Centrosaurus
Encyclopedia
Centrosaurus is a genus
of herbivorous ceratopsian
dinosaurs from the late Cretaceous
of Canada
. Their remains have been found in the Dinosaur Park Formation
and uppermost Oldman Formation
, dating from 76.5 to 75.5 million years ago.
The name Centrosaurus means "pointed lizard" (from Greek
kentron/κεντρον = "point or prickle" + sauros/σαυρος = "lizard"), and refers to the series of small hornlets placed along the margin of their frills, not to the nasal horns (which were unknown when the dinosaur was named). The genus is not to be confused with the stegosaur Kentrosaurus
, the name of which is derived from the same Greek word.
The massive bodies of Centrosaurus were borne by stocky limbs, although at up to 18–20 ft (6m) they was not particularly large dinosaurs. Like other centrosaurines, Centrosaurus bore single large horns over their noses. These horns curved forwards or backwards depending on the species.
A pair of small horns is also found over the eyes; in Centrosaurus apertus these are directed upwards, whereas they are directed to the sides in C. brinkmani. The frills of Centrosaurus were moderately long, with fairly large fenestrae
and small hornlets along the outer edges.
C. apertus is distinguished by having two large hornlets which hook forwards over the frill, while in C. brinkmani these hornlets are small and covered with small, finger-like growths.
in strata along the Red Deer River
in Alberta
, Canada
. Later, vast bonebeds of Centrosaurus were found in Dinosaur Provincial Park
, also in Alberta
. Some of these beds extend for hundreds of meters and contain thousands of individuals of all ages and all levels of completion.
Scientists have speculated that the high density and number of individuals would be explained if they had perished while trying to cross a flooded river. A discovery of thousands of Centrosaurus fossils near the town of Hilda
, Alberta
, is believed to be the largest bed of dinosaur bones ever discovered.
characterized by their "prominent nasal horns, subordinate brow horns, short squamosal
s in a short frill, a tall, deep face relative to the ceratopines, and a projection into the rear of the nasal fenestra." Its closest relatives appear to be Styracosaurus
and Monoclonius
. It so closely resembles the latter of these that some paleontologists have considered them to represent the same animal.
Other members of the Centrosaurinae clade
include Pachyrhinosaurus
, Avaceratops
, Einiosaurus
, Albertaceratops
, Achelousaurus
, and possibly Brachyceratops
, although Brachyceratops is dubious
. Because of the variation between species and even individual specimens of centrosaurines, there has been much debate over which genera and species are valid, particularly whether Centrosaurus and/or Monoclonius are valid genera, undiagnosable, or possibly members of the opposite sex. In 1996, Peter Dodson
found enough variation between Centrosaurus, Styracosaurus, and Monoclonius to warrant separate genera, and that Styracosaurus resembled Centrosaurus more closely than either resembled Monoclonius. Dodson also believed one species of Monoclonius, M. nasicornis, may actually have been a female Styracosaurus. His assessments have been partially followed, with other researchers not accepting Monoclonius nasicornis as a female Styracosaurus, or Monoclonius as a valid genus. While sexual dimorphism
has been proposed for an earlier ceratopsian, Protoceratops
, there is no firm evidence for sexual dimorphism in any ceratopsid.
Like other ceratopsids, the jaws of Centrosaurus were adapted to shear through tough plant material; their frills provided an attachment for large jaw muscles. The discovery of gigantic bone beds of Centrosaurus in Canada suggest that they were gregarious animals and could have traveled in large herds. A bone bed composed of Centrosaurus and Styracosaurus remains is known from the Dinosaur Park Formation
in what is now Alberta. The mass deaths may have been caused by otherwise non-herding animals gathering around a waterhole during a drought. Centrosaurus is found lower in the formation than Styracosaurus, indicating that Centrosaurus was displaced by Styracosaurus as the environment changed over time.
The large frills and nasal horns of the ceratopsians are among the most distinctive facial adornments of all dinosaurs. Their function has been the subject of debate since the first horned dinosaurs were discovered. Common theories concerning the function of ceratopsian frills and horns include defense from predators, combat within the species, and visual display. A 2009 study of Triceratops
and Centrosaurus skull lesions found that bone injuries on the skulls were more likely caused by intraspecific combat (horn-to-horn combat) rather than predatory attacks. The frills of Centrosaurus were too thin to be used for defense against predators, although the thicker, solid frills of Triceratops might have evolved to protect their necks. The frills of Centrosaurus were most likely used "for species recognition and/or other forms of visual display".
even though they are among the most abundant Judithian
dinosaurs in the region. Large herbivores like the ceratopsians living in North America during the Late Cretaceous had "remarkably small geographic ranges" despite their large body size and high mobility. This restricted distribution strongly contrasts with modern mammalian faunas whose large herbivores' ranges "typical[ly] ... span much of a continent."
