''Regaliceratops'' (meaning "Royal horned face") is a

monospecific In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispe ...

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 ...

chasmosaurine Chasmosaurinae is a subfamily of ceratopsid dinosaurs. They were one of the most successful groups of herbivores of their time. Chasmosaurines appeared in the early Campanian, and became extinct, along with all other non-avian dinosaurs, during ...

ceratopsid Ceratopsidae (sometimes spelled Ceratopidae) is a family of ceratopsian dinosaurs including ''Triceratops'', '' Centrosaurus'', and '' Styracosaurus''. All known species were quadrupedal herbivores from the Upper Cretaceous. All but one species ar ...

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 ...

from

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 ...

that lived during 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'', ...

(middle

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, 68.5 to 67.5 Ma) in what is now the

St. Mary River Formation The St. Mary River Formation is a geologic formation of Late Cretaceous (71.9-67 Ma) age of the Western Canada Sedimentary Basin in southwestern Alberta and northwesternmost Montana. It was first described from outcrops along the St. Mary River ...

. The type and only species, ''Regaliceratops peterhewsi'', is known only from an adult individual with a nearly complete

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, t ...

lacking the

lower jaw In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

, which was nicknamed "

Hellboy Hellboy is a fictional superhero created by writer-artist Mike Mignola. The character first appeared in ''San Diego Comic-Con Comics'' #2 (August 1993), and has since appeared in various eponymous miniseries A miniseries or mini-series is a t ...

". ''Regaliceratops'' was named in

2015 File:2015 Events Collage new.png, From top left, clockwise: Civil service in remembrance of November 2015 Paris attacks; Germanwings Flight 9525 was purposely crashed into the French Alps; the rubble of residences in Kathmandu following the April ...

by Caleb M. Brown and Donald M. Henderson. ''Regaliceratops'' has an estimated length of and body mass of . The skull of ''Regaliceratops'' displays features more similar to

centrosaurines Centrosaurinae (from the Greek, meaning "pointed lizards") is a subfamily of ceratopsid dinosaurs, a group of large quadrupedal ornithischians. Centrosaurine fossil remains are known primarily from the northern region of Laramidia (modern day Alb ...

, which suggests

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

in display morphology in ceratopsids.

Discovery and naming

In 2005, a skull of a

was discovered by

geologist A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, earth science, or geophysics, alt ...

Peter Hews from the

, along the

Oldman River The Oldman River is a river in southern Alberta, Canada. It flows roughly west to east from the Rocky Mountains, through the communities of Fort Macleod, Lethbridge, and on to Grassy Lake, where it joins the Bow River to form the South Saskatche ...

in southwestern

. The skull was located in well cemented

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, ...

and with the tip of the snout sticking out of a cliff. The skull was excavated in 2006 and 2008 by a team of the

Royal Tyrrell Museum The Royal Tyrrell Museum of Palaeontology (RTMP, and often referred to as the Royal Tyrrell Museum) is a palaeontology museum and research facility in Drumheller, Alberta, Canada. The museum was named in honour of Joseph Burr Tyrrell, and is situ ...

and was removed in blocks. The excavation was described as being complicated as the specimen was in close proximity to protected spawning habitat of

bull trout The bull trout (''Salvelinus confluentus'') is a Salvelinus, char of the family Salmonidae native to northwestern North America. Historically, ''S. confluentus'' has been known as the "Dolly Varden trout, Dolly Varden" (''S. malma''), but was re ...

in the river. The specimen was nicknamed "

" due to difficultly and time consuming excavation, in addition to the hard matrix, and the presence of small

postorbital The ''postorbital'' is one of the bones in vertebrate skulls which forms a portion of the dermal skull roof and, sometimes, a ring about the orbit. Generally, it is located behind the postfrontal and posteriorly to the orbital fenestra. In some v ...

horncores with resorption pits. The specimen was subsequently named and described in

by Caleb M. Brown and Donald M. Henderson. 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 ...

specimen, TMP 2005.055.0001, consists of a nearly complete

that is missing only the

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ships * Ros ...

. The skull was deformed by compression and its rear and underside are obscured by the

matrix Matrix most commonly refers to: * ''The Matrix'' (franchise), an American media franchise ** '' The Matrix'', a 1999 science-fiction action film ** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchi ...

