''Scolosaurus'' is an
extinct genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...
of
ankylosaurid
Ankylosauridae () is a family of armored dinosaurs within Ankylosauria, and is the sister group to Nodosauridae. The oldest known Ankylosaurids date to around 122 million years ago and went extinct 66 million years ago during the Cretaceous–Pal ...
dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
s within the subfamily
Ankylosaurinae
Ankylosaurinae is a subfamily of ankylosaurid dinosaurs, existing from the Early Cretaceous about 105 million years ago until the end of the Late Cretaceous, about 66 mya. Many genera are included in the clade, such as '' Ankylosaurus'', '' Pin ...
. It is known from the lower levels of the
Dinosaur Park Formation
The Dinosaur Park Formation is the uppermost member of the Belly River Group (also known as the Judith River Group), a major geologic unit in southern Alberta. It was deposited during the Campanian stage of the Late Cretaceous, between about 7 ...
and upper levels of the
Oldman Formation
The Oldman Formation is a stratigraphic unit of Late Cretaceous (Campanian stage) age that underlies much of southern Alberta, Canada. It consists primarily of sandstones that were deposited in fluvial channel and floodplain environments. It was n ...
in the
Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger 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 ''creta'', ...
(latest middle
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. Campani ...
stage, about 76.5 Ma ago) of
Alberta
Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...
,
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tota ...
. It contains two
species
In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
, ''S. cutleri'' and ''S. thronus''.
The type species, ''S. cutleri'', measured up to in length and in body mass.
Discovery

''Scolosaurus'' was named by
Franz Nopcsa von Felső-Szilvás
Baron Franz Nopcsa von Felső-Szilvás (also Baron Nopcsa von Felső-Szilvás, Baron Nopcsa, Ferenc Nopcsa, báró felsőszilvási Nopcsa Ferenc, Baron Franz Nopcsa, and Franz Baron Nopcsa; May 3, 1877 – April 25, 1933) was a Hungarian aristoc ...
in
1928
Events January
* January – British bacteriologist Frederick Griffith reports the results of Griffith's experiment, indirectly proving the existence of DNA.
* January 1 – Eastern Bloc emigration and defection: Boris Bazhano ...
, based on
holotype
A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...
NHMUK
The Natural History Museum in London is a museum that exhibits a vast range of specimens from various segments of natural history. It is one of three major museums on Exhibition Road in South Kensington, the others being the Science Museum (Lo ...
R.5161, a nearly complete specimen that preserves the entire skeleton except for the distal end of the tail, the right forelimb, the right hindlimb, and the skull. The rare preservation of
osteoderms
Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct ...
and skin impression are also present. The fossil skeleton was discovered by
William Edmund Cutler
William is a masculine given name of Norman French origin.Hanks, Hardcastle and Hodges, ''Oxford Dictionary of First Names'', Oxford University Press, 2nd edition, , p. 276. It became very popular in the English language after the Norman conq ...
, an independent fossil collector in 1914 at Quarry 80 of the
Deadlodge Canyon locality.
It was collected from the bottom of the Dinosaur Park Formation
The Dinosaur Park Formation is the uppermost member of the Belly River Group (also known as the Judith River Group), a major geologic unit in southern Alberta. It was deposited during the Campanian stage of the Late Cretaceous, between about 7 ...
in fine-grained sandstone and fine-grained claystone sediments that were deposited during the 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. Campani ...
stage
Stage or stages may refer to:
Acting
* Stage (theatre), a space for the performance of theatrical productions
* Theatre, a branch of the performing arts, often referred to as "the stage"
* ''The Stage'', a weekly British theatre newspaper
* Sta ...
of the Late Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
period, approximately 76.5 million years ago. The holotype specimen is housed in the collection of the Natural History Museum
A natural history museum or museum of natural history is a scientific institution with natural history collections that include current and historical records of animals, plants, fungi, ecosystems, geology, paleontology, climatology, and more ...
in London
London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...
, England.
In 2013, Arbour and Currie reassigned specimen MOR 433, upon which the genus ''Oohkotokia'' was based, to ''Scolosaurus''. This specimen consists of a partial skull, both humeri, a caudal vertebra and several osteoderms and was recovered in the Upper Member of the Two Medicine Formation
The Two Medicine Formation is a geological formation, or rock body, in northwestern Montana and southern Alberta that was deposited between and (million years ago), during Campanian (Late Cretaceous) time. It crops out to the east of the Rocky M ...
