''Yehuecauhceratops'' (meaning "ancient horned face") is a genus of horned

centrosaurine 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 Al ...

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 are k ...

dinosaur from 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'', the ...

Coahuila Coahuila (), formally Coahuila de Zaragoza (), officially the Free and Sovereign State of Coahuila de Zaragoza ( es, Estado Libre y Soberano de Coahuila de Zaragoza), is one of the 32 states of Mexico. Coahuila borders the Mexican states of N ...

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

. It contains a single species, ''Y. mudei'', described from two partial specimens by Rivera-Sylva ''et al.'' in 2016 and formally named by Rivera-Sylva ''et al.'' in 2017. It was a small centrosaurine with a body length of , making it smaller than ''

Agujaceratops ''Agujaceratops'' (meaning "horned face from Aguja") is a genus of horned dinosaur from the Late Cretaceous (Campanian) of west Texas. It is a chasmosaurine (long-frilled) ceratopsian. Two species are known, ''Agujaceratops mariscalensis'', and ...

'' and '' Coahuilaceratops'', the other two ceratopsids in its environment; the three may have been ecologically segregated. A ridge bearing a single roughened projection near the bottom of the

squamosal bone 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 ...

, which probably supported a small horn, allows ''Yehuecauhceratops'' to be distinguished from other centrosaurines. Its affinities to

nasutoceratops ''Nasutoceratops'' is an extinct genus of ceratopsian dinosaur. It is a basal centrosaurine which lived during the Late Cretaceous Period (late Campanian, about 76.0-75.5 Ma). Fossils have been found in southern Utah, United States. ''Nasutocer ...

in centrosaurines, such as ''

Avaceratops ''Avaceratops'' is a genus of small herbivorous ceratopsian dinosaurs which lived during the late Campanian during the Late Cretaceous Period in what are now the Northwest United States. Most fossils come from the Judith River Formation. Discove ...

'' and ''

Nasutoceratops ''Nasutoceratops'' is an extinct genus of ceratopsian dinosaur. It is a basal centrosaurine which lived during the Late Cretaceous Period (late Campanian, about 76.0-75.5 Ma). Fossils have been found in southern Utah, United States. ''Nasutocer ...

'', are supported by various morphological similarities to the former.

Discovery and naming

Specimens of ''Yehuecauhceratops'' were recovered during excavations from 2007 to 2011 in a locality near the town of La Salada, in Ocampo,

, about south of

Big Bend National Park Big Bend National Park is an American national park located in West Texas, bordering Mexico. The park has national significance as the largest protected area of Chihuahuan Desert topography and ecology in the United States, and was named after ...

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

. The rocks exposed in this locality belong to 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. Campanian s ...

Aguja Formation The Aguja Formation is a geological formation in North America, exposed in Texas, United States and Chihuahua and Coahuila in Mexico, whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered f ...

, although its precise location within the temporal range of the formation is difficult to establish. Specimens attributed to ''Yehuecauhceratops'' are stored in the palaeontological collection of the Museo del Desierto. 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 several ...

of ''Yehuecauhceratops'' has been given the specimen number CPC 274. It consists of a nearly complete left

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 The quadratojugal is a skull bone present in many vertebrates, including ...

, three fragments from the parietal, one fragment each from the

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 b ...

and

dentary 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 tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

, a complete

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 ...

and

femur 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 ...

, the portion of the ilium in front of the

acetabulum The acetabulum (), also called the cotyloid cavity, is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint. Structure There are three bones of the ''os coxae'' (hip bone) that c ...