. The specimen represents an adult individual as the cranial elements are fused together and the bone surface texture is rugose, unlike that of juvenile and subadult ceratopsids. The

generic Generic or generics may refer to: In business * Generic term, a common name used for a range or class of similar things not protected by trademark * Generic brand, a brand for a product that does not have an associated brand or trademark, other ...

name, ''Regaliceratops'', is derived from the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

word "''regalis''" (royal) and 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 "''keras''", (horn), and "''ops''", (face). The generic name is in reference to the

crown A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, partic ...

-shaped parietosquamosal frill and the Royal Tyrrell Museum. The

specific Specific may refer to: * Specificity (disambiguation) * Specific, a cure or therapy for a specific illness Law * Specific deterrence, focussed on an individual * Specific finding, intermediate verdict used by a jury in determining the final ...

name, ''peterhewsi'', honours the geologist Peter Hews, who discovered the type specimen.

Description

Size and distinguishing traits

''Regaliceratops'' was a large ceratopsian, reaching in length and in body mass. Brown & Henderson (2015) diagnosed ''Regaliceratops'' based on the presence of a single, midline epiparietal ossification that is offset from the plane of the frill and other epiparietals towards the

with parietals projecting towards the posterior end that have a roughly

triangular A triangle is a polygon with three edges and three vertices. It is one of the basic shapes in geometry. A triangle with vertices ''A'', ''B'', and ''C'' is denoted \triangle ABC. In Euclidean geometry, any three points, when non-collinear, ...

transverse cross-section; a prominent midline ridge on that parietal that merges with the median epiparietal; paired epiparietal ossifications that are long, flat, and roughly

pentagon In geometry, a pentagon (from the Greek language, Greek πέντε ''pente'' meaning ''five'' and γωνία ''gonia'' meaning ''angle'') is any five-sided polygon or 5-gon. The sum of the internal angles in a simple polygon, simple pentagon is ...

al shaped; a prominent postorbital ridge that runs diagonally from the supraorbital horncore to the base of 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 ...

; parietal

fenestra A fenestra (fenestration; plural fenestrae or fenestrations) is any small opening or pore, commonly used as a term in the biological sciences. It is the Latin word for "window", and is used in various fields to describe a pore in an anatomical ...

e that are small in size to

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such a ...

as in ''

Kosmoceratops ''Kosmoceratops'' () is a genus of ceratopsid dinosaur that lived in North America about 76–75.9 million years ago during the Late Cretaceous period. Specimens were discovered in Utah in the Kaiparowits Formation of the Grand Staircase–Esc ...

''; and

nasal Nasal is an adjective referring to the nose, part of human or animal anatomy. It may also be shorthand for the following uses in combination: * With reference to the human nose: ** Nasal administration, a method of pharmaceutical drug delivery * ...

horncores that are larger than the postorbital horncores as in '' Chasmosaurus bellis'' and ''

Vagaceratops ''Vagaceratops'' (meaning "wandering (''vagus'', Latin) horned face", in reference to its close relationship with '' Kosmoceratops'' from Utah) is a genus of herbivorous ceratopsian dinosaur. It is a chasmosaurine ceratopsian which lived durin ...

''.

Cranium

The

snout A snout is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw. In many animals, the structure is called a muzzle, rostrum, or proboscis. The wet furless surface around the nostrils of the nose of many mammals is ...

of the holotype specimen is short and tall, although it has been exaggerated by the tectonic shortening of the skull. The paired

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has ...

e form the median premaxillary

septum In biology, a septum (Latin for ''something that encloses''; plural septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Human anatomy * Interat ...

, with the rostral portion of the median premaxillary septum being thin forming the prominent septal

fossa Fossa may refer to: Animals * Fossa (animal), the common name of a carnivoran mammal of genus ''Cryptoprocta'' endemic to Madagascar * ''Fossa'', the Latin genus name of the Malagasy civet, a related but smaller mammal endemic to Madagascar Pla ...

. Unlike ''

Triceratops ''Triceratops'' ( ; ) is a genus of herbivorous chasmosaurine ceratopsid dinosaur that first appeared during the late Maastrichtian stage of the Late Cretaceous period, about 68 million years ago in what is now North America. It is ...

'' and ''

Titanoceratops ''Titanoceratops'' (meaning "titanic horned face") is a controversial genus of herbivorous ceratopsian dinosaur. It was a giant chasmosaurine ceratopsian that lived in the Late Cretaceous period (Campanian stage, about 75 million years agoFowle ...