, in Montana
Montana () is a U.S. state, state in the Mountain states, Mountain West List of regions of the United States#Census Bureau-designated regions and divisions, division of the Western United States. It is bordered by Idaho to the west, North ...
, which has been dated at approximately 74 million years. The remains were collected in 1986-1987 in grey siltstone that was deposited during the 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. Campani ...
stage of the Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
period.[ The specimen is housed in the collection of the ]Museum of the Rockies
Museum of the Rockies is a museum in Bozeman, Montana. Originally affiliated with Montana State University in Bozeman, and now also, the Smithsonian Institution, the museum is largely known for its paleontological collections. The Museum houses ...
in Bozeman, Montana
Bozeman is a city and the county seat of Gallatin County, Montana, United States. Located in southwest Montana, the 2020 census put Bozeman's population at 53,293, making it the fourth-largest city in Montana. It is the principal city of ...
.
The generic name ''Scolosaurus'' means "pointed stake lizard" and is derived from the Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
words ''skolos'' (σκῶλος) meaning "pointed stake", and ''saûros'' (σαύρα) meaning "lizard". The specific name, ''cutleri'', honours its discoverer and the collector of the holotype
A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...
, W. E. Cutler,[ who was seriously injured when the specimen fell on him as he was excavating it.
]
Classification
In 1928, Nopcsa assigned the specimen to the family Ankylosauridae
Ankylosauridae () is a family of armored dinosaurs within Ankylosauria, and is the sister group to Nodosauridae. The oldest known Ankylosaurids date to around 122 million years ago and went extinct 66 million years ago during the Cretaceous–P ...
, and drew morphological comparisons with the fossil material known from '' Dyoplosaurus''. In 1971, Walter Coombs concluded that there was only one species of ankylosaurid during the 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. Campani ...
age of the Late Cretaceous of North America. He synonymized the species ''Anodontosaurus lambei
''Anodontosaurus'' is an extinct genus of ankylosaurid dinosaurs within the subfamily Ankylosaurinae. It is known from the entire span of the Late Cretaceous Horseshoe Canyon Formation (mid Late Campanian to "middle" Maastrichtian stage, abou ...
'', ''Dyoplosaurus acutosquameus
''Dyoplosaurus'' (meaning “double-armoured lizard”) is a monospecific genus of ankylosaurid dinosaur from Alberta that lived during the Late Cretaceous (middle Campanian, ~76.5–75 Ma) in what is now the Dinosaur Park Formation. ''Dyoplosau ...
'', and ''Scolosaurus cutleri'' with ''Euoplocephalus tutus
''Euoplocephalus'' ( ) is a genus of very large, herbivorous ankylosaurid dinosaurs, living during the Late Cretaceous of Canada. It has only one named species, ''Euoplocephalus tutus''.
The first fossil of ''Euoplocephalus'' was found in 1897 i ...
'' but did not provide any justification for these synonymies.[Coombs W. (1971) The Ankylosauridae. Ph.D. thesis, Columbia University, New York, NY, 487 p.] The synonymization of ''Scolosaurus cutleri'' and ''Euoplocephalus tutus'' was generally accepted and thus NHMUK R.5161 was assigned to ''E. tutus''. However, a redescription of ''Scolosaurus'' published in 2013 in the ''Canadian Journal of Earth Sciences
The ''Canadian Journal of Earth Sciences'' is a monthly peer-reviewed scientific journal established in 1963, which reports current research on all aspects of the Earth sciences. It is published by NRC Research Press. The journal also publishes s ...
'' by Paul Penkalski and William T. Blows suggested that the genus is a valid taxon. They concluded that ''Scolosaurus'' can be distinguished from ''Euoplocephalus'' by the form
Form is the shape, visual appearance, or configuration of an object. In a wider sense, the form is the way something happens.
Form also refers to:
* Form (document), a document (printed or electronic) with spaces in which to write or enter dat ...
of their cervical
In anatomy, cervical is an adjective that has two meanings:
# of or pertaining to any neck.
# of or pertaining to the female cervix: i.e., the ''neck'' of the uterus.
*Commonly used medical phrases involving the neck are
**cervical collar
**cervic ...
armour, the details of other armour
Armour (British English
British English (BrE, en-GB, or BE) is, according to Lexico, Oxford Dictionaries, "English language, English as used in Great Britain, as distinct from that used elsewhere". More narrowly, it can refer specificall ...
and the structure of the forelimb. They also concluded that ''Scolosaurus'' and ''Dyoplosaurus'' are distinct, due to differences noted in the pelvis and armour.[ Due to its completeness, the holotype of ''Scolosaurus'' has formed the basis for most ''Euoplocephalus'' reconstructions since 1971; therefore, most images of ''Euoplocephalus'' actually depict ''Scolosaurus'' instead.