, and part of a

dorsal vertebra In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical ...

with the

neural spine The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...

broken off. Parts of the ribs, fragments of the ossified tendons that supported the tail, and miscellaneous fragments are also known. Additionally, there is a

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 ...

l fragment that is too small to belong to CPC 274; this second specimen, not referred in 2017, has been labelled with the specimen number CPC 1478. Although these two specimens were initially described by Rivera-Sylva ''et al.'' in 2016 as an indeterminate centrosaurine, they were formally named in 2017 by Héctor Eduardo Rivera-Sylva, Eberhard Frey, Wolfgang Stinnesbeck, José Rubén Guzmán-Gutiérrez and Arturo Homero González-González, based on the diagnostic characters in the squamosal. The generic name ''Yehuecauhceratops'', pronounced "Ye-OO-ek-au-ceratops", is derived from the

Nahuatl Nahuatl (; ), Aztec, or Mexicano is a language or, by some definitions, a group of languages of the Uto-Aztecan language family. Varieties of Nahuatl are spoken by about Nahua peoples, most of whom live mainly in Central Mexico and have smaller ...

word ''yehuecauh'' ("ancient") 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 ...

suffix ''ceratops'' ("horned face"). Meanwhile, the specific name ''mudei'' references the acronym of the Museo del Desierto (MUDE).

Description

''Yehuecauhceratops'' was a small ceratopsid, with a length of about . The type specimen was likely a late subadult or adult, judging by the degree of fusion in the

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

Cranial material

The

of ''Yehuecauhceratops'' is the only element that allows it to be confidently distinguished from other

ceratopsids 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 are k ...

. It has a stepped edge on its border with the parietal, which is characteristic of all

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 ...

. Unlike more

derived Derive may refer to: * Derive (computer algebra system), a commercial system made by Texas Instruments * ''Dérive'' (magazine), an Austrian science magazine on urbanism *Dérive, a psychogeographical concept See also * *Derivation (disambiguatio ...

centrosaurines like ''

Styracosaurus ''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&nbs ...

'', ''

Centrosaurus ''Centrosaurus'' ( ; ) is a genus of herbivorous ceratopsian dinosaur from the Late Cretaceous of Canada. Their remains have been found in the Dinosaur Park Formation, dating from 76.5 to 75.5 million years ago. Discovery and naming The firs ...

'', and ''

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 discove ...

'', but more similarly to ''

'', the squamosal is longer than it is wide. The expanded rear portion of the squamosal is twice the length of the rest of the bone. At its top margin, the squamosal contributed to the outline of the supratemporal fenestra, the slit in the frill base. Along the outer edge of the squamosal, there are three prominent undulations that probably supported epiossifications, although the epiossifications themselves are missing. The second undulation is deflected slightly upwards like more derived centrosaurines. In ''

Wendiceratops ''Wendiceratops'' is a genus of herbivorous centrosaurine ceratopsian dinosaur from the Late Cretaceous of Canada. Discovery In 2010, Canadian fossil hunter Wendy Sloboda found a centrosaurine bonebed in the Pinhorn Provincial Grazing Reser ...

'' and more derived centrosaurines, however, there are at least four or five undulations, instead of three. There is a ridge running across the squamosal near the bottom of the bone; it is less prominent than in ''

'', and does not extend onto the fan-like back of the bone. Unlike ''Avaceratops'', ''Wendiceratops'', and ''

Albertaceratops ''Albertaceratops'' (meaning "Alberta horned face") was a genus of centrosaurine horned dinosaur from the middle Campanian-age Upper Cretaceous Oldman Formation of Alberta, Canada. Description ''Albertaceratops'' is unusual in combining long ...

'', the three smooth protuberances along the ridge are missing; instead, there is only one roughened protuberance near the middle of the ridge, which probably supported a small horn. These two characteristics, the position of the ridge and the single protuberance, are the

autapomorphies In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to t ...

of ''Yehuecauhceratops'', traits allowing it to be distinguished from other centrosaurines. Yehuecauhceratops-3

Judging by the fragments of the parietal, it was a relatively smooth bone. The largest and most thickened pieces, which originate from near the centre of the frill, suggest that ''Yehuecauhceratops'' probably had relatively small fenestrae, in contrast to most other centrosaurines but not to ''Avaceratops''. A parietal epiossification is preserved; it has a simple, crescent-shaped edge, not unlike the squamosal undulations in terms of its shape, and its surface is roughened. Like ''

Diabloceratops ''Diabloceratops'' is an extinct genus of centrosaurine ceratopsian dinosaur that lived approximately 81.4-81 million years ago during the latter part of the Cretaceous Period in what is now Utah, in the United States. ''Diabloceratops'' was ...

