The Triassic Period of Earth's geologic history occurred from 250 million years to 200 million years ago as the first part of the Mesozoic Era. The Triassic was the first stage after the Permian extinction, an event that caused more than 90 percent of the Earth's species to die. Life forms that dominated this period of the planet's history include dinosaurs, coniferous trees and palm-like plants called cycads.
The climate of the Triassic Period was generally warm and dry at the beginning. Much of the landforms of Earth were connected as one large continent called Pangaea. There were no polar ice caps during this period, as the planet was warmer. By the end of the period, oceans became deeper and continental drift began, and life forms diversified as a result.
In the oceans, ammonites, mollusks and sea urchins evolved into greater varieties after the Permian extinction. Larger reptilian sea creatures, such as icthyosaurs and plesiosaurs, evolved towards the end of the Triassic Period. Microscopic phytoplankton first appeared in this period.
Huge ferns and conifers covered the land, providing shade and shelter for frogs, insects, salamanders and snakes. Dinosaurs first evolved nearly 230 million years ago, in the middle of the Triassic, and these giant creatures ruled the Earth for 165 million years.