Ceratopsians

The ceratopsians group is probably one of the most familiar group to people. These dinosaurs had big frills at the back of their heads. Many of them had horns on their faces. They all walked on four legs (although some of them may have run up on their hind legs). These dinosaurs were also some of the most common at the end of the Cretaceous period. There are three groups of ceratopsians, the protoceratopsians, the chasmosaurs, and the centrosaurs.

Protoceratopsians

Protoceratopsians were the smallest of the ceratopsian group. They did not have the elaborate horns on their faces that other ceratopsians did. Some did have the beginnings of a bump on their nose, but it was not the long horn of the other groups. They have been found in large numbers, especially Protoceratops (over 100 have been found, making them one of the best known dinosaurs).

They ranged in size from about 0.76 meters (Microceratops) to 4 meters (Udanoceratops). They have been found both in Asia and in North America. They are more common in Asia, where the climate was drier. Protoceratopsians include animals such as Protoceratops, Leptoceratops, Udanoceratops, Microceratops, Bagaceratops, and Breviceratops.

Chasmosaurs

Chasmosaurs are known from many specimens. They had long brow (above the eye) horns and short nose horns. They also had very long frills on the back of their heads (except for Triceratops, which had a short frill). These frills had very large holes in them to make them lighter. They probably used these long frills as display items during mating season, just like a peacock uses its tail. Other than the frill and the brow horns, there were very few differences between chasmosaurs and centrosaurs. Triceratops was a very strange chasmosaurs because it did not have a long frill. The short frill that it did have was solid. For many years, it was put in with the centrosaurs group. Triceratops was the most common dinosaur found at the end of the Dinosaur Era.

Chasmosaurs ranged from 6 meters (Chasmosaurus) to about 10 meters (Triceratops). They have only been found in North America, where they are very common. Chasmosaurs include Triceratops, Anchiceratops, Arrhinoceratops, Chasmosaurus, Torosaurus, and Pentaceratops.

Centrosaurs

Centrosaurs have been found in huge numbers, all in one area, which makes scientists think that they travelled in large herds. Some of these huge graveyards (called bonebeds) have hundreds of the same animal. On idea of why they have been found in large herds was that they were migrating, just like birds in the fall and spring. Seeing this many large animals at once, all going in the same direction must have been a fantastic sight.

Centrosaurs had short frills, although some, such as Styracosaurus, had large horns on the back of the frill that made it look longer. They had short brow horns, but long nose horns (up to 1 meter in some animals). They would have been able to use these for defence and for matches to see who was in charge of the herd. Like the chasmosaurs, they had big holes in their frills to lighten them.

Centrosaurs ranged from 6 meters (Centrosaurus) to about 8 meters (Pachyrhinosaurus). They have only been found in North America, but there are pieces of bone that might be from centrosaurs from South America and Asia. Centrosaurs include Centrosaurus, Styracosaurus, Monoclonius, Pachyrhinosaurus, Einiosaurus, and Achelousaurus.

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