Jurassic Period: Dinosaur Domination

Although the entire Mesozoic era is often referred to as the age of dinosaurs, dino domination really took hold during the Jurassic period 200 to 145 million years ago. Some of the world’s largest and most vicious beasts walked the Earth then, such as Allosaurus, which could chop victims into pieces with its axe-like jaws. Reptiles ruled not only the land, but also the sea and air, with the first known birds emerging during the Jurassic. This explosion of life was made possible by dramatic geological changes that put an end to supercontinent Pangea while beginning the land reconfigurations that would help to shape our present-day world.

Jurassic Geology and Climate

The rifts within Pangea that began its break-up during the Triassic widened, causing Africa to split from South America and India to move toward Asia. North America broke off and drifted to the west. As a result of such widespread continental movement, the Atlantic Ocean was born between newly separated landmasses. North America’s drift triggered volcanic activity that eventually would lead to the rise of the Rocky Mountains.

The new bodies of water resulted in moist winds that brought rain to formerly dry and barren regions. Instead of severe heat, most areas now experienced comfortably warm conditions. Evidence of widespread coral reefs also suggests the overall atmosphere was moist and temperate or tropical, providing the perfect backdrop for animal and plant life.

Plants

Although many plants and trees fared well during the Triassic, the Jurassic was by far more lush and verdant. Relatives of today’s pines, giant sequoias and monkey puzzle trees towered over many areas. Palm-like cycadeoids and ginkgoes also flourished. Ferns and horsetails grew in abundance, becoming the staple food for the Jurassic’s iconic life-form, dinosaurs.

Plant-Eating Dinosaurs

Plant-eating dinosaurs, known as prosauropods, were one of the more common vertebrates during the Early Jurassic. By the later phase of this period, however, large sauropods became the predominant herbivores. Apatosaurus, for example, grew up to 90 feet in length and ate incredible amounts of foliage to sustain its 30-ton body. At up to 148 feet in length, Seismosaurus, meaning "Earthquake Lizard," outgrew even Apatosaurus. Its head was so small and its body so big that more than 200 gastroliths, or stomach stones, were needed to help pulverize the constantly incoming food. Stegosaurs formed another common Jurassic herbivorous group. These slow movers spent much of their time feasting on leaves and other plant material with their horned, toothless beaks.

Carnivorous Dinosaurs

With so many dinosaurs roaming the planet, the Jurassic proved to be a dino eat dino world, since carnivorous beasts arose to feast on the bounty. Each predator developed its own unique set of weapons and hunting techniques. Dilophosaurus, with its double head crest, possessed a devilish look matched by its sharp hand and feet claws. Cryolophosaurus, sometimes nicknamed Elvisaurus because of its Elvis-like pompadour-shaped head crest, ran after prey with its powerful legs. Gasosaurus, on the other hand, possessed such strong jaw muscles that it could bite into the thickest of flesh, tearing off hunks with near effortless head tosses. Perhaps one of the most aggressive predators, based on fossil remains of its victims, was Piatnitzkysaurus. The mangled prey bones suggest this 20-foot-long killer from Argentina could rip its victims to shreds with ease.