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of herbivorous ceratopsian
Ceratopsidae
Ceratopsidae is a speciose group of marginocephalian dinosaurs including Triceratops and Styracosaurus...
dinosaurs from the late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
of Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. Their remains have been found in 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. The formation is made up of deposits of a high-sinuosity fluvial system, and is capped...
and uppermost Oldman Formation
Oldman Formation
The Oldman Formation is the middle member of the Judith River Group, a major geologic unit in southern Alberta. The formation is widely recognized as bearing a great number of well preserved dinosaur skeletons, as well as other fossils.-Age:...
, dating from 76.5 to 75.5 million years ago.
The name Centrosaurus means "pointed lizard" (from Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
kentron/κεντρον = "point or prickle" + sauros/σαυρος = "lizard"), and refers to the series of small hornlets placed along the margin of their frills, not to the nasal horns (which were unknown when the dinosaur was named). The genus is not to be confused with the stegosaur Kentrosaurus
Kentrosaurus
Kentrosaurus is a genus of stegosaurid dinosaur from the Late Jurassic of Tanzania. Its fossils have been found only in the Tendaguru Formation of Tanzania, dated to the Kimmeridgian stage, between about 155.7 ± 4 Ma and 150.8 ± 4 Ma . Apparently, all finds belong to one species, K...
, the name of which is derived from the same Greek word.
Description
A pair of small horns is also found over the eyes; in Centrosaurus apertus these are directed upwards, whereas they are directed to the sides in C. brinkmani. The frills of Centrosaurus were moderately long, with fairly large fenestrae
Fenestrae
Fenestræ is a Latin word that means "window".* In histology, fenestræ are small pores in endothelial cells that allow for rapid exchange of molecules between sinusoid blood vessels and surrounding tissue...
and small hornlets along the outer edges.
C. apertus is distinguished by having two large hornlets which hook forwards over the frill, while in C. brinkmani these hornlets are small and covered with small, finger-like growths.
Discovery
The first Centrosaurus remains were discovered by paleontologist Lawrence LambeLawrence Lambe
Lawrence Morris Lambe was a Canadian geologist and palaeontologist from the Geological Survey of Canada .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...
in strata along the Red Deer River
Red Deer River
The Red Deer River is a river in Alberta, Canada. It is a major tributary of the South Saskatchewan River.Red Deer River has a total length of and a drainage area of...
in Alberta
Alberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. Later, vast bonebeds of Centrosaurus were found in Dinosaur Provincial Park
Dinosaur Provincial Park
Dinosaur Provincial Park is a UNESCO World Heritage Site located about two and a half hours drive southeast of Calgary, Alberta, Canada or , about a half hour drive, northeast of Brooks....
, also in Alberta
Alberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
. Some of these beds extend for hundreds of meters and contain thousands of individuals of all ages and all levels of completion.
Scientists have speculated that the high density and number of individuals would be explained if they had perished while trying to cross a flooded river. A discovery of thousands of Centrosaurus fossils near the town of Hilda
Hilda, Alberta
Hilda is a hamlet in southern Alberta, Canada within Cypress County, located east of Highway 41, approximately northeast of Medicine Hat.In 1910, the post master named the post office "Hilda" after his infant daughter.- References :...
, Alberta
Alberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
, is believed to be the largest bed of dinosaur bones ever discovered.
Classification
The genus Centrosaurus gives its name to the Centrosaurinae subfamily. These were large North American horned dinosaursCeratopsia
Ceratopsia or Ceratopia is a group of herbivorous, beaked dinosaurs which thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassic. The earliest known ceratopsian, Yinlong downsi, lived between 161.2 and 155.7...
characterized by their "prominent nasal horns, subordinate brow horns, short squamosal
Squamosal
The squamosal is a bone of the head of higher vertebrates. It is the principal component of the cheek region in the skull, lying below the temporal series and otic notch and bounded anteriorly by postorbital. Posteriorly, the squamosal articulates with the posterior elements of the palatal complex,...
s in a short frill, a tall, deep face relative to the ceratopines, and a projection into the rear of the nasal fenestra." Its closest relatives appear to be Styracosaurus
Styracosaurus
Styracosaurus was a genus of herbivorous ceratopsian dinosaur from the Cretaceous Period , about 76.5 to 75.0 million years ago...
and 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 . Monoclonius was described by Edward Drinker Cope in 1876...
. It so closely resembles the latter of these that some paleontologists have considered them to represent the same animal.
