Mesozoic Era
Triassic, Jurassic & Cretaceous

Late
Triassic Dinosaurs

Late Triassic dinosaurs such as the predator Staurikosaurus and the herbivore Othosaurus had a nearly worldwide distribution, although not conspicuous or abundant. They were small on average, up to 3 meters in size and had an advantage over other reptiles due to their upright limb posture.

The
Jurassic Period

Early - Middle Jurassic Dinosaurs: Thecodonts ("socket-toothed" reptiles) became extinct; together with most of the large amphibians. Dinosaurs ruled the land. All the big meat eaters (Dilophosaurus) and all the big plant eaters (Datousaurus) were dinosaurs. All other terrestrial (ground-dwelling) animals were rather small (pterosaur, turtles, crocodiles, etc.). First significant extinction of a dinosaur group was the disappearance of the prosauropods at the end or the lower Jurassic.

Late Jurassic Dinosaurs: Known as the ‘golden age of the dinosaurs’. The largest animals evolved during the Late Jurassic period. Extensive fossil records show it as the Zenith of the sauropods and stegosaurid. Other major herbivore groups are the hypsilophodontids and iguanodontids. The ceratosaurs dwindle, while the allosaurids become the major predators.

The
Cretaceous Period

Due to high sea levels the interior of North America was flooded by a shallow epicontinental sea. High average global temperatures meant there were no glaciers or ice caps. Dinosaur and other Fauna assemblages existed closer to the poles. The deep ocean waters were anoxic (oxygen poor) with black shale deposits forming. The Cordillera region of Western North America was lifting up accompanied by increased volcanism.

Early Cretaceous: Major changes occurred in climate and vegetation with the appearance of flowering plants. This caused new types of dinosaurs to evolve: carnosaurs, iguanodon, ankylosaurs and ornithopods become larger. Sauropods became smaller and by the end of the early cretaceous they went extinct (except in South America). Allosaurs are replaced by other theropods (coelurosaurs and carnosaurs). Stegosaurs, iguanodontids and hypsilophodontids went practically extinct by the end of the Early Cretaceous. Heterodontosaurids died out completely.

Middle – Late Cretaceous: Dinosaurs were generally not as large, but very diverse and widespread. New types of dinosaurs appeared – better suited to feed on the new type vegetation. There was migration between Asia and North America. Major groups included the hadrosaurs, ceratopsians, ankylosaurs, tyrannosaurids, coelurosaurids and pachycephalosaurids. Sauropods restricted to South America.

Dinosaurs were the major terrestrial animals of the Mesozoic. They were extremely successful as a group, filling every niche of the ecosystem. Their existence, way of life and final disappearance is the subject of scientific research and limitless public interest.

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