Climate and Geography The Jurassic witnessed the breakup of the Pangaean supercontinent into two big pieces, Gondwana in the south and Laurasia in the north, as well as the formation of intra-continental lakes and rivers that opened new evolutionary niches for aquatic and terrestrial animals. The climate was hot and humid, with steady rainfall, ideal conditions for the explosive spread of lush, green plants.
Terrestrial Life During the Jurassic, the small, quadrupedal, plant-eating prosauropods of the Triassic gradually evolved into gigantic sauropods like Brachiosaurus and Diplodocus. This period also saw the rise of medium-sized carnivores like Allosaurus and Megalosaurus, which helps explain the evolution of the earliest ankylosaurs (armored herbivores). The first mouse-sized mammals kept a low profile, scurrying around at night so as not to get squashed.
Aquatic Life Just as dinosaurs grew to bigger and bigger sizes on land, so aquatic reptiles gradually reached shark- (or even whale-) sized proportions. The Jurassic seas were filled with fierce pliosaurs like Liopleurodon and Cryptoclidus, as well as sleeker, less frightening swimmers like Plesiosaurus. Fish were abundant, as were squids and sharks, providing a steady source of food for these and other marine reptiles.
Avian Life By the end of the Jurassic, the skies were filled with relatively advanced pterosaurs like Pterodactylus, Dimorphodon and the (smaller) Archaeopteryx. It's probable that at least a few of these avian reptiles were covered with feathers, as were some of their land-based cousins.
Plant Life Gigantic herbivores like Barosaurus and Apatasaurus couldn’t have evolved if they didn’t have a reliable source of food: the landmasses of the Jurassic were blanketed with thick coats of vegetation, including ferns, conifers, cycads, club mosses and horsetails.
Next Page: The Cretaceous Period
