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Pachyrhinosaurus

Pachyrhinosaurus!<-- This template has to be "warmed up" before it can be used, for some reason -->

Eugnathostomata

Pachyrhinosaurus (meaning "thick-nosed lizard") is a genus of ceratopsid dinosaur 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. Twelve partial skulls and a large assortment of fossils have been found in total 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. Two species have been identified. P. lakustai, from the upper Bearpaw and lower Horseshoe Canyon Formations, 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.[1]

Contents

Description

Instead of horns, the skull bears massive, flattened bosses, the largest being over the nose. These were probably used in butting and shoving matches, as in musk oxen. A single pair of horns grew from the frill and extended upwards. It appears that that both the shape and size of the frill was highly individualized, reliant on gender and perhaps other factors. Pachyrhinosaurus is most closely related to Achelousaurus.

Pachyrhinosaurus was 8 metres (26 ft) long.[2] It weighed about four tons. It was herbivorous and possessed strong cheek teeth to help it chew tough, fibrous plants.

Discovery and species

P. lakustai skull

The type species, 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 the 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 did indeed care 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.[3]

In popular culture

In addition to appearing in Walt Disney Pictures Dinosaur, Pachyrhinosaurus appeared in the Jurassic Fight Club episode "River of Death", about the Pipestone Creek site. However, the pachyrhinosaurs in this episode were portrayed with a rhinoceros-like horn, something which recent fossil evidence argues against. It also appeared in documentaries like Messages in Stone, and the Nova special, Arctic Dinosaurs. It is also the mascot for the 2010 Arctic Winter Games to be held in Grande Prairie, Alberta.[4]

The genus has also been used in the Land Before Time series as Mr. Thicknose.

References

  1. ^ Arbour, V. M.; Burns, M. E.; and Sissons, R. L. (2009). "A redescription of the ankylosaurid dinosaur Dyoplosaurus acutosquameus Parks, 1924 (Ornithischia: Ankylosauria) and a revision of the genus". Journal of Vertebrate Paleontology 29 (4): 1117–1135. doi:10.1671/039.029.0405. 
  2. ^ Holtz, Thomas R. Jr. (2008) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages Supplementary Information
  3. ^ Currie, P.J., Langston, W., and Tanke, D.H. (2008). "A new species of Pachyrhinosaurus (Dinosauria, Ceratopsidae) from the Upper Cretaceous of Alberta, Canada." pp. 1-108. In: Currie, P.J., Langston, W., and Tanke, D.H. 2008. A New Horned Dinosaur from an Upper Cretaceous Bone Bed in Alberta. NRC Research Press, Ottawa, Ontario, Canada. 144 pp. ISBN 978-0-660-19819-4
  4. ^ "2010 Arctic Winter Games Hosts One-Year-Out Celebration". Arctic Winter Games Host Society. 2009-03-08. http://www.awg2010.org/news_article/36.aspx. Retrieved 11 December 2009. 

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