'', ''Avaceratops'', ''

Xenoceratops ''Xenoceratops'' (meaning "alien horned face") is a genus of centrosaurine ceratopsid dinosaur known from the Late Cretaceous (middle Campanian stage), and is known to have lived in what is currently Alberta, Canada. The genus has one known speci ...

'', and ''Nasutoceratops'', this epiossification is not immediately adjacent to or overlapped by another epiossification; instead, there is an inward undulation in the bone right next to the epiossification. A portion of the

contains the edge of the nostril; a ridge extending diagonally across the bone is, like that of ''Diabloceratops'', more prominent than that of ''Avaceratops''. The interior surface of the bone was roughened save for the top portion surrounding the nostril, which is also the thickest part of the bone. A piece of the

likely comes from the rear third of the jaw, judging by the presence of the

coronoid process of the mandible In human anatomy, the mandible's coronoid process (from Greek ''korōnē'', denoting something hooked) is a thin, triangular eminence, which is flattened from side to side and varies in shape and size. Its anterior border is convex and is continuou ...

. It preserves a row of teeth, containing six

tooth sockets Dental alveoli (singular ''alveolus'') are sockets in the jaws in which the roots of teeth are held in the alveolar process with the periodontal ligament. The lay term for dental alveoli is tooth sockets. A joint that connects the roots of the ...

with three fully erupted teeth, that was offset towards the midline of the animal from the centre of the bone.

Postcranial material

As is typical of centrosaurines, the

forms about half of the glenoid articulation. Like other ceratopsids, the

acromion In human anatomy, the acromion (from Greek: ''akros'', "highest", ''ōmos'', "shoulder", plural: acromia) is a bony process on the scapula (shoulder blade). Together with the coracoid process it extends laterally over the shoulder joint. The acro ...

was prominent and very roughened. On the bottom edge of the bone, there is an abrupt angle of 25° at the thickest point in the bone instead of a gradual curve. The top end of the scapula was widened to form a paddle-like shape, more prominently so than other centrosaurines. As in other ceratopsians, the ilium was strongly deflected, with the deflected portion of the bone being straight when viewed from the top. The robustly shafted

is straightened and minimally curved as in ''Avaceratops'', although part of this may be an artifact of crushing. On the femur, the

femoral head The femoral head (femur head or head of the femur) is the highest part of the thigh bone (femur). It is supported by the femoral neck. Structure The head is globular and forms rather more than a hemisphere, is directed upward, medialward, and a l ...

is rounded and globe-shaped, the

greater trochanter The greater trochanter of the femur is a large, irregular, quadrilateral eminence and a part of the skeletal system. It is directed lateral and medially and slightly posterior. In the adult it is about 2–4 cm lower than the femoral head.Stan ...

is separated from and rises above the level of the femoral head, and the fourth trochanter forms a prominent crest like in other centrosaurines. The

cnemial crest The cnemial crest is a crestlike prominence located at the front side of the head of the tibiotarsus or tibia in the legs of many mammals and reptiles (including birds and other dinosaurs). The main extensor muscle of the thigh In human anatomy ...

of the

is expanded and is about 40% of the width of the expanded end of the bone, which is similar to ''Avaceratops''. A

, which likely comes from near the neck-torso transition judging by the large

neural canal In the developing chordate (including vertebrates), the neural tube is the embryonic precursor to the central nervous system, which is made up of the brain and spinal cord. The neural groove gradually deepens as the neural fold become elevated, a ...

, has slightly pinched edges, with a depression on either side at the level of the neural canal. The articular ends of the vertebra are rounded and concave on both sides (or amphicoelous). The neural canal itself was about 25% taller than it was wide. The neural arch, which encloses the neural canal, is almost entirely fused to the rest of the bone; however, a small trace of the suture is slightly visible in some places.