'', the prominent septal fossa lacks the accessory strut. The fossa is further thinned at the caudal portion and is spreaded throughout by the presence of a large interpremaxillary fenestra as in ''

Anchiceratops ''Anchiceratops'' ( ) is an extinct genus of chasmosaurinae, chasmosaurine ceratopsid dinosaur that lived approximately 72 to 71 million years ago during the latter part of the Cretaceous Period (geology), Period in what is now Alberta, Canada. ' ...

'', ''

Arrhinoceratops ''Arrhinoceratops'' (meaning "no nose-horn face", derived from the Ancient Greek "a-/α-" "no", rhis/ῥίς "nose" "keras/κέρας" "horn", "-ops/ὤψ" "face") is a genus of herbivorous ceratopsian dinosaur. The name was coined as its origina ...

'' and ''

''. ''Regaliceratops'', and other chasmosaurines, has the caudal wall of the interpremaxillary

bounded by a condensed narial strut that moves back and forth from the floor of the premaxillae to the upper process of the premaxillae. Unlike ''Titanoceratops'' and ''Triceratops'', the narial strut isn't as broad and triangular but is, instead, sinuous in shape. The premaxillae flare towards the sides which form the rostroventral margin of the external nares on the rostral and ventral margins. The maxillary process projects caudodorsally from the flared underside aspect of the premaxilla. Unlike

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 ...

chasmosaurines such as ''

Chasmosaurus ''Chasmosaurus'' ( ) is a genus of ceratopsid dinosaur from the Upper Cretaceous Period of North America. Its name means 'opening lizard', referring to the large openings (fenestrae) in its frill (Greek ''chasma'' meaning 'opening' or 'hollow' ...

'' and ''

Utahceratops ''Utahceratops'' is an extinct genus of ceratopsian dinosaur that lived approximately 76.4~75.5 million years ago during the Late Cretaceous period in what is now Utah. ''Utahceratops'' was a large-sized, robustly-built, ground-dwelling, quadru ...

'', the caudoventral process of Regaliceratops tapers caudally without forking, and inserts between the

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The ...

and

towards the sides. The upper margin of the external naris is formed by the rostral process and horncore base, and extends caudal to the rostral margin of the

maxillary Maxillary means "related to the maxilla (upper jaw bone)". Terms containing "maxillary" include: * Maxillary artery *Maxillary nerve In neuroanatomy, the maxillary nerve (V) is one of the three branches or divisions of the trigeminal nerve, ...

tooth row. As in ''

Bravoceratops ''Bravoceratops'' is a genus of large chasmosaurine ceratopsid dinosaur that lived approximately 70 million years ago, and is known from the Late Cretaceous Javelina Formation in what is now Texas, United States. Discovery and naming ''Bravoce ...

'', the nasal shows no constriction situated caudal to the horncore. As in ''Chasmosaurus'', the midpoint of the horncore is positioned at the caudal extreme of the external naris. The nasal horncore has an estimated preserved height of 148 mm and an estimated total height range of 240 to 280mm when the side slopes of the horncore are extrapolated. The nasal horncore is straight and has a tear drop shape in horizontal cross section. Regaliceratops_Royal_Tyrrell_1

The orbital margin shows a sharp ridge that flares towards the sides, which may be a result of post-depositional deformation, and a smooth confluent margin on the right and left margins. The

orbits In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a ...

are highly

ellipsoid An ellipsoid is a surface that may be obtained from a sphere by deforming it by means of directional scalings, or more generally, of an affine transformation. An ellipsoid is a quadric surface; that is, a surface that may be defined as the ...

al, unlike other ceratopsids that have slightly ellipsoidal orbits. The rostrodorsal margin of the orbital rim consists of the palpebral, and swells towards the sides and rostrums which forms an antorbital buttress. The antorbital buttress is larger than that of most chasmosaurines. Unlike ''Kosmoceratops'', the postorbital horncore of ''Regaliceratops'' is arranged slightly caudal to the orbit but shares the narrow base. The postorbital horncores are also directed upwards and are procurved towards the rostrum in side view, as in ''

Pentaceratops ''Pentaceratops'' ("five-horned face") is a genus of herbivorous ceratopsid dinosaur from the late Cretaceous Period of what is now North America. Fossils of this animal were first discovered in 1921, but the genus was named in 1923 when its t ...

