Pachyrhinosaurus
Encyclopedia
Pachyrhinosaurus is a genus
of ceratopsid dinosaur
s 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 have been found in Alberta
and Alaska
. A great number were not available for study until the 1980s, resulting in a relatively recent increase of interest in the Pachyrhinosaurus. Three species have been identified. P. lakustai, from the upper Bearpaw
and lower Horseshoe Canyon Formation
s, is known to have existed from about 73.5-72.5 million years ago. P. canadensis is younger, known only from the lower Horseshoe Canyon Formation, about 71.5-71 Ma ago. Fossils of the youngest species, unofficially named P. "perotorum", have been recovered from the Prince Creek Formation
of Alaska, and date to 70-69 million years ago.
The largest Pachyrhinosaurus species were 8 metres (26.2 ft) long. It weighed about four ton
s. They were herbivorous
and possessed strong cheek teeth to help them chew tough, fibrous plants.
Instead of horns, their skulls bore massive, flattened bosses; a large boss over the nose and a smaller one over the eyes. A prominent pair of horns grew from the frill and extended upwards. The skull also bore several smaller horns or ornaments that varied between individuals and between species. In P. canadensis and P. perotorum, the bosses over the nose and eyes nearly grew together, and were separated only by a narrow groove. In P. lakustai, the two bosses were separated by a wide gap. In P. canadensis and P. lakustai, the frill bore two additional small, curved, backward-pointed horns. These were not present in P. perotorum, and in fact some specimens of P. lakustai also lack them, which may indicate that the presence of these horns varied by age or sex.
Various ornaments of the nasal boss have also been used to distinguish between different species of Pachyrhinosaurus. Both P. lakustai and P. perotorum bore a jagged, comb-like extension at the tip of the boss which was missing in P. canadensis. P. perotorum was unique in having a narrow dome in the middle of the back portion of the nasal boss, and P. lakustai had a pommel-like structure projecting from the front of the boss (the boss of P. canadensis was mainly flat on top and rounded). P. perotorum bore two unique, flattened horns which projected forward and down from the top edge of the frill, and P. lakustai bore another comb-like horn arising from the middle of the frill behind the eyes.
, Pachyrhinosaurus canadensis, was described in 1950 by Charles Mortram Sternberg
. This specimen and others came from the Scabby Butte locality near Lethbridge, Alberta and was among the first dinosaur sites found in the province (in the 1880s), but its significance was not understood until shortly after World War II when some preliminary excavations were conducted. Two skulls were collected by Charles M. Sternberg from the Scabby Butte site and another location on the Little Bow River
nearby. Another Pachyrhinosaurus skull was taken out of the Scabby Butte locality in 1955, and then in 1957 Wann Langston Jr. and a small crew excavated additional pachyrhinosaur remains. The University of Calgary
has plans to reopen this important site some day as a field school for university-level paleontology students.
Another Pachyrhinosaurus bonebed, on the Wapiti River south of Beaverlodge in northwestern Alberta, was worked briefly by staff of the Royal Tyrrell Museum in the late 1980s but is now worked annually for a couple weeks each summer (since 2006) by the University of Alberta. Material from this site appears referable to Pachyrhinosaurus canadensis.
In 1972, Grande Prairie, Alberta science teacher Al Lakusta found a large bonebed along Pipestone Creek
in Alberta
. When the area was finally excavated between 1986 and 1989 by staff and volunteers of the Royal Tyrrell Museum of Palaeontology
, paleontologists discovered an amazingly large and dense selection of bones—up to 100 per square meter, with a total of 3500 bones and 14 skulls. This was apparently the site of a mass mortality, perhaps a failed attempt to cross a river during a flood. Found amongst the fossils were the skeletons of four distinct age groups ranging from juveniles to full grown dinosaurs, indicating that the Pachyrhinosaurus cared for their young.
The adult skulls had both convex and concave bosses as well as unicorn
-style horns on the parietal bone just behind their eyes. The concave boss types might be related to erosion only and not reflect male/female differences. In 2008, a detailed monograph describing the skull of the Pipestone Creek pachyrhinosaur, and penned by Philip J. Currie, Wann Langston, Jr.
, and Darren Tanke
, classified the specimen as a second species of Pachyrhinosaurus, named P. lakustai after its discoverer.
During the Edmontonian
, in North America's northern biome, there is a general trend of reduced centrosaurine diversity, with only Pachyrhinosaurus surviving. Inland faunas are distinguished by a Saurolophus
-Anchiceratops
association while more coastal areas were characterized by Pachyrhinosaurus and Edmontosaurus
.
