The Mesozoic Era spans from about 252 million years ago to about 66 million years ago that means it began roughly around the time of the end-Permian extinction. The amphibians were declining after a long period of supremacy among the animals and the reptiles were gradually replacing them. Many of them became very large fearsome and came to dominate the animal life practically everywhere and spread into all habitats. For this reason, the Mesozoic era is also called the Age of Reptiles or the Age of Dinosaurs.