The Two Medicine Formation is a

geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock expo ...

, or rock body, in northwestern

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

and southern

Alberta Alberta is a Provinces and territories of Canada, province in Canada. It is a part of Western Canada and is one of the three Canadian Prairies, prairie provinces. Alberta is bordered by British Columbia to its west, Saskatchewan to its east, t ...

that was deposited between 82.4 Ma and 74.4 Ma, during

Campanian The Campanian is the fifth of six ages of the Late Cretaceous epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campa ...

(

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

) time. It crops out to the east of the

Rocky Mountain The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of Western Canada, to New Mexico in ...

Overthrust Belt, and the western portion (about thick) of this formation is folded and faulted while the eastern part, which thins out into the Sweetgrass Arch, is mostly undeformed plains. Below the formation are the nearshore (beach and tidal zone) deposits of the Virgelle Sandstone, and above it is the marine Bearpaw Shale. Throughout the Campanian, the Two Medicine Formation was deposited between the western shoreline of the Late Cretaceous Interior Seaway and the eastward advancing margin of the Cordilleran Overthrust Belt. The Two Medicine Formation is mostly

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

, deposited by rivers and deltas.

History of research

1913 Events January * January – Joseph Stalin travels to Vienna to research his ''Marxism and the National Question''. This means that, during this month, Stalin, Hitler, Trotsky and Tito are all living in the city. * January 3 &ndash ...

, a

US Geological Survey The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on March ...

crew headed by Eugene Stebinger and a US National Museum crew headed by Charles Gilmore worked together to excavate the first dinosaur of the formation. Stebinger was the first to identify the Two Medicine Formation and formally described the first fossils in a scientific paper published in

1914 This year saw the beginning of what became known as the First World War, after Archduke Franz Ferdinand of Austria, heir to the Austrian throne was Assassination of Archduke Franz Ferdinand, assassinated by Serbian nationalist Gavrilo Princip ...

. Gilmore returned to the Formation in

1928 Events January * January – British bacteriologist Frederick Griffith reports the results of Griffith's experiment, indirectly demonstrating that DNA is the genetic material. * January 1 – Eastern Bloc emigration and defection: Boris B ...

and

1935 Events January * January 7 – Italian premier Benito Mussolini and French Foreign Minister Pierre Laval conclude an agreement, in which each power agrees not to oppose the other's colonial claims. * January 12 – Amelia Earhart ...

. During this time frame only three species were named and of these only '' Styracosaurus ovatus'' and '' Edmontonia rugosidens'' are still regarded as valid.

Barnum Brown Barnum Brown (February 12, 1873 – February 5, 1963), commonly referred to as Mr. Bones, was an American paleontologist. He discovered the first documented remains of ''Tyrannosaurus'' during a career that made him one of the most famous fossil ...

prospected the formation in

1933 Events January * January 11 – Australian aviator Sir Charles Kingsford Smith makes the first commercial flight between Australia and New Zealand. * January 17 – The United States Congress votes in favour of Philippines independen ...

, but found nothing significant. Both of their research were interrupted by

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

. In

1977 Events January * January 8 – 1977 Moscow bombings, Three bombs explode in Moscow within 37 minutes, killing seven. The bombings are attributed to an Armenian separatist group. * January 10 – Mount Nyiragongo erupts in eastern Zaire (no ...

, Trexler reports finding

hadrosaur Hadrosaurids (), also hadrosaurs or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod fami ...

remains west of

Choteau, Montana Choteau is a city in and the county seat of Teton County, Montana, United States. The population was 1,721 at the 2020 census. Choteau is named after French fur merchant, trader and explorer Pierre Chouteau, Jr., who is also the namesake of ...

. During the next year baby hadrosaurs were discovered. In

1979 Events January * January 1 ** United Nations Secretary-General Kurt Waldheim heralds the start of the ''International Year of the Child''. Many musicians donate to the ''Music for UNICEF Concert'' fund, among them ABBA, who write the song ...

, Horner and Makela referred these hadrosaur bones to '' Maiasaura peeblesorum''. The announcement attracted renewed scientific interest to the formation and many new kinds of dinosaurs were discovered. More nesting sites were discovered later, including the Devil's Coulee site yielding '' Hypacrosaurus stebingeri'' in southern

1987 Events January * January 1 – Bolivia reintroduces the Boliviano currency. * January 2 – Chadian–Libyan conflict – Battle of Fada: The Military of Chad, Chadian army destroys a Libyan armoured brigade. * January 3 – Afghan leader ...

