Jurassic
From The Art and Popular Culture Encyclopedia
|
Related e |
|
Featured: |
The Jurassic is a geologic period and system that extends from Ma (million years ago) to Template:Period endTemplate:Period end error Ma; that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles. The start of the period is marked by the major Triassic–Jurassic extinction event. Another extinction event, the Late Piensbachian/Early Toarcian event, occurred in the Early Jurassic, and a third extinction event, the Late Tithonian event, occurred at the end of the Jurassic; however neither of these two events rank among the 'Big Five' mass extinction. The Jurassic is named after the Jura Mountains within the European Alps, where limestone strata from the period was first identified.
By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses, Laurasia to the north and Gondwana to the south. This created more coastlines and shifted the continental climate from dry to humid, and many of the arid deserts of the Triassic were replaced by lush rainforests. On land, the fauna transitioned from the Triassic fauna, dominated by both dinosauromorph and crocodilomorph archosaurs, to one dominated by dinosaurs. The first birds also appeared during the Jurassic, having evolved from a branch of theropod dinosaurs. Other major events include the appearance of the earliest lizards, and the evolution of therian mammals, including primitive placentals. Crocodylians made the transition from a terrestrial to an aquatic mode of life. The oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, while pterosaurs were the dominant flying vertebrates.
