Permian-Triassic Period

The Permian-Triassic Period was an extinction event, also known as the “Great Dying.” It was Earth’s most severe mass extinction, which occurred approximately 252 million years ago, wiping out about 90% of all species, especially marine species. The cause was massive volcanic activity from the Siberian Traps, which released large amounts of carbon dioxide into the atmosphere, leading to extreme global warming, ocean acidification, and oxygen depletion. Marine life would recover from the “Great Dying,” creating the first modern reef-building corals, and aquatic reptiles like ichthyosaurs and notosaurs would also emerge in the Triassic Period.

Triassic Period

Dinosaurs would first appear during the Triassic Period, about 230 to 245 million years ago. The Triassic Period was warm and dry, and featured early dinosaurs such as small, carnivorous Eoraptor and Herrerasaurus, as well as the large, herbivorous Plateosaurus and the bipedal carnivore Coelophysis. Other dinosaurs would include the Liliensternus, Riojasaurus, and Melanorosaurus.  Theropoda is one of the three major dinosaur clades, alongside Ornithischia and  Sauropodomorpha. Theropods, both extant and extinct, are characterised by hollow bones, three toes, and claws on each limb. Herbivores would consume tough, fibrous plants like cyclades and ferns, while carnivorous dinosaurs would hunt small insects, small reptiles, and other dinosaurs. Some omnivorous dinosaurs ate meat and plants. By the end of the Triassic era, some of these dinosaurs had become large, such as Riojasaurus and Lessemaurus. 

Jurassic Period

About 201 to 145 million years ago was the Jurassic period, also known as “Age of The Dinosaurs.” The climate was warm and humid around this time period. Marine life is thriving, including ammonites, fish, and large marine reptiles. The Pterosaurs dominated the skies, while small, shrew-like mammals survived in the undergrowth. In this period, dinosaurs grew to be enormous, including large herbivores like the Brachiosaurus and Diplodocus, and fierce carnivores such as the Allosaurus. The first birds, like the Archaeopteryx, also evolved during this time period.

Cretaceous period

The Cretaceous period happened 145 to 66 million years ago. The climate would be generally warmer and more humid than today on Earth, with polar regions free of ice and covered with forests. Flowering plants would first appear, leading to a co-evolutionary relationship with insects. Bees would make their appearance in this time period and act as the pollinators, which we still have today. Other insects, like butterflies and ants, would thrive and diversify. Marine invertebrates flourished, and the bony fish would evolve. Dinosaurs in this period would reach the peak of evolution and transform into many forms, including Tyrannosaurus rex, Triceratops, and the extremely massive titanosaurs. At the end of this period, there would be a mass extinction event that would eliminate roughly 16% of marine families and 18% of land vertebrate families, including all non-avian dinosaurs. This event was likely caused by a meteorite impact on the Earth, leading to widespread fires and a drastic change in climate.