Geology

The loosely consolidated fine grain sediments composing the formation allow for fast plant growth in

badland Badlands are a type of dry terrain where softer sedimentary rocks and clay-rich soils have been extensively eroded."Badlands" in '' Chambers's Encyclopædia''. London: George Newnes, 1961, Vol. 2, p. 47. They are characterized by steep slopes ...

areas, limiting the number of exposed outcrops. Paleosols,

fluvial A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it ru ...

deposits and bentonitic layers are common in the Two Medicine Formation.

Age

The Two Medicine Formation spans from 82.4 to 74.4 Ma, nearly the entire length of the

stage. The age of the different members of the formation are as follows: * Rock City Member: 82.4-80.8 Ma * Shields Crossing Member: 80.8-80.2 Ma * Hagans Crossing Member: 80.2-77 Ma * Flag Butte Member: 77-74.8 Ma

Equivalents

There are several equivalents to the Two Medicine Formation, as with many geologic formations (most of which are named after their type locality). The Sweetgrass Arch in Montana divides the Two Medicine from the Judith River Formation, Bearpaw Shale, Claggett Shale, and

Eagle Sandstone The Eagle Sandstone, originally the Eagle Formation, is a geological formation in Montana whose strata date back to the Late Cretaceous. It is a light to brownish gray to pale yellow-orange, fine-grained sandstone. It contains areas of crossbedd ...

. Across the

Canada–United States border The international border between Canada and the United States is the longest in the world by total length. The boundary (including boundaries in the Great Lakes, Atlantic, and Pacific coasts) is long. The land border has two sections: Canada' ...

, the Two Medicine Formation correlates to the Belly River Group in southwest Alberta, and the Pakowki Formation eastward.

Stratigraphy

The Two Medicine overlies the Virgelle Sandstone, which formed from the beach sands exposed on northern and western shores of the receding Colorado Sea. A Cretaceous Interior Seaway transgression submerged the area briefly early on in Two Medicine history leaving anomalous paralic sediments and isolated

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

bodies about 100 m above the base of the formation. The Middle portion of the two medicine formation is about 225 m thick, deposited while the Clagette Sea was receding and the Bearpaw Sea transgressing. This portion is stratigraphically equivalent to the Judith River Formation and Judith River Group. The sediments are mainly bentonitic

siltstones Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed ...

and mudstones with "occasional

lenses." These sediments are thought to be the remains of a coastal plain "far removed" from the interior sea. The upper portion is about one half of the formation. Its sediments are similar to the middle portions but punctuated by extensive red beds and

caliche Caliche () is a soil accumulation of soluble calcium carbonate at depth, where it precipitates and binds other materials—such as gravel, sand, clay, and silt. It occurs worldwide, in aridisol and mollisol soil orders—generally in arid or se ...

horizons. The uppermost 80 m were deposited after the inundation of the Judith River equivalent sediments by the Bearpaw Sea. They are thought to have been deposited in only 500,000 years. Bentonitic ash is common in the Two Medicine. To the south extrusive volcanic activity occurred in association with the Boulder Batholith collectively called the Elkhorn Volcanics.

Taphonomy

Most of the vertebrate fossils are preserved by CaCo₃

permineralization Permineralization is a process of fossilization of bones and tissues in which mineral deposits form internal Casting, casts of organisms. Carried by water, these minerals fill the spaces within organic tissue. Because of the nature of the casts, p ...

. This type of preservation preserves high levels of detail, even down to the microscopic level. However, it also leaves specimens vulnerable to

weathering Weathering is the deterioration of rocks, soils and minerals (as well as wood and artificial materials) through contact with water, atmospheric gases, sunlight, and biological organisms. It occurs '' in situ'' (on-site, with little or no move ...

when exposed to the surface.

Paleoenvironment

Climate

The Two Medicine Formation was deposited in a seasonal, semi-arid climate with possible rainshadows from the Cordilleran highlands. This region during the Campanian experienced a long dry season and warm temperatures. Lithologies,

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

faunas, and plant and pollen data support the above interpretation. The extensive red beds and

horizons of the upper Two Medicine are evidence of at least seasonally arid conditions. Some of the dinosaurs from the formation have been speculated to have shown signs of drought-related death.

