This app is about Dinosaurs - The First Giants; which are a diverse group of reptiles of the clade Dinosauria. The Mesozoic Era is an interval of geological time from about 252 to 66 million years ago. It is also called the Age of Reptiles or Age of Conifers. Dinosaurs first appeared during the Triassic period and became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201 million years ago; their dominance continued through the Jurassic and Cretaceous periods.