Agujaceratops Squamosal By Nick Longrich
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''Agujaceratops'' (meaning "horned face from Aguja") 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 ...
of horned
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 ...
from the Late Cretaceous (
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 ...
) of west
Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...
. It is a
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 ...
(long-frilled)
ceratopsian Ceratopsia or Ceratopia ( or ; Greek: "horned faces") is a group of herbivorous, beaked dinosaurs that thrived in what are now North America, Asia and Europe, during the Cretaceous Period, although ancestral forms lived earlier, in the Late Ju ...
. Two species are known, ''Agujaceratops mariscalensis'', and ''A''. ''mavericus''.


Discovery and species

In 1938, three dinosaur bone beds were excavated, and ceratopsian material was collected from
Big Bend National Park Big Bend National Park is a List of national parks of the United States, national park of the United States located in West Texas, bordering Mexico. The park has national significance as the largest protected area of Chihuahuan Desert topograph ...
(Texas) by William Strain. This material was studied by Lehman in 1989 and named ''Chasmosaurus mariscalensis''. It is known only from 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 ...
UTEP The University of Texas at El Paso (UTEP) is a public research university in El Paso, Texas, United States. Founded in 1913 as the State School of Mines and Metallurgy, it is the third oldest academic component of the University of Texas Syste ...
 P.37.7.086 a partial adult
skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...
which includes a
braincase In human anatomy, the neurocranium, also known as the braincase, brainpan, brain-pan, or brainbox, is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calv ...
, left supraorbital horncore, left
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 ...
and a right
dentary In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone ...
. Additional material was associated with the holotype, but not considered to be part of it. All specimens of ''Agujaceratops'' were collected from the lower part of the Upper Shale member of the
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 ...
, dating to about 77
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 the
Big Bend National Park Big Bend National Park is a List of national parks of the United States, national park of the United States located in West Texas, bordering Mexico. The park has national significance as the largest protected area of Chihuahuan Desert topograph ...
,
Brewster County Brewster County is a county located in the U.S. state of Texas. It is in West Texas and its county seat (and only city) is Alpine. It is one of the nine counties that comprise the Trans-Pecos region, and borders Mexico. Brewster County is the ...
. Additional material was recovered from elsewhere in west Texas, including a nearly complete skull from Rattlesnake Mountain designated TMM 43098-1. Originally described as ''
Chasmosaurus ''Chasmosaurus'' ( ) is a genus of ceratopsid dinosaur from the Late Cretaceous Period in North America. Its given name means 'opening lizard', referring to the large openings ( fenestrae) in its frill (Greek ''chasma'', meaning 'opening', 'hol ...
mariscalensis'' by Lehman in
1989 1989 was a turning point in political history with the "Revolutions of 1989" which ended communism in Eastern Bloc of Europe, starting in Poland and Hungary, with experiments in power-sharing coming to a head with the opening of the Berlin W ...
, subsequent analysis resulted in the taxon being put in its own genus. ''Agujaceratops'' was named by Spencer G. Lucas, Robert M. Sullivan and Adrian Hunt in
2006 2006 was designated as the International Year of Deserts and Desertification. Events January * January 1– 4 – Russia temporarily cuts shipment of natural gas to Ukraine during a price dispute. * January 12 – A stampede during t ...
, and the
type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...
is ''Agujaceratops mariscalensis''. Later, Lehman and colleagues revisited the ''Agujaceratops'' material and found substantial variation. They described the Rattlesnake Mountain skull as a new species, ''Agujaceratops mavericus''.


Description

''Agujaceratops'' was a relatively large horned dinosaur, reaching in length and in body mass. It was similar to other chasmosaurines such as ''
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 ...
'' in having a short nose horn, long brow horns, and an elongate frill circled by small hornlets. The back of the frill has a strong notch, 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 ty ...
'' and ''
Chasmosaurus ''Chasmosaurus'' ( ) is a genus of ceratopsid dinosaur from the Late Cretaceous Period in North America. Its given name means 'opening lizard', referring to the large openings ( fenestrae) in its frill (Greek ''chasma'', meaning 'opening', 'hol ...
'', giving it a heart shape, with three or four pairs of spike-like hornlets. The edges of the frill bear numerous low, blunt hornlets, giving it a strongly scalloped appearance. The brow horns are oriented up and out, and curve backwards in side view. Two species are known, ''Agujaceratops mariscalensis'' and ''A''. ''mavericus''. ''A''. ''mariscalensis'' has shorter brow horns and a shorter frill.