''. The postorbital horncores are smaller in size to the nasal horncore and has a surface that is oriented

vascular Blood vessels are the structures of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away from ...

grooves. A prominent postorbital ridge is present caudomedially to the horncore which is equivalent to the supraorbital

scale row. The laterotemporal fenestrae are bounded by the

jugal The jugal is a skull bone found in most reptiles, amphibians and birds. In mammals, the jugal is often called the malar or zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species. Anat ...

towards the rostrum and squamosal towards the posterior. The orbital margin is smooth and not thickened. The base of the epijugal is only slightly smaller than the postorbital horncores. The jugal's caudal margin forms the border of the laterotemporal fenestrae, which is also bordered by the laterotemporal process of the squamosal. However, this may not have been the true morphology due to the lack of a distinct

quadratojugal The quadratojugal is a skull bone present in many vertebrates, including some living reptiles and amphibians. Anatomy and function In animals with a quadratojugal bone, it is typically found connected to the jugal (cheek) bone from the front an ...

. Bounded by the squamosal towards the posterior is the jugal notch. Triceratops_skull_FMNH

The frill of ''Regaliceratops'' is nearly

semicircle In mathematics (and more specifically geometry), a semicircle is a one-dimensional locus of points that forms half of a circle. The full arc of a semicircle always measures 180° (equivalently, radians, or a half-turn). It has only one line ...

in shape in rostrodorsal view, with ossifications along the circumference. The frill is also short and wide, with the greatest transverse width being located at its midlength as in ''

Torosaurus ''Torosaurus'' ("perforated lizard", in reference to the large openings in its frill) is a genus of herbivorous ceratopsid dinosaur that lived during the late Maastrichtian stage of the Cretaceous period, between 68 and 66 million years ago, tho ...

'' and ''Triceratops''. The left squamosal has an elongated caudal portion, with a lateral margin that has a prominent jugal notch that is followed by a margin towards the rostrum that is continuous with that of the parietal caudal margin and bears triangular epiossifications. The lateral margin of the parietal has a straight suture with the medial edge of the squamosals and the caudal margin forms the middle half of the broad semicircle of the frill. The frill's caudalmost portion is located in the midline and the midline bars ends in a rostrally projecting bone. A prominent sagittal swelling is dominant on the midline of the parietal and forms a keel. The large, medial epiparietal is positioned where the sideways curving epiparietal hooks of ''Anchiceratops'' are and differs from the epiparietal hooks as it is confluent with the median ridge and is triangular in cross-section. A median epiossification on the parietal of the frill is possibly similar to those of ''Ojoceratops'' and ''Bravoceratops''. The frill is also adorned with seven paired epiossifications that gradually decrease in size, which are similar in shape to those of ''Anchiceratops'' but are similar in placement to ''Triceratops''. Two epiparietals are pentagonal in shape and may represent the largest epiossifications recorded in chasmosaurines. Triangular in shape are three rostralmost episquamosals which decrease in size towards the rostrum, while spade-shaped is the caudalmost episquamosal. The large pentagonal epiparietals and the smaller caudalmost episquamosal are both transitional in size and shape. The cranial ornamentation of ''Regaliceratops'' is similar to that of centrosaurine ceratopsids as the nasal

horn Horn most often refers to: * Horn (acoustic), a conical or bell shaped aperture used to guide sound ** Horn (instrument), collective name for tube-shaped wind musical instruments * Horn (anatomy), a pointed, bony projection on the head of various ...

and epiossifications are represented as larger relative to the postorbital horns and frill length. The similarities between the cranial ornamentation of ''Regaliceratops'' and centrosaurines indicates

in horn morphology. Brown & Henderson (2015) hypothesised that, not only did it convergently evolve morphologically, but also behaviourally after the

extinction Extinction is the termination of a kind of organism or of a group of kinds ( taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed ...

in the early Maastrichtian as convergent horn evolution in mammals often correlates with convergent social behaviours.

Classification

Brown & Henderson (2015) originally placed ''Regaliceratops'' within

Triceratopsini Triceratopsini is a tribe of herbivorous chasmosaurine dinosaurs that lived between the late Campanian to the late Maastrichtian stages of the Cretaceous period, between 74.73 and 66 million years ago. Fossils of these animals have been found in ...

, in a

polytomy An internal node of a phylogenetic tree is described as a polytomy or multifurcation if (i) it is in a rooted tree and is linked to three or more child subtrees or (ii) it is in an unrooted tree and is attached to four or more branches. A tr ...

with ''

Eotriceratops ''Eotriceratops'' (meaning "dawn three-horned face") is a genus of herbivorous ceratopsian dinosaurs which lived in the area of North America during the late Cretaceous period. The only named species is ''Eotriceratops xerinsularis''. Discovery ...

