a plant-eating centrosaurine ceratopsid dinosaur from the Late Cretaceous of Canada.
C.M. Sternberg (1950
is derived from the Greek "pakhys" (thick), "rhin" (nose) and "sauros" (lizard") because of a thick bony nasal "boss" where most large ceratopsians have a horn. Some researchers think that this boss was merely a platform to support a huge boneless horn made of keratine - a naturally occuring protein that is a major component of things like fingernails, hooves, claw and horn coverings, and hair. Unfortunately it doesn't fossilize so evidence is sadly lacking.
The species epithet
, is derived from "Canada" (its place of discovery) and the Latin "ensis" (from).
The first Pachyrhinosaurus
fossils were discovered at Little Bow River in the St. Mary River Formation, Alberta, Canada, by Charles M. Sternberg in 1946.
(NMC 8867) is a skull.
Remains of Pachyrhinosaurus canadensis
have also been discovered at the unfortunately named Scabby Butte locality of Alberta's lower Horseshoe Canyon Formation. And a particularly handsome skull (NMC 9485) was found by Wann Langston in 1967 at Munson Ferry near Drumheller.
: Late Cretaceous
: 80-67 mya
Est. max. length
: 8 meters
Est. max. hip height
Est. max. weight
: 3 tons
(DMNH21200—a partial skull), long known simply as "the Perot Dinosaur", was recovered from Kikak-Tegoseak Quarry in Alaska's Prince Creek Formation (70-69 mya), in 2006. As in Pachyrhinosaurus canadensis
, the bosses over its nose and eyes nearly grew together, separated only by a narrow groove, but its frill lacked the two small, hook-like horns. It was named in 2011, and a juvenile specimen was discovered just over a year after that, loitering in blocks that had been removed from the same quarry at the same time, which allowed paleontologists to plot the growth pattern of its facial lumps. The epithet, perotorum
, is named for Margot and Ross Perot and their children.
(TMP 1986.55.258)is named for Al Lakusta who discovered its first remains along Pipestone Creek, (Wapiti Formation), Alberta, in 1972. When workers from the Royal Tyrrell Museum finally excavated the site between 1986-1989 they discovered thousands of bones and 14 skulls from juvenile to geriatric specimens. Unlike Pachyrhinosaurus canadensis
and Pachyrhinosaurus perotorum
whose bosses virtually merge into one, those of Pachyrhinosaurus lakustai
are separated by a wide gap.
Some specimens sport two small frill horns present in Pachyrhinosaurus canadensis
, though some don't which suggests their presence depended on age or gender.
is the oldest species of Pachyrhinosaurus
(84 to 71 Mya) so could well be the direct ancestor of the other two.
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