Classification

phylogenetic analysis In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

conducted in 2016 found that ''Yehuecauhceratops'' occupied a fairly basal position in the

Centrosaurinae 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 Al ...

, being in the same clade as ''

'' and ''

'' (a clade subsequently named

ini). Indeed, ''Yehuecauhceratops'' and ''Avaceratops'' share a number of characters. The strict consensus of the phylogenetic trees recovered by the analysis is reproduced below. The unique, roughened protrusion of the

of ''Yehuecauhceratops'' is only otherwise seen among centrosaurines in '' Menefeeceratops'' from the much earlier

Menefee Formation The Menefee Formation is a lower Campanian geologic formation found in Colorado and New Mexico, United States. Description The Menefee Formation consists of fluvial sandstone, shale, and coal. Based on ammonite biostratigraphy, the age of the Me ...

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ker ...

, and ''

Crittendenceratops ''Crittendenceratops'' (meaning "horned face from the Fort Crittenden Formation") is a genus of horned centrosaurine ceratopsid dinosaur from the late Campanian Fort Crittenden Formation of Arizona. It contains a single species, ''C. krzyzanows ...

'', from the likewise earlier

Fort Crittenden Formation The Fort Crittenden Formation is a geological formation in Arizona whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.Weishampel, David B; et al. (2004). "Dinosaur dis ...

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

. However, since these specimens are separated in time by more than one million years, it is unlikely that they belong to the same genus. Additionally, the specimen UMNH VP16704, referred to as the "Nipple Butte skull", also resembles ''Yehuecauhceratops'' and ''Menefeeceratops'' in having a fan-shaped end of the squamosal, though it lacks this singular protrusion.

Paleoecology

The environment ''Yehuecauhceratops'' lived in, corresponding to the lower part of the upper

, would have been a freshwater-to-brackish

coastal marsh A tidal marsh (also known as a type of "tidal wetland") is a marsh found along rivers, coasts and estuaries which floods and drains by the tidal movement of the adjacent estuary, sea or ocean. Tidal marshes are commonly zoned into lower marshes ( ...

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 ...

that were part of a

river delta A river delta is a landform shaped like a triangle, created by deposition (geology), deposition of sediment that is carried by a river and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, res ...

. Sediments also record the presence of

oxbow lake An oxbow lake is a U-shaped lake or pool that forms when a wide meander of a river is cut off, creating a free-standing body of water. In South Texas, oxbows left by the Rio Grande are called '' resacas''. In Australia, oxbow lakes are call ...

s and some coastal marine deposits. Although the Mexican strata of the Aguja Formation have not been solidly dated, dating of other deposits belonging to the Aguja and the contemporary

Cerro del Pueblo Formation The Cerro del Pueblo Formation is a geological Formation (geology), formation in Coahuila, Mexico whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.Weishampel et al., ...

s has produced date ranges that overlap around 72.5 Ma. In

, the diversity of animals in the Aguja Formation is somewhat limited. Asides from ''Yehuecauhceratops'', other discovered remains include the

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, durin ...

'' Agujaceratops mavericus'',

pachycephalosaur Pachycephalosauria (; from Greek παχυκεφαλόσαυρος for 'thick headed lizards') is a clade of ornithischian dinosaurs. Along with Ceratopsia, it makes up the clade Marginocephalia. With the exception of two species, most pachyc ...

teeth; large

e from

hadrosaurid 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 ...

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 living ...

n teeth; and shell fragments from baenid and trionychid turtles. From contemporaneous deposits of the Aguja Formation in

, numerous dinosaurs are known; they include the chasmosaurine ''

Agujaceratops mariscalensis ''Agujaceratops'' (meaning "horned face from Aguja") is a genus of horned dinosaur from the Late Cretaceous (Campanian) of west Texas. It is a chasmosaurine (long-frilled) ceratopsian. Two species are known, ''Agujaceratops mariscalensis'', and ' ...