A 2013 study found that the ankylosaurine '']Oohkotokia
''Oohkotokia'' ( ) is a genus of ankylosaurid dinosaur within the subfamily Ankylosaurinae. It is known from the upper levels of the Two Medicine Formation (late Campanian stage, about 74 Ma ago) of Montana, United States. The discovery of ''Ooh ...
'' was indistinguishable from ''Scolosaurus'', and was therefore considered a junior synonym. However, this synonymization is contentious as ''Oohkotokia'' was subsequently recognized as valid. Thus, much of the material illustrated as belonging to ''Scolosaurus'' may actually pertain to ''Oohkotokia''.
The following cladogram
A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...
is based on a 2015 phylogenetic analysis
In biology
Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that pro ...
of the Ankylosaurinae conducted by Victoria Arbour and Phillip J. Currie. The cladogram follows the biogeographical family tree provided by that study, which is a fusion of the study's 50% majority rule tree as well as the maximum agreement subtree. The study's 50% majority rule tree was a cladogram formed by a collection of clades
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term ...
, although it only included clades that appear in more than 50% of the family trees found during the analysis. The maximum agreement subtree is the cladogram that results from an algorithm which attempts to maximize the amount of taxa included in the result while also retaining the fundamental shape of all other trees in the sample. Some controversial taxa thus had to be omitted by the subtree in order for the resulting cladogram to fulfill the second requirement. The biogeographical tree (i.e. the following cladogram) is basically the 50% majority rule tree, except with some of the polytomies resolved according to the results of the maximum agreement subtree:
The following cladogram
A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...
is based on a 2017 phylogenetic analysis
In biology
Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that pro ...
of the Ankylosaurinae conducted by Victoria Arbour and David Evans. The cladogram depicts the majority rule (average result) of 10 most parsimonious trees, which each are considered to have the fewest evolutionary steps, thus being the most accurate under the principle of Occam's razor
Occam's razor, Ockham's razor, or Ocham's razor ( la, novacula Occami), also known as the principle of parsimony or the law of parsimony ( la, lex parsimoniae), is the problem-solving principle that "entities should not be multiplied beyond neces ...
:
Referred material
In 1874, G. M. Dawson excavated specimen USNM 7943 at the Milk River locality of the Frenchman Formation
The Frenchman Formation is stratigraphic unit of Late Cretaceous (late Maastrichtian) age in the Western Canada Sedimentary Basin. It is present in southern Saskatchewan and the Cypress Hills of southeastern Alberta. The formation was defined by ...
in Alberta. It was collected from terrestrial sediments that are considered to be from the Maastrichtian
The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interv ...
stage of the Late Cretaceous, approximately 70.6 to 66 million years old. The specimen consisted of a partial first cervical ring, which is part of the dinosaur's neck. In 2013, this material was assigned to ''Scolosaurus'' by Arbour and Curry who conducted a detailed phylogenetic analysis of the ankylosauridae. It is currently housed at the Smithsonian Institution in Washington, DC.
In 1928, George F. Sternberg, collected specimen USNM 11892, from the ''Montanazhdarcho
''Montanazhdarcho'' is a genus of azhdarchoid pterosaur from the Late Cretaceous period (Campanian stage) of what is now the state of Montana, United States. ''Montanazhdarcho'' is known from only one species, ''M. minor''.
Discovery
The holo ...
'' holotype locality, high up in the Two Medicine Formation
The Two Medicine Formation is a geological formation, or rock body, in northwestern Montana and southern Alberta that was deposited between and (million years ago), during Campanian (Late Cretaceous) time. It crops out to the east of the Rocky M ...
in Glacier County
Glacier County is located in the U.S. state of Montana. As of the 2020 census, the population was 13,778. The county is located in northwestern Montana between the Great Plains and the Rocky Mountains, known to the Blackfeet as the "Backbone ...
, Montana
Montana () is a U.S. state, state in the Mountain states, Mountain West List of regions of the United States#Census Bureau-designated regions and divisions, division of the Western United States. It is bordered by Idaho to the west, North ...
