Hell Creek Formation - AbsoluteAstronomy.com

The Hell Creek Formation is an intensely-studied division of Upper Cretaceous to lower Paleocene

Paleocene

The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...

rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana

Jordan, Montana

Jordan is a town in and the county seat of Garfield County, Montana, United States. The population was 364 at the 2000 census.-History:Originally settled in 1896, Jordan received a post office on July 11, 1899...

. The formation spans about 1.3 million years, terminating at the K-Pg boundary, dated to 65.5 million years ago.

The Hell Creek Formation occurs in Montana

Montana

Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "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 portions of North Dakota

North Dakota

North Dakota is a state located in the Midwestern region of the United States of America, along the Canadian border. The state is bordered by Canada to the north, Minnesota to the east, South Dakota to the south and Montana to the west. North Dakota is the 19th-largest state by area in the U.S....

, South Dakota

South Dakota

South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...

, and Wyoming

Wyoming

Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...

. In Montana, the Hell Creek Formation overlies the Fox Hills Formation

Fox Hills Formation

The Fox Hills Formation is a Cretaceous geologic formation in the northwestern Great Plains of North America. It is present from Alberta on the north to Colorado in the south....

and is the uppermost formation of the Cretaceous period. "Pompey's Pillar" at the Pompeys Pillar National Monument

Pompeys Pillar National Monument

Pompeys Pillar National Monument is a rock formation located in south central Montana, United States. Designated a National Monument on January 17, 2001, and managed by the U.S. Bureau of Land Management, it consists of only , making it one of the smallest National Monuments in the U.S...

is a small isolated section of the Hell Creek Formation.

It is a series of fresh and brackish-water clays, 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...

s, and sandstones deposited during the Maastrichtian

Maastrichtian

The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...

, the last part of the Cretaceous period, by fluvial

Fluvial

Fluvial is used in geography and Earth science to refer to the processes associated with rivers and streams and the deposits and landforms created by them...

activity in fluctuating river channels and deltas and very occasional peaty swamp deposits along the low-lying eastern continental margin

Continental margin

The continental margin is the zone of the ocean floor that separates the thin oceanic crust from thick continental crust. Continental margins constitute about 28% of the oceanic area....

fronting the late Cretaceous Western Interior Seaway

Western Interior Seaway

The 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 climate was mild, and the presence of crocodilians suggests a sub-tropical climate, with no prolonged annual cold. The famous iridium

Iridium

Iridium is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second-densest element and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C...

-enriched K–Pg boundary, which separates the Cretaceous from the Cenozoic

Cenozoic

The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...

, occurs as a discontinuous but distinct thin marker bedding within the Formation, near its uppermost strata.

The world's largest collection of Hell Creek fossils is housed and exhibited at the Museum of the Rockies

Museum of the Rockies

The Museum of the Rockies, is located in Bozeman, Montana. The museum, originally affiliated with Montana State University in Bozeman, and now, also the Smithsonian Institution, is known for its paleontological collections, although these are not its sole focus...

, in Bozeman, Montana

Bozeman, Montana

Bozeman is a city in and the county seat of Gallatin County, Montana, United States, in the southwestern part of the state. The 2010 census put Bozeman's population at 37,280 making it the fourth largest city in the state. It is the principal city of the Bozeman micropolitan area, which consists...

. The specimens displayed are the result of the museum's Hell Creek Project, a joint effort between the museum, Montana State University, the University of California, Berkeley

University of California, Berkeley

The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...

, the University of North Dakota

University of North Dakota

The University of North Dakota is a public university in Grand Forks, North Dakota, USA. Established by the Dakota Territorial Assembly in 1883, six years before the establishment of the state of North Dakota, UND is the oldest and largest university in the state and enrolls over 14,000 students. ...

and the University of North Carolina

University of North Carolina

Chartered in 1789, the University of North Carolina was one of the first public universities in the United States and the only one to graduate students in the eighteenth century...

which began in 1998. The formation is also a popular location for commercial excavations.

Paleobiota

The formation has produced impressive assemblages of invertebrates, plants, mammals, fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

, reptiles, and amphibians. Notable dinosaur finds include Tyrannosaurus
Tyrannosaurus
Tyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other...

and Triceratops
Triceratops
Triceratops is a genus of herbivorous ceratopsid dinosaur which lived during the late Maastrichtian stage of the Late Cretaceous Period, around 68 to 65 million years ago in what is now North America. It was one of the last dinosaur genera to appear before the great Cretaceous–Paleogene...

. The most complete Hadrosaurid

Hadrosaurid

Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...

dinosaur ever found was retrieved in 2000 from the Hell Creek Formation and widely publicised in a National Geographic documentary aired in December 2007. A few bird

Bird

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

, mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

, and pterosaur

Pterosaur

Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...

fossils have also been found. Teeth of shark

Shark

Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s and rays

Batoidea

Batoidea is a superorder of cartilaginous fish commonly known as rays and skates, containing more than 500 described species in thirteen families...

are sometimes found in the riverine Hell Creek Formation, suggesting that some of these taxa were tolerant of fresh water then as now.