Elevation

A more upland environment existed in the south of the Two Medicine Formation. Streams had a northeasterly flow away from these southwestern uplands. The southern part of the Two medicine formation grades into brackish water siltstone/sandstone series called the Horsethief Formation. The sediments of the Horsethief represent shallower water deposits than the Bearpaw Shale adding further evidence of higher elevation areas existing in the south.

Egg Mountain site

Egg Mountain, which is near

, was discovered in 1977 by Marion Brandvold, owner of the Trex Agate Rock Shop in Bynum, Montana, who discovered the bones of juvenile dinosaurs at this site. It is a colonial nesting site on the Willow Creek

Anticline In structural geology, an anticline is a type of Fold (geology), fold that is an arch-like shape and has its oldest Bed (geology), beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex curve, c ...

in the Two Medicine Formation that is famous for its fossil eggs of Maiasaura, which demonstrated for the first time that at least some dinosaurs cared for their young. The eggs were arranged in dug-out earthen nests, each nest about a parent's body length from the next, and baby dinosaurs were also found with skeletons too cartilaginous for them to walk - similar to those of

altricial Precocial species in birds and mammals are those in which the young are relatively mature and mobile from the moment of birth or hatching. They are normally nidifugous, meaning that they leave the nest shortly after birth or hatching. Altricial ...

(helpless) baby

birds Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

. The parent(s) must then have brought food to the young, and there is plant matter in the nests that may be evidence of either this or for incubation of the eggs. ''Maiasaura'' also grew extremely fast, at rates comparable to modern birds. Skeletons of '' Orodromeus'' and skeletons and eggs of ''

Troodon ''Troodon'' ( ; ''Troödon'' in older sources) is a controversial genus of relatively small, bird-like theropod dinosaurs definitively known from the Campanian age of the Late Cretaceous period (about 77 million years ago). It includes at l ...

'' were also found at Egg Mountain.

Biostratigraphy

Most dinosaur-bearing rock formations do not contain multiple distinct faunas at different positions within the formation's stratigraphic column. Usually the lower sediments of a given formation will contain the same kinds of dinosaurs as the upper sediments, or the species composition changes only gradually. However, some researchers had argued that the Two Medicine Formation was an exception, preserving multiple distinct dinosaur faunas. Later research came to find that the supposedly distinct dinosaur faunas at different levels of the formations were more similar than had been previously thought. While the dinosaur fauna of the lower and middle sections Two Medicine was apparently diverse, the quality of preservation was low and few of these remains can be referred to individual species. The middle Two Medicine is a better source of fossils, but still poor overall. This makes it difficult to argue that these sections of the formation preserve distinct faunas. The upper portion of the formation is more diverse and preserves better quality fossils. However, many of the taxa that supposedly distinguished it as a separate fauna have since been found in older sediments. In particular, '' Gryposaurus latidens'' and ''

Hypacrosaurus ''Hypacrosaurus'' (meaning "near the highest lizard" reek υπο-, ''hypo-'' = less + ακρος, ''akros'', high because it was almost but not quite as large as ''Tyrannosaurus'') is an extinct genus of hadrosaurid, duckbill dinosaur simila ...

'' have been found to coexist with '' Maiasaura''. Further, there are fossil teeth that seem to show the presence of certain taxa are unbroken throughout the whole formation. Nevertheless, some true changes in faunal composition seem to occur in the upper Two Medicine. The appearance of ''Maiasaura'' in the formation precedes the arrival of a diverse variety of other ornithischians. According to David Trexler, thorough examination of strata found along the Two Medicine River (which exposes the entire upper half of the Two Medicine Formation) indicates that the apparent diversification was a real event rather than a result of preservational biases. The timeline below follows the stratigraphic chart presented by Horner ''et al.'' 2001.Horner, J. R., Schmitt, J. G., Jackson, F., & Hanna, R. (2001). Bones and rocks of the Upper Cretaceous Two Medicine-Judith River clastic wedge complex, Montana. In Field trip guidebook, Society of Vertebrate Paleontology 61st Annual Meeting: Mesozoic and Cenozoic Paleontology in the Western Plains and Rocky Mountains. Museum of the Rockies Occasional Paper (Vol. 3, pp. 3-14). ImageSize = width:1000px height:auto barincrement:15px PlotArea = left:10px bottom:50px top:10px right:10px Period = from:-81 till:-72.5 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:1 start:-81 ScaleMinor = unit:year increment:1 start:-74 TimeAxis = orientation:hor AlignBars = justify Colors = #legends id:CAR value:claret id:ANK value:rgb(0.4,0.3,0.196) id:HER value:teal id:HAD value:green id:OMN value:blue id:black value:black id:white value:white id:cretaceous value:rgb(0.675,0.675,0.35) id:jurassic value:rgb(0.753,0.753,0.486) id:triassic value:rgb(0.827,0.827,0.65) id:mesozoic value:rgb(0.54,0.54,0.258) BarData= bar:eratop bar:space bar:NAM1 bar:NAM2 bar:NAM3 bar:NAM4 bar:NAM15 bar:NAM5 bar:NAM6 bar:NAM7 bar:NAM8 bar:NAM9 bar:NAM10 bar:NAM11 bar:NAM12 bar:NAM13 bar:NAM14 bar:space bar:period bar:space bar:era PlotData= align:center textcolor:black fontsize:M mark:(line,black) width:25 shift:(7,-4) bar:eratop from: -81 till: -72.5 color:mesozoic text:Late Cretaceous PlotData= align:left fontsize:M mark:(line,white) width:5 anchor:till align:left color:HAD bar:NAM1 from: -80.6 till: -76.9 text: Gryposaurus latidens color:CAR bar:NAM2 from: -80.6 till: -76.9 text:

