Drifting Continents And Globetrotting Dinosaurs
dinosaurs got around. Their fossilized remains occur on every continent and from pole to pole, encompassing a tremendous variety of ancient environments: forests, savannahs, deserts, seashores, river floodplains, and mountain valleys, among others. How did these prehistoric landlubbers disperse across oceanic barriers to populate the globe? Did they make marathon swims (particularly challenging for tyrannosaurs, given their tiny arms), or climb aboard vast mats of floating vegetation? No, we now know that earlier dinosaurs spread over great distances simply by walking, whereas many of their descendants hitchhiked aboard continental rafts. And it turns out that the processes underlying continental movements have influenced life in other profound ways—in particular, through effects on climate. This chapter explores a pivotal subplot of the dinosaurian saga: the impact of physical processes on life.
During the early portion of the Mesozoic, including the Late Triassic when dinosaurs appeared, all continents were united in a supercontinent called Pangaea. From the Jurassic onward, the Mesozoic world witnessed the fragmentation of this monster continent into successively smaller landmasses. Beginning in the mid-Jurassic, Pangaea split into northern and southern blocks. A massive tear in Earth's continental crust began in the east and proceeded slowly westward, as if the world were being unzipped. The widening rupture filled steadily with water, giving birth to a new ocean, the Tethys Sea. The now-distinct yet still-gargantuan supercontinents, known as Laurasia in the north and Gondwana in the south, continued to fragment until, by the close of the Mesozoic, Earth
- 67 Ma
Cretaceous
Cretaceous
- 152 Ma
Jurassic
Jurassic
- 220 Ma
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