'', the

saurolophine Saurolophinae is a subfamily (biology), subfamily of hadrosaurid dinosaurs. It has since the mid-20th century generally been called the Hadrosaurinae, a group of largely non-crested hadrosaurs related to the crested sub-family Lambeosaurinae. How ...

Kritosaurus ''Kritosaurus'' is an incompletely known genus of hadrosaurid (duck-billed) dinosaur. It lived about 74.5-66 million years ago, in the Late Cretaceous of North America. The name means "separated lizard" (referring to the arrangement of the cheek ...

'', the pachycephalosaur ''

Texacephale ''Texacephale'' is a pachycephalosaurid dinosaur from the Campanian stage of the Late Cretaceous. Its fossils come from the Aguja Formation of Big Bend National Park, in Texas, and were described in 2010 by Longrich, Sankey and Tanke. The gen ...

'', and the tooth taxon ''

Richardoestesia ''Richardoestesia'' is a morphogenus of theropod dinosaur teeth, originally described from the Late Cretaceous of what is now North America. It currently contains two species, ''R. gilmorei'' and ''R. isosceles''. It has been used as a morphota ...

'', as well as unnamed lambeosaurines, nodosaurs,

tyrannosaurs Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent be ...

ornithomimids Ornithomimidae (meaning "bird-mimics") is a family of theropod dinosaurs which bore a superficial resemblance to modern ostriches. Ornithomimids were fast, omnivorous or herbivorous dinosaurs known mainly from the Late Cretaceous Period of Lauras ...

caenagnathids Caenagnathidae is a family of bird-like maniraptoran theropod dinosaurs from the Cretaceous of North America and Asia. They are a member of the Oviraptorosauria, and close relatives of the Oviraptoridae. Like other oviraptorosaurs, caenagnathids ...

, and

dromaeosaurs 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 ...

. Non-dinosaurs include the giant

alligatoroid Alligatoroidea is one of three superfamilies of crocodylians, the other two being Crocodyloidea and Gavialoidea. Alligatoroidea evolved in the Late Cretaceous period, and consists of the alligators and caimans, as well as extinct members mor ...

Deinosuchus ''Deinosuchus'' () is an extinct genus of alligatoroid crocodilian, related to modern alligators and caimans, that lived 82 to 73 million years ago (Ma), during the late Cretaceous period. The name translates as "terrible crocodile" and is ...

'' and a

goniopholidid Goniopholididae is an extinct family of moderate-sized semi-aquatic neosuchian crocodyliformes. Their bodyplan and morphology are convergent on living crocodilians. They lived across Laurasia (Asia, Europe and North America) between the Middle Ju ...

; the

squamates Squamata (, Latin ''squamatus'', 'scaly, having scales') is the largest order of reptiles, comprising lizards, snakes, and amphisbaenians (worm lizards), which are collectively known as squamates or scaled reptiles. With over 10,900 species, i ...

Odaxosaurus ''Odaxosaurus'' is an extinct genus of anguid lizards that existed in western North America from the Late Cretaceous to the Paleocene. Fossils of the type species ''Odaxosaurus piger'' and the species ''O. priscus'' are widespread throughout Lat ...

'', '' Proxestops'', '' Restes'', '' Sauriscus'', and various unnamed taxa; the turtles "''

Baena Baena is a town and municipalities in Spain, municipality of Spain located in the Córdoba Province, Spain, province of Córdoba, Andalusia. It is situated near the on the slope of a hill southeast of Córdoba, Spain, Córdoba by road. The popu ...

''" and "''

Aspideretes ''Nilssonia'' is a genus of softshell turtles (family Trionychidae) from rivers, streams, ponds, and lakes in South Asia and Burma. In many treatments, it is monotypic, with the single species Burmese peacock softshell (''N. formosa''). However, ...

''", as well as an additional chelonian; the

amphibians Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arbore ...

