The Upper Jurassic is a geological period that lasted from about 163 to 145 million years ago. It is the final stage of the Jurassic period, which is known for its diverse range of dinosaurs and the development of early mammals. During this time, the climate was generally warm, and large landmasses were positioned differently than today, influencing the distribution of flora and fauna. This period is characterized by significant geological formations, including the Morrison Formation in North America, which is rich in dinosaur fossils. The Upper Jurassic also saw the emergence of new species, such as the large sauropods and the first birds, marking important evolutionary advancements.