Late Cretaceous Edmontonian

Horseshoe Canyon Formation

Pachyrhinosaurus

Centrosaurines were large horned dinosaurs known only from Late Cretaceous of North America. They all looked similar except for the head and frills. The frills were short. The nasal horns or bosses well developed with no significant brow horns. The frill and skull can be covered with varied horns, hornlets and bosses. They is considerable variation between species and individuals and they are often asymmetric. Centrosaurines were declining from the Judithian to the Edmontonian.

updated 0192416

Pachyrhinosaurus was the last of centrosaurines

The juvenile has a low nasal horn like most centrosaurs. The adults have a nasal and brow boses that combine into a masive structure. The frill can have a sideways sweeping spikes and it may have two small horns pointing inward with small hornlets along the rim. Along the center strut are iregulat horns.

They lived in well watered forests and marshes and along the coastal swamps from Montana to Alaska. The varied spieces must have had a toleration for cool or cold winters.