The JURASSIC ( /dʒʊˈræsɪk/ ; from
Jura Mountains ) was a
geologic period and system that spanned 56 million years from the end
Triassic Period 201.3 million years ago (Mya ) to the beginning
Cretaceous Period 145 Mya. The
Jurassic constituted the middle
period of the
Mesozoic Era , also known as the Age of Reptiles. The
start of the period was marked by the major Triassic–Jurassic
extinction event . Two other extinction events occurred during the
period: the Pliensbachian/
Toarcian event in the Early Jurassic, and
Tithonian event at the end; however, neither event ranks among the
"Big Five" mass extinctions .
Jurassic is named after the
Jura Mountains within the European
Alps , where limestone strata from the period were first identified.
By the beginning of the Jurassic, the supercontinent
Pangaea had begun
rifting into two landmasses:
Laurasia to the north, and
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 crocodylomorph archosaurs , to one dominated
by dinosaurs alone. 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. Crocodilians 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 .
* 1 Etymology
* 2 Divisions
* 3 Paleogeography and tectonics
* 4 Fauna
* 4.1 Aquatic and marine
* 4.2 Terrestrial
* 5 Flora
* 6 See also
* 7 Explanatory notes
* 8 Notes
* 9 References
* 10 External links
The chronostratigraphic term "Jurassic" is directly linked to the
Jura Mountains . During a tour of the region in 1795, Alexander von
Humboldt recognized the mainly limestone dominated mountain range of
Jura Mountains as a separate formation that had not been included
in the established stratigraphic system defined by Abraham Gottlob
Werner , and he named it "Jura-Kalkstein" ('Jura limestone') in 1799.
The name "Jura" is derived from the Celtic root *jor via Gaulish
*iuris "wooded mountain", which, borrowed into Latin as a place name,
evolved into Juria and finally Jura.
Jurassic period is divided into the
Early Jurassic , Middle , and
Late Jurassic epochs . The
Jurassic System, in stratigraphy , is
divided into the
Lower Jurassic , Middle , and
Upper Jurassic series
of rock formations, also known as Lias, Dogger and Malm in
The separation of the term JURASSIC into three sections goes back to
Leopold von Buch . The faunal stages from youngest to oldest are:
(152.1 ± 4 – 145 ± 4 Mya )
(157.3 ± 4 – 152.1 ± 4 Mya)
(163.5 ± 4 – 157.3 ± 4 Mya)
(166.1 ± 4 – 163.5 ± 4 Mya)
(168.3 ± 3.5 – 166.1 ± 4 Mya)
(170.3 ± 3 – 168.3 ± 3.5 Mya)
(174.1 ± 2 – 170.3 ± 3 Mya)
(182.7 ± 1.5 – 174.1 ± 2 Mya)
(190.8 ± 1.5 – 182.7 ± 1.5 Mya)
(199.3 ± 1 – 190.8 ± 1.5 Mya)
(201.3 ± 0.6 – 199.3 ± 1 Mya)
PALEOGEOGRAPHY AND TECTONICS
Early Jurassic environment preserved at the St.
Dinosaur Discovery Site at Johnson Farm, with D. wetherilli in
bird-like resting pose
During the early
Jurassic period, the supercontinent
Pangaea broke up
into the northern supercontinent
Laurasia and the southern
Gondwana ; the
Gulf of Mexico opened in the new rift
North America and what is now Mexico's
Yucatan Peninsula . The
Atlantic Ocean was relatively narrow, while the South
Atlantic did not open until the following
Cretaceous period, when
Gondwana itself rifted apart. The Tethys Sea closed, and the
Neotethys basin appeared. Climates were warm, with no evidence of
glaciation . As in the Triassic, there was apparently no land over
either pole, and no extensive ice caps existed.
Jurassic geological record is good in western
Europe , where
extensive marine sequences indicate a time when much of that future
landmass was submerged under shallow tropical seas; famous locales
World Heritage Site
World Heritage Site in southern England and
the renowned late
Jurassic lagerstätten of
Holzmaden and Solnhofen in
Germany. In contrast, the North American
Jurassic record is the
poorest of the Mesozoic, with few outcrops at the surface. Though the
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 .
Jurassic was a time of calcite sea geochemistry in which
low-magnesium calcite was the primary inorganic marine precipitate of
Carbonate hardgrounds were thus very common, along
with calcitic ooids , calcitic cements, and invertebrate faunas with
dominantly calcitic skeletons (Stanley and Hardie, 1998, 1999).
The first of several massive batholiths were emplaced in the northern
American cordillera beginning in the mid-Jurassic, marking the Nevadan
orogeny . Important
Jurassic exposures are also found in Russia,
India, South America, Japan, Australasia and the United Kingdom.
Early Jurassic strata are distributed in a similar fashion
Triassic beds, with more common outcrops in the south and less
common fossil beds which are predominated by tracks to the north. As
Jurassic proceeded, larger and more iconic groups of dinosaurs
like sauropods and ornithopods proliferated in Africa. Middle
Jurassic strata are neither well represented nor well studied in
Late Jurassic strata are also poorly represented apart from
the spectacular Tendaguru fauna in Tanzania. The
Late Jurassic life
of Tendaguru is very similar to that found in western North America's
Morrison Formation .
Jurassic limestones and marls (the
Matmor Formation ) in southern
Morrison Formation in
Colorado is one of the most
fertile sources of dinosaur fossils in North America.
Gigandipus, a dinosaur footprint in the
Lower Jurassic Moenave
Formation at the St. George
Dinosaur Discovery Site at Johnson Farm,
Jurassic stratigraphy of the
area of southeastern
AQUATIC AND MARINE
Jurassic period, the primary vertebrates living in the sea
were fish and marine reptiles . The latter include ichthyosaurs ,
which were at the peak of their diversity, plesiosaurs , pliosaurs ,
and marine crocodiles of the families
Metriorhynchidae . Numerous turtles could be found in lakes and
In the invertebrate world, several new groups appeared, including
rudists (a reef -forming variety of bivalves ) and belemnites .
Calcareous sabellids (
Glomerula ) appeared in the Early Jurassic.
Jurassic also had diverse encrusting and boring (sclerobiont)
communities, and it saw a significant rise in the bioerosion of
carbonate shells and hardgrounds. Especially common is the ichnogenus
(trace fossil )
Jurassic period, about four or five of the twelve clades
of planktonic organisms that exist in the fossil record either
experienced a massive evolutionary radiation or appeared for the first
Pliosaurus (right) harassing a
Leedsichthys in a
Ichthyosaurus from lower (early)
Jurassic slates in southern Germany
featured a dolphin -like body shape.
Gastropod and attached mytilid bivalves on a
bedding plane in southern
Example of Rare
Early Jurassic (Pliensbachian) Ecosystem, the
Drzewica Formation of
Poland . This zone was
characterised by a very Damp ecosystem a populated by Dinosaur
Megafauna, more related in several aspects to Middle or Late Jurassic
On land, various archosaurian reptiles remained dominant. The
Jurassic was a golden age for the large herbivorous dinosaurs known as
the sauropods —
Brachiosaurus , and many others—that roamed the land late in the
period; their foraging grounds were either the prairies of ferns ,
palm-like cycads and bennettitales , or the higher coniferous growth,
according to their adaptations. The smaller Ornithischian herbivore
dinosaurs, like stegosaurs and small ornithopods were less
predominant, but played important roles. They were preyed upon by
large theropods , such as
Megalosaurus , Torvosaurus
Allosaurus . All these belong to the 'lizard hipped' or
saurischian branch of the dinosaurs . During the Late Jurassic, the
first avialans , like
Archaeopteryx , evolved from small
coelurosaurian dinosaurs. In the air, pterosaurs were common; they
ruled the skies, filling many ecological roles now taken by birds ,
and may have already produced some of the largest flying animals of
all time. Within the undergrowth were various types of early mammals
, as well as tritylodonts , lizard-like sphenodonts , and early
lissamphibians . The rest of the
Lissamphibia evolved in this period,
introducing the first salamanders and caecilians .
Diplodocus , reaching lengths over 30 m, was a common sauropod during
the late Jurassic.
Allosaurus was one of the largest land predators during the Jurassic.
Stegosaurus is one of the most recognizable genera of dinosaurs and
lived during the mid to late Jurassic.
Archaeopteryx , a primitive bird-like dinosaur, appeared in the Late
Aurornis xui , which lived in the late Jurassic, may be the most
primitive avialan dinosaur known to date, and is one of the earliest
avialans found to date.
Conifers were the dominant land plants of the
Various dinosaurs roamed forests of similarly large conifers during
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. Gymnosperms were relatively diverse during the
Jurassic period. The
Conifers in particular 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
Taxodiaceae . The extinct
Mesozoic conifer family
Cheirolepidiaceae dominated low latitude vegetation, as did the
Bennettitales . Cycads , similar to palm trees, were also
common, as were ginkgos and Dicksoniaceous 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.
were particularly common in the mid- to high northern latitudes. In
the Southern Hemisphere, podocarps were especially successful, while
Ginkgos and Czekanowskiales were rare.
In the oceans, modern coralline algae appeared for the first time.
However, they were a part of another major extinction that happened
within the next major time period.
* Geology portal
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* Time portal
* ^ A 140 Ma age for the Jurassic-
Cretaceous instead of the usually
accepted 145 Ma was proposed in 2014 based on a stratigraphic study of
Vaca Muerta Formation in
Neuquén Basin , Argentina. Víctor Ramos ,
one of the authors of the study proposing the 140 Ma boundary age,
sees the study as a "first step" toward formally changing the age in
International Union of Geological Sciences .
