The Jurassic time period lasted from 208 to 146 million
years ago, a time span of 62 million years. The term Jurassic was first
used in the 1830s to describe a sequence of rocks in the Jura Mountains
in Switzerland. These Jurassic rocks were defined based on a particular
type of fossil assemblage contained within them. They are located above
the rocks of the Triassic System and below
the rocks of the Cretaceous System.