Original Dinosaurs Introduction

Introduction

Dinosaurs walked the Earth from 248 to 65 million years ago (about 183 million years). This time is also called the Mesozoic Era or the Age of Reptiles. It is divided into three periods: Triassic, Jurassic and Cretaceous (Lower and Upper).
The Triassic Period occurred from 248-208 million years ago. The first dinosaurs and mammals appeared during this time. The Triassic Period ended with the extinction of 35% of all animal families, including all marine reptiles except Ichthyosaurs. Dinosaurs expand their range.
The Jurassic Period occurred from 208-146 million years ago. The first birds appear. Dinosaurs flourish.
The Cretaceous Period is divided into two parts: the Lower Cretaceous Period, 146-98 million years ago, and the Upper Cretaceous Period, 98-65 million years ago.
The Lower Cretaceous Period is the time of the Dinosaurs. The first Butterflies, Ants and Bee appear.
The Upper Cretaceous Period, 98-65 million years ago, was a time of great volcanic activity. Primitive marsupials develop. A asteroid impact ended this period.

Dinosaurs and 50% of the marine invertebrate species became extinct.