Introduction
The Jurassic (/dʒʊˈræsɪk/ juurr-ASS-ik) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period 201.4 million years ago (Mya) to the beginning of the Cretaceous Period, approximately 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era and is named after the Jura Mountains, where limestone strata from the period were first identified.
The start of the Jurassic was marked by the major Triassic–Jurassic extinction event, associated with the eruption of the Central Atlantic Magmatic Province (CAMP). The beginning of the Toarcian Stage started around 183 million years ago and is marked by the Toarcian Oceanic Anoxic Event, a global episode of oceanic anoxia, ocean acidification, and elevated global temperatures associated with extinctions, likely caused by the eruption of the Karoo-Ferrar large igneous provinces. The end of the Jurassic, however, has no clear, definitive boundary with the Cretaceous and is the only boundary between geological periods to remain formally undefined. By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses: Laurasia to the north and Gondwana to the south. The climate of the Jurassic was warmer than the present, and there were no ice caps. Forests grew close to the poles, with large arid expanses in the lower latitudes. (Full article...) (Full article...) Selected article on the Jurassic world and its legacies
Several mammals are known from the Mesozoic of Madagascar. The Bathonian (middle Jurassic) Ambondro, known from a piece of jaw with three teeth, is the earliest known mammal with molars showing the modern, tribosphenic pattern that is characteristic of marsupial and placental mammals. Interpretations of its affinities have differed; one proposal places it in a group known as Australosphenida with other Mesozoic tribosphenic mammals from the southern continents (Gondwana) as well as the monotremes, while others favor closer affinities with northern (Laurasian) tribosphenic mammals or specifically with placentals. At least five species are known from the Maastrichtian (late Cretaceous), including a yet undescribed species known from a nearly complete skeleton that may represent a completely new group of mammals. The gondwanathere Lavanify, known from two teeth, is most closely related to other gondwanatheres found in India and Argentina. Two other teeth may represent another gondwanathere or a different kind of mammal. One molar fragment is one of the few known remains of a multituberculate mammal from Gondwana and another (UA 8699) has been interpreted as either a marsupial or a placental. (see more...)
Selected article on the Jurassic in human science, culture and economics![]() In 1858, Charles Darwin and Alfred Russel Wallace published a new evolutionary theory that was explained in detail in Darwin's On the Origin of Species (1859). Unlike Lamarck, Darwin proposedcommon descent and a branching tree of life. The theory was based on the idea of natural selection, and it synthesized a broad range of evidence from animal husbandry, biogeography, geology, morphology, and embryology. The debate over Darwin's work led to the rapid acceptance of the general concept of evolution, but the specific mechanism he proposed, natural selection, was not widely accepted until it was revived by developments in biology that occurred during the 1920s through the 1940s. Before that time most biologists argued that other factors were responsible for evolution. The synthesis of natural selection with Mendelian genetics during the 1920s and 1930s founded the new discipline of population genetics. Throughout the 1930s and 1940s, population genetics became integrated with other biological fields, resulting in a widely applicable theory of evolution that encompassed much of biology—the modern evolutionary synthesis. (see more...) Selected image
Did you know?![]()
Need help?Do you have a question about Abyssal/Portal:Jurassic that you can't find the answer to? Consider asking it at the Wikipedia reference desk. GeochronologyEpochs - Early Jurassic - Middle Jurassic - Late Jurassic Landmasses - Baltica - Gondwana - Laurentia - Siberia Fossil sites - Beecher's Trilobite Bed - Walcott–Rust quarry Researchers - Charles Emerson Beecher - Charles Lapworth - Charles Doolittle Walcott Quality ContentFeatured Mesozoic articles - Bone Sharps, Cowboys, and Thunder Lizards - Bone Wars - Edward Drinker Cope - Geology of the Capitol Reef area - Geology of the Death Valley area -Geology of the Grand Canyon area - Geology of the Zion and Kolob canyons area Good Mesozoic articles - Chitinozoan - Coal ball - Dimetrodon - History of paleontology - Evolutionary history of life - Ornatifilum - Opabinia - Paleontology- Schinderhannes - Small shelly fauna - Temnospondyli - Tiktaalik - Waptia SubcategoriesRelated contentAssociated WikimediaThe following Wikimedia Foundation sister projects provide more on this subject:
|