Albanerpeton ''Albanerpeton'' is an extinct genus of salamander-like lissamphibian found in North America and Europe, first appearing in Cretaceous-aged strata. There are eight described members of the genus, and one undiagnosed species from the Paskapoo Form ...

'', a scapherpetonid, a

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 ...

, and a

frog A frog is any member of a diverse and largely Carnivore, carnivorous group of short-bodied, tailless amphibians composing the order (biology), order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-f ...

; 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 gen ...

'', ''

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 ...

'', ''

Alphadon ''Alphadon'' (meaning "first tooth") is an extinct genus of small, primitive mammal that was a member of the metatherians, a group of mammals that includes modern-day marsupials. Its fossils were first discovered and named by George Gaylord Sim ...

'', '' Turgidodon'', '' Pediomys'', '' Gallolestes'', and others; various

bony fish Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartilag ...

; and the

cartilaginous fish Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissue ...

Hybodus ''Hybodus'' (from el, ύβος , 'crooked' and el, ὀδούς 'tooth') is an extinct genus of hybodont, a group of shark-like elasmobranchs that lived from the Late Devonian to the end of the Cretaceous. Species closely related to the type sp ...

'', ''

Lissodus ''Lissodus'' is an extinct genus of freshwater shark. It lived from the Early Carboniferous stage to the Albian age of the Cretaceous. It was about long and had flat teeth that it used for eating clams Clam is a common name for several ...

'', '' Scapanorhynchys'', ''

Onchopristis ''Onchopristis'' is an extinct genus of sclerorhynchoid from the Cretaceous of North Africa, Europe, and North America. Its name is derived from the Ancient Greek ''ónkos'' ( ὄγκος, 'barb') and ''prístis'' ( πρίστις, 'saw' or 'sa ...

'', ''

Ischyrhiza ''Ischyrhiza'' is an extinct genus of sclerorhynchoid ray from the Late Cretaceous and Early Paleogene. It had a large, toothed rostrum closely resembling that of a modern-day sawfish. Despite formerly being classified within a family of ex ...

'', ''

Squatirhina ''Squatirhina'' is a genus of Late Cretaceous cartilaginous fish whose fossils have been found in the Aguja and Pen Formations of Big Bend National Park, Texas, USA. See also * List of prehistoric cartilaginous fish This list of prehistori ...

'', '' Ptychotrygon'', and others. Although

are very common in

Laramidia Laramidia was an island continent that existed during the Late Cretaceous period (99.6–66 Ma), when the Western Interior Seaway split the continent of North America in two. In the Mesozoic era, Laramidia was an island land mass separated from A ...

n deposits north of

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...

, there are very few of them from the south, and even fewer of them actually preserve any diagnostic material.

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 ...

, despite their limited material, appeared to have been somewhat more common in the south. However, several chasmosaurines are also known from Mexico, namely ''Agujaceratops mavericus'' and '' Coahuilaceratops magnacuerna'' (from the Cerro de Pueblo Formation). This is consistent with a likely climate-related separation of flora between the northern and southern parts of Laramidia during the

. Particularly, in the Texan Aguja Formation,

dicotyledon The dicotyledons, also known as dicots (or, more rarely, dicotyls), are one of the two groups into which all the flowering plants (angiosperms) were formerly divided. The name refers to one of the typical characteristics of the group: namely, t ...

s '' Metcalfeoxylon'' and '' Agujoxylon'' were predominant. In contrast, coniferous plants are more abundant in northern regions. Within the Aguja fauna, ''Yehuecauhceratops'' was relatively small compared to the giant ''Coahuilaceratops'', with ''Agujaceratops'' in between; this suggests some level of size-based diet partitioning among the three ceratopsids.

References

{{Taxonbar, from=Q28610332 Centrosaurines Campanian genus first appearances Campanian genus extinctions Late Cretaceous dinosaurs of North America Cretaceous Mexico Fossils of Mexico Fossil taxa described in 2017 Nahuatl Ornithischian genera