'', ''

Ojoceratops ''Ojoceratops'' ( meaning "Ojo Alamo horned face") is a genus of ceratopsian dinosaur which lived in what is now New Mexico, United States. ''Ojoceratops'' fossils have been recovered from strata of the Ojo Alamo Formation (Naashoibito Member), d ...

'', and a clade containing more nested taxa such as ''

Nedoceratops ''Nedoceratops'' (meaning "insufficient horned face") is a controversial genus of Ceratopsidae, ceratopsid dinosaur from the Late Cretaceous geologic period, period Lance Formation of North America. It is known only from a single skull discovered ...

'', ''

'' and ''

''. However, Mallon ''et al.'' (2016) found ''Regaliceratops'' to be outside of Triceratopsini, in a polytomy with ''

'', ''

'' and Triceratopsini. Dalman ''et al.'' (2022) once more recovered ''Regaliceratops'' within Triceratopsini, sister taxon to ''

Triceratops horridus ''Triceratops'' ( ; ) is a genus of herbivorous chasmosaurine ceratopsid dinosaur that first appeared during the late Maastrichtian stage of the Late Cretaceous period, about 68 million years ago in what is now North America. It is one of ...

'', ''

Triceratops prorsus ''Triceratops'' ( ; ) is a genus of herbivorous chasmosaurine ceratopsid dinosaur that first appeared during the late Maastrichtian stage of the Late Cretaceous period, about 68 million years ago in what is now North America. It is one ...

'' and ''Ojoceratops''. A phylogenetic analysis conducted by Mallon ''et al.'' (2016) is reproduced below. The results of an earlier analysis by Brown & Henderson (2015) are reproduced below.

Paleoenvironment

''Regaliceratops'' is known from the St. Mary River Formation which has been dated to the middle

stage of the

period. The lower St. Mary River Formation was deposited in

brackish water Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

environments, with the remainder of the formation being deposited in

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does in ...

fluvial In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluv ...

and

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...

environments. The formation is characterized by fine-grained

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

s, grey

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especia ...

s, coquinoid beds,

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes ...

aceous mudstones, coal beds, interbedded sandstone and

, with minor occurrences of carbonaceous shale.

Fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except ...

ginkgo ''Ginkgo'' is a genus of non-flowering seed plants. The scientific name is also used as the English name. The order to which it belongs, Ginkgoales, first appeared in the Permian, 270 million years ago, and is now the only living genus withi ...

es,

conifer Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All ex ...

Trapa The water caltrop is any of three extant species of the genus ''Trapa'': ''Trapa natans'', ''Trapa bicornis'' and the endangered ''Trapa rossica''. It is also known as buffalo nut, bat nut, devil pod, ling gok ( Chinese: 菱角), ling nut, lin ko ...

-like plants, sabaloid palms and at least six types of large

monocot Monocotyledons (), commonly referred to as monocots, ( Lilianae '' sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one embryonic leaf, or cotyledon. They constitute on ...

leaves are known from the formation.Riley, M.G. and Stockey, R.A.(2004). ''Cardstonia tolmanii'' gen. et sp. nov (Limnocharitaceae) from the Upper Cretaceous of Alberta, Canada. International Journal of Plant Sciences 165(5): 897-916. The fauna of the St. Mary River Formation consists of the

nodosaurid Nodosauridae is a family of ankylosaurian dinosaurs, from the Late Jurassic to the Late Cretaceous period in what is now North America, South America, Europe, and Asia. Description Nodosaurids, like their close relatives the ankylosaurids, w ...

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 ...

'', the leptoceratopsid

ceratopsia Ceratopsia or Ceratopia ( or ; Greek: "horned faces") is a group of herbivorous, beaked dinosaurs that thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassi ...

n ''

Montanoceratops ''Montanoceratops'' is an extinct genus of small ceratopsian dinosaur that lived approximately 70 million years ago during the latter part of the Cretaceous Period in what is now Montana and Alberta. ''Montanoceratops'' was a small sized, mode ...

'', the centrosaurine ceratopsid ''

Pachyrhinosaurus ''Pachyrhinosaurus'' (meaning in Greek "thick-nosed lizard", from ' (), thick; ' (), nose; and (), lizard) is an extinct genus of centrosaurine ceratopsid dinosaur from the Late Cretaceous period of North America. The first examples were disco ...

'', a ceratopsid that was previously considered to be ''Anchiceratops'', the albertosaurine

tyrannosaurid 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 genera ...