Amphibians

Amphibian Amphibian Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods... s reported from the Hell Creek Formation Hell Creek Formation The Hell Creek Formation is an intensely-studied division of Upper Cretaceous to lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana...
Genus	Species	State	Stratigraphic position	Material	Notes	Images
Barbourula Barbourula Barbourula is a genus of amphibian commonly referred to as jungle toads. They are small toads of the fire-bellied toad family, Bombinatoridae, found in the Philippines and Borneo.- Species :...	Indeterminate	Montana
Eopelobates Eopelobates Eopelobates is an extinct genus of frog.-Reference:*Spinar, Z.V. & Rocek, Z. 1984. . Amphibia-Reptilia 5: 87-95....	Indeterminate	Montana
Habrosaurus Habrosaurus Habrosaurus is an extinct genus of prehistoric salamander, and the oldest known member of the family Sirenidae. Two species are known, Habrosaurus prodilatus from the Campanian of Alberta, and Habrosaurus dilatus from the late Maastrichtian and Paleocene of western North America...	H. dilatus	Montana
Lisserpeton Lisserpeton Lisserpeton is an extinct genus of prehistoric amphibian.-See also:* Prehistoric amphibian* List of prehistoric amphibians...	L. bairdi	Montana
Opisthotriton Opisthotriton Opisthotriton is an extinct genus of prehistoric salamanders that lived in North America between at least the Upper Cretaceous and the Paleocene....	O. kayi	Montana
Proamphiuma Proamphiuma Proamphiuma is an extinct genus of prehistoric amphibian.-See also:* Prehistoric amphibian* List of prehistoric amphibians...	P. cretacica	Montana
Prodesmodon Prodesmodon Prodesmodon is an extinct genus of prehistoric amphibian.-See also:* Prehistoric amphibian* List of prehistoric amphibians...	P. copei	Montana
Scapherpeton Scapherpeton Scapherpeton is an extinct genus of prehistoric amphibian.-See also:* Prehistoric amphibian* List of prehistoric amphibians...	S. tectum	Montana
Scotiophryne	S. pustulosa	Montana

Bony fishes

Bony fishes reported from the Hell Creek Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Acipenser Acipenser Acipenser is genus of sturgeons. With about 19 species, many of which are threatened, it is the largest genus in the order Acipenseriformes.-Species:Acipenser baerii J. F. Brandt, 1869*Acipenser baerii baerii J. F...	A. eruciferus	Montana
Amia Amia Amia, AMIA, or AMiA can refer to:American Medical Informatics AssociationBowfin, a fish genusAnglican Mission in the AmericasAsociación Mutual Israelita Argentina, a Jewish community center located in Buenos Aires, Argentina...	A. fragosa	Montana
Belonostomus Belonostomus Belonostomus or Diphyodus is a genus of prehistoric fish that was described by Louis Agassiz in 1844. Fossils range from to Belonostomus (meaning "big long mouth") or Diphyodus (meaning "double tooth") is a genus of prehistoric fish that was described by Louis Agassiz in 1844. Fossils range...	B. longirostris	Montana
Coriops Coriops Coriops is a genus of prehistoric fish. Its fossils are found in Campanian , Maastrichtian , and possibly Paleocene age deposits...	C. amnicolus	Montana
Lepisosteus Lepisosteus Lepisosteus is a genus of gars in the family Lepisosteidae.There are four species:* Lepisosteus oculatus Winchell, 1864 * Lepisosteus osseus...	L. occidentalis	Montana
Palaeolabrus	P. montanensis	Montana
Paleopsephurus Paleopsephurus Paleopsephurus is an extinct genus of paddlefish in the Acipenseriformes family Polyodontidae. At present the genus contains the single species Paleopsephurus wilsoni....	P. wilsoni	Montana
Paralbula Paralbula Paralbula is an extinct genus of prehistoric bony fish.-See also:* Prehistoric fish* List of prehistoric bony fish...	P. casei	Montana
Platacodon	P. nanus	Montana
Protamia	Indeterminate	Montana
Protoscaphirhynchus Protoscaphirhynchus Protoscaphirhynchus squamosus is an extinct sturgeon that lived from the Turonian to the Campanian.-See also:* Prehistoric fish* List of prehistoric bony fish...	P. squamosus	Montana

Cartilaginous fishes

Cartilaginous fishes reported from the Hell Creek Formation
Genus	Species	Location	Stratigraphic position	Material	Notes
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...	I. avonicola	Montana
Lonchidion	L. selachos	Montana
Myledaphus	M. bipartitus	Montana

Ankylosaurs

Ankylosaurs reported from the Hell Creek Formation
Genus	Species	State	Stratigraphic position	Material	Notes	Images
Ankylosaurus Ankylosaurus Ankylosaurus is a genus of ankylosaurid dinosaur, containing one species, A. magniventris...	Ankylosaurus magniventris	Montana			An ankylosaur. Also found in the Lance Lance Formation The Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas... and Scollard Formation Scollard Formation -References:* Ryan, M. J., and Russell, A. P., 2001. Dinosaurs of Alberta : In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, pp. 279-297.... s.
?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:...	Unnamed and indeterminate remains	Montana North Dakota South Dakota			An ankylosaur.

