(Thick nosed lizard).
Named By: Charles Mortram Sternberg - 1950.
Classification: Chordata, Reptilia, Dinosauria, Ornithischia, Ceratopsia, Ceratopsidae, Centrosaurinae, Pachyrostra.
Species: P. canadensis (type), P. lakustai, P. perotorum.
Size: 8 meters long.
Known locations: Canada, Alberta - Bearpaw Formation, Horseshoe Canyon Formation. USA, Alaska - Prince Creek Formation.
Time period: Campanian of the Cretaceous.
Fossil representation: Skulls of many individuals as well as hundreds of associated bones.
Even though it did not have the elaborate horns of some ceratopsians like Einiosaurus, Pachyrhinosaurus has become a favourite amongst ceratopsian dinosaur enthusiasts because of the large bony growth called a boss that is present on top of its snout. A second smaller boss was also present over the eyes and is sometimes close to the nasal boss. Pachyrhinosaurus still possessed some small horns, particularly around the edges of the frill. Some of these characteristics are shared amongst the Pachyrhinosaurus species while some are unique to just one species.Distinguishing characteristics of Pachyrhinosaurus species
|Distinguishing feature||P. canadensis||P. lakustai||P. perotorum|
|Eye and snout bosses almost together?||Yes||No||Yes|
|Two curved backwards pointing horns on frill?||Yes||Sometimes||No|
|Jagged 'comb' extension on tip of nasal boss?||No||Yes||Yes|
|Narrow dome in centre of upper portion of nasal boss?||No||No||Yes|
|Pommel on the front of nasal boss?||No||Yes||No|
|Two flattened horns that point forwards and down from top of frill?||Yes||No||No|
|Flat and rounded nasal boss?||Yes||No||No|
|Comb-like horn rising from middle of frill behind the eyes?||No||Yes||No|
|Known formations for the species||Horseshoe Canyon||Bearpaw, Horseshoe canyon||Prince Creek|
first Pachyrhinosaurus fossils were actually
discovered way back in
1880, but they did not get the attention they deserved until the
late 1940s which would result in the establishment of the type
species in 1950. The most significant discovery relating to
Pachyrhinosaurus however was the excavation of the
Pipestone Creek bone
bed in the late eighties (originally discovered by Al Lakusta in
1972) which ultimately yielded three and a half thousand
Pachyrhinosaurus bones as well as fourteen skulls.
represent individuals of all ages from fully grown adults to
juveniles, suggesting that ceratopsians like Pachyrhinosaurus
around in herds, possibly as a protection against large tyrannosaurid
predators like Albertosaurus.
One explanation for this bone bed occurring is that the Pachyrhinosaurus were crossing a river that may have been swollen with flood water, resulting in treacherous conditions that claimed the lives of many of the herd. Similar bone beds are also known for other ceratopsian dinosaurs like Centrosaurus and Styracosaurus. Specimens from this bone bed display a mix of convex (curved outward) and concave (curved inward) bosses. While speculation for this has been cited as representing male and female specimens, the differences may have been caused by erosion of the material. Individuals from this bone bed were named Pachyrhinosaurus lakustai after Al Lakusta.
- Pachyrhinosaurus canadensis, representing a new family of the Ceratopsia, from southern Alberta - National Museum of Canada Bulletin 118:109-120 - Charles M. Sternberg - 1950.
- The thick-headed ceratopsian dinosaur Pachyrhinosaurus (Reptilia: Ornithischia), from the Edmonton Formation near Drumheller, Canada - Canadian Journal of Earth Sciences 4:171-186 - W. Langston - 1967.
- A further note on Pachyrinosaurus (Reptilia: Ceratopsia) - Journal of Paleontology 42(5):1303-1304 - W. Langston - 1968.
- A new species of Pachyrhinosaurus (Dinosauria, Ceratopsidae) from the Upper Cretaceous of Alberta, Canada - in A New Horned Dinosaur from an Upper Cretaceous Bone Bed in Alberta. NRC Research Press, Ottawa 1-108 - P. J. Currie, W. Langston & D. H. Tanke - 2008.
- A new species of the centrosaurine ceratopsid Pachyrhinosaurus from the North Slope (Prince Creek Formation: Maastrichtian) of Alaska - Acta Palaeontologica Polonica 57 (3): 561–573 - Anthony R. Fiorillo & Ronald S. Tykosk- 2012.
- An Immature Pachyrhinosaurus perotorum (Dinosauria: Ceratopsidae) Nasal Reveals Unexpected Complexity of Craniofacial Ontogeny and Integument in Pachyrhinosaurus - PLoS ONE 8(6) - Anthony R. Fiorillo & Ronald S. Tykosk- 2013.