Dinosaurs lived during the Mesozoic Era, commonly known as the “Age of Reptiles,” which lasted from approximately 252 to 66 million years ago (mya). This era is divided into three distinct geological periods: the Triassic, Jurassic, and Cretaceous. 

1. Triassic Period (252 – 201 mya) 

The Triassic began after the “Great Dying” extinction event, which wiped out 90% of life on Earth. 

• Early Triassic: The world was a single supercontinent called Pangaea, largely covered by deserts.
• The Dawn of Dinosaurs (~243–233 mya): The first dinosaurs emerged as small, bipedal creatures.
• Key Dinosaurs:
  • Nyasasaurus: One of the earliest possible dinosaurs.
  • Eoraptor: A dog-sized meat-eater.
  • Herrerasaurus: One of the first large carnivores.
  • Coelophysis: A small, slender predator. 

2. Jurassic Period (201 – 145 mya) 

Following a mass extinction at the end of the Triassic, dinosaurs became the dominant land animals as the climate became warm and humid. 

• Middle to Late Jurassic: Pangaea began to split into two smaller landmasses, Laurasia (North) and Gondwana (South).
• Rise of Giants: This period is famous for the evolution of massive long-necked herbivores (sauropods).
• Key Dinosaurs:
  • Brachiosaurus & Diplodocus: Giant sauropods reaching over 20m in length.
  • Allosaurus: The apex predator of the late Jurassic.
  • Stegosaurus: An iconic armoured herbivore.
  • Archaeopteryx: Often considered the first bird, appearing in the Late Jurassic. 

3. Cretaceous Period (145 – 66 mya) 

The longest period of the Mesozoic saw the greatest diversity of dinosaurs and the appearance of flowering plants. 

• Peak Diversity: Continents continued to drift toward their modern positions, creating isolated environments where unique species flourished.
• Famous Predators & Herbivores:
  • Tyrannosaurus rex: One of the largest land predators, dominating the Late Cretaceous.
  • Triceratops: A three-horned herbivore.
  • Velociraptor: A small, feathered pack hunter.
  • Spinosaurus: A massive semi-aquatic carnivore.
• The K-Pg Extinction (66 mya): A massive asteroid impact in the Yucatan Peninsula triggered a global catastrophe that wiped out all non-avian dinosaurs.