Ceratopsians

Ceratopsians reported from the Hell Creek Formation
Genus	Species	State	Stratigraphic position	Material	Notes	Images
Leptoceratops Leptoceratops Leptoceratops , was a primitive ceratopsian dinosaur genus from the Late Cretaceous Period of what is now Western North America, at the same time as its giant...	Indeterminate	Montana			A small primitive-looking ceratopsia Ceratopsia Ceratopsia or Ceratopia is a group of herbivorous, beaked dinosaurs which thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassic. The earliest known ceratopsian, Yinlong downsi, lived between 161.2 and 155.7... n.
?Tatankaceratops Tatankaceratops Tatankaceratops is a controversial genus of herbivorous ceratopsian dinosaur. It is a small chasmosaurine ceratopsian which lived during the Late Cretaceous period in what is now South Dakota. It is known from a single partial skull which was collected from the Hell Creek Formation, dating to...	?T. sacrisonorum	South Dakota			A ceratopsian possibly synonymous with Triceratops
?Torosaurus Torosaurus Torosaurus is a genus of ceratopsid dinosaur that lived during the late Cretaceous period , between 70 and 65 million years ago. It possessed one of the largest skulls of any known land animal. The frilled skull reached in length...	?T. latus	Montana North Dakota South Dakota			A ceratopsian possibly synonymous with Triceratops. Also found in the Frenchman Frenchman Formation The Frenchman Formation is a division of Upper Cretaceous rocks found in Saskatchewan, Canada. More accurately described as Late Maastrichtian, these rocks contain the youngest of dinosaur genera, much like the Hell Creek Formation in the United States.... and Lance Formation Lance Formation The Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas... s.
Triceratops Triceratops Triceratops is a genus of herbivorous ceratopsid dinosaur which lived during the late Maastrichtian stage of the Late Cretaceous Period, around 68 to 65 million years ago in what is now North America. It was one of the last dinosaur genera to appear before the great Cretaceous–Paleogene...	T. horridus	Montana North Dakota South Dakota		Very common.	A ceratopsian, very common. Also found in the Evanston Evanston Formation The Evanston Formation is a geological formation in Wyoming whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.-Vertebrate paleofauna:* Alamosaurus sp.* Triceratops horridus... , Frenchman Frenchman Formation The Frenchman Formation is a division of Upper Cretaceous rocks found in Saskatchewan, Canada. More accurately described as Late Maastrichtian, these rocks contain the youngest of dinosaur genera, much like the Hell Creek Formation in the United States.... , Kirtland Kirtland Formation The Kirtland Formation is a sedimentary geological formation. It is the product of alluvial muds and overbank sand deposits from the many channels draining the coastal plain that existed on the inland seashore of North America, in the late Cretaceous period. It overlies the Fruitland Formation... , Lance Lance Formation The Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas... , Laramie Laramie Formation The Laramie Formation is a geologic formation of Cretaceous age, named by Clarence King in 1876 for exposures in northeastern Colorado, in the United States.... , and Scollard Formation Scollard Formation -References:* Ryan, M. J., and Russell, A. P., 2001. Dinosaurs of Alberta : In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, pp. 279-297.... s.
	T. maximus	Montana		"[Eight] vertebrae, [two] ribs."	Later found to be indeterminate ceratopsid remains.
	T. prorsus	Montana		Very common.	Also found in the Frenchman Frenchman Formation The Frenchman Formation is a division of Upper Cretaceous rocks found in Saskatchewan, Canada. More accurately described as Late Maastrichtian, these rocks contain the youngest of dinosaur genera, much like the Hell Creek Formation in the United States.... and Lance Formation Lance Formation The Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas... s.
	T. serratus	Montana			Later referred to T. horridus.