Dromaeosaurus ''Dromaeosaurus'' (; ) is a genus of Dromaeosauridae, dromaeosaurid theropod dinosaur that lived during the Late Cretaceous period (middle late Campanian and Maastrichtian), sometime between 80 and 69 million years ago, in Alberta, Canada and th ...

sp. color:CAR bar:NAM3 from: -80.6 till: -76.9 text: Richardoestesia sp. color:CAR bar:NAM4 from: -80.6 till: -76.6 text:

Saurornitholestes ''Saurornitholestes'' ("lizard-bird thief") is a genus of carnivorous dromaeosaurid theropod dinosaur from the late Cretaceous of Canada (Alberta and Saskatchewan) and the United States (Montana, New Mexico, Alabama, and South Carolina). Two spe ...

sp. color:HAD bar:NAM15 from: -79.2 till: -79 text: Acristavus gagslarsoni color:HAD bar:NAM5 from: -76.9 till: -76.6 text: Maiasaura peeblesorum color:HAD bar:NAM6 from: -76.9 till: -76.6 text: Orodromeus makelai color:CAR bar:NAM7 from: -76.9 till: -76.6 text:

Troodon formosus ''Troodon'' ( ; ''Troödon'' in older sources) is a controversial genus of relatively small, bird-like theropod dinosaurs definitively known from the Campanian age of the Late Cretaceous period (about 77 million years ago). It includes at l ...

color:CAR bar:NAM8 from: -76.9 till: -76.6 text: Bambiraptor feinbergorum color:HAD bar:NAM9 from: -76.6 till: -74 text: Hypacrosaurus stebingeri color:HAD bar:NAM10 from: -76.6 till: -74 text: Prosaurolophus maximus color:ANK bar:NAM11 from: -76.6 till: -74 text: Scolosaurus cutleri color:HER bar:NAM12 from: -74.7 till: -74.5 text: Rubeosaurus ovatus color:HER bar:NAM13 from: -74.5 till: -74 text: Einiosaurus procurvicornis color:HER bar:NAM14 from: -74.2 till: -74 text: Achelousaurus horneri PlotData= align:center textcolor:black fontsize:M mark:(line,black) width:25 bar:period from: -72.5 till: -74 color:triassic text: BPF from: -76.6 till: -74 color:triassic text:Unit 5 from: -76.9 till: -76.6 color:jurassic text:4 from: -80.6 till: -76.9 color:triassic text:Unit 3 from: -80.8 till: -80.6 color:jurassic text:2 from: -81 till: -80.8 color:triassic text:1 bar:era from: -81 till: -80.5 color:mesozoic text:E. Camp. from: -80.5 till: -75.9 color:cretaceous text:Middle Campanian from: -75.9 till: -72.5 color:jurassic text:Late Campanian

Dinosaurs

Some of the dinosaurs from the formation have been speculated to show signs of drought related death. Very few articulated dinosaurs have been found in the formation; most specimens are isolated, bone bed, poorly preserved or broken remains. Early studies assumed that the Two Medicine Formation would have the same dinosaurs as the Judith River Formation. It was only in 1978, that it was discovered that the formation had endemic dinosaurs. Even some genera regarded as wide-ranging predators exhibited a species difference between the Two Medicine and other formations. No ecological barriers have been postulated apart from upland/lowland habitat preference differences between the Two Medicine and Judith River Formation. There is no unequivocal evidence for intermingling between the wildlife of the Two Medicine and geographically adjacent contemporary formations. Dinosaur remains are more common in the upper part of the Two Medicine.

