Pachyrhinosaurus

Live reconstruction of Pachyrhinosaurus

• North America

• Pachyrhinosaurus canadensis
• Pachyrhinosaurus lakustai

Pachyrhinosaurus ( "Dick nose lizard" ) from the Late Cretaceous of North America is a dinosaur genus of the family of Ceratopsidae within the ceratopsians.

Features

With an estimated 5.5 to 7 meters long Pachyrhinosaurus was a rather large representatives of Ceratopsidae. His physique was like the other representatives of this group. It was built stocky animals with massive head and powerful limbs, the hind legs were much longer than the front legs. Instead of a nose horn as related dinosaurs wore Pachyrhinosaurus a thick, bony ridge on the nasal bone. It is sometimes speculated that a horn sat on this bony of keratin, signs in the fossil record does not exist for it. The neck shield was formed as with all Ceratopsidae from the parietal and squamosal. He was thin and had paired windows. The rear edge of the plate were one to three large spikes.

The Rostralknochen (in the upper jaw ) and the Praedentale (before the lower jaw) were as in all Ceratopsidae a tapered nose, which allowed a selective feeding. The dentition was like all Ceratopsidae from dental batteries that are in rows spaced teeth that are replaced by the following tooth when worn. The occlusal surfaces of the teeth were nearly vertical, the teeth were adapted to one overlapping but not milled chewing. This dinosaur was like all ceratopsians herbivores, he probably ate mainly tough, fibrous plants.

Paleobiology

From Pachyrhinosaurus are bone beds ( " bone stock " ) are known in which the remains of numerous animals have been found from different ages together. It is thought that these animals at least temporarily living together in larger groups.

Horns and neck shields of Ceratopsidae are often associated with the defense against predators in context. However, the bony on the nose of Pachyrhinosaurus and the horns on the edge of the shield are unlikely to have been eligible for defense purposes. Also the neck shield was too thin to act as protection against neck bites. After today's perspective, the headdress was primarily the identification of the individual species as well as the interaction with other dogs - either by exhibition, threatening gestures or in fighting. It may be decreased by territorial boundaries or mating privileges.

Fund localities and stratigraphic classification

Locations of Pachyrhinosaurus are in North America in the Canadian province of Alberta ( Horseshoe Canyon Formation, St. Mary River Formation, Waptiti Formation) and in the U.S. state of Alaska ( Colville Group). The findings of twelve incomplete skulls and other material from bonebeds come from rock layers, the sediments in the times of the early Maastrichtian ( million years ago, about 72 to 69), the last stage of the Cretaceous ( and thus the entire Mesozoic ), deposited have. This is one of these dinosaurs of the youngest known representatives of Centrosaurinae.

The first description of the genus comes from Charles Mortram Sternberg from the year 1950. Their name is derived from the Greek words pachys ( = " fat" ), rhinos ( = " nose " ) and sauros ( = " lizard" ) from. In addition to the same time established the genus type species P. canadensis is since 2008 from the late Campanian -derived ( million years ago, about 76 to 72) species P. lakustai known.

System

Pachyrhinosaurus is incorporated within the Ceratopsidae in the Centrosaurinae. Its closest relative may have been the also characterized by the lack of nose horn Achelousaurus. Together they formed the tribe Pachyrhinosaurini.