Ornithopods

Ornithopods reported from the Hell Creek Formation
Genus	Species	State	Stratigraphic position	Material	Notes	Images
Anatosaurus	A. annectens				Reclassified as Edmontosaurus annectens
Anatotitan Anatotitan Anatotitan is a genus of flat-headed or hadrosaurine hadrosaurid ornithopod dinosaur from the very end of the Cretaceous Period, in what is now North America...	A. copei				Junior synonym of Edmontosaurus annectens.
Bugenasaura	B. garbanii				Junior synonym of 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... garbanii
Bugenasaura	B. infernalis				Reclassified as 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...
Diclonius Diclonius Diclonius is a genus of dinosaur from the Late Cretaceous. It was a hadrosaur based solely on teeth. Its fossils have been found in North America. The name is in reference to the method of tooth replacement, in which newly erupting replacement teeth could be in functional use at the same time as...	D. mirabilis				Junior synonym of Trachodon mirabilis, remains actually belong to E. annectens
Edmontosaurus Edmontosaurus Edmontosaurus is a genus of crestless hadrosaurid dinosaur. It contains two species: Edmontosaurus regalis and Edmontosaurus annectens. Fossils of E. regalis have been found in rocks of western North America that date from the late Campanian stage of the Cretaceous Period 73 million years ago,...	E. annectens	Montana South Dakota		Very common.	A hadrosaur. Also found in the Denver Denver Formation The Denver Formation is a geological formation in Colorado whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.-Ornithischians:-Saurischians:-References:... , Frenchman Frenchman Formation The Frenchman Formation is a division of Upper Cretaceous rocks found in Saskatchewan, Canada. More accurately described as Late Maastrichtian, these rocks contain the youngest of dinosaur genera, much like the Hell Creek Formation in the United States.... , Lance Lance Formation The Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas... , Laramie Laramie Formation The Laramie Formation is a geologic formation of Cretaceous age, named by Clarence King in 1876 for exposures in northeastern Colorado, in the United States.... , and Scollard Formation Scollard Formation -References:* Ryan, M. J., and Russell, A. P., 2001. Dinosaurs of Alberta : In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, pp. 279-297.... s.
	E. regalis				Common hadrosaur remains are often referred to this genus, but all fossils diagnosable as E. regalis specifically are only known from older deposits.
Parasaurolophus Parasaurolophus Parasaurolophus is a genus of ornithopod dinosaur that lived in what is now North America during the Late Cretaceous Period, about 76.5–73 million years ago. It was an herbivore that walked both as a biped and a quadruped. Three species are recognized: P. walkeri , P. tubicen, and the...	P. walkeri	Montana			A possible lambeosaurine hadrosaur potentially similar to the Campanian Campanian The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ... genus Parasaurolophus Parasaurolophus Parasaurolophus is a genus of ornithopod dinosaur that lived in what is now North America during the Late Cretaceous Period, about 76.5–73 million years ago. It was an herbivore that walked both as a biped and a quadruped. Three species are recognized: P. walkeri , P. tubicen, and the...
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...	?T. garbanii	Montana South Dakota
	T. infernalis				Nomen dubium
	T. neglectus	South Dakota			A small ornithopod Ornithopod Ornithopods or members of the clade Ornithopoda are a group of ornithischian 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... . Also found in the Frenchman Frenchman Formation The Frenchman Formation is a division of Upper Cretaceous rocks found in Saskatchewan, Canada. More accurately described as Late Maastrichtian, these rocks contain the youngest of dinosaur genera, much like the Hell Creek Formation in the United States.... , Lance Lance Formation The Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas... , Laramie Laramie Formation The Laramie Formation is a geologic formation of Cretaceous age, named by Clarence King in 1876 for exposures in northeastern Colorado, in the United States.... , and Scollard Formation Scollard Formation -References:* Ryan, M. J., and Russell, A. P., 2001. Dinosaurs of Alberta : In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, pp. 279-297.... s. Sometimes misspelled as T. garbani.
	Indeterminate	North Dakota
Trachodon Trachodon Trachodon is a dubious genus of hadrosaurid dinosaur based on teeth from the Campanian-age Upper Cretaceous Judith River Formation of Montana, U.S.A...	T. mirabilis				Misclassified, remains now referred to Edmontosaurus annectens

Pachycephalosaurs

An undescribed Pachycephalosaur is present in North Dakota.