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 ceratopsid dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s 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...
period of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
. The first examples were discovered by Charles M. Sternberg 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...
, in 1946, and named in 1950. Over a dozen partial skulls and a large assortment of other fossils from various species have been found 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...
and Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
. A great number were not available for study until the 1980s, resulting in a relatively recent increase of interest in the Pachyrhinosaurus. Three species have been identified. P. lakustai, from the upper Bearpaw
Bearpaw Formation
The Bearpaw Formation, also called the Bearpaw Shale, is a sedimentary rock formation found in northwestern North America. It is exposed in the U.S. state of Montana, as well as the Canadian provinces of Alberta and Saskatchewan, east of the Rocky Mountains...
and lower Horseshoe Canyon Formation
Horseshoe Canyon Formation
The Horseshoe Canyon Formation is part of the Edmonton Group and is up to 230m in thickness. It is Late Campanian to Early Maastrichtian in age and is composed of mudstone, sandstone, and carbonaceous shales...
s, is known to have existed from about 73.5-72.5 million years ago. P. canadensis is younger, known only from the lower Horseshoe Canyon Formation, about 71.5-71 Ma ago. Fossils of the youngest species, unofficially named P. "perotorum", have been recovered from the Prince Creek Formation
Prince Creek Formation
The Prince Creek Formation is a geological formation in Alaska with strata from the early Maastrichtian stage of the Upper Cretaceous, dating to between 70 and 69 million years ago...
of Alaska, and date to 70-69 million years ago.
Description
Ton
The ton is a unit of measure. It has a long history and has acquired a number of meanings and uses over the years. It is used principally as a unit of weight, and as a unit of volume. It can also be used as a measure of energy, for truck classification, or as a colloquial term.It is derived from...
s. They were herbivorous
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
and possessed strong cheek teeth to help them chew tough, fibrous plants.
Instead of horns, their skulls bore massive, flattened bosses; a large boss over the nose and a smaller one over the eyes. A prominent pair of horns grew from the frill and extended upwards. The skull also bore several smaller horns or ornaments that varied between individuals and between species. In P. canadensis and P. perotorum, the bosses over the nose and eyes nearly grew together, and were separated only by a narrow groove. In P. lakustai, the two bosses were separated by a wide gap. In P. canadensis and P. lakustai, the frill bore two additional small, curved, backward-pointed horns. These were not present in P. perotorum, and in fact some specimens of P. lakustai also lack them, which may indicate that the presence of these horns varied by age or sex.
Various ornaments of the nasal boss have also been used to distinguish between different species of Pachyrhinosaurus. Both P. lakustai and P. perotorum bore a jagged, comb-like extension at the tip of the boss which was missing in P. canadensis. P. perotorum was unique in having a narrow dome in the middle of the back portion of the nasal boss, and P. lakustai had a pommel-like structure projecting from the front of the boss (the boss of P. canadensis was mainly flat on top and rounded). P. perotorum bore two unique, flattened horns which projected forward and down from the top edge of the frill, and P. lakustai bore another comb-like horn arising from the middle of the frill behind the eyes.
Discovery and species
The type speciesType species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
, Pachyrhinosaurus canadensis, was described in 1950 by Charles Mortram Sternberg
Charles Mortram Sternberg
Charles M. Sternberg was an American-Canadian fossil collector and paleontologist, son of Charles Hazelius Sternberg.Late in his career, he collected and described Pachyrhinosaurus, Brachylophosaurus, Parksosaurus and Edmontonia...
. This specimen and others came from the Scabby Butte locality near Lethbridge, Alberta and was among the first dinosaur sites found in the province (in the 1880s), but its significance was not understood until shortly after World War II when some preliminary excavations were conducted. Two skulls were collected by Charles M. Sternberg from the Scabby Butte site and another location on the Little Bow River
Little Bow River
The Little Bow River is a tributary of the Oldman River in southern Alberta, Canada. It is about long. From its headwaters near High River, it flows south, then turns east and flows into Travers Reservoir. Afterwards, it flows southeast into the Oldman near Picture Butte...
nearby. Another Pachyrhinosaurus skull was taken out of the Scabby Butte locality in 1955, and then in 1957 Wann Langston Jr. and a small crew excavated additional pachyrhinosaur remains. The University of Calgary
University of Calgary
The University of Calgary is a public research university located in Calgary, Alberta, Canada. Founded in 1966 the U of C is composed of 14 faculties and more than 85 research institutes and centres.More than 25,000 undergraduate and 5,500 graduate students are currently...
has plans to reopen this important site some day as a field school for university-level paleontology students.
