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Chasmosaurus ( KAZ-mo-sawr-us) is a genus
Genus

A genus is a low-level taxonomic rank used in the classification of living and fossil organisms. The taxonomic ranks are domain , kingdom , phylum, class , order , family , genus, and species....
 of ceratopsid
Ceratopsidae

Ceratopsidae is a speciose group of marginocephalian dinosaurs including Triceratops and Styracosaurus. All known species were quadrupedal herbivores from the Upper Cretaceous of Western North America and are characterized by beaks, rows of shearing teeth in the back of the jaw, and elaborate horns and frills....
 dinosaur
Dinosaur

Dinosaurs were the dominant vertebrate animals of Landform ecosystems for over 160 million years, from the late Triassic Period until the end of the Cretaceous Period , when most of them became extinct in the Cretaceous?Tertiary extinction event....
 from the Upper Cretaceous
Cretaceous

The Cretaceous , usually abbreviated K for its German translation Kreide, is a geologic period from circa to million years ago . In the geologic timescale, the Cretaceous follows on the Jurassic period and is followed by the Paleogene period....
 Period of North America
North America

North America is the northern continent of the Americas, situated in the Earth's northern hemisphere and almost totally in the western hemisphere....
. Its name means 'opening lizard', referring to the large openings (fenestrae
Fenestrae

Fenestr? also from the Latin for window,are small pores in epithelial cells to allow for rapid exchange of molecules between blood vessels and surrounding tissue....
) in its frill (Greek
Ancient Greek

Ancient Greek is the historical stage in the development of the Greek language spanning across the Archaic Greece , Classical Greece , and Hellenistic civilization periods of ancient Greece and the classical antiquity....
 chasma meaning 'opening' or 'hollow' or 'gulf' and sauros meaning 'lizard'). With a length of and a weight of , Chasmosaurus was a ceratopsian of average size. Like all ceratopsians, it was purely herbivorous
Herbivore

Herbivory is a form of predation in which an organism, known as an herbivore, heterotrophs principally autotrophs such as plants, algae and photosynthesizing bacteria....
.






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Chasmosaurus ( KAZ-mo-sawr-us) is a genus
Genus

A genus is a low-level taxonomic rank used in the classification of living and fossil organisms. The taxonomic ranks are domain , kingdom , phylum, class , order , family , genus, and species....
 of ceratopsid
Ceratopsidae

Ceratopsidae is a speciose group of marginocephalian dinosaurs including Triceratops and Styracosaurus. All known species were quadrupedal herbivores from the Upper Cretaceous of Western North America and are characterized by beaks, rows of shearing teeth in the back of the jaw, and elaborate horns and frills....
 dinosaur
Dinosaur

Dinosaurs were the dominant vertebrate animals of Landform ecosystems for over 160 million years, from the late Triassic Period until the end of the Cretaceous Period , when most of them became extinct in the Cretaceous?Tertiary extinction event....
 from the Upper Cretaceous
Cretaceous

The Cretaceous , usually abbreviated K for its German translation Kreide, is a geologic period from circa to million years ago . In the geologic timescale, the Cretaceous follows on the Jurassic period and is followed by the Paleogene period....
 Period of North America
North America

North America is the northern continent of the Americas, situated in the Earth's northern hemisphere and almost totally in the western hemisphere....
. Its name means 'opening lizard', referring to the large openings (fenestrae
Fenestrae

Fenestr? also from the Latin for window,are small pores in epithelial cells to allow for rapid exchange of molecules between blood vessels and surrounding tissue....
) in its frill (Greek
Ancient Greek

Ancient Greek is the historical stage in the development of the Greek language spanning across the Archaic Greece , Classical Greece , and Hellenistic civilization periods of ancient Greece and the classical antiquity....
 chasma meaning 'opening' or 'hollow' or 'gulf' and sauros meaning 'lizard'). With a length of and a weight of , Chasmosaurus was a ceratopsian of average size. Like all ceratopsians, it was purely herbivorous
Herbivore

Herbivory is a form of predation in which an organism, known as an herbivore, heterotrophs principally autotrophs such as plants, algae and photosynthesizing bacteria....
. It was initially to be called Protorosaurus
Protorosaurus

Protorosaurus , a lizard-like reptile of the order Prolacertiformes, is the earliest known archosauromorph. It lived during the Late Permian period in Germany, and grew up to 2 meters in length....
, but this name had been previously published for another animal.

Discoveries and species

In 1898, Lawrence Lambe of the Geological Survey of Canada
Geological Survey of Canada

The Geological Survey of Canada is part of the Earth Sciences Sector of Natural Resources Canada. GSC is responsible for performing Geology surveys of the country, developing Canada's natural resources and protecting the environment....
 made the first discovery of Chasmosaurus remains- part of a neck frill. Although recognizing that his find represented a new species, Lambe thought to be from a previously-known short-frilled ceratopsian - Monoclonius
Monoclonius

Monoclonius was a ceratopsian dinosaur from the Judith River Formation of Late Cretaceous Montana and Canada. It is often confused with Centrosaurus, a similar genus of ceratopsian ....
. He erected the new species Monoclonius belli to describe his finding.