Albertosaurus ''Albertosaurus'' (; meaning "Alberta lizard") is a genus of tyrannosaurid theropod dinosaurs that lived in western North America during the Late Cretaceous Period (geology), Period, about 71 million years ago. The type species, ''A. sarc ...

'', the saurornitholestine

dromaeosaurid 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 ...

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 ...

'', the

troodontid Troodontidae is a clade of bird-like theropod dinosaurs. During most of the 20th century, troodontid fossils were few and incomplete and they have therefore been allied, at various times, with many dinosaurian lineages. More recent fossil disco ...

Troodon ''Troodon'' ( ; ''Troödon'' in older sources) is a wastebasket taxon and a dubious genus of relatively small, bird-like dinosaurs known definitively from the Campanian age of the Late Cretaceous period (about 77 mya). It includes at least ...

'', the mammals ''

Cimolomys ''Cimolomys'' is a mammal genus from the Upper Cretaceous of North America. It was a member of the extinct order Multituberculata within the suborder Cimolodonta and family Cimolomyidae. The genus ''Cimolomys'' was named by Othniel Charles Mar ...

'', ''

Meniscoessus ''Meniscoessus'' is a genus of extinct mammal from the Upper Cretaceous Period of what is now North America. It was a member of the extinct order Multituberculata, lying within the suborder Cimolodonta and family Cimolomyidae. Taxonomy The ...

'', ''

Mesodma ''Mesodma'' is an extinct genus of mammal, a member of the extinct order Multituberculata within the suborder Cimolodonta, family Neoplagiaulacidae. It lived during the upper Cretaceous and Paleocene Periods of what is now North America. The e ...

'', ''

Cimolodon ''Cimolodon'' is a genus of the extinct mammal order of Multituberculata within the suborder Cimolodonta and the family Cimolodontidae. Specimens are known from the Late Cretaceous of North America. Systematics The genus ''Cimolodon'' was nam ...

'', ''Pediomys'', ''

Didelphodon ''Didelphodon'' (from ''is''/nowiki>">/nowiki>''is''/nowiki> "opossum" plus "tooth") is a genus of stagodont metatherians from the Late Cretaceous of North America. Description Although perhaps little larger than a Virginia opossum, with a ...

'' and ''

Eodelphis ''Eodelphis'', from eo- plus /nowiki>''delphis''">/nowiki>/nowiki>''delphis'', thus meaning "very early opossum", is a genus of stagodont metatherians from the Late Cretaceous of North America, with distinctive crushing dentition. Named speci ...

'', the

fish Fish are aquatic, craniate, gill-bearing 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. Approximately 95% ...

Myledaphus ''Myledaphus'' is a genus of Late Cretaceous cartilaginous fish whose fossils are known from Canada, the Midwest of the United States, Olmos Formation of the Difunta Group of Mexico, and the Beshtyubin and Bissekty Formations of Uzbekistan. It ...

'' and ''

Lepisosteus ''Lepisosteus'' is a genus of gars in the family Lepisosteidae. Distribution While in the present day, ''Lepisosteus'' is only known across North America, fossil remains show it was much more widespread in the past, with specimens known from ...

'', the

crocodylomorph Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction. During Mesozoic and early Cenozoic times, cro ...

Leidyosuchus ''Leidyosuchus'' (meaning " Leidy's crocodile") is an extinct genus of alligatoroid from the Late Cretaceous of Alberta. It was named in 1907 by Lawrence Lambe, and the type species is ''L. canadensis''. It is known from a number of specimens f ...

'', and the

choristodere Choristodera (from the Greek χωριστός ''chōristos'' + δέρη ''dérē'', 'separated neck') is an extinct order of semiaquatic diapsid reptiles that ranged from the Middle Jurassic, or possibly Triassic, to the late Miocene (168 to ...

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 , () ...

''.Sloan, R.E. and Russell, L.S. 1974. Mammals of the St. Mary River Formation (Cretaceous) of southwestern Alberta. Life Sciences Contributions, Royal Ontario Museum, Number 95.

References

{{Taxonbar, from=Q20035817 Chasmosaurines Late Cretaceous dinosaurs of North America Fossil taxa described in 2015 Paleontology in Alberta Maastrichtian genus first appearances Maastrichtian genus extinctions Ornithischian genera

Discovery and naming

Description

Size and distinguishing traits

Cranium

Classification

Paleoenvironment

See also

References