. The material, a partial skull, was recovered from channel sandstone sediments that were deposited during the Campanian stage, approximately 74 million years ago. This is also housed at the Smithsonian Institution.
Other referred specimens include FPDM V-31, NSM PV 20381 and TMP 2001.42.9. FPDM V-31 and TMP 2001.42.9 are both skulls, in various states of preservation. NSM PV 20381 includes a skull, dorsal vertebrae, caudal vertebrae, ribs, both scapula
The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eithe ...
e, both ilia
Ilia may refer to:
Science and medicine
*''Apatura ilia'' or lesser purple emperor, a butterfly
*Ilium (bone) (plural: "ilia"), pelvic bone
People
* Ilia (name), numerous
**Ilia II, the current Catholicos-Patriarch of All Georgia
Places
*Ilia, ...
, partial ischia
Ischia ( , , ) is a volcanic island in the Tyrrhenian Sea. It lies at the northern end of the Gulf of Naples, about from Naples. It is the largest of the Phlegrean Islands. Roughly trapezoidal in shape, it measures approximately east to wes ...
, and both femora
The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with t ...
, both tibia
The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...
e and fibula
The fibula or calf bone is a human leg, leg bone on the Lateral (anatomy), lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long ...
e.
Distinguishing anatomical features
A differential diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism.
According to Arbour and Currie (2013), ''Scolosaurus'' (including the Two Medicine material) can be distinguished from other ankylosaurines based on the following characteristics:
* the squamosal The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone.
In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestral co ...
horns are proportionately longer, are backswept, and have distinct apices (unlike ''Anodontosaurus lambei'' and ''Euoplocephalus tutus'')
* the presence of a small circular caputegula at the bases of the squamosal and quadratojugal bones (unlike ''Euoplocephalus tutus'')
* the postacetabular process of the ilium
Ilium or Ileum may refer to:
Places and jurisdictions
* Ilion (Asia Minor), former name of Troy
* Ilium (Epirus), an ancient city in Epirus, Greece
* Ilium, ancient name of Cestria (Epirus), an ancient city in Epirus, Greece
* Ilium Building, a ...
is proportionately longer (compared to ''Anodontosaurus lambei'', ''Dyoplosaurus acutosquameus'' and ''Euoplocephalus tutus'')
* the presence of proportionately large circular medial osteoderms with low central prominences, and compressed, half-moon shaped lateral/distal osteoderms on the cervical half rings (unlike ''Anodontosaurus lambei'' and ''Euoplocephalus tutus'')
* the sacral ribs are laterally-directed (unlike ''Dyoplosaurus acutosquameus'')
* the osteoderms are conical, with centrally positioned apices on the lateral sides of the anterior portion of the tail (unlike ''Dyoplosaurus acutosquameus'')
* the tail club knob appears circular in dorsal view, unlike that of ''Anodontosaurus'', which appears wider than it is long or that of ''Dyoplosaurus'', which appears longer than it is wide
* the presence of anteriorly-directed nares, and the absence of a continuous keel between the squamosal horn and the supraorbital bones (unlike ''Ankylosaurus magniventris'')
Paleoecology
Habitat
Argon-argon radiometric dating indicates that the Two Medicine Formation was deposited between 83.5 and 70.6 million years ago, during the Campanian stage of the Late Cretaceous period, in what is now northwestern Montana. If ''Oohkotokia'' is the same as ''Scolosaurus'' it would mean that ''Scolosaurus'' existed for around 3 million years. The Two Medicine Formation correlates to the Belly River Group in southwest Alberta, and the Pakowki Formation eastward. The Two Medicine Formation was deposited by rivers and deltas between the western shoreline of the Western Interior Seaway
The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, and the Western Interior Sea) was a large inland sea that split the continent of North America into two landmasses. The ancient se ...
and the eastward advancing margin of the Cordilleran Overthrust Belt. Since the mid-Cretaceous, North America had been divided in half by this seaway, with much of Montana and Alberta below the surface of the water. However, the uplift of the Rocky Mountains
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 ...
forced the seaway to retreat eastwards and southwards. Rivers flowed down from the mountains and drained into the seaway, carrying sediment that formed the Two Medicine Formation and the Judith River Group. About 73 million years ago, the seaway began to advance westwards and northwards again, and the entire region was covered by the Bearpaw Sea, now preserved throughout the Western US and Canada by the massive Bearpaw Shale
The Bearpaw Formation, also called the Bearpaw Shale, is a geologic formation of Late Cretaceous ( Campanian) age. It outcrops in the U.S. state of Montana, as well as the Canadian provinces of Alberta and Saskatchewan, and was named for the Bear ...