Another Pachyrhinosaurus bonebed, on the Wapiti River south of Beaverlodge in northwestern Alberta, was worked briefly by staff of the Royal Tyrrell Museum in the late 1980s but is now worked annually for a couple weeks each summer (since 2006) by the University of Alberta. Material from this site appears referable to Pachyrhinosaurus canadensis.
In 1972, Grande Prairie, Alberta science teacher Al Lakusta found a large bonebed along Pipestone Creek
Pipestone Creek
Pipestone Creek is a waterway that runs through central Alberta, Canada. For example, over of Pipestone Creek parkland is situated in Millet, Alberta, with a combination of meadows and urban forest.It originates east of Pigeon Lake and flows east...
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...
. When the area was finally excavated between 1986 and 1989 by staff and volunteers of the Royal Tyrrell Museum of Palaeontology
Royal Tyrrell Museum of Palaeontology
The Royal Tyrrell Museum is a popular Canadian tourist attraction and a leading centre of palaeontological research noted for its collection of more than 130,000 fossils....
, paleontologists discovered an amazingly large and dense selection of bones—up to 100 per square meter, with a total of 3500 bones and 14 skulls. This was apparently the site of a mass mortality, perhaps a failed attempt to cross a river during a flood. Found amongst the fossils were the skeletons of four distinct age groups ranging from juveniles to full grown dinosaurs, indicating that the Pachyrhinosaurus cared for their young.
The adult skulls had both convex and concave bosses as well as unicorn
Unicorn
The unicorn is a legendary animal from European folklore that resembles a white horse with a large, pointed, spiraling horn projecting from its forehead, and sometimes a goat's beard...
-style horns on the parietal bone just behind their eyes. The concave boss types might be related to erosion only and not reflect male/female differences. In 2008, a detailed monograph describing the skull of the Pipestone Creek pachyrhinosaur, and penned by Philip J. Currie, Wann Langston, Jr.
Wann Langston, Jr.
Wann Langston, Jr. is an American paleontologist and professor at the University of Texas at Austin. He has worked on a number of different reptiles and amphibians in his long career, beginning with the 1950 description of the theropod dinosaur Acrocanthosaurus...
, and Darren Tanke
Darren Tanke
Darren H. Tanke is a Canadian fossil preparation technician of the Dinosaur Research Program at the Royal Tyrrell Museum of Palaeontology in Drumheller, Alberta. Born in Calgary, Tanke became interested in natural history at an early age. In 1979, Tanke began working for Philip J...
, classified the specimen as a second species of Pachyrhinosaurus, named P. lakustai after its discoverer.
Paleobiogeography
Modern life at high elevations in lower latitudes resembles life at low elevation in higher latitudes. There may be parallels to this phenomenon in Cretaceous ecosystems, for instance, Pachyrhinosaurus species are found in both Alaska and upland environments in southern Alberta.During the Edmontonian
Edmontonian
-Paleobiogeography:In southern North America, little changed in the transition from the Judithian to the Edmontonian. However, the northern biome experienced a general trend in reduction of centrosaurines, with only Pachyrhinosaurus surviving. Likewise among lambeosaurs, only the single genus...
, in North America's northern biome, there is a general trend of reduced centrosaurine diversity, with only Pachyrhinosaurus surviving. Inland faunas are distinguished by a Saurolophus
Saurolophus
Saurolophus is a genus of large hadrosaurine duckbill that lived about 69.5-68.5 million years ago, in the Late Cretaceous of North America and Asia; it is one of the few genera of dinosaurs known from multiple continents. It is distinguished by a spike-like crest which projects up and back...
-Anchiceratops
Anchiceratops
Anchiceratops is a genus of chasmosaurine ceratopsid dinosaur from the Late Cretaceous Period of western North America. Like other ceratopsids, it was a quadrupedal herbivore with three horns on its face, a parrot-like beak, and a long frill extending from the back of its head. The two horns above...
association while more coastal areas were characterized by Pachyrhinosaurus and Edmontosaurus
Edmontosaurus
Edmontosaurus is a genus of crestless hadrosaurid dinosaur. It contains two species: Edmontosaurus regalis and Edmontosaurus annectens. Fossils of E. regalis have been found in rocks of western North America that date from the late Campanian stage of the Cretaceous Period 73 million years ago,...
.
In popular culture
A Pachyrhinosaurus was selected as the mascot for the 2010 Arctic Winter Games held in Grande Prairie, Alberta.External links
- Pachyrhinosaurus at DinoData
- Pachyrhinosaurus, from the Dinosaur Encyclopaedia at Dino Russ' Lair