''Coahuilaceratops'' (meaning "horned face from

Coahuila Coahuila, formally Coahuila de Zaragoza, officially the Free and Sovereign State of Coahuila de Zaragoza, is one of the 31 states of Mexico. The largest city and State Capital is the city of Saltillo; the second largest is Torreón and the thi ...

") is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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 ...

ceratopsia 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, Asia and Europe, during the Cretaceous Period (geology), Period, although ance ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

that lived during the early

Maastrichtian The Maastrichtian ( ) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (geology), age (uppermost stage (stratigraphy), stage) of the Late Cretaceous epoch (geology), Epoch or Upper Cretaceous series (s ...

age of the

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

epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided b ...

, about 71.5 to 70.5

million years ago Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...

in what is now northern

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

. It contains a single species, ''Coahuilaceratops magnacuerna''.

Discovery and naming

Fossils of ''Coahuilaceratops'' were discovered by Claudio de Leon near the town of Porvenir de Jalpa in the south of Coahuila, Mexico in 2001 and excavated in 2003. The deposits where the remains were found were originally assigned to the Cerro del Pueblo Formation (upper

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

; ca. 73–72.5 Ma), but in a 2024

stratigraphic Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithost ...

revision they were assigned to the overlying Cerro Huerta Formation (lower Maastrichtian; about 71.5–70.5 million years). This makes ''Coahuilaceratops'' the first dinosaur described from the Cerro Huerta Formation. The lower Maastrichtian age of the deposits is consistent with the relatively derived

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

position of ''Coahuilaceratops''. Over the course of two years, the ''Coahuilaceratops'' fossils were prepared by volunteer preparator Jerry Golden at the

Natural History Museum of Utah The Natural History Museum of Utah is a museum located in Salt Lake City, Utah, United States. The museum shows exhibits of natural history subjects, with an emphasis on Utah and the Intermountain West. The mission of the museum is to illumina ...

. The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

CPC 276 is represented mainly by unarticulated bones of the skull of an adult individual:

rostral bone 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, Asia and Europe, during the Cretaceous Period (geology), Period, although ance ...

, left

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 mammals h ...

, right

maxilla In vertebrates, the maxilla (: maxillae ) 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 two maxil ...

, fused

nasal bones The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face and by their junction, form the bridge of the upper one third of the nose. Eac ...

, incomplete left and right supraorbital horncores, part of the parietosquasomal frill,

predentary Ornithischia () is an extinct clade of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Ancient ...

, both dentaries, and unprepared postcranial material. Another specimen, CPC 277, contains unarticulated juvenile skeletal elements, including predentary, dentary, and unprepared postcranial material. The name of the dinosaur was mentioned in the press in 2008 as an informal designation (''

nomen nudum In Taxonomy (biology), taxonomy, a ''nomen nudum'' ('naked name'; plural ''nomina nuda'') is a designation which looks exactly like a scientific name of an organism, and may have originally been intended to be one, but it has not been published ...

''). ''Coahuilaceratops magnacuerna'' was

formally described A species description is a formal scientific description of a newly encountered species, typically articulated through a scientific publication. Its purpose is to provide a clear description of a new species of organism and explain how it differ ...

by paleontologists Mark A. Loewen,

Scott D. Sampson Scott Donald Sampson (born April 22, 1961) is a Canadian-American paleontologist and science communicator. Sampson is currently the Executive Director of California Academy of Sciences in San Francisco, California. He was previously Vice Preside ...

, Eric K. Lund, Andrew A. Farke, , Claudio A. de Leon, Rubén A. Rodríguez de la Rosa, Michael A. Getty, and David A. Eberth in 2010. The generic name combines "Coahuila", the state of origin, with the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

suffix "''-ceratops''", meaning "horned face", which is common for ceratopsians. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

refers to the large size of horns and comes from the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

word "''magna''", meaning "great", and the

Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many countries in the Americas **Spanish cuisine **Spanish history **Spanish culture ...

word "''cuerna''", meaning "horn". Geographic and stratigraphic setting of Coahuilaceratops.png, Geographic and

setting of the site where the fossils of ''Coahuilaceratops'' were found (belonging to the Cerro Huerta Formation) Skull reconstruction of Coahuilaceratops (cropped).png, Skull reconstruction CoahuilaceratopsMaterialFound.png, Diagram of the

skull with known material in white.

Description

According to estimates given in a press release from the Natural History Museum of Utah (2010), an adult ''Coahuilaceratops'' was about long, tall at the shoulders and hips, with a skull and horns, and probably weighed about four to five tons.

Gregory S. Paul Gregory Scott Paul (born December 24, 1954) is an American freelance researcher, author and illustrator who works in paleontology. He is best known for his work and research on theropoda, theropod dinosaurs and his detailed illustrations, both l ...

estimated its length at and weight at in 2016 and in 2024. Although the horns of ''Coahuilaceratops'' are not completely preserved, their absolute size is comparable to the size of the horns of the largest chasmosaurines, such as ''

Triceratops ''Triceratops'' ( ; ) is a genus of Chasmosaurinae, chasmosaurine Ceratopsia, ceratopsian dinosaur that lived during the late Maastrichtian age of the Late Cretaceous Period (geology), period, about 68 to 66 million years ago on the island ...

'' and ''

Torosaurus ''Torosaurus'' (meaning "perforated lizard", in reference to the large openings in its frill) is a genus of herbivorous Chasmosaurinae, chasmosaurine Ceratopsia, ceratopsian dinosaur that lived during the late Maastrichtian age of the Late Cret ...

''. The hyperrobust morphology of the horns of ''Coahuilaceratops'' (relative lack of constriction in the distal region) is more reminiscent of large specimens of ''

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 ty ...

'' than of ''

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

''.

Classification

In the phylogenetic analysis performed by the authors of the ''Coauilaceratops'' description, Loewen et al. (2010), it was found 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 tree ...

with ''

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. ' ...

'' and '' Arrhinoceratops'', with which it was found in a

sister A sister is a woman or a girl who shares parents or a parent with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to ref ...

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

of Triceratopsini. Triceratopsins include ''Triceratops'' and all taxa closer to ''Triceratops'' than to ''Anchiceratops'' and ''Arrhinoceratops''. According to analysis conducted by Brown & Henderson (2015), ''Coahuiceratops'' is a sister genus of ''Bravoceratops'' within a clade that includes a number of other non-triceratopsin chasmosaurines, with ''Anchiceratops'' and ''Arrhinoceratops'' still forming a sister clade of Triceratopsini. One of the Mallon al. (2016) analyzes confirmed that ''Coahuilaceratops'' and ''Bravoceratops'' are sister taxa, but the study authors had to remove the fragmentary ''Bravoceratops'' from the analysis to obtain more meaningful results. Dalman et al. (2022) found ''Coahuilaceratops'' in a polytomy with ''Bravoceratops'' and '' Sierraceratops''. The researchers suggested that a clade containing these three genera was

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to southern

Laramidia Laramidia was an island continent that existed during the Late Cretaceous period (99.6–66 Year#SI prefix multipliers, Ma), when the Western Interior Seaway split the continent of North America in two. In the Mesozoic era, Laramidia was an island ...

. Loewen et al. (2010) Brown & Henderson (2015) Dalman et al. (2022)

References

{{Taxonbar, from=Q133122 Chasmosaurinae Dinosaur genera Campanian dinosaurs Fossil taxa described in 2010 Taxa named by Scott D. Sampson Dinosaurs of Mexico

Discovery and naming

Description

Classification

See also

References