, which overlies the Two Medicine. Below this formation are the nearshore deposits of the Virgelle Sandstone. Lithologies, invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
faunas, and plant and pollen data support that the Two Medicine Formation was deposited in a seasonal, semi-arid climate with possible rainshadows from the Cordilleran highlands. This region experienced a long dry season and warm temperatures. The extensive red beds and caliche
Caliche () is a sedimentary rock, a hardened natural cement of calcium carbonate that binds other materials—such as gravel, sand, clay, and silt. It occurs worldwide, in aridisol and mollisol soil orders—generally in arid or semiarid regio ...
horizons of the upper Two Medicine are evidence of at least seasonally arid conditions.
Paleofauna
''Scolosaurus'' shared its paleoenvironment
Paleoecology (also spelled palaeoecology) is the study of interactions between organisms and/or interactions between organisms and their environments across geologic timescales. As a discipline, paleoecology interacts with, depends on and informs ...
with other dinosaurs, such as the duck-billed hadrosaurs
Hadrosaurids (), 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 family, which inclu ...
''Hypacrosaurus
''Hypacrosaurus'' (meaning "near the highest lizard" reek υπο-, ''hypo-'' = less + ακρος, ''akros'', high
Reek may refer to:
Places
* Reek, Netherlands, a village in the Dutch province of North Brabant
* Croagh Patrick, a mountain in the west of Ireland nicknamed "The Reek"
People
* Nikolai Reek (1890-1942), Estonian military commander
* Salme Reek ( ...
because it was almost but not quite as large as ''Tyrannosaurus'') was a genus of hadrosaurid, duckbill dinosaur similar in app ...
'', ''Acristavus
''Acristavus'' (meaning "non-crested grandfather") is a genus of saurolophine dinosaur. Fossils have been found from the Campanian Two Medicine Formation in Montana and Wahweap Formation in Utah, United States. The type species ''A. gagslarsoni'' ...
'', ''Gryposaurus
''Gryposaurus'' (meaning "hooked-nosed (Greek ''grypos'') lizard"; sometimes incorrectly translated as "griffin (Latin ''gryphus'') lizard") was a genus of duckbilled dinosaur that lived about 80 to 75 million years ago, in the Late Cretaceo ...
'', ''Brachylophosaurus
''Brachylophosaurus'' ( or ; meaning "short-crested lizard", Greek ''brachys'' = short + ''lophos'' = crest + ''sauros'' = lizard, referring to its small crest) was a mid-sized member of the hadrosaurid family of dinosaurs. It is known from sev ...
'', ''Glishades
''Glishades'' (from the Latin "gilia" meaning "mud", and the Greek "Hades", the mythological lord of the underworld; also meaning "unseen"; together meaning "concealed in mud", referring to being found in sedimentary strata while metaphorically ...
'', ''Prosaurolophus
''Prosaurolophus'' (; meaning "before ''Saurolophus''", in comparison to the later dinosaur with a similar head crest) is a genus of hadrosaurid (or duck-billed) dinosaur from the Late Cretaceous of North America. It is known from the remains of ...
'' and ''Maiasaura
''Maiasaura'' (from the Greek ''μαῖα'', meaning "good mother" and ''σαύρα'', the feminine form of ''saurus'', meaning "reptile") is a large herbivorous saurolophine hadrosaurid ("duck-billed") dinosaur genus that lived in the area curr ...
'', and the ankylosaur
Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. ...
''Edmontonia
''Edmontonia'' is a genus of panoplosaurin nodosaurid dinosaur from the Late Cretaceous Period. It is part of the Nodosauridae, a family within Ankylosauria. It is named after the Edmonton Formation (now the Horseshoe Canyon Formation in Canad ...
