multiple fairly complete, partially articulated skeletons including cranial material  | A thescelosaurine thescelosaurid.  | Fona

Hippodraco

H. scutodens

|  |

* Upper Yellow Cat Member

| Partial skull, cervical vertebrae, dorsal vertebrae, dorsal rib, partial sacrum, sternal, scapula, humerus, ischium, femur, tibia, astragalus, calcaneum, distal tarsal, phalanxes, and metatarsals.  | A basal styracostern ornithopod.  | Hippodraco
Iani | I. smithi |  |

* Lower Mussentuchit Member

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.

| A basal rhabdodontomorph ornithopod.

Iguanacolossus

I. fortis

|  |

* Lower Yellow Cat Member

| Partial dentary, maxilla, squamosal, quadrates, axial neural arch, dorsal vertebrae, dorsal rib, caudal vertebrae, chevrons, scapula, ilium, pubis, fibula, and metatarsals.  | A basal styracostern ornithopod.

Iguanodon

I. ottingeri

|  |

* Yellow Cat Member

| An upper jaw fragment and two teeth.[23] |

A dubious taxon.

Planicoxa

P. venenica

|  |

* Poison Strip Member

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 [24]

| A basal styracostern ornithopod.  | Planicoxa

Tenontosaurus[13]

| Indeterminate  |  |

* Lower Ruby Ranch Member[13]

Various partial specimens.[25]

| Teeth attributed to this genus have also been found in the Upper Ruby Ranch Member and the Mussentuchit Member.

#### Sauropods

Sauropods reported from the Cedar Mountain Formation

Genus  | Species  | Location  | Member  | Material  | Notes  | Images

Abydosaurus

A. mcintoshi

|  |

* Mussentuchit Member

| [Two] nearly complete skulls, braincase with a partial skull roof, cervical vertebrae, partial pelvis and sacrum with articulated caudal vertebrae, scapula, humerus, and metacarpus.  | A brachiosaurid sauropod.  |  Abydosaurus Cedarosaurus Mierasaurus

File:Colored Fig 36 Moabo Skeleton.tif

cf. Astrodon

Indeterminate

|  |

* Ruby Ranch Member.

|  |

Brontomerus

B. mcintoshi

|  |

* Ruby Ranch Member, and possibly the upper Yellow Cat Member

| An ilium, crushed presacral centrum, mid-to-posterior caudal vertebra, partial distal caudal centrum, anterior dorsal rib, nearly complete scapula missing anterior portion, partial sternal plates, and other fragments.  | A dubious camarasauromorph.

Cedarosaurus

C. weiskopfae

|  |

* Upper Yellow Cat Member, and possibly also the lower Yellow Cat Member

Articulated dorsal vertebrae, caudal vertebrae, chevrons, proximal portions of 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. [26]

| A brachiosaurid sauropod.

Mierasaurus[27]

M. bobyoungi

|  |

* Lower Yellow Cat Member

| A partial skull and jaw, teeth, cervical vertebrae, cervical ribs, dorsal vertebrae, dorsal ribs, sacral ribs, caudal vertebrae, chevrons, scapulae, radius, ulna, manus, complete pelvic elements, femora, tibia, fibula, astragalus pes, a possible juvenile dentary, and juvenile femur.  | One of the last-surviving members of turiasauria.

Moabosaurus

M. utahensis

|  |

* Upper Yellow Cat Member

[Eighteen] braincases, premaxillas, maxillas, dentaries, postorbital, quadrate, cervical vertebrae, dorsal vertebrae, caudal vertebrae, cervical ribs, ribs, sacrum, sternal plate, humerus, ulna and femur.[28]

| One of the last-surviving members of turiasauria.

Venenosaurus

V. dicrocei

|  |

* Poison Strip Member

Disarticulated caudal vertebrae, scapula, radius, ulna, metacarpals, manus phalanges, pubis, ischium, metatarsals, astragalus, chevrons, and ribs.[29]

| A brachiosaurid sauropod.

#### Theropods

Indeterminate allosauroid material present in the Lower Yellow Cat, Upper Yellow Cat and Ruby Ranch Members.[30] Indeterminate dromaeosaurine present in the Mussentuchit Member. Indeterminate remains of a 3m deinonychosaurian present in the Mussentuchit member.[31] 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 the Mussentuchit Member. Possible indeterminate hesperornithiformes present in the Mussentuchit Member.

Theropods reported from the Cedar Mountain Formation

Genus  | Species  | Location  | Member  | Material  | Notes  | Images

cf. Acrocanthosaurus

Indeterminate

|  |

* Ruby Ranch Member.

| An isolated tooth.  | May represent a similar taxon instead based on the morphology of the tooth.  |  Deinonychus Falcarius Moros Nedcolbertia Siats Utahraptor

Deinonychus

Indeterminate

|  |

* Mussentuchit Member.

|  |

Falcarius

F. utahensis

|  |

* Lower Yellow Cat Member.

| Numerous elements belonging to immature and mature individuals.  | A basal therizinosaur theropod.

Geminiraptor

G. suarezarum

|  |

* Lower Yellow Cat Member.

| A maxilla.  | A troodontid theropod.

Martharaptor

M. greenriverensis

|  |

* Upper Yellow Cat Member.

| A cervical neural arch, cranial dorsal vertebra, distal caudal centrum, ulna?, radius, scapula, ischium, distal pubis?, metacarpal, manual phalanxes, manual unguals, metatarsals, pedal phalanxes and pedal unguals.  | A possible therizinosauroid therizinosaur.

Moros

M. intrepidus

|  |

* Mussentuchit Member.

| Portions of the femur, tibia, metatarsals and phalanges.  | A pantyrannosaurian tyrannosauroid.

Nedcolbertia

N. justinhofmanni

|  |

* Upper Yellow Cat Member.

"Partial skeletons of [three] individuals."[32]

| A basal ornithomimosaur.

cf. Richardoestesia

Indeterminate

|  |

* Mussentuchit Member.

| Teeth.  | An indeterminate coelurosaur.

Siats

S. meekerorum

|  |

* Mussentuchit Member.

| Dorsal vertebrae, partial ilium and ischium, partial fibula, caudal vertebrae, a chevron, a pedal phalanx and several indeterminate bone fragments.  | A neovenatorid allosauroid.

Utahraptor

U. ostrommaysi

|  |

* Upper Yellow Cat Member.

Pedal unguals, tibia, femur, premaxillae, nasal, quadratojugal, caudal vertebrae, cervical vertebrae, dorsal vertebrae, sacral vertebrae, proximal caudal vertebrae, coracoid, partial ilium, incomplete ischium, femora, astragalus, metatarsal, phalanxes and undescribed material. [33]

| A dromaeosaurine dromaeosaurid.

Indeterminate

|  |

* Poison Strip Member.

| Pelvic element?  |

Yurgovuchia

Y. doellingi

|  |

* Lower Yellow Cat Member.

| Cervical vertebrae, dorsal vertebrae, caudal vertebrae, and the proximal end of a pubis.  | A dromaeosaurine dromaeosaurid.
Allosauroidea indet.  | Indeterminate  |  |

* Upper Yellow Cat Member

| Teeth, vertebrae and ribs  | Large indeterminate allosauroids (~10m~).[34] [35]

### Other vertebrate fossils

Map of Utah showing the location of the Cedar Mountain Formation (red). The San Rafael Swell is the dome-like structure that the formation jogs around. Base map data courtesy of geodata.gov

Besides dinosaurs, the Cedar Mountain Formation has produced a wealth of small fossils and 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.[16]

* Fish include primitive fresh or brackish water sharks (e.g., Hybodus) and rays (cf., Ischyrhiza), the lungfish (Ceratodus) and several bony fishes known from vertebrae. Lungfish are able to breathe air when pond water becomes 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 skinks 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.[16] 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; Paracimexomys), 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.[7] Ostracods, small crustaceans with clam-like shells, also occur in fresh water deposits, along with "finger-clams" or conchostracans. 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),[15] Cifelli et al. (1999),[16] Kirkland and Madsen (2007), and The Paleobiology Database.

#### Other reptiles

Indeterminate isolated pterosaur remains have been recovered from the Yellow Cat and Mussentuchit Members.

A partial neochoristodere femur is known from the Yellow Cat Member.[36]

##### Crurotarsans

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.

Crurotarsans of the Cedar Mountain Formation

Genus  | Species  | Location  | Member  | Abundance  | Description  | Images

cf. Bernissartia

cf. Bernissartia sp.

|  |

* Mussentuchit Member

|  |  |  Bernissartia

Dakotasuchus

Dakotasuchus kingi

|  |

* Mussentuchit Member.

|  |

##### Lepidosaurs

Lepidosaurs of the Cedar Mountain Formation

Genus  | Species  | Location  | Member  | Abundance  | Description  | Images

Toxolophosaurus

Toxolophosaurus sp.

|  |

* Yellow Cat Member.

|  |  |

Harmodontosaurus

Harmodontosaurus emeryensis

|  |

* Mussentuchit Member.

|  |

Dimekodontosaurus

Dimekodontosaurus madseni

|  |

* Mussentuchit Member.

|  |

Dicothodon

Dicothodon moorensis

|  |

* Mussentuchit Member.

|  |

Pseudosaurillus

Pseudosaurillus sp.

|  |

* Mussentuchit Member.

|  |
Bicuspidon | Bicuspidon numerosus |  |

* Mussentuchit Member.

|  |

Bothriagenys

Bothriagenys mysterion

|  |

* Mussentuchit Member.

|  |

Primaderma

Primaderma nessovi

|  |

* Mussentuchit Member.

|  |

Coniophis

Coniophis sp.

|  |

* Mussentuchit Member.

|  |

##### Turtles

Indeterminate baenid remains present in the Mussentuchit Member.

Turtles of the Cedar Mountain Formation

Genus  | Species  | Location  | Member  | Abundance  | Description  | Images

Glyptops

Glyptops sp.

|  |

* Yellow Cat Member
* Mussentuchit Member

|  |  | Peripherals

Naomichelys

Naomichelys sp.

|  |

* Mussentuchit Member.

|  |
gen. nov.[37] | sp. nov.  |  |

* Yellow Cat Member

|  |

#### Amphibians

Indeterminate anuran remains present in the Mussentuchit Member.

Amphibians of the Cedar Mountain Formation

Genus  | Species  | Location  | Member  | Abundance  | Description  | Images

Albanerpeton

Albanerpeton cf. A. nexuosus

|  |

* Mussentuchit Member

|  |  |  Albanerpeton

#### Fish

##### Bony fish

Indeterminate amiiform present in the Yellow Cat and Mussentuchit Members. Indeterminate neopterygian 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

Genus  | Species  | Location  | Member  | Abundance  | Description  | Images

Semionotus?

Semionotus? sp.

|  |

* Yellow Cat Member

|  |  |  Semionotus Ceratodus

Ceratodus

C. kempae[38]

|  |

* Yellow Cat Member

|  |

C. kirklandi

|  |

* Yellow Cat Member

|  |

C. molossus

|  |

* Mussentuchit Member

|  |

##### Cartilaginous fish

A new genus and species of orectolobid present in the Mussentuchit Member.

Cartilaginous Fishes of the Cedar Mountain Formation

Genus  | Species  | Location  | Member  | Abundance  | Description  | Images

Hybodus

Hybodus sp.

|  |

* Ruby Ranch Member
* Mussentuchit Member

|  |  |  Hybodus

Polyacrodus

Polyacrodus parvidens

|  |

* Mussentuchit Member

|  |

Lissodus

Lissodus sp.

|  |

* Mussentuchit Member

|  |

Ischyrhiza

Ischyrhiza sp.

|  |

* Mussentuchit Member

|  |

Pseudohypolophus

Pseudohypolophus sp.

|  |

* Mussentuchit Member

|  |

cf. Baibisha

New species

|  |

* Mussentuchit Member

|  |

Cretorectolobus

Indeterminate

|  |

* Mussentuchit Member

|  |

#### Mammaliaformes

New genus and species of pappotheriid present in the Mussentuchit Member. Indeterminate genus and species of picopsid present in the Mussentuchit Member.

Mammals of the Cedar Mountain Formation

Genus  | Species  | Location  | Member  | Abundance  | Description  | Images

Ameribaatar

Ameribaatar zofiae

|  |

* Mussentuchit

|  | An unspecified multituberculate.  |

Astroconodon

Astroconodon delicatus

|  |

* Mussentuchit

|  | A predatory triconodont with a debate on whether it was fully terrestrial or semiaquatic.

Bryceomys

Bryceomys intermedius

|  |

* Mussentuchit

|  | An unspecified multituberculate, probably a cimolodont.

Cedaromys

Cedaromys bestia

|  |

* Mussentuchit

|  |

Cedaromys parvus

|  |

* Mussentuchit

|  |

Cifelliodon[39]

Cifelliodon wahkermoosuch

|  |

* Yellow Cat Member

|  |

a haramiyidan mammaliaform

Corviconodon

Corviconodon utahensis

|  |

* Mussentuchit

|  |

Dakotadens[40]

Dakotadens pertritus

|  |

* Mussentuchit

|  |

Janumys

Janumys erebos

|  |

* Mussentuchit

|  |  |

Jugulator

Jugulator amplissimus

|  |

* Mussentuchit

|  |  |

Kokopellia

Kokopellia juddi

|  |

* Mussentuchit

|  |

Possible metatherian

Paracimexomys

Paracimexomys perplexus

|  |

* Mussentuchit

|  |

Paracimexomys robisoni

|  |

* Mussentuchit

|  |

Spalacolestes

Spalacolestes cretulablatta

|  |

* Mussentuchit

|  |

Spalacolestes inconcinnus

|  |

* Mussentuchit

|  |

Spalacotheridium

Spalacotheridium noblei

|  |

* Mussentuchit

|  |

## See also

* List of dinosaur-bearing rock formations

## References

1. ↑ Stokes 1944.
2. ↑ 2.0 2.1 Joeckel, Robert M.; Suarez, Celina A.; McLean, Noah M.; Möller, Andreas; Ludvigson, Gregory A.; Suarez, Marina B.; Kirkland, James I.; Andrew, Joseph et al. (February 2023). "Berriasian–Valanginian Geochronology and Carbon-Isotope Stratigraphy of the Yellow Cat Member, Cedar Mountain Formation, Eastern Utah, USA" (in en). Geosciences 13 (2): 32. doi:10.3390/geosciences13020032. ISSN 2076-3263. Bibcode: 2023Geosc..13...32J.
3. ↑ Kowallis et al. 1998.
4. ↑ 4.0 4.1 Stokes 1952.
5. ↑ Aubrey 1998.
6. ↑ Carpenter, K., 2014. Where the sea meets the land—the unresolved Dakota problem in Utah. Utah Geological Association Publication, 43, pp.357-372.
7. ↑ 7.0 7.1 Kirkland et al. 1997b.
8. ↑ Roca-Argemi & Nadon 2003.
9. ↑ DiCroce & Carpenter 2001, p. 186, "Geological and Taphonomic Setting".
10. ↑ Tidwell, Carpenter & Meyer 2001, p. 140, "Depositional Setting".
11. ↑ DiCroce & Carpenter 2001, p. 186, "Introduction".
12. ↑ DiCroce & Carpenter 2001, p. 185, "Introduction".
13. ↑ 13.0 13.1 13.2 DiCroce & Carpenter 2001, p. 187, "Geological and Taphonomic Setting".
14. ↑ Chure et al. 2010.
15. ↑ 15.0 15.1 15.2 Carpenter 2006.
16. ↑ 16.0 16.1 16.2 16.3 Cifelli et al. 1999.
17. ↑ Weishampel, Dodson & Osmólska 2004, p. 366, "Table 17.1".
18. ↑ 18.0 18.1 18.2 18.3 18.4 Carpenter et al. 2008.
19. ↑ Weishampel, Dodson & Osmólska 2004, p. 365, "Table 17.1".
20. ↑ 20.0 20.1 20.2 Kinneer, Carpenter & Shaw 2016.
21. ↑ Scheetz, Britt & Higgerson 2010.
22. ↑ Avrahami, Haviv M.; Makovicky, Peter J.; Tucker, Ryan T.; Zanno, Lindsay E. (2024-07-09). "A new semi-fossorial thescelosaurine dinosaur from the Cenomanian-age Mussentuchit Member of the Cedar Mountain Formation, Utah" (in en). The Anatomical Record 307 (12): 3717–3781. doi:10.1002/ar.25505. ISSN 1932-8486. PMID 38979930.
23. ↑ Weishampel, Dodson & Osmólska 2004, p. 417, "Table 19.1".
24. ↑ Weishampel, Dodson & Osmólska 2004, p. 414, "Table 19.1".
25. ↑ "EARLY CRETACEOUS DINOSAURS OF UTAH". https://geology.utah.gov/popular/general-geology/dinosaurs-fossils/age-of-dinosaurs/early-cretaceous-dinosaurs-of-utah/.
26. ↑ Weishampel, Dodson & Osmólska 2004, p. 267, "Table 13.1".
27. ↑ Royo-Torres et al. 2017.
28. ↑ Weishampel, Dodson & Osmólska 2004, p. 268, "Table 13.1".
29. ↑ Weishampel, Dodson & Osmólska 2004, p. 269, "Table 13.1".
30. ↑ Oswald, T.; Boisvert, C.; D'amore, D.; Curtice, B. (2025). ""Here be Dragons": Shed Teeth Potentially Indicate the Presence of Multiple Unidentified Allosauroids from the Early Cretaceous Cedar Mountain Formation of Utah". Journal of the Arizona-Nevada Academy of Science 50 (2): 55–129. doi:10.2181/036.050.0204.
31. ↑ Britt, Brooks B. Chure, Daniel, Currie, Philip, Holmes, Aaron, Theurer, Brandon, Scheetz, Rodney. (2021). A NEW DEINONYCHOSAURIAN THEROPOD FROM THE MID-CRETACEOUS (ALBIAN) MUSSENTUCHIT MEMBER OF THE CEDAR MOUNTAIN FORMATION IN DINOSAUR NATIONAL MONUMENT, NORTH EASTERN UTAH, USA. The Society of Vertebrate Paleontology.
32. ↑ Weishampel, Dodson & Osmólska 2004, p. 76, "Table 4.1".
33. ↑ Weishampel, Dodson & Osmólska 2004, p. 198, "Table 10.1".
34. ↑ Frewin, Jacob (2025-05-19). "NEW EVIDENCE OF A LARGE THEROPOD DINOSAUR FROM THE YELLOW CAT MEMBER (BARREMIAN, EARLY CRETACEOUS) OF THE CEDAR MOUNTAIN FORMATION, UTAH" (in English). The Geologic Society of America (GSA). https://gsa.confex.com/gsa/2025RM/webprogram/Paper410351.html#:~:text=A number of theropod taxa,to a relatively large theropod..
35. ↑ Curtice, Brian (2023). "THE DRAGONS OF CEDAR MOUNTAIN: SHED TEETH INDICATE THE PRESENCE OF ONE OR MORE LARGE ALLOSAUROIDS FROM THE YELLOW CAT MEMBER OF THE CEDAR MOUNTAIN FORMATION". https://vertpaleo.org/wp-content/uploads/2023/10/2023_SVP_Program-Final-10032023.pdf.
36. ↑ Britt, Brooks B.; Scheetz, Rodney D.; Brinkman, Donald B.; Eberth, David A. (2006-12-11). "A Barremian neochoristodere from the Cedar Mountain Formation, Utah, U.S.A." (in en). Journal of Vertebrate Paleontology 26 (4): 1005–1008. doi:10.1671/0272-4634(2006)26[1005:ABNFTC2.0.CO;2]. ISSN 0272-4634. http://www.tandfonline.com/doi/abs/10.1671/0272-4634(2006)26[1005:ABNFTC]2.0.CO;2.
37. ↑ Brinkman et al. 2015.
38. ↑ Frederickson & Cifelli 2017.
39. ↑ Huttenlocker et al. 2018.
40. ↑ Cifelli, Cohen & Davis 2016.

### Bibliography and further reading

* Aubrey, W.M. (1998). "A newly discovered, widespread fluvial facies and unconformity marking the Upper Jurassic/Lower Cretaceous boundary, Colorado Plateau". Modern Geology 22: 209–233.
* Brinkman, D.B.; Scheetz, R.D.; Jensen, C.; Britt, B.B.; Ortiz, N. (2015). "A basal baenid turtle provides insights into the aquatic fauna of the Early Cretaceous (Aptian) Cedar Mountain Formation of west-central Utah [abs.]". Journal of Vertebrate Paleontology, Abstracts and Program: 96.
* Carpenter, K. (2006). "Assessing dinosaur faunal turnover in the Cedar Mountain Formation (Lower Cretaceous) of eastern Utah, USA". Ninth International Symposium on Mesozoic Terrestrial Ecosystems and Biota, Abstract and Proceedings Volume. pp. 21–25. https://www.researchgate.net/publication/314880935. Retrieved 18 March 2021.
* Carpenter, Kenneth; Bartlett, Jeff; Bird, John; Barrick, Reese (2008). "Ankylosaurs from the Price River Quarries, Cedar Mountain Formation (Lower Cretaceous), east-central Utah". Journal of Vertebrate Paleontology 28 (4): 1089–1101. doi:10.1671/0272-4634-28.4.1089. Bibcode: 2008JVPal..28.1089C.
* Chure, Daniel; Britt, Brooks; Whitlock, John A.; Wilson, Jeffrey A. (2010). "First complete sauropod dinosaur skull from the Cretaceous of the Americas and the evolution of sauropod dentition". Naturwissenschaften 97 (4): 379–91. doi:10.1007/s00114-010-0650-6. PMID 20179896. Bibcode: 2010NW.....97..379C.
* Cifelli, Richard L.; Cohen, Joshua E.; Davis, Brian M. (2016). "New tribosphenic mammals from the Mussentuchit Local Fauna (Cedar Mountain Formation, Cenomanian), Utah, USA". Palaeontologia Polonica 67: 67–81. http://www.palaeontologia.pan.pl/PP67/Cifelli.pdf. Retrieved 2 July 2022.
* Cifelli, R. L.; Nydam, R. L.; Gardner, J. D.; Weil, A.; Eaton, J. G.; Kirkland, J. I.; Madsen, S. (1999). "Medial Cretaceous vertebrates from the Cedar Mountain Formation, Emery County, Utah: the Mussentuchit Local Fauna". Vertebrate Paleontology in Utah. Utah Geological Survey Miscellaneous Publication 99-1. Utah Geological Survey. pp. 219–242. ISBN 978-1557916341.
* DiCroce, T.; Carpenter, K. (2001). "New ornithopod from the Cedar Mountain Formation (Lower Cretaceous) of Eastern Utah". in Tanke, Darren. Mesozoic Vertebrate Life: New Research Inspired by the Paleontology of Philip J. Currie. Indiana University Press. pp. 166–180. ISBN 0-253-33907-3. https://archive.org/details/mesozoicvertebra0000unse/page/166.
* Frederickson, Joseph A.; Cifelli, Richard L. (January 2017). "New Cretaceous lungfishes (Dipnoi, Ceratodontidae) from western North America". Journal of Paleontology 91 (1): 146–161. doi:10.1017/jpa.2016.131. Bibcode: 2017JPal...91..146F.
* Huttenlocker, Adam K.; Grossnickle, David M.; Kirkland, James I.; Schultz, Julia A.; Luo, Zhe-Xi (June 2018). "Late-surviving stem mammal links the lowermost Cretaceous of North America and Gondwana". Nature 558 (7708): 108–112. doi:10.1038/s41586-018-0126-y. PMID 29795343. Bibcode: 2018Natur.558..108H.
* Joeckel, R. M.; Ludvigson, G. A.; Möller, A.; Hotton, C. L.; Suarez, M. B.; Suarez, C. A.; Sames, B.; Kirkland, J. I. et al. (2020). "Chronostratigraphy and terrestrial palaeoclimatology of Berriasian–Hauterivian strata of the Cedar Mountain Formation, Utah, USA". Geological Society, London, Special Publications 498 (1): 75–100. doi:10.1144/SP498-2018-133. Bibcode: 2020GSLSP.498...75J.
* Kinneer, Billy; Carpenter, Kenneth; Shaw, Allen (2016). "Redescription of Gastonia burgei (Dinosauria: Ankylosauria, Polacanthidae), and description of a new species". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 282 (1): 37–80. doi:10.1127/njgpa/2016/0605. Bibcode: 2016NJGPA.282...37K.
* Kirkland, J.I.; Britt, B.; Burge, D.; Carpenter, K.; Cifelli, R.; DeCourten, F.; Eaton, J.; Hasiotis, S. et al. (1997b). "Lower to Middle Cretaceous dinosaur faunas of the Central Colorado Plateau: a key to understanding 35 million years of tectonics, sedimentology, evolution, and biogeography". Brigham Young University Geology Studies 42: 69–103.
* Kirkland, J.I.; Madsen, S.K. (2007). "The Lower Cretaceous Cedar Mountain Formation, eastern Utah: the view up an always interesting learning curve". Fieldtrip Guidebook, Geological Society of America, Rocky Mountain Section.
* Kowallis, B. J.; Christiansen, E. H.; Deino, A. L.; Peterson, F.; Turner, C.E.; Kunk, M. J.; Obradovich, J. D. (1998). "The age of the Morrison Formation". Modern Geology 22: 235–260.
* Roca-Argemi, X.; Nadon, G. C. (2003). "The Buckhorn Conglomerate as the upper member of the Morrison Formation: new evidence from the type section, Cedar Mountain, Utah". Geological Society of America, Rocky Mountain Section, 55th Annual Meeting 14-1.
* Royo-Torres, R.; Upchurch, P.; Kirkland, J.I.; DeBlieux, D.D.; Foster, J.R.; Cobos, A.; Alcalá, L. (2017). "Descendants of the Jurassic turiasaurs from Iberia found refuge in the Early Cretaceous of western USA". Scientific Reports 7 (1): 14311. doi:10.1038/s41598-017-14677-2. PMID 29085006. Bibcode: 2017NatSR...714311R.
* Scheetz, R. A.; Britt, B. B.; Higgerson, J. (2010). "A large, tall-spined iguanodontid dinosaur from the Early Cretaceous (Early Albian) basal Cedar Mountain Formation of Utah". Journal of Vertebrate Paleontology 30 (Supplement 2): 158A. doi:10.1080/02724634.2010.10411819.
* Stokes, W. L. (1944). "Morrison and related deposits in the Colorado Plateau". Geological Society of America Bulletin 55: 951–992. doi:10.1130/GSAB-55-951.
* Stokes, W.L. (1952). "Lower Cretaceous in the Colorado Plateau". AAPG Bulletin 36 (9): 1766–1776. doi:10.1306/5CEADB93-16BB-11D7-8645000102C1865D. Bibcode: 1952BAAPG..36.1766S.
* Tidwell, V.; Carpenter, K.; Meyer, S. (2001). "New titanosauriform (Sauropoda) from the poison strip member of the cedar mountain formation (Lower Cretaceous), Utah". in Tanke, Darren. Mesozoic Vertebrate Life: New Research Inspired by the Paleontology of Philip J. Currie. Indiana University Press. pp. 166–180. ISBN 0-253-33907-3. https://archive.org/details/mesozoicvertebra0000unse/page/166.
* The Dinosauria (2nd ed.). Berkeley: University of California Press. 2004. ISBN 0-520-24209-2.

## Further reading

* Shapiro, R.S.; Fricke, H.C.; Fox, K. (2009). "Dinosaur-bearing oncoids from ephemeral lakes of the Lower Cretaceous Cedar Mountain Formation, Utah". PALAIOS 2 (4): 51–58. doi:10.2110/palo.2008.p08-013r. Bibcode: 2009Palai..24...51S.
* Sanders, F.; Manley, K.; Carpenter, K. (2001). "Gastroliths from the Lower Cretaceous sauropod Cedarosaurus weiskopfae". in Tanke, Darren. Mesozoic Vertebrate Life: New Research Inspired by the Paleontology of Philip J. Currie. Indiana University Press. pp. 166–180. ISBN 0-253-33907-3. https://archive.org/details/mesozoicvertebra0000unse/page/166.

## External links

* Dinosaurs of the Cedar Mountain Formation presented by the Utah Geological Survey
* Utah's Newly Recognized Dinosaur Record from the Early Cretaceous Cedar Mountain Formation

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