Pachycephalosaurs reported from the Hell Creek Formation
Genus	Species	State	Stratigraphic position	Material	Notes	Images
?Dracorex Dracorex Dracorex is a dinosaur genus of the family Pachycephalosauridae, from the Late Cretaceous of North America.The type species is Dracorex hogwartsia, meaning "dragon king of Hogwarts". It is known from one nearly complete skull , as well as four cervical vertebrae including the atlas, third, ninth...	?D. hogwartsia	South Dakota	Middle		A pachycephalosaur, possibly synonymous with Pachycephalosaurus Pachycephalosaurus Pachycephalosaurus is a genus of pachycephalosaurid dinosaur. It lived during the Late Cretaceous Period of what is now North America. Remains have been excavated in Montana, South Dakota, and Wyoming. It was an herbivorous or omnivorous creature which is only known from a single skull and a few... .
Pachycephalosaurus Pachycephalosaurus Pachycephalosaurus is a genus of pachycephalosaurid dinosaur. It lived during the Late Cretaceous Period of what is now North America. Remains have been excavated in Montana, South Dakota, and Wyoming. It was an herbivorous or omnivorous creature which is only known from a single skull and a few...	P. wyomingensis	Montana South Dakota			A pachycephalosaur. Also found in the Judith River Judith River Formation The Judith River Formation is a fossil-bearing geologic formation in Montana, and is part of the Judith River Group. It dates to the upper Cretaceous, between 80 and 75 million years ago, corresponding to the "Judithian" land vertebrate age... and Lance Formation Lance Formation The Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas... s.
Sphaerotholus Sphaerotholus Sphaerotholus is a genus of pachycephalosaurid dinosaur from the Upper Cretaceous of the western United States. To date, two species have been described: the type species, S. goodwini, from the Den-na-zin Member of the Kirtland Formation of San Juan County, New Mexico, and a second species, S...	S. buchholtzae	Montana		"Skull material."	A pachycephalosaur, possibly synonymous with Prenocephale Prenocephale Prenocephale was a small pachycephalosaurid dinosaur genus from the Late Cretaceous and was similar in many ways to its close relative, Homalocephale, which may simply represent Prenocephale juveniles. Adult Prenocephale probably weighed around and measured around long... . Also found in the Kirtland Formation Kirtland Formation The Kirtland Formation is a sedimentary geological formation. It is the product of alluvial muds and overbank sand deposits from the many channels draining the coastal plain that existed on the inland seashore of North America, in the late Cretaceous period. It overlies the Fruitland Formation...
	S. goodwini	Montana		"Skull material."
Stegoceras Stegoceras Stegoceras is a genus of plant-eating pachycephalosaurid dinosaur that lived in what is now North America during the Late Cretaceous period....	S. edmontonense				Pachycephalosaurid remains from Montana and south Dakota have been erroneously referred to this Campanian Campanian The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ... species.
?Stygimoloch Stygimoloch Stygimoloch is a putative genus of pachycephalosaurid dinosaur from the end of the Cretaceous period, roughly 65 million years ago...	?S. spinifer	Montana			A pachycephalosaur, possibly synonymous with Pachycephalosaurus Pachycephalosaurus Pachycephalosaurus is a genus of pachycephalosaurid dinosaur. It lived during the Late Cretaceous Period of what is now North America. Remains have been excavated in Montana, South Dakota, and Wyoming. It was an herbivorous or omnivorous creature which is only known from a single skull and a few... . Also found in the Lance Formation Lance Formation The Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas... .
	Indeterminate	South Dakota

Plants

Plant Plant Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or... s of the Hell Creek Formation
Genus	Species	Presence	Description	Images
Metasequoia Metasequoia Metasequoia is a fast-growing, deciduous tree, and the sole living species, Metasequoia glyptostroboides, is one of three species of conifers known as redwoods. It is native to the Sichuan-Hubei region of China. Although the least tall of the redwoods, it grows to at least 200 feet in height...	Indeterminate		Casts of Dawn Redwood seed cones are known from the Hell Creek.
Cobbania	C. corrugata		A prehistoric species of water lettuce, previously assigned to the genus Pistia Pistia Pistia is a genus of aquatic plant in the arum family, Araceae. The single species it comprises, Pistia stratiotes, is often called water cabbage, water lettuce, or Nile cabbage. Its native distribution is uncertain, but probably pantropical; it was first described from the Nile near Lake Victoria... .
Araucaria Araucaria Araucaria is a genus of evergreen coniferous trees in the family Araucariaceae. There are 19 extant species in the genus, with a highly disjunct distribution in New Caledonia , Norfolk Island, eastern Australia, New Guinea, Argentina, Chile, and southern Brazil.-Description:Araucaria are mainly...	A. araucana		Casts of Monkey-puzzle leaves are found in Hell Creek.

Pterosaurs

Pterosaur Pterosaur Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight... s of the Hell Creek Formation
Taxa	Species	Location	Description	Images
Quetzalcoatlus Quetzalcoatlus Quetzalcoatlus was a pterodactyloid pterosaur known from the Late Cretaceous of North America , and one of the largest known flying animals of all time. It was a member of the Azhdarchidae, a family of advanced toothless pterosaurs with unusually long, stiffened necks...	Indeterminate	Montana	A single azhdarchid Azhdarchidae Azhdarchidae is a family of pterosaurs known primarily from the late Cretaceous Period, though an isolated vertebrae apparently from an azhdarchid is known from the early Cretaceous as well... neck bone may belong to the genus Quetzalcoatlus.

Theropods

Theropod tracks have been found in South Dakota. An unnamed alvarezsaurid is known from Montana.