Ecology

Like other ceratopsids, ''Agujaceratops'' was a four-legged plant eater. The elaborate frill and horns suggest a complex social life, perhaps involving displays towards and fights with other members of the species over territory or mating. Multiple individuals are found in a single quarry. It is unclear whether this represents animals brought together by a drought or flood event, or perhaps a herd. Although it is common to find multiple individuals of
centrosaurine Centrosaurinae (from the Greek, meaning "pointed lizards") is a subfamily of ceratopsid, a group of large quadrupedal ornithischian dinosaur. Centrosaurine fossil remains are known primarily from the northern region of Laramidia (modern day Alber ...
ceratopsids together - large bonebeds are known for ''
Centrosaurus ''Centrosaurus'' ( ; ) is a genus of centrosaurine ceratopsian dinosaur from Campanian age of Late Cretaceous Canada. Their remains have been found in the Dinosaur Park Formation, dating from 76.5 to 75.5 million years ago. Discovery and nami ...
'' and ''
Pachyrhinosaurus ''Pachyrhinosaurus'' (from Ancient Greek ' (), thick; ' (), nose; and (), lizard) is a genus of centrosaurine ceratopsid dinosaur from the Late Cretaceous period of North America. The first examples were discovered by Charles M. Sternberg in ...
'', for example - bonebeds are rarer for chasmosaurines. At the time, the Aguja Formation lay along the western margin of the
Western Interior Seaway The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, or the Western Interior Sea) was a large inland sea (geology), inland sea that existed roughly over the present-day Great Plains of ...
. The habitat ''Agujaceratops'' lived in (at least where the fossil material was found) may have been a swamp, due to the nature of the sediments. ''Agujaceratops'' lived alongside a fauna that included the
feathered dinosaur A feathered dinosaur is any species of dinosaur possessing feathers. That includes all species of birds, and in recent decades evidence has accumulated that many non-avian dinosaur species also possessed feathers in some shape or form. The exte ...
''
Leptorhynchos gaddisi ''Leptorhynchos'' () is an extinct genus of caenagnathid theropod from the Late Cretaceous of what is now the US state of Texas, although it has been suggested to also exist in Alberta and South Dakota. The type species is ''L. gaddisi'', and i ...
'' and the small
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 pachycepha ...
''
Texacephale ''Texacephale'' is a possibly dubious genus of 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, S ...
''. Predators would have included
tyrannosaurs Tyrannosauroidea (meaning 'tyrant lizard forms') is a Taxonomic rank, superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family (biology), family Tyrannosauridae as well as more basal (phylogenetics), basal relatives. ...
and the giant
crocodilia Crocodilia () is an order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorph pseudosuchia ...
n ''
Deinosuchus ''Deinosuchus'' is an extinct genus of eusuchian, either an Alligatoroidea, alligatoroid Crocodilia, crocodilian or a stem-group crocodilian, which lived during the Late Cretaceous around . The first remains were discovered in North Carolina ...
riograndensis''.


See also

*
Timeline of ceratopsian research This timeline of ceratopsian research is a chronological listing of events in the History of paleontology, history of paleontology focused on the ceratopsians, a group of herbivorous marginocephalian dinosaurs that evolved parrot-like beaks, b ...
*
2016 in paleontology Flora Plants Fungi Cnidarians Research * ''Yunnanoascus haikouensis'', previously thought to be a member of Ctenophora, is reinterpreted as a Crown group, crown-group medusozoan by Han ''et al.'' (2016). * A study on the fossil corals fro ...


References

*


External links


DinoGeorge's List of Dinosaurs, including ''Agujaceratops''


an



{{Taxonbar, from=Q132534 Chasmosaurinae Dinosaur genera Campanian dinosaurs Dinosaurs of the United States Fossil taxa described in 2006 Taxa named by Spencer G. Lucas