Jurassic

The Jurassic Period is a major unit of the geologic timescale that extends from about 199.6 ± 0.6 Ma (million years ago) to 145.4 ± 4.0 Ma, the end of the Triassic to the beginning of the Cretaceous. As with other geologic periods, the rock beds that define the start and end of the period are well identified but the exact dates are uncertain by 5 - 10 million years. The Jurassic constitutes the middle period of the Mesozoic era, also known as the "Age of Dinosaurs". The start of the period is marked by the major Triassic-Jurassic extinction event.

The Jurassic was named by Alexandre Brogniart for the extensive marine limestone exposures of the Jura Mountains, in the region where Germany, France and Switzerland meet.