* ^ Image:Sauerstoffgehalt-1000mj.svg
* ^ File:OxygenLevel-1000ma.svg
* ^ Image:
Phanerozoic Carbon Dioxide.png
* ^ Image:All palaeotemps.png
* ^ Vennari, Verónica V.; Lescano, Marina; Naipauer, Maximiliano;
Aguirre-Urreta, Beatriz; Concheyro, Andrea; Schaltegger, Urs;
Armstrong, Richard; Pimentel, Marcio; Ramos, Victor A. (2014). "New
constraints on the Jurassic–
Cretaceous boundary in the High Andes
using high-precision U–Pb data".
Gondwana Research . 26: 374–385.
doi :10.1016/j.gr.2013.07.005 . Retrieved 16 January 2016.
* ^ Jaramillo, Jessica. "Entrevista al Dr. Víctor Alberto Ramos,
Premio México Ciencia y Tecnología 2013" (in Spanish). Si logramos
publicar esos nuevos resultados, sería el primer paso para cambiar
formalmente la edad del Jurásico-Cretácico. A partir de ahí, la
Unión Internacional de la Ciencias Geológicas y la Comisión
Internacional de Estratigrafía certificaría o no, depende de los
resultados, ese cambio.
* ^ Alexander von Humboldt, Kosmos, volume 4 (Stuttgart: Cotta,
1858), p. 632: "Ich hatte mich auf einer geognostischen Reise, die ich
1795 durch das südliche Franken, die westliche Schweiz und
Ober-Italien machte, davon überzeugt, daß der Jura-Kalkstein,
welchen Werner zu seinem Muschelkalk rechnete, eine eigne Formation
bildete. In meiner Schrift über die unterirdischen Gasarten, welche
mein Bruder Wilhelm von Humboldt 1799 während meines Aufenthalts in
Südamerika herausgab, wird der Formation, die ich vorläufig mit dem
Namen Jura-Kalkstein bezeichnete, zuerst (S. 39) gedacht." ('On a
geological tour that I made in 1795 through southern France, western
Switzerland and upper Italy, I convinced myself that the Jura
limestone, which Werner included in his shell limestone, constituted a
separate formation. In my paper about subterranean types of gases,
which my brother Wilhelm von Humboldt published in 1799 during my stay
in South America, the formation, which I provisionally designated with
the name "Jura limestone", is first conceived (p. 39).'
* ^ Alexander von Humboldt, Ueber die unterirdischen Gasarten und
die Mittel, ihren Nachteil zu vermindern, ein Beitrag zur Physik der
praktischen Bergbaukunde (Braunschweig: Vieweg, 1799), p. 39: " die
ausgebreitete Formation, welche zwischen dem alten Gips und neueren
Sandstein liegt, und welchen ich vorläufig mit dem Nahmen
Jura-Kalkstein bezeichne." ('… the widespread formation which lies
between the old gypsum and the more recent sandstone and which I
provisionally designate with the name "Jura limestone".')
* ^ A B Hölder, H. 1964. Jura – Handbuch der stratigraphischen
Geologie, IV. Enke-Verlag, Stuttgart.
* ^ A B Arkell, W.J. 1956.
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Schudack, M.E.; Bosák, P.; Enay, R.; Feldman-Olszewska, A.; Golonka,
J.; Gutowski, J.; Herngreen, G.F.W.; Jordan, P.; Krobicki, M.;
Lathuiliere, B.; Leinfelder, R.R.; Michalík, J.; Mönnig, E.;
Noe-Nygaard, N.; Pálfy, J.; Pint, A.; Rasser, M.W.; Reisdorf, A.G.;
Schmid, D.U.; Schweigert, G.; Surlyk, F.; Wetzel, A. Rabi, Márton;
Schneider, Jörg W.; Schwermann, Leonie; Sun, Ge; Zhou, Chang-Fu;
Joyce, Walter G. (2012), "An enormous
Jurassic turtle bone bed from
the Turpan Basin of Xinjiang, China", Naturwissenschaften: The Science
of Nature, 114: 925–935,
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* ^ Gannon, Megan (October 31, 2012), "
Jurassic turtle graveyard
found in China", Livescience.com
* ^ Vinn, O.; Mutvei, H. (2009). "Calcareous tubeworms of the
Phanerozoic" (PDF). Estonian Journal of Earth Sciences. 58 (4):
286–296. doi :10.3176/earth.2009.4.07 . Retrieved 2012-09-16.
* ^ Vinn, O.; ten Hove, H.A.; Mutvei, H. (2008). "On the tube
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* ^ Taylor, P. D.; Wilson, M. A. (2003). "Palaeoecology and
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