It is thought that the mammals which survived though the Jurassic period were small nocturnal or burrowing animals with little need to see color. Later, after the extinction of the dinosaurs, many lines adapted to be more active in the daytime. Most developed a form of color vision, which is much more useful in the daytime. Primates developed full (trichromacy) color vision. For them, the ability to distinguish the color of fruit from leaves always was essential.