''. Volcanic eruption
Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are ...
s from the west periodically blanketed the region with ash, resulting in large-scale mortality, while simultaneously enriching the soil for future plant growth. Fluctuating sea levels also resulted in a variety of other environments at different times and places within the Judith River Group, including offshore and nearshore marine habitats, coastal wetlands, deltas and lagoons, in addition to the inland floodplains. The Two Medicine Formation was deposited at higher elevations farther inland than the other two formations. A large variety of ceratopsians
Ceratopsia or Ceratopia ( or ; Ancient Greek, Greek: "horned faces") is a group of herbivore, herbivorous, beaked dinosaurs that thrived in what are now North America, Europe, and Asia, during the Cretaceous Period (geology), Period, although anc ...
coexisted in this region, which included ''Achelousaurus
''Achelousaurus'' () is a genus of centrosaurine ceratopsid dinosaur that lived during the Late Cretaceous Period of what is now North America, about 74.2 million years ago. The first fossils of ''Achelousaurus'' were collected in Mon ...
'', ''Brachyceratops
''Brachyceratops'' ('short horned face') is a dubious genus of ceratopsian dinosaur known only from partial juvenile specimens dating to the late Cretaceous Period of Montana, United States.
''Brachyceratops'' has historically been known from ...
'', '' Cerasinops'', ''Einiosaurus
''Einiosaurus'' is a genus of herbivorous centrosaurine ceratopsian dinosaur from the Upper Cretaceous (Campanian stage) of northwestern Montana. The name means 'buffalo lizard', in a combination of Blackfeet Indian ''eini'' and Latinized Ancien ...
'', ''Prenoceratops
''Prenoceratops'', (meaning 'bent or prone-horned face' and derived from Greek ''prene-/πρηνη-'' meaning 'bent forwards' or 'prone', ''cerat-/κερατ-'' meaning 'horn' and ''-ops/ωψ'' meaning 'face') is a genus of ceratopsian dinosaur f ...
'' and ''Rubeosaurus
''Styracosaurus'' ( ; meaning "spiked lizard" from the Ancient Greek / "spike at the butt-end of a spear-shaft" and / "lizard") is a genus of herbivorous ceratopsian dinosaur from the Cretaceous Period (Campanian stage), about 75.5 to 74.5  ...
''. Carnivores included an unnamed troodontid, possibly ''Stenonychosaurus
''Stenonychosaurus'' (meaning "narrow claw lizard") is a genus of troodontid dinosaur from the Late Cretaceous Dinosaur Park Formation of Alberta, Canada, as well as possibly the Two Medicine Formation. The type and only species, ''S. inequalis ...
'', the dromaeosaur
Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...
s ''Bambiraptor
''Bambiraptor'' is a Late Cretaceous, 72-million-year-old, bird-like dromaeosaurid theropod dinosaur described by scientists at the University of Kansas, Yale University, and the University of New Orleans.
The holotype fossil is less than one m ...
'' and ''Saurornitholestes
''Saurornitholestes'' ("lizard-bird thief") is a genus of carnivorous dromaeosaurid theropod dinosaur from the late Cretaceous of Canada (Alberta) and the United States (Montana, New Mexico, Alabama, North Carolina, and South Carolina).
Two spec ...
'', and the large tyrannosaurids
Tyrannosauridae (or tyrannosaurids, meaning " tyrant lizards") is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to thirteen genera, including the eponymous '' Tyrannosaurus''. The exact number of ...
''Daspletosaurus
''Daspletosaurus'' ( ; meaning "frightful lizard") is a genus of tyrannosaurid dinosaur that lived in Laramidia between about 79.5 and 74 million years ago, during the Late Cretaceous Period. The genus ''Daspletosaurus'' contains three ...
'' and ''Gorgosaurus
''Gorgosaurus'' ( ; ) is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period (Campanian), between about 76.6 and 75.1 million years ago. Fossil remains have been found in the ...
''.["3.11 Montana, United States; 2. Lower Two Medicine Formation," in Weishampel, et al. (2004).]
The excellent vertebrate
Vertebrates () comprise all animal taxon, taxa within the subphylum Vertebrata () (chordates with vertebral column, backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the ...
fossil record of Two Medicine and Judith River rocks resulted from a combination of abundant animal life, periodic natural disasters, and the deposition of large amounts of sediment. Many types of freshwater and estuarine fish
Coastal fish, also called inshore fish or neritic fish, inhabit the sea between the shoreline and the edge of the continental shelf. Since the continental shelf is usually less than deep, it follows that pelagic coastal fish are generally ep ...
are represented, including shark
Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachi ...
s, rays
Ray may refer to:
Fish
* Ray (fish), any cartilaginous fish of the superorder Batoidea
* Ray (fish fin anatomy), a bony or horny spine on a fin
Science and mathematics
* Ray (geometry), half of a line proceeding from an initial point
* Ray (gra ...