Ornithomimosaurs

Ornithomimids reported from the Hell Creek Formation
Genus	Species	State	Stratigraphic position	Material	Notes	Images
"Orcomimus Orcomimus "Orcomimus" is the name given to an as yet undescribed genus of dinosaur from the Late Cretaceous period around 84–65 million years ago. The dinosaur was an ornithomimid which lived in what is now South Dakota, in the United States... "	Nomen nudum	South Dakota			An ornithomimid.
Ornithomimus Ornithomimus Ornithomimus is a genus of ornithomimid dinosaur from the Late Cretaceous Period of what is now North America.In 1890 Ornithomimus velox was named by Othniel Charles Marsh on the basis of a foot and partial hand from the Maastrichtian Denver Formation. Another seventeen species have been named since...	Indeterminate	Montana North Dakota South Dakota			An ornithomimid
Struthiomimus Struthiomimus Struthiomimus is a genus of ornithomimid dinosaur from the late Cretaceous of Alberta, Canada. It was a long-legged, ostrich-like dinosaur.The bipedal Struthiomimus stood about long and tall at the hips and weighed around...	S. sedens				A large ornithomimid.
	Indeterminate	North Dakota South Dakota

Oviraptorosaurs

Oviraptorosaurs reported from the Hell Creek Formation
Genus	Species	State	Stratigraphic position	Material	Notes	Images
Caenagnathus Caenagnathus Caenagnathus is a genus of oviraptorosaurian dinosaur from the late Cretaceous . It is known from a single lower jaw, found in the Dinosaur Park Formation of Alberta, Canada.-Taxonomic history:...	C. collinsi	South Dakota			Sometimes considered a junior synonym of Chirostenotes Chirostenotes Chirostenotes is a genus of oviraptorosaurian dinosaur from the late Cretaceous of Alberta, Canada. The type species is Chirostenotes pergracilis. Some researchers recognize a second species, C... , but type material actually from the Dinosaur Park Formation Dinosaur Park Formation The Dinosaur Park Formation is the uppermost member of the Judith River Group, a major geologic unit in southern Alberta. It was laid down over a period of time between about 76.5 and 75 million years ago. The formation is made up of deposits of a high-sinuosity fluvial system, and is capped...
	Indeterminate	South Dakota		Known from the articular region of a lower jaw catalogued as BHM 2033.
Chirostenotes Chirostenotes Chirostenotes is a genus of oviraptorosaurian dinosaur from the late Cretaceous of Alberta, Canada. The type species is Chirostenotes pergracilis. Some researchers recognize a second species, C...	C. elegans	Montana		Partial foot catalogued as MOR 752.	A large oviraptorosaur, also found in the Dinosaur Park Dinosaur Park Formation The Dinosaur Park Formation is the uppermost member of the Judith River Group, a major geologic unit in southern Alberta. It was laid down over a period of time between about 76.5 and 75 million years ago. The formation is made up of deposits of a high-sinuosity fluvial system, and is capped... and Two Medicine Formation Two Medicine Formation The Two Medicine Formation is a geologic formation, or rock body, that was deposited between 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma , during Campanian time, and is located in northwestern Montana... s.
	C. sp.	South Dakota		Based on the undescribed "Triebold specimen"
Elmisaurus Elmisaurus Elmisaurus is an extinct genus of dinosaur from the Late Cretaceous. It was a theropod belonging to the Oviraptorosauria. Its fossils have been found in Asia and North America. It is known from only its feet and hands....	E. elegans				Junior synonym of Chirostenotes Chirostenotes Chirostenotes is a genus of oviraptorosaurian dinosaur from the late Cretaceous of Alberta, Canada. The type species is Chirostenotes pergracilis. Some researchers recognize a second species, C... elegans.

