Information AboutJurassic |
| CATEGORIES ABOUT JURASSIC | |
| jurassicjurassic | |
| mesozoic | |
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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. DIVISIONS The Jurassic period of time is usually broken into Early , Middle , and Late subdivisions, also known as ''Lias'', ''Dogger'' and ''Malm''. The corresponding terms for the rocks are Lower, Middle, and Upper Jurassic. The Faunal Stage s from youngest to oldest are: PALEOGEOGRAPHY During the early Jurassic, the closed, and the Neotethys basin appeared. Climates were warm, with no evidence of Glaciation . As in the Triassic, there was apparently no land near either pole, and no extensive ice caps existed. The Jurassic geological record is good in western Sundance Sea left marine deposits in parts of the northern plains of the United States and Canada during the late Jurassic, most exposed sediments from this period are continental, such as the Alluvial deposits of the Morrison Formation . The first of several massive Batholith s were emplaced in the northern Cordillera beginning in the mid-Jurassic, marking the Nevadan Orogeny .Monroe and Wicander, 607. Important Jurassic exposures are also found in Russia , India , South America , Japan , Australasia , and the United Kingdom . FAUNA Aquatic and marine During the Jurassic, the 'highest' life forms living in the seas were Fish and marine Reptile s. The latter include Ichthyosaur s, Plesiosaurs and marine Crocodiles , of the families Teleosauridae and Metriorhynchidae . In the Invertebrate world, several new groups appeared, such as: Rudists , a Reef -forming variety of Bivalves and Belemnites The Jurassic had diverse encrusting and boring (sclerobiont) communities; see Taylor & Wilson (2003). It also saw a significant rise in the Bioerosion of carbonate shells and hardgrounds. Especially common is the Ichnogenus (trace fossil) ''Gastrochaenolites''. Terrestrial , Diplodocus , Brachiosaurus and some little pterosaurs.]] On land, large Archosaur ian reptiles remained dominant. The Jurassic was the golden age of the great Sauropod s— Camarasaurus , Diplodocus , Brachiosaurus , and many others—that roamed the land late in the period; their mainstays were either the Prairie s of Fern s, palm-like Cycad s and Bennettitales , or the higher coniferous growth, according to their adaptations. They were preyed upon by large Theropod s ( Ceratosaurs , Megalosaurs , and Allosaurs ). All these belong to the 'lizard hipped' or Saurischia n branch of the dinosaurs. During the Late Jurassic, the first Birds Evolved from small Coelurosaur dinosaurs. Ornithischia n dinosaurs were less predominant than saurischian dinosaurs, although some like Stegosaur s and small Ornithopod s played important roles as small and medium-to-large (but not sauropod-sized) herbivores. In the air, Pterosaur s were common; they ruled the skies, filling many ecological roles now taken by Bird s. FLORA The arid, continental conditions characteristic of the Triassic steadily eased during the Jurassic period, especially at higher latitudes; the warm, humid climate allowed lush jungles to cover much of the landscape.Haines, 2000. Conifers dominated the flora, as during the Triassic; they were the most diverse group and constituted the majority of large trees. Extant conifer families that flourished during the Jurassic included the Araucariaceae , Cephalotaxaceae , Pinaceae , Podocarpaceae , Taxaceae and Taxodiaceae .Behrensmeyer ''et al'', 1992, 349. The extinct Mesozoic conifer family Cheirolepidiaceae dominated low latitude vegetation, as did the shrubby Bennettitales .Behrensmeyer ''et al.'', 1992, 352 Cycad s were also common, as were Ginkgo s and Tree Ferns in the forest. Smaller Ferns were probably the dominant undergrowth. Caytoniaceous Seed Ferns were another group of important plants during this time and are thought to have been shrub to small-tree sized.Behrensmeyer ''et al.'', 1992, 353 Ginkgo-like plants were particularly common in the mid- to high northern latitudes. In the Southern Hemisphere, Podocarps were especially successful, while Ginkgos and Czekanowskiales were rare.Haines, 2000.,Behrensmeyer ''et al.'', 1992, 352 NOTES: REFERENCES
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