, sturgeons, gar
Gars are members of the family Lepisosteidae, which are the only surviving members of the Ginglymodi, an ancient holosteian group of ray-finned fish, which first appeared during the Triassic, over 240 million years ago. Gars comprise seven livin ...
s and others. This region preserves the remains of many aquatic amphibians and reptiles
Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephali ...
, including bivalves
Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, biv ...
, gastropods
The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda ().
This class comprises snails and slugs from saltwater, from freshwater, and from land. ...
, frog
A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" '' Triadobatrachus'' is ...
s, salamander
Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten ...
s, turtle
Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked ...
s, ''Champsosaurus
''Champsosaurus'' is an extinct genus of crocodile-like choristodere reptile, known from the Late Cretaceous and early Paleogene periods of North America and Europe (Campanian-Paleocene). The name ''Champsosaurus'' is thought to come from , () ...
'' and crocodilia
Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest livi ...
ns. Terrestrial lizards, including whiptails, skink
Skinks are lizards belonging to the family Scincidae, a family in the infraorder Scincomorpha. With more than 1,500 described species across 100 different taxonomic genera, the family Scincidae is one of the most diverse families of lizards. S ...
s, monitors
Monitor or monitor may refer to:
Places
* Monitor, Alberta
* Monitor, Indiana, town in the United States
* Monitor, Kentucky
* Monitor, Oregon, unincorporated community in the United States
* Monitor, Washington
* Monitor, Logan County, West Vir ...
and alligator lizards
An alligator lizard is any one of various species of lizards in the family Anguidae that have some shared characteristics.
The term may specifically refer to:
Species of the genus ''Elgaria'':
* Northern alligator lizard (''Elgaria coerulea'')
* ...
have also been discovered. Pterosaur
Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the Order (biology), order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cre ...
s like ''Montanazhdarcho
''Montanazhdarcho'' is a genus of azhdarchoid pterosaur from the Late Cretaceous period (Campanian stage) of what is now the state of Montana, United States. ''Montanazhdarcho'' is known from only one species, ''M. minor''.
Discovery
The holo ...
'' and ''Piksi
''Piksi'' is a potential pterosaurLongrich, N.R., Martill, D.M., and Andres, B. (2018). Late Maastrichtian pterosaurs from North Africa and mass extinction of Pterosauria at the Cretaceous-Paleogene boundary. PLoS Biology, 16(3): e2001663. genu ...
'' as well as birds
Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...
like ''Apatornis
''Apatornis'' is a genus of prehistoric birds endemic to North America during the late Cretaceous. It currently contains a single species, ''Apatornis celer'', which lived around the Santonian-Campanian boundary, dated to about 83.5 million year ...
'' and ''Avisaurus
''Avisaurus'' (meaning "bird lizard") is a genus of Enantiornithes, enantiornithine bird from the Late Cretaceous of North America.
Discovery
''Avisaurus archibaldi'' was discovered in the Late Cretaceous Hell Creek Formation of North America (M ...
'' flew overhead. Several varieties of mammals, such as the multituberculate ''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 t ...
'' coexisted with dinosaurs in the Two Medicine Formation and the various other formations that make up the Judith River wedge. Fossilized eggs belonging to a dromaeosaur
Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...
have been recovered here. When water was plentiful, the region could support a great deal of plant and animal life, but periodic droughts often resulted in mass mortality.
See also
* Timeline of ankylosaur research
This timeline of ankylosaur research is a chronological listing of events in the history of paleontology focused on the ankylosaurs, quadrupedal herbivorous dinosaurs who were protected by a covering bony plates and spikes and sometimes by a clu ...
*2018 in paleontology
Flora Plants
Fungi
Cnidarians
Research
* New three dimensionally phosphatized microfossils of coronate scyphozoan '' Qinscyphus necopinus'', including a new type of fossil embryo, are described from the Cambrian (Fortunian) Kuanchuanpu F ...
References
{{Taxonbar, from=Q7434319
Ankylosaurids
Late Cretaceous dinosaurs of North America
Fossil taxa described in 1928
Taxa named by Franz Nopcsa von Felső-Szilvás
Dinosaur Park fauna
Oldman fauna
Paleontology in Alberta
Fossils of Canada
Cretaceous Canada
Paleontology in Montana
Campanian genus first appearances
Campanian genus extinctions
Ornithischian genera