61 Facts About Jurassic


Jurassic is a geologic period and stratigraphic system that spanned from the end of the Triassic Period 201.

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The end of the Jurassic has no clear boundary with the Cretaceous and is the only boundary between geological periods to remain formally undefined.

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The climate of the Jurassic was warmer than the present, and there were no ice caps.

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Chronostratigraphic term "Jurassic" is linked to the Jura Mountains, a forested mountain range that mainly follows the France–Switzerland border.

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Jurassic Period is divided into three epochs: Early, Middle, and Late.

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Jurassic stratigraphy is primarily based on the use of ammonites as index fossils.

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Oldest part of the Jurassic Period has historically been referred to as the Lias or Liassic, roughly equivalent in extent to the Early Jurassic, but including part of the preceding Rhaetian.

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Jurassic's name was chosen by Albert Oppel for this stratigraphical stage because the Tithonian finds itself hand in hand with the dawn of the Cretaceous.

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Upper boundary of the Jurassic is currently undefined, and the Jurassic–Cretaceous boundary is currently the only system boundary to lack a defined GSSP.

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The Arabian Intrashelf Basin, deposited during the Middle and Late Jurassic, is the setting of the world's largest oil reserves, including the Ghawar Field, the world's largest oil field.

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The rifting between North America and Africa was the first to initiate, beginning in the early Jurassic, associated with the emplacement of the Central Atlantic Magmatic Province.

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Sea level within the long-term trends across the Jurassic was cyclical, with 64 fluctuations, 15 of which were over 75 metres.

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The most noted cyclicity in Jurassic rocks is fourth order, with a periodicity of approximately 410,000 years.

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The rise of calcareous plankton during the Middle Jurassic profoundly altered ocean chemistry, with the deposition of biomineralized plankton on the ocean floor acting as a buffer against large CO2 emissions.

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The first part of the Jurassic was marked by the Early Jurassic cool interval between 199 and 183 million years ago.

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The end of the Jurassic was marked by the Tithonian–early Barremian cool interval, beginning 150 million years ago and continuing into the Early Cretaceous.

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End-Jurassic transition was originally considered one of eight mass extinctions, but is considered to be a complex interval of faunal turnover, with the increase in diversity of some groups and decline in others, though the evidence for this is primarily European, probably controlled by changes in eustatic sea level.

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Dicroidium, a seed fern that was a dominant part of Gondwanan floral communities during the Triassic, declined at the Triassic–Jurassic boundary, surviving as a relict in Antarctica into the Sinemurian.

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The Late Triassic and Jurassic was a major time of diversification of conifers, with most modern conifer groups appearing in the fossil record by the end of the Jurassic, having evolved from voltzialean ancestors.

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Also abundant during the Jurassic is the extinct family Cheirolepidiaceae, often recognised through their highly distinctive Classopolis pollen.

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Jurassic representatives include the pollen cone Classostrobus and the seed cone Pararaucaria.

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Ginkgoales, of which the sole living species is Ginkgo biloba, were more diverse during the Jurassic: they were among the most important components of Eurasian Jurassic floras and were adapted to a wide variety of climatic conditions.

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Several other lineages of ginkgoaleans are known from Jurassic rocks, including Yimaia, Grenana, Nagrenia and Karkenia.

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Cyatheales, the group containing most modern tree ferns, appeared during the Late Jurassic, represented by members of the genus Cyathocaulis, which are suggested to be early members of Cyatheaceae on the basis of cladistic analysis.

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Only a handful of possible records exist of the Hymenophyllaceae from the Jurassic, including Hymenophyllites macrosporangiatus from the Russian Jurassic.

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The morphological diversity of crocodylomorphs during the Early Jurassic was around the same as those of Late Triassic pseudosuchians, but they occupied different areas of morphospace, suggesting that they occupied different ecological niches to their Triassic counterparts and that there was an extensive and rapid radiation of crocodylomorphs during this interval.

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The morphological diversity of crocodylomorphs during the Early and Middle Jurassic was relatively low compared to that in later time periods and was dominated by terrestrial small-bodied, long-legged sphenosuchians, early crocodyliforms and thalattosuchians.

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Jurassic stem-turtles belong to two progressively more advanced clades, the Mesochelydia and Perichelydia.

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Rhynchocephalians reached their highest morphological diversity in their evolutionary history during the Jurassic, occupying a wide range of lifestyles, including the aquatic pleurosaurs with long snake-like bodies and reduced limbs, the specialized herbivorous eilenodontines, as well as Oenosaurus, which had broad tooth plates indicative of durophagy.

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Squamates first appear in the fossil record during the Middle Jurassic and included early members of the snake lineage and Scincomorpha, though many Jurassic squamates have unclear relationships to living groups.

