Triassic Triassic The Triassic () is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.9 million years ago (Mya), to the beginning of the Jurassic Period Mya. The Triassic is the first period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. The Triassic began in the wake of the Permian–Triassic extinction event, which left the Earth's biosphere impoverished; it would take well into the middle of this period for life to recover its former diversity. Therapsids and archosaurs were the chief terrestrial
Late Jurassic Late Jurassic The Late Jurassic is the third epoch of the Jurassic period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "malm" indicates rocks of Late Jurassic age. In the past, this name was also used to indicate the unit of geological time, but this usage is now discouraged to make a clear distinction between lithostratigraphic and geochronologic/chronostratigraphic units. The Late Jurassic is divided into three ages, which correspond with the three (faunal) stages of Upper Jurassic rock: