Geologic Time Scales
Dating from 208-146mya, the Jurassic Period saw the dinosaurs become the dominant land animals on Earth. During this time, bony fish dominated the seas, and the first mammal evolved. Herbivorous dinosaurs put more pressure on the dominant land plant, gymnosperms, pushing them to new strategies to survive this predator. During the Jurassic, a group of Theropods developed feathers, possibly as a defense against the cold in a similar manner to fur in mammals. This group of Theropods eventually gave rise to the first birds, who outlived the dinosaurs.