The Jurassic was a period of Earth's geologic history that began about 200 million years ago, after the end of the Triassic period of the Mesozoic era. Dinosaurs thrived during the Jurassic.
Earth's Mesozoic era, often referred to as the "Age of the Dinosaurs," is divided into three periods, and the middle one was the Jurassic. It's named after the Jura Mountains on the French-Swiss border, where a geologist first noticed a difference between Jurassic rocks and those from the period that came just before it. We associate the Jurassic with dinosaurs like giant, long-necked sauropods; carnivorous apex predators like allosaurus; plated dinosaurs like stegosaurus; and the bird-like archaeopteryx, sometimes called the "first bird." During the Jurassic, Earth's continents continued splitting apart into separate landmasses.