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The other is Coeruleodraco from the Late Jurassic of China, which is a more advanced choristodere, though still small and lizard-like in morphology.

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Ophthalmosaurids were diverse by the Late Jurassic, but failed to fill many of the niches that had been occupied by ichthyosaurs during the Early Jurassic.

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The Middle Jurassic saw the evolution of short-necked and large-headed thalassophonean pliosaurs from ancestrally small-headed, long-necked forms.

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Anurognathids, which first appeared in the Middle Jurassic, possessed short heads and densely furred bodies, and are thought to have been insectivores.

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Jurassic pterodactyloids include the ctenochasmatids, like Ctenochasma, which have closely spaced needle-like teeth that were presumably used for filter feeding.

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Coelurosaurs first appeared during the Middle Jurassic, including early tyrannosaurs such as Proceratosaurus from the Bathonian of Britain.

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Some Jurassic sauropods reached gigantic sizes, becoming the largest organisms to have ever lived on land.

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The Middle-Late Jurassic saw the first appearance of derived neosauropod groups, including Brachiosauridae and Diplodocidae.

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The Early Jurassic Prosalirus thought to represent the first frog relative with a morphology capable of hopping like living frogs.

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Salamanders dispersed into North America by the end of the Jurassic, as evidenced by Iridotriton, found in the Late Jurassic Morrison Formation.

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The fourth group of lissamphibians, the extinct albanerpetontids, first appeared in the Middle Jurassic, represented by Anoualerpeton priscus from the Bathonian of Britain, as well as indeterminate remains from equivalently aged sediments in France and the Anoual Formation of Morocco.

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Important groups of Jurassic Mammaliaformes include Morganucodonta, Docodonta, Eutriconodonta, Dryolestida, Haramiyida and Multituberculata.

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Therian mammals, represented today by living placentals and marsupials, appear during the early Late Jurassic, represented by Juramaia, a eutherian mammal closer to the ancestry of placentals than marsupials.

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Archaic "palaeoniscoid" fish, which were common in both marine and freshwater habitats during the preceding Triassic declined during the Jurassic, being largely replaced by more derived actinopterygian lineages.

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Amiiform fish first appeared during the Early Jurassic, represented by Caturus from the Pliensbachian of Britain; after their appearance in the western Tethys, they expanded to Africa, North America and Southeast and East Asia by the end of the Jurassic.

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The Pachycormiformes, a group of marine stem-teleosts, first appeared in the Early Jurassic and included both tuna-like predatory and filter-feeding forms, the latter included the largest bony fish known to have existed: Leedsichthys, with an estimated maximum length of over 15 metres, known from the late Middle to Late Jurassic.

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Jurassic batoids known from complete remains retain a conservative, guitarfish-like morphology.

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The oldest known mackerel sharks are from the Middle Jurassic, represented by the genus Palaeocarcharias, which has an orectolobiform-like body but shares key similarities in tooth histology with lamniformes, including the absence of orthodentine.

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The Middle to Late Jurassic was a time of major diversification for beetles.

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Weevils first appear in the fossil record during the Middle to Late Jurassic, but are suspected to have originated during the Late Triassic to Early Jurassic.

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The Jurassic saw saw the first appearances of several other groups of insects, including Phasmatodea, Mantophasmatidae, Embioptera, and Raphidioptera.

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The only scorpion known from the Jurassic is Liassoscorpionides from the Early Jurassic of Germany, of uncertain placement.

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Late Jurassic reefs were similar in form to modern reefs but had more microbial carbonates and hypercalcified sponges, and had weak biogenic binding.

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Reefs sharply declined at the close of the Jurassic, which caused an associated drop in diversity in decapod crustaceans.

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Crinoids diversified throughout the Jurassic, reaching their peak Mesozoic diversity during the Late Jurassic, primarily due to the radiation of sessile forms belonging to the orders Cyrtocrinida and Millericrinida.

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Echinoids underwent substantial diversification beginning in the Early Jurassic, primarily driven by the radiation of irregular forms, which were adapting to deposit feeding.

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Jurassic was a significant time for the evolution of decapods.

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Jurassic barnacles were of low diversity compared to present, but several important evolutionary innovations are known, including the first appearances of calcite shelled forms and species with an epiplanktonic mode of life.

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Bivalve family level diversity after the Early Jurassic was static, though genus diversity experienced a gradual increase throughout the period.

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Ammonite faunas during the Jurassic were regional, being divided into around 20 distinguishable provinces and subprovinces in two realms, the northern high latitude Pan-Boreal realm, consisting of the Arctic, northern Panthalassa and northern Atlantic regions, and the equatorial–southern Pan-Tethyan realm, which included the Tethys and most of Panthalassa.

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The earliest octopuses appeared during the Middle Jurassic, having split from their closest living relatives, the vampyromorphs, during the Triassic to Early Jurassic.

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