Eumaniraptorans

Eumaniraptorans reported from the Hell Creek Formation
Genus	Species	State	Stratigraphic position	Material	Notes	Images
Avisaurus Avisaurus Avisaurus is a genus of enantiornithine bird from the Late Cretaceous of North America.Two species are known; the type species A. archibaldi and A. gloriae...	A. archibaldi	Montana		Two adult and one juvenile specimens, all based on lower leg elements.	An enantiornithine.
?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. The name means 'running lizard'....	Indeterminate	Montana South Dakota		Teeth	Dromaeosaurid teeth similar to the older Dromaeosaurus albertensis
Paronychodon Paronychodon Paronychodon was a theropod dinosaur genus. It is a tooth taxon, considered dubious because of the fragmentary nature of the fossils, which include "buckets" of teeth but no other remains...	P. lacustris	Montana North Dakota South Dakota		Teeth	Indeterminate troodontid, actually from the Dinosaur Park Dinosaur Park Formation The Dinosaur Park Formation is the uppermost member of the Judith River Group, a major geologic unit in southern Alberta. It was laid down over a period of time between about 76.5 and 75 million years ago. The formation is made up of deposits of a high-sinuosity fluvial system, and is capped... , Frenchman Frenchman Formation The Frenchman Formation is a division of Upper Cretaceous rocks found in Saskatchewan, Canada. More accurately described as Late Maastrichtian, these rocks contain the youngest of dinosaur genera, much like the Hell Creek Formation in the United States.... , Judith River Judith River Formation The Judith River Formation is a fossil-bearing geologic formation in Montana, and is part of the Judith River Group. It dates to the upper Cretaceous, between 80 and 75 million years ago, corresponding to the "Judithian" land vertebrate age... , Kirtland Kirtland Formation The Kirtland Formation is a sedimentary geological formation. It is the product of alluvial muds and overbank sand deposits from the many channels draining the coastal plain that existed on the inland seashore of North America, in the late Cretaceous period. It overlies the Fruitland Formation... and Milk River Formation Milk River Formation The Milk River Formation is a near- shore to terrestrial sedimentary unit deposited during the Late Cretaceous in southern Alberta... s but absent in the Hell Creek.
	Indeterminate	South Dakota		Teeth	Indeterminate troodontid
Richardoestesia	R.? isosceles	Montana North Dakota South Dakota		Teeth
	R. cf. gilmorei	North Dakota		Teeth
	Indeterminate	South Dakota		Teeth
Saurornithoides Saurornithoides Saurornithoides is a genus of troodontid maniraptoran dinosaur, living during the Late Cretaceous period. These creatures were predators, which could run fast on their hind legs and had excellent sight and hearing...	Indeterminate.	Montana		Teeth	Remains tentatively attributed to the Mongolian genus Saurornithoides Saurornithoides Saurornithoides is a genus of troodontid maniraptoran dinosaur, living during the Late Cretaceous period. These creatures were predators, which could run fast on their hind legs and had excellent sight and hearing... were later referred to 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... .
?Saurornitholestes Saurornitholestes Saurornitholestes is a genus of carnivorous dromaeosaurid theropod dinosaur from the late Cretaceous of Alberta, Montana and New Mexico....	Indeterminate	Montana North Dakota South Dakota		Teeth, partial dentary	Dromaeosaurid remains similar to the older Saurornitholestes langstoni
Stenonychosaurus	S. inequalis	Montana			Junior synonym of Troodon formosus.
?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	Montana		Teeth	A troodontid, actually an indeterminate species of Troodon
	Indeterminate	Montana South Dakota		Teeth	Troodontid teeth similar to the older Troodon formosus
Velociraptor Velociraptor Velociraptor is a genus of dromaeosaurid theropod dinosaur that existed approximately 75 to 71 million years ago during the later part of the Cretaceous Period. Two species are currently recognized, although others have been assigned in the past. The type species is V. mongoliensis; fossils...	Indeterminate	Montana		Teeth, partial dentary	Remains tentatively attributed to the Mongolian genus Velociraptor Velociraptor Velociraptor is a genus of dromaeosaurid theropod dinosaur that existed approximately 75 to 71 million years ago during the later part of the Cretaceous Period. Two species are currently recognized, although others have been assigned in the past. The type species is V. mongoliensis; fossils... were later tentatively referred to Saurornitholestes Saurornitholestes Saurornitholestes is a genus of carnivorous dromaeosaurid theropod dinosaur from the late Cretaceous of Alberta, Montana and New Mexico.... .
"Unnamed ornithurine B"	Indeterminate	Montana		Partial coracoid	An ornithurine possibly similar to Cimolopteryx Cimolopteryx Cimolopteryx is a prehistoric bird genus from the late Cretaceous Period. Remains attributed to Cimolopteryx have been found in the Frenchman Formation of Saskatchewan, the Lance Formation of Wyoming, and possibly the Hell Creek Formation of Montana. All date to the end of the Maastrichtian age,...
"Unnamed ornithurine C"	Indeterminate			Partial coracoid	An ornithurine, also present in the Fort Union Formation Fort Union Formation The Fort Union Formation is a geologic unit containing sandstones, shales, and coal beds in Wyoming, Montana, and parts of adjacent states. In the Powder River Basin, it contains important economic deposits of coal, uranium, and coalbed methane.... , the only individual bird species known to have survived the K-Pg extinction
"Unnamed ornithurine D"	Indeterminate			Partial coracoid	An ornithurine
"Unnamed hesperornithiform A"	Indeterminate			Tarsometatarsus	A primitive hesperornithiform

