The Earth as it appeared near the middle of the Jurassic Period (213 to 144 mya). Pangaea is starting to split into two smaller pieces called Laurasia (top) and Gondwanaland (bottom). The Atlantic Ocean, just starting to open up, is a narrow strip of water between the future east coast of North America and west coast of Africa. During the Jurassic the dinosaurs grew in number, type, and size. This was the "age of giants," when the monster Supersaurus, Seismosaurus, and Ultrasaurus lived. There were also smaller dinosaurs including the well-known Stegosaurus and the bird-like Archaeopteryx. Map courtesy of Ronald C. Blakey at NAU.