The Jurassic period is a geological time frame that lasted from about 201 to 145 million years ago. It is known for the rise of large dinosaurs, such as Brachiosaurus and Stegosaurus, which dominated the land. This period also saw the first appearance of birds, evolving from small theropod dinosaurs. During the Jurassic period, the Earth's continents were arranged differently than today, forming a supercontinent called Pangaea. The climate was generally warm and humid, leading to lush vegetation and diverse ecosystems. Marine life thrived in the oceans, with many species of ammonites and ichthyosaurs flourishing during this time.