Tyrannosaurids

Tyrannosaurids reported from the Hell Creek Formation
Genus	Species	State	Stratigraphic position	Material	Notes	Images
Albertosaurus Albertosaurus Albertosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, more than 70 million years ago. The type species, A. sarcophagus, was apparently restricted in range to the modern-day Canadian province of Alberta, after which...	A. lancensis	Montana			Remains later referred to Nanotyrannus Nanotyrannus Nanotyrannus is a genus of tyrannosaurid dinosaur, known only from two juvenile specimens, which may in fact represent juvenile specimens of the contemporary species Tyrannosaurus rex.-History:... lancensis.
	A. "megagracilis"	Montana			Nomen nudum, remains later referred to Tyrannosaurus rex.
Aublysodon Aublysodon Aublysodon is a name given to a large number of carnivorous dinosaur teeth of a certain form found in numerous late Cretaceous period geological formations...	A. mirandus	Montana			Now considered indeterminate tyrannosauroid remains.
	A. molnari	Montana			Remains later referred to Tyrannosaurus rex.
Deinodon Deinodon Deinodon is a name assigned to tyrannosaurid teeth of the Late Cretaceous of Montana by paleontologist Joseph Leidy in 1856...	D. lancensis	Montana			Remains later referred to Nanotyrannus Nanotyrannus Nanotyrannus is a genus of tyrannosaurid dinosaur, known only from two juvenile specimens, which may in fact represent juvenile specimens of the contemporary species Tyrannosaurus rex.-History:... lancensis.
Dinotyrannus	D. megagracilis	Montana			Remains later referred to Tyrannosaurus rex.
Gorgosaurus Gorgosaurus Gorgosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, between about 76.5 and 75 million years ago. Fossil remains have been found in the Canadian province of Alberta and possibly the U.S. state of Montana....	G. lancensis	Montana			Remains later referred to Nanotyrannus Nanotyrannus Nanotyrannus is a genus of tyrannosaurid dinosaur, known only from two juvenile specimens, which may in fact represent juvenile specimens of the contemporary species Tyrannosaurus rex.-History:... lancensis.
?Nanotyrannus Nanotyrannus Nanotyrannus is a genus of tyrannosaurid dinosaur, known only from two juvenile specimens, which may in fact represent juvenile specimens of the contemporary species Tyrannosaurus rex.-History:...	?N. lancensis	Montana		"Nearly complete skull."	A small tyrannosaur, possibly synonymous with Tyrannosaurus Tyrannosaurus Tyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other... .
Tyrannosaurus Tyrannosaurus Tyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other...	T. rex	Montana North Dakota South Dakota			A tyrannosaur, known from several specimens including a juvenile nicknamed "Jane Jane (dinosaur) Jane is a fossil specimen of small tyrannosaurid dinosaur , officially known as BMRP 2002.4.1, discovered in the Hell Creek Formation in southern Montana.... ". Also found in the Denver Denver Formation The Denver Formation is a geological formation in Colorado whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.-Ornithischians:-Saurischians:-References:... , Frenchman Frenchman Formation The Frenchman Formation is a division of Upper Cretaceous rocks found in Saskatchewan, Canada. More accurately described as Late Maastrichtian, these rocks contain the youngest of dinosaur genera, much like the Hell Creek Formation in the United States.... , Hill Creek South, Javelina Javelina Formation The Javelina Formation is a geological formation in Texas. Dating has shown that the strata date to the mid-late Maastrichtian stage of the Late Cretaceous, with the middle part of the formation dated to about 69 million years ago plus or minus 1 Ma and the top situated near the K-Pg boundary,... , Kirtland Kirtland Formation The Kirtland Formation is a sedimentary geological formation. It is the product of alluvial muds and overbank sand deposits from the many channels draining the coastal plain that existed on the inland seashore of North America, in the late Cretaceous period. It overlies the Fruitland Formation... , Lance Lance Formation The Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas... , McRae McRae Formation The McRae Formation is a geological formation in New Mexico whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.-References:... , North Horn North Horn Formation The North Horn Formation is a geological formation in Utah whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.-Vertebrate paleofauna:... , Scollard Scollard Formation -References:* Ryan, M. J., and Russell, A. P., 2001. Dinosaurs of Alberta : In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, pp. 279-297.... , and Willow Creek Formation Willow Creek Formation The Willow Creek 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.... s.

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 reported from the Hell Creek Formation
Genus	Species	State	Stratigraphic position	Material	Notes
Adocus	Indeterminate	Montana
Compsemys Compsemys Compsemys is a genus of prehistoric turtle from the Late Cretaceous and Paleocene of North America. Although several species have been described, they are all considered synonyms of one species, C. victa, first described by Joseph Leidy in 1856...	C. victa	Montana
Eubaena	E. cephalica	Montana
Gamerabaena Gamerabaena Gamerabaena is an extinct genus of baenid turtle which existed in North Dakota during the late Cretaceous period. It is known from a single fragmentary skull that was found in the Maastrichtian-age Hell Creek Formation. It contains the species Gamerabaena sonsalla...	G. sonsalla	North Dakota
Trionyx	Indeterminate	Montana

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