However, in 1913, Charles Sternberg
Charles Hazelius Sternberg

Charles Hazelius Sternberg , was an United States fossil collector and amateur paleontology. His older brother, Dr. George M. Sternberg was a military surgeon assigned to Fort Harker near Ellsworth, Kansas and brought the rest of Sternberg family to Kansas to live on his ranch about 1868....
 and his sons found several complete "M. belli" skulls in Alberta
Alberta

Alberta is one of Canada Canadian Prairies Provinces and territories of Canada. It became a province on September 1, 1905.Alberta is located in western Canada, bounded by the provinces of British Columbia to the west and Saskatchewan to the east, the Northwest Territories to the north, and the U.S....
, Canada
Canada

Canada is a country occupying most of northern North America, extending from the Atlantic Ocean in the east to the Pacific Ocean in the west and northward into the Arctic Ocean....
. These were finally described as the new genus Chasmosaurus in 1914, again by Lawrence M. Lambe
Lawrence Lambe

Lawrence Morris Lambe was a Geology and Palaeontology from the Geological Survey of Canada . He was Canada's first great geologist. His published work, describing the diverse and plentiful dinosaur discoveries from the fossil beds in Alberta, did much to bring dinosaurs into the public eye and helped usher in the Golden Age of Dinosaurs...
. Since that date, more Chasmosaurus remains, including skulls, have been found. There appears to be morphological variation among the known sample of Chasmosaurus skulls.

There are a number of known species
Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring....
 of Chasmosaurus. Lambe's original C. belli ('Bell's cleft lizard') was joined by C. canadensis ('chasm lizard from Canada') in the same year. The latter species had been described as Eoceratops canadensis by Lambe but was later reclassified as a chasmosaur by Lehman. Lull named an unusual, short-muzzled skull, collected in 1926, C. brevirostris. C. M. Sternberg added C. russelli, in 1940, from southwestern Alberta. The most recently described species is C. irvinensis, which stems from the uppermost beds of the Dinosaur Park Formation
Dinosaur Park Formation

The Dinosaur Park Formation is the uppermost member of the Judith River Group, a major geologic unit in southern Alberta. It was laid down over a period of time between about 76.5 and 75 million years ago....
.

Thomas Lehman described C. mariscalensis in 1989 from Texas
Texas

Texas is a U.S. state located in the South Central United States, nicknamed the Lone Star State. Texas is the second largest U.S. state in both area and population, spanning , and with a growing population of 24.3 million residents....
, which has now been renamed Agujaceratops
Agujaceratops

Agujaceratops is a newly reclassified genus of ceratopsian dinosaur. Originally known as Chasmosaurus mariscalensis and described by Lehman in 1989, it was moved to a new genus by Lucas, Sullivan and Hunt in 2006....
.

Characteristics

Ceratopsians are split into two subfamilies by taxonomists
Taxonomy

Taxonomy is the practice and science of classification. The word comes from the Greek language ', taxis and ', nomos .Taxonomies, or taxonomic schemes, are composed of taxonomic units known as taxa , or kinds of things that are arranged frequently in a hierarchical structure....
; those with short frills (centrosaurines), such as Centrosaurus
Centrosaurus

Centrosaurus is an herbivorous Ceratopsidae dinosaur from the late Cretaceous of North America, approximately 75 million years ago.The name refers to the series of small hornlets placed along the margin of the frill, and not to the horn on its nose ....
 and those with long frills (chasmosaurines), of which Chasmosaurus was one. In addition to the larger frill, the long-frilled ceratopsians typically had longer faces and jaws and it is suggested by some paleontologists that they were more selective about the plants they ate. Long frills were a relatively late development in dinosaur evolution
Evolution

In biology, evolution is change in the heritability trait of a population of organisms from one generation to the next. These changes are caused by a combination of three main processes: variation, reproduction, and selection....
, since even Chasmosaurus dates from the late Cretaceous
Cretaceous

The Cretaceous , usually abbreviated K for its German translation Kreide, is a geologic period from circa to million years ago . In the geologic timescale, the Cretaceous follows on the Jurassic period and is followed by the Paleogene period....
 Period, 76 to 70 million years ago. The frill of Chasmosaurus has been described as "heart-shaped", since its bone structure consists of two large 'loops' from a central bone.

Some finds include a number of smaller ossifications (called epoccipitals), which may have grown from the perimeter of the frill. The frill may also have been brightly colored, to draw attention to its size or as part of mating display. However, the frill was so large and yet so flimsy (since it was mainly skin stretched between the bones) that it could not have provided much functional defense. It is possible that it was simply used to appear imposing or conceivably for thermoregulation
Thermoregulation

Thermoregulation is the ability of an organism to keep its core temperature within certain boundaries, even when the surrounding temperature is very different....
. In the event of a chasmosaur herd being attacked by a predator (such as Tyrannosaurus
Tyrannosaurus

Tyrannosaurus is a genus of theropod dinosaur. The famous species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture around the world....
), the males could have formed a ring and, with all the frills facing outwards, would have presented a formidable sight.
Sketch Chasmosaurus
Like many ceratopsians, chasmosaurs had three main facial horn
Horn (anatomy)

A horn is a pointed projection of the skin on the head of various mammals, consisting of a covering of horn surrounding a core of living bone....
s - one on the nose and two on the brow. Different fossil finds have produced inconclusive results - one species of Chasmosaurus, named C. kaiseni, bore long brow horns, while C. belli had only short ones. Although these were initially named as different species, it now seems possible that the long horns belonged to males and the shorter horns to females.

Interestingly, a Chasmosaurus specimen recovered by Sternberg was accompanied by fossilized skin
Skin

The skin is the outer covering of the body, also known as the epidermis. It is the largest organ of the integumentary system made up of multiple layers of epithelial biological tissue, and guards the underlying muscles, bones, ligaments and organ s....
. The skin appears to have had many bony knobs (osteoderms) in evenly spaced rows, with five or six sides per knob. Unfortunately, nothing can be learned about the coloration of Chasmosaurus from the known fossil skin samples.

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