Other members of the Centrosaurinae clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
include Pachyrhinosaurus
Pachyrhinosaurus
Pachyrhinosaurus is a genus of ceratopsid dinosaurs from the Late Cretaceous period of North America. The first examples were discovered by Charles M. Sternberg in Alberta, Canada, in 1946, and named in 1950. Over a dozen partial skulls and a large assortment of other fossils from various species...
, Avaceratops
Avaceratops
Avaceratops is a genus of small ceratopsian dinosaur which lived during the late Campanian during the Late Cretaceous Period in what are now the Northwest United States.-Discoveries and species:...
, Einiosaurus
Einiosaurus
Einiosaurus is a medium-sized centrosaurine ceratopsian from the Upper Cretaceous of northwestern Montana. The name means 'buffalo lizard', in a combination of Blackfeet Indian and Latinized Ancient Greek; the specific name Einiosaurus is a medium-sized centrosaurine (“short-frilled”)...
, Albertaceratops
Albertaceratops
Albertaceratops was a genus of centrosaurine horned dinosaur from the middle Campanian-age Upper Cretaceous Oldman Formation of Alberta, Canada....
, Achelousaurus
Achelousaurus
Achelousaurus is a genus of centrosaurine ceratopsid dinosaurs from the Late Cretaceous Period of what is now North America, dated to 74 million years ago...
, and possibly Brachyceratops
Brachyceratops
Brachyceratops is a dubious genus of ceratopsian dinosaur known only from partial juvenile specimens dating to the late Cretaceous Period of Montana, United States....
, although Brachyceratops is dubious
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
. Because of the variation between species and even individual specimens of centrosaurines, there has been much debate over which genera and species are valid, particularly whether Centrosaurus and/or Monoclonius are valid genera, undiagnosable, or possibly members of the opposite sex. In 1996, Peter Dodson
Peter Dodson
Peter Dodson is an American paleontologist who has published many papers and written and collaborated on books about dinosaurs. An authority on Ceratopsians, he has also authored several papers and textbooks on hadrosaurs and sauropods, and is a co-editor of The Dinosauria, widely considered the...
found enough variation between Centrosaurus, Styracosaurus, and Monoclonius to warrant separate genera, and that Styracosaurus resembled Centrosaurus more closely than either resembled Monoclonius. Dodson also believed one species of Monoclonius, M. nasicornis, may actually have been a female Styracosaurus. His assessments have been partially followed, with other researchers not accepting Monoclonius nasicornis as a female Styracosaurus, or Monoclonius as a valid genus. While sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
has been proposed for an earlier ceratopsian, Protoceratops
Protoceratops
Protoceratops is a genus of sheep-sized herbivorous ceratopsian dinosaur, from the Upper Cretaceous Period of what is now Mongolia. It was a member of the Protoceratopsidae, a group of early horned dinosaurs...
, there is no firm evidence for sexual dimorphism in any ceratopsid.
Palaeobiology
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. The formation is made up of deposits of a high-sinuosity fluvial system, and is capped...
in what is now Alberta. The mass deaths may have been caused by otherwise non-herding animals gathering around a waterhole during a drought. Centrosaurus is found lower in the formation than Styracosaurus, indicating that Centrosaurus was displaced by Styracosaurus as the environment changed over time.
The large frills and nasal horns of the ceratopsians are among the most distinctive facial adornments of all dinosaurs. Their function has been the subject of debate since the first horned dinosaurs were discovered. Common theories concerning the function of ceratopsian frills and horns include defense from predators, combat within the species, and visual display. A 2009 study of Triceratops
Triceratops
Triceratops is a genus of herbivorous ceratopsid dinosaur which lived during the late Maastrichtian stage of the Late Cretaceous Period, around 68 to 65 million years ago in what is now North America. It was one of the last dinosaur genera to appear before the great Cretaceous–Paleogene...
and Centrosaurus skull lesions found that bone injuries on the skulls were more likely caused by intraspecific combat (horn-to-horn combat) rather than predatory attacks. The frills of Centrosaurus were too thin to be used for defense against predators, although the thicker, solid frills of Triceratops might have evolved to protect their necks. The frills of Centrosaurus were most likely used "for species recognition and/or other forms of visual display".
Paleobiogeography
Thomas M. Lehman has observed that Centrosaurus fossils haven't been found outside of southern AlbertaAlberta
Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
even though they are among the most abundant Judithian
Judithian
The Judithian was a North American faunal stage lasting from 83.5 to 70.6 million years ago. It overlaps with the Campanian global stage.-Fauna:Dinosaur faunas of the Judithian age may represent the peak of dinosaur evolution in North America...
dinosaurs in the region. Large herbivores like the ceratopsians living in North America during the Late Cretaceous had "remarkably small geographic ranges" despite their large body size and high mobility. This restricted distribution strongly contrasts with modern mammalian faunas whose large herbivores' ranges "typical[ly] ... span much of a continent."