Ankylosaurs

Avialans

Ceratopsians

Non-avialan eumaniraptorans

Ornithopods

An unidentified lambeosaurine has been collected from the same stratigraphic placement, west of Bynum, and is in preparation at The Montana Dinosaur Center

Oviraptorosaurs

The first find of an oviraptorosaur in Montana was an

articular The articular bone is part of the lower jaw of most vertebrates, including most jawed fish, amphibians, birds and various kinds of reptiles, as well as ancestral mammals. Anatomy In most vertebrates, the articular bone is connected to two o ...

region from the lower jaw of '' Caenagnathus sternbergi'', from the Two Medicine Formation, according to a 2001 paper by David J. Varrichio. This species had previously only been known from the Canadian province of

. Varricchio observes that during the late

, Alberta and Montana had very similar

theropods Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...

despite significant differences in the types of herbivorous dinosaur faunas.

Tyrannosauroids

Other fauna

Many other fossil animals have been found, such as freshwater

bivalves Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed by a calcified exoskeleton consis ...

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

turtle Turtles are reptiles of the order (biology), order Testudines, characterized by a special turtle shell, shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Crypt ...

s, lizards such as '' Magnuviator'', and champsosaurs. The multituberculate mammal ''

Cimexomys ''Cimexomys'' is an extinct North American mammal that lived from the Upper Cretaceous to the Paleocene. For a while, it shared the world with dinosaurs, but outlived them. It was a member of the extinct order Multituberculata and lies within the ...

'' has been found on Egg Mountain. The species '' Piksi barbarulna'' was described based on forelimb bones from the Two Medicine Formation; it was initially thought to be a

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

, but subsequently it was reinterpreted as a

pterosaur Pterosaurs are an extinct clade of flying reptiles in the order Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 million to 66 million years ago). Pterosaurs are the earli ...

, likely a member of Ornithocheiroidea. Azhdarchoid pterosaurs are also known from the Two Medicine Formation, including a very large, yet-unnamed azhdarchid, the estimated wingspan of which was , and smaller '' Montanazhdarcho minor'', a non-azhdarchid azhdarchoid.

Insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

and

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

burrow file:Chipmunk-burrow (exits).jpg, An eastern chipmunk at the entrance of its burrow A burrow is a hole or tunnel excavated into the ground by an animal to construct a space suitable for habitation or temporary refuge, or as a byproduct of Animal lo ...

s have also been discovered, as well as dinosaur

coprolites A coprolite (also known as a coprolith) is fossilized feces. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour (in this case, diet) rather than morphology. The name i ...

References

Bibliography

* Dodson, P., C.A. Forster, and S.D. Sampson. 2004. Ceratopsidae in Weishampel, D.B., P. Dodson, and H. Osmolska (eds.) ''The Dinosauria''. 2nd Edition, University of California Press. * * Trexler, D., 2001, Two Medicine Formation, Montana: geology and fauna: In: ''Mesozoic Vertebrate Life'', edited by Tanke, D. H., and Carpenter, K., Indiana University Press, pp. 298–309. * * Varricchio, D. J. 2001. Late Cretaceous oviraptorosaur (Theropoda) dinosaurs from Montana. pp. 42–57 in D. H. Tanke and K. Carpenter (eds.), Mesozoic Vertebrate Life. Indiana University Press, Indianapolis. * {{cite book , editor-last1= Weishampel , editor-first1=David B. , editor-last2= Dodson , editor-first2=Peter , editor-last3= Osmólska , editor-first3=Halszka , year=2004 , title=The Dinosauria, 2nd edition , url=https://books.google.com/books?id=vtZFDb_iw40C , location=Berkeley , publisher=University of California Press , pages=1–880 , accessdate=2019-02-21 , isbn=0-520-24209-2 Geologic formations of Alberta Geologic formations of Montana Upper Cretaceous Series of North America Cretaceous Alberta Cretaceous Montana Campanian Stage Sandstone formations of Canada Sandstone formations of the United States Fluvial deposits Deltaic deposits Ichnofossiliferous formations Ooliferous formations Fossiliferous stratigraphic units of North America Paleontology in Alberta Paleontology in Montana Glacier National Park (U.S.)