Copyright © 2007 Dorling Kindersley
Not all the dinosaurs lived at the same time. Nor did they all live in the same part of the world. During the 180 million years that dinosaurs walked the Earth, the break-up of the supercontinent Pangaea and the resulting major changes of climate produced many different habitats. Continental drift changed the world’s climate because it altered the flow of ocean currents and controlled how much of the world was covered in ice. Different dinosaurs evolved to live in different environments. Those that had existed on the dry Triassic supercontinent were quite different from those that lived on the scattered landmasses of the Cretaceous.
During the Triassic, all the landmasses of the world were joined together, forming the single supercontinent, Pangaea. Because the continent was so huge, most inland areas were a long way from the ocean and there were extensive deserts. Only around the edges of the continent was there enough moisture for any vegetation. This was the time of the first dinosaurs and they lived everywhere.
Plant and animal life was most common along the banks of rivers near the sea. The river banks were covered with ferns and the shallow water supported reed beds of horsetails. Early carnivorous dinosaurs such as Herrerasaurus hunted in these thickets.
By the Jurassic, Pangaea had begun to break up. Rift valleys produced long arms of ocean that reached into the depths of the continent, very like today’s Red Sea in Egypt. Shallow seas spread across the lowlands and reached into the former deserts, giving rise to damper climates in most areas. There was much more vegetation than during the Triassic, although the plants were the same types.
As in the Triassic, the areas most covered by vegetation were by the riversides. Seasonal rainfall produced forests of tree ferns and ginkgoes, with an undergrowth of ferns and horsetails. These provided good feeding for herbivores such as Stegosaurus.
By the Cretaceous, the continents had broken apart, many of them beginning to look like the continents of today. The presence of so many different land areas meant that the climates were much more varied. The animal life was different on each continent as each group of animals evolved separately. So, for example, the dinosaurs of North America were different from those of South America.
Swamps and river deltas are ideal places for the preservation of fossils. Steamy swamps existed along the edges of the Cretaceous continents. Wet-loving trees such as swamp cypresses dominated these areas. They provided the perfect habitat for fish-eating dinosaurs such as Spinosaurus.
By the Cretaceous, flowering plants had begun to evolve. Dinosaurs with efficient chewing mechanisms, such as Corythosaurus, could both browse from trees and graze close to the ground. This led to the evolution of plants with seeds that could survive this treatment.
Little is known about the vegetation of mountain habitats because most fossils come from lowland regions. But bones of armoured dinosaurs, such as Edmontonia, that look as though they have been washed down from mountain areas, have been found.
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