Jurassic ( /dʒʊˈræsɪk/; from Jura Mountains) was a geologic
period and system that spanned 56 million years from the end of the
Triassic Period 201.3 million years ago (Mya) to the beginning of the
Cretaceous Period 145 Mya.[note 1] 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.
3 Paleogeography and tectonics
4.1 Aquatic and marine
6 See also
7 Explanatory notes
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 Europe. 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. George
Dinosaur Discovery Site at Johnson Farm, with
in bird-like resting pose
During the early
Jurassic period, the supercontinent
Pangaea broke up
into the northern supercontinent
Laurasia and the southern
supercontinent Gondwana; the
Gulf of Mexico
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
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
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.
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
Colorado Plateau area
of southeastern Utah.
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 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) Gastrochaenolites.
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 Israel.
Example of Rare
Early Jurassic (Pliensbachian) Ecosystem, the Drzewica
Formation of Szydłowiec, 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 Dinosaurs
On land, various archosaurian reptiles remained dominant. The Jurassic
was a golden age for the large herbivorous dinosaurs known as the
sauropods—Camarasaurus, Apatosaurus, Diplodocus, 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
Torvosaurus and 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 Jurassic
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
the Araucariaceae, Cephalotaxaceae, Pinaceae, Podocarpaceae, Taxaceae
and Taxodiaceae. The extinct
Mesozoic conifer family
Cheirolepidiaceae dominated low latitude vegetation, as did the
shrubby 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.
Ginkgo 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.
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.
^ 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
the International Union of Geological Sciences.
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
^ 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 ['On the types of subterranean gases and
means of minimizing their harm, a contribution to the physics of
practical mining'] (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".')
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Geologic history of Earth
Quaternary (present–2.588 Mya)
Holocene (present–11.784 kya)
Pleistocene (11.784 kya–2.588 Mya)
Neogene (2.588–23.03 Mya)
Pliocene (2.588–5.333 Mya)
Miocene (5.333–23.03 Mya)
Paleogene (23.03–66.0 Mya)
Oligocene (23.03–33.9 Mya)
Eocene (33.9–56.0 Mya)
Paleocene (56.0–66.0 Mya)
Cretaceous (66.0–145.0 Mya)
Late (66.0–100.5 Mya)
Early (100.5–145.0 Mya)
Jurassