Judith River Formation

The Judith River Formation is a fossil

Fossil

Fossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous rock formations and sedimentary layers is known as the fossil record...

-bearing geologic formation

Geologic formation

A formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties...

 in Montana

Montana

Montana is a state in the Western United States. The western third of the state contains numerous mountain ranges; other 'island' ranges are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...

, and is part of the Judith River Group

Judith River Group

The Judith River Group is a group of geologic formations in western North America dating from the late Cretaceous and noted as a site for the extensive excavation of dinosaur fossils. The formation is named after the Judith River in Montana. The group is also called the Judith River Wedge...

. It dates to the upper Cretaceous

Cretaceous

The Cretaceous , Latin language for "chalky", 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 on the Jurassic period and is followed by the Paleogene period of the...

.
It is an historically important formation, explored by early American paleontologists such as Edward Drinker Cope

Edward Drinker Cope

Edward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope quickly distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of...

, who named several dinosaurs from scrappy remains found here on his 1876 expedition (such as Monoclonius

Monoclonius

Monoclonius was a ceratopsian dinosaur from the Judith River Formation of Late Cretaceous Montana and Canada. It is often confused with Centrosaurus, a similar genus of ceratopsian...

). Modern work has found nearly complete skeletons of the hadrosaurid Brachylophosaurus

Brachylophosaurus

Brachylophosaurus Brachylophosaurus Brachylophosaurus ( or ; meaning "short-crested lizard" (Greek brachy = short + lophos = crest + sauros = lizard, referring to its small crest) was a mid-sized member of the hadrosaurid family of dinosaurs...

.

Lithology

The Judith River Formation is composed of 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...

, siltstone

Siltstone

Siltstone is a sedimentary rock which has a composition intermediate in grain size between the coarser sandstones and the finer mudstones and shales.- Description :...

 and sandstone

Sandstone

Sandstone 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 color, but the most common colors are tan, brown, yellow,...

. Coal

Coal

Coal is a readily combustible black or brownish-black sedimentary rock normally occurring in rock strata in layers or veins called coal beds. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

 beds, bentonite

Bentonite

Bentonite is an absorbent aluminium phyllosilicate, generally impure clay consisting mostly of montmorillonite. There are a few types of bentonites and their names depend on the dominant elements, such as K, Na, Ca, and Al. As noted in several places in the geologic literature, there are some...

 and coquina

Coquina

Coquina is an incompletely consolidated sedimentary rock. Coquina was formed in association with marine reefs and is a variety of "coral rag", technically a subset of limestone.-Composition and distribution:...

s are also observed.

Amphibians

Amphibian Amphibian Amphibians , such as frogs, toads, salamanders, newts, and caecilians, are ectothermic animals that metamorphose from a juvenile water-breathing form, to an adult air-breathing form. Though amphibians typically have four limbs, the Caecilians are notable for being limbless. Unlike other land... s of the Judith River Formation
Taxa	Presence	Description	Images
Family: Discoglossidae Discoglossidae Discoglossidae is a family of primitive frogs, with the common name Disc-Tongued Frogs. They are native to Europe and North-West Africa.... 3 potential species		Disc-tongued frogs
Genus: Habrosaurus Habrosaurus Habrosaurus is an extinct genus of prehistoric amphibian.-See also:* Prehistoric amphibian* List of prehistoric amphibians... H. dilatus		A siren Siren (amphibian) Sirenidae, or sirens, are a family of aquatic salamanders. Family members have very small fore limbs, and lack hind limbs altogether. In one species, the skeleton in their forelimbs is made of only cartilage. Sirens are found only in the south-eastern United States, and northern Mexico... .
Genus: Lisserpeton Lisserpeton Lisserpeton is an extinct genus of prehistoric amphibian.-See also:* Prehistoric amphibian* List of prehistoric amphibians... L. bairdi		A scapherpetonid salamander Salamander Salamander is a common name of approximately 500 species of amphibians. They are typically characterized by their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant species are grouped together as the Urodela... .
Genus: Opisthotriton Opisthotriton Opisthotriton is an extinct genus of prehistoric amphibian.-See also:* Prehistoric amphibian* List of prehistoric amphibians... O. kayi		A possible lungless salamander Lungless salamander The Plethodontidae, or Lungless salamanders, are a family of salamanders. Most species are native to the western hemisphere, from British Columbia to Brazil, although a few species are found in Sardinia and Europe south of the Alps... .
Family: Pelobatidae Pelobatidae The European spadefoot toads are a family of frogs, the Pelobatidae, with only one extant genus Pelobates, containing four species. They are native to Europe, the Mediterranean, northwestern Africa and western Asia.... ?	Hip bones, possibly representing a North American member of the European spadefoot toad European spadefoot toad The European spadefoot toads are a family of frogs, the Pelobatidae, with only one genus Pelobates, containing four species. They are native to Europe, the Mediterranean, northwestern Africa and western Asia....  family.
Genus: Prodesmodon Prodesmodon Prodesmodon is an extinct genus of prehistoric amphibian.-See also:* Prehistoric amphibian* List of prehistoric amphibians... P. copei		A lungless salamander Lungless salamander The Plethodontidae, or Lungless salamanders, are a family of salamanders. Most species are native to the western hemisphere, from British Columbia to Brazil, although a few species are found in Sardinia and Europe south of the Alps... .
Genus: Scapherpeton Scapherpeton Scapherpeton is an extinct genus of prehistoric amphibian.-See also:* Prehistoric amphibian* List of prehistoric amphibians... S. tectum		A scapherpetonid salamander.

Ankylosaurian dinosaurs

Ankylosaurs of the Judith River Formation
Taxa	Presence	Description	Images
Genus: Edmontonia Edmontonia Edmontonia was an armoured dinosaur, a part of the nodosaur family from the Late Cretaceous Period. It is named after the Edmonton Formation , the unit of rock it was found in.-Description:... E. longiceps		Isolated tooth possibly belonging to Edmontonia.
Genus: Paleoscincus P. costatus		Isolated tooth that formed the basis of the dubious genus Paleoscincus.

Bony fish

bony fish Osteichthyes Osteichthyes , also called bony fish, are a taxonomic group of fish that includes the ray-finned fish and lobe-finned fish . The split between these two classes occurred about 450 million years ago....  of the Judith River Formation
Taxa	Presence	Description	Images
Genus: Belonostomus Belonostomus Belonostomus or Diphyodus is a genus of prehistoric fish that was described by Louis Agassiz in 1844. Fossils range from 99.6mya to 65.5mya Belonostomus (meaning "big long mouth") or Diphyodus (meaning "double tooth") is a genus of prehistoric fish that was described by Louis Agassiz in 1844.... B. longirostris		An aspidorhynchiform Aspidorhynchiformes Aspidorhynchiformes is an extinct order of prehistoric fish that was described by Bleeker in 1859.Aspidorhynchiformes has one family, which is divided into two genuses:... .
Genus: Kindleia K. fragosa		A bowfin Bowfin Bowfins are an order of primitive ray-finned fish. Only one species, the bowfin Amia calva, family Amiidae, survives today, although additional species in six families are known from Jurassic, Cretaceous, and Eocene fossils... .
Genus: Lepisosteus Lepisosteus Lepisosteus is a genus of gars in the family Lepisosteidae.There are four species:* Lepisosteus oculatus Spotted gar.* Lepisosteus osseus Longnose gar.* Lepisosteus platostomus Shortnose gar.* Lepisosteus platyrhynchus, Florida gar.... L. occidentalis		A gar Gar In American English the name gar is strictly applied to members of the Lepisosteidae, a family including seven living species of fish in two genera that inhabit fresh, brackish, and occasionally marine, waters of eastern North America, Central America, and the Caribbean islands.-Etymology:In... .
Genus: ?Paralbula Paralbula is an extinct genus of prehistoric bony fish.... ?P. sp.		A bonefish Bonefishes The bonefishes are a family of ray-finned fish that are popular as game fish in Florida, select locations in the South Pacific, and the Bahamas where two bonefish are on their 10 cent coin, and elsewhere. The family is small, with eight species in two genera.Presently the bonefishes are in their... .

Cartilaginous fish

Cartilaginous fish Chondrichthyes Chondrichthyes or cartilaginous fishes are jawed fish with paired fins, paired nares, scales, two-chambered hearts, and skeletons made of cartilage rather than bone...  of the Judith River Formation
Taxa	Presence	Description	Images
Genus: Myledaphus M. bipartitus		A stingray Stingray The stingrays are a family—Dasyatidae—of rays, cartilaginous fishes related to sharks. They are common in coastal tropical and subtropical marine waters throughout the world, but the family also includes species found in warmer temperate oceans such as Dasyatis thetidis, and species entirely... .

Ceratopsian dinosaurs

Ceratopsia Ceratopsia Ceratopsia or Ceratopia is a group of herbivorous, beaked dinosaurs which thrived in what are now North America and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassic. Early members such as Psittacosaurus were small and bipedal... ns of the Judith River Formation
Taxa	Presence	Description	Images
Genus: Albertaceratops Albertaceratops Albertaceratops was a genus of centrosaurine horned dinosaur from the middle Campanian-age Upper Cretaceous Oldman Formation of Alberta, Canada, and Judith River Formation of Montana, USA.... Albertaceratops nesmoi
Genus: Avaceratops Avaceratops Avaceratops is a genus of small ceratopsian dinosaur which lived during the late Campanian during the Late Cretaceous Period in what are now the Northwest United States.-Discoveries and species:... Avaceratops lammersi
Genus: Ceratops Ceratops Ceratops was a ceratopsian dinosaur which lived during the Late Cretaceous. Its fossils have been found in Montana and Alberta, Canada. Although poorly known, Ceratops is important in the history of dinosaurs, since it is the type species upon which both Ceratopsia and Ceratopsidae are based... C. montanus
Genus: Monoclonius Monoclonius Monoclonius was a ceratopsian dinosaur from the Judith River Formation of Late Cretaceous Montana and Canada. It is often confused with Centrosaurus, a similar genus of ceratopsian... Monoclonius crassus

Choristoderes

Choristoderes Choristodera Choristodera is an order of semi-aquatic diapsid reptiles which ranged from the Middle Jurassic, or possibly Late Triassic, to at least the early Miocene. Choristoderes have been found in North America, Asia, and Europe. The most common fossils are typically found from the Late Cretaceous to the... s of the Judith River Formation
Taxa	Presence	Description	Images
Genus: Champsosaurus Champsosaurus Champsosaurus is an extinct genus of diapsid reptile belonging to the order Choristodera. It grew to about 1.50 m long.Champsosaurus resembled a gharial and, like gharials, hunted in rivers and swamps, catching fish with its long, tooth-lined jaws... C. sp.

Crocodilians

Crocodilia Crocodilia Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria... ns of the Judith River Formation
Taxa	Presence	Description	Images
Genus: Brachychampsa Brachychampsa Brachychampsa is an extinct genus of alligatoroid. Specimens have been found from New Mexico, Colorado, Wyoming, Montana, North and South Dakota, New Jersey, and Saskatchewan. One specimen has been found from the Darbasa Formation of Kazakhstan, although the species status is indeterminant for the... B. montana		An alligatorid.
Genus: Leidyosuchus Leidyosuchus Leidyosuchus is an extinct genus of alligatorid from the Late Cretaceous of Alberta. It was named in 1907 by Lawrence Lambe, and the type species is L. canadensis. It is known from a number of specimens from the middle Campanian age Dinosaur Park Formation... L. canadensis		An alligatorid.

Lizards

Lizard Lizard Lizards are a very large and widespread group of squamate reptiles, with nearly 5,000 species, ranging across all continents except Antarctica as well as most oceanic island chains... s of the Judith River Formation
Taxa	Presence	Description	Images
Genus: Chamops C. segnis		A whiptail Teiidae Teiidae is a family of lizards native to the Americas, generally known as whiptails. The group includes the parthenogenic genera Cnemidophorus and Aspidoscelis, and the non-parthenogenic Tupinambis.- Morphology :... .
Genus: Exostinus E. lancensis		A knob-scaled lizard Xenosauridae The Xenosauridae is a family of lizards native to Central America and China. Also known as knob-scaled lizards, they have rounded, bumpy scales and osteoderms. Most species prefer moist or semi-aquatic habitats, although they are widespread within their native regions, with some even inhabiting... .
Genus: Leptochamops L. denticulatus		A whiptail.
Genus: Paraderma P. bogerti		A parasaniwid.
Genus: Parasaniwa P. wyomingensis		A parasaniwid.
Genus: Peltosaurus Peltosaurus Peltosaurus is an extinct genus of anguid lizard from North America that lived from the Middle Eocene to the Early Miocene. It was named in 1873 by Edward Drinker Cope... P. piger		An anguid Anguidae The Anguidae is a large and diverse family of lizards native to the northern hemisphere. The group includes the slowworms, glass lizards, and alligator lizards, among others. Their closest living relatives are the helodermatid lizards... .

Ornithopod dinosaurs

Ornithopod Ornithopod Ornithopods are a group of bird-hipped dinosaurs that started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American landscape... s of the Judith River Formation
Taxa	Presence	Description	Images
Genus: Brachylophosaurus Brachylophosaurus Brachylophosaurus Brachylophosaurus Brachylophosaurus ( or ; meaning "short-crested lizard" (Greek brachy = short + lophos = crest + sauros = lizard, referring to its small crest) was a mid-sized member of the hadrosaurid family of dinosaurs... B. canadensis
Family: Hadrosauridae ?"Kritosaurus Kritosaurus Kritosaurus is an incompletely known but historically important genus of hadrosaurid dinosaur... " breviceps
Subfamily: Lambeosaurinae ?Lambeosaurus paucidens
Genus: Thescelosaurus Thescelosaurus Thescelosaurus was a genus of small ornithopod dinosaur that appeared at the very end of the Late Cretaceous period in North America. It was a member of the last dinosaurian fauna before the Cretaceous-Tertiary extinction event around 65.5 million years ago... cf. T. neglectus		Isolated teeth possibly belonging to Thescelosaurus.

Pachycephalosaurian dinosaurs

Pachycephalosaurs of the Judith River Formation
Taxa	Presence	Description	Images
Genus: ?Stegoceras Stegoceras Stegoceras was a genus of plant-eating ornithischian pachycephalosaurid dinosaur that lived in what is now North America during the Late Cretaceous period. It had an estimated length of up to... ?S. validum		Isolated teeth possibly belonging to Stegoceras or a similar dinosaur.

Theropod dinosaurs

Theropods of the Judith River Formation
Taxa	Presence	Description	Images
Genus: Aublysodon Aublysodon Aublysodon is a carnivorous dinosaur taxon named by Joseph Leidy in 1868. It is a dubious name, since the type specimen consists only of an isolated premaxillary tooth, found in strata from the Late Cretaceous Period. This specimen is now lost. Identical teeth have been found in many US states,... A. mirandus		Isolated tyrannosaur teeth assigned to the dubious genus Aublysodon.
Genus: Deinodon Deinodon Deinodon is a name assigned to tyrannosaurid teeth of the Late Cretaceous of Montana by paleontologist Joseph Leidy in 1856... D. horridus		Isolated tyrannosaur teeth that formed the basis of the dubious genus Deinodon.
Genus: Dromaeosaurus Dromaeosaurus Dromaeosaurus was a genus of theropod dinosaur which lived during the Late Cretaceous period , sometime between 76.5 and 74.8 million years ago, in the western United States and Alberta, Canada... D. albertensis
Genus: Paronychodon Paronychodon Paronychodon was a theropod dinosaur genus. It lived during the Late Cretaceous in what is now Montana. This genus is a tooth taxon.... P. lacustris
Subamily: Tyrannosaurinae Unnamed tyrannosaur
Genus: Troodon Troodon Troodon is a genus of relatively small, bird-like dinosaur from the Late Cretaceous period . Discovered in 1855, it was among the first dinosaurs found in North America.... T. formosus

Turtles

Turtle Turtle Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield... s of the Judith River Formation
Taxa	Presence	Description	Images
Genus: Basilemys B. sp.		A Mesoamerican river turtle.

Relationship with other units

The Judith River Formation conformably overlies the Claggett Formation and Pakowki Formation. It is overlain by the Bearpaw Formation

Bearpaw Formation

The Bearpaw Formation, also called the Bearpaw Shale, is a sedimentary rock formation found in northwestern North America. It is exposed in the U.S. state of Montana, as well as the Canadian provinces of Alberta and Saskatchewan, east of the Rocky Mountains...

. It is equivalent to the Belly River Formation in the southern Canadian Rockies

Canadian Rockies

The Canadian Rockies comprise the Canadian segment of the North American Rocky Mountains range. They are the eastern part of the Canadian Cordillera, extending from the Interior Plains of Alberta to the Rocky Mountain Trench of British Columbia. The southern end borders Idaho and Montana of the USA...

 foothills, the Lea Park Formation

Lea Park Formation

The Lea Park Formation is a stratigraphical unit of Late Cretaceous age in the Western Canadian Sedimentary Basin.It takes the name from the settlement of Lea Park, Alberta, located north-west of Lloydminster on the banks of the North Saskatchewan River. It was first defined in an outcrop on the...

 in central Alberta

Central Alberta

Central Alberta is a region located in the Canadian province of Alberta.Central Alberta is the most densely populated rural area in the province...

 and the Wapiti Formation

Wapiti Formation

The Wapiti Formation is a geological formation in Alberta, Canada whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.-References:...

 in the northwestern plains. To the east, it correlates with the sum of Oldman Formation

Oldman Formation

The Oldman Formation is the middle member of the Judith River Group, a major geologic unit in southern Alberta. The formation is widely recognized as bearing a great number of well preserved dinosaur skeletons, as well as other fossils....

 and Foremost Formation

Foremost Formation

The Foremost Formation is a geological formation in Alberta, Canada whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.-References:...

.

Sub-divisions

The Birch Lake Member and Ribstone Creek Member are sandstone units recognized inside the Judith River Formation. Other informal subdivisions include the Brosseau Member and Victoria Member, which are considered obsolete due to their inconsistent lateral distribution.