What is Mesozoic?
The '''Mesozoic Era''' was the [[era|geological era]] in which [[dinosaur]]s lived, as well as the first [[mammal]]s. It lasted about 186 million years, starting 252.2 mya (million years ago) with the [[Permian–Triassic extinction event|P/Tr extinction]] and ending 65 mya with the [[K/T extinction event|K/T extinction]] (the one that killed all dinosaurs except birds).<ref>Gradstein, Felix M. James G. Ogg, Alan G. Smith (eds) 2005. ''A geologic time scale 2004''. Cambridge University Press. {{ISBN|0-521-78673-8}}</ref> Dinosaurs appeared around 231 mya (21 million years after the beginning of the Mesozoic). They [[evolved]] from the reptiles called [[archosaur]]s. Modern birds and [[crocodile]]s are part of that group. Although [[mammal]]s originated in the [[Upper Triassic]], they did not live like dinosaurs. Mammals spent most of the long Jurassic and Cretaceous periods as small [[nocturnal animals]] living mainly in forests. Most lost their [[color vision]]. Mammals today have some color vision. Most have red-green color blindness, with only two types of [[cone cell]]s. Some [[primate]]s evolved a third type of cone cell, which gives them [[trichromacy]]. Color is needed in forests to spot ripe fruit. The Mesozoic is the middle of the three eras that make up the [[Phanerozoic|Phanerozoic eon]]. Before the Mesozoic was the [[Palaeozoic]] era. The K/T extinction in 65 mya also marks the beginning of the [[Cenozoic|Cenozoic era]], the one we live in. The three Mesozoic periods were: * [[Triassic]] (252–201 mya) **[[Lower Triassic]] (252–247 mya) **[[Middle Triassic]] (247–237 mya) **[[Upper Triassic]] (237–201 mya) * [[Jurassic]] (201–145 mya) **[[Lower Jurassic]] (201–176 mya) **[[Middle Jurassic]] (176–161 mya) **[[Upper Jurassic]] (161–145 mya) * [[Cretaceous]] (145–66 mya) **[[Lower Cretaceous]] (145–100 mya) **[[Upper Cretaceous]] (100–65 mya) == Ecology == The ecology of this world was quite different to that of the [[Pleistocene]], the relatively cold era in which humans evolved and live. The Mesoz