The Triassic time period lasted from 245 to 208 million years ago, a time span of 37 million years. The Triassic is the first period of the Mesozoic Era. The term Triassic was first used in the 1830s to describe a sequence of rocks in Germany that consisted of three distinct units. These Triassic rocks were defined based on a particular type of fossil assemblage contained within them. They are located above the rocks of the Permian System and below the rocks of the Jurassic System.