File:Pachyrhinosaurus lakustai skull.jpg

English: Pachyrhinosaurus sp. - fossil ceratopsian dinosaur skull (cast) from the Cretaceous of North America. (CM 81683, Carnegie Museum of Natural History, Pittsburgh, Pennsylvania, USA)

Ceratopsians are the "horned dinosaurs". They were large, quadrupedal, herbivorous dinosaurs having a beaked skull and a frill - an extension of bone behind the skull that partially covered the neck. Ceratopsian dinosaurs are known from the Jurassic and Cretaceous. The last members of the group died out at the Cretaceous-Tertiary boundary, 65 million years ago.

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Exhibit signage:

Pachyrhinosaurus sp. CM 81683 (cast)

Members of the Ceratopsidae are split into two main groups: the short-frilled Centrosaurinae and the longer-frilled Chasmosaurinae. Centrosaurines tended to evolve long nose horns and shorter brown horns. Some of the latest, such as Pachyrhinosaurus, even lost their bony horns altogether. The skull of this bizarre ceratopsid is adorned with thickened knobs of bone, which may have anchored one of more horns made of a material that does not typically fossilize. This is comparable to today's rhinos, which have horns composed of keratin, the same substance of which fingernails are made.

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Classification: Animalia, Chordata, Vertebrata, Reptilia, Archosauria, Dinosauria, Ornithischia, Marginocephalia, Ceratopsia, Ceratopsidae

Stratigraphy: undisclosed

Locality: undisclosed

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Info. at:

en.wikipedia.org/wiki/Pachyrhinosaurus