- This era began approximately 252 million years ago and ended about 66 million years ago.
- This era can be subdivided into 3 periods – these include the Triassic, the Jurassic and the Cretaceous Periods.
The Triassic Period:
- Starting approximately 250 million years ago and ending about 200 million years ago, the Triassic is a period of which is usually broken down into 3 major epochs – The Early Triassic, The Middle Triassic, and the Late Triassic Epochs.
- During this period, a variety of different animals began evolving including nothosaurs and ichthyosaurs.
- All types of crustaceans and corals also began to proliferate.
- By the end of the Triassic Period, there was an explosion in reptilian evolution and dinosaurs also began to evolve.
- However, as temperatures on Earth began to rise, the Fourth Major Extinction occurred – also known as the Triassic-Jurassic Extinction Event.
- This event killed off all archosaurs, except for crocodiles, and almost all of the large amphibians that existed at the time.
- It also killed off over 30% if all marine animals.
The Jurassic Period:
- The Jurassic Period ran from 200 to 145 million years ago and is one of the most famous of the Periods on the Geologic Time Scale.
- This period can be subdivided into its three major epochs which include the Early Jurassic, the Middle Jurassic, and the Late Jurassic Epochs.
- During this beginning of this period on the geological time scale, huge prairies of ferns crossed the land masses and dinosaurs such as Diplodocus and Brachiosaurus fed off of these fern forests.
- True crocodiles began to evolve during this time as well.
- It was also the time when mammals began to evolve.
- By the end of the Jurassic Period, there was an extinction called the Jurassic-Cretaceous Extinction Event that killed off a fair number of species during this time.
- However, this extinction event is not considered to be one of the major ones on the prehistoric timeline.
The Cretaceous Period:
- The Cretaceous Period occurred on Earth’s timeline from about 145 million to 66 million years ago.
- This period can be subdivided into two epochs – the Early Cretaceous Epoch and the Late Cretaceous Epoch.
- During this time, dinosaurs such as Eustreptospondylus, Carcharodontosaurus and Spinosaurus began to evolve and the Iguanodon managed to spread its kind to every continent on the planet.
- It was during this period that the K-T Extinction, also known as the Fifth Major Extinction (the most recent one) occurred.
- This extinction event would bring an end to the dinosaurs and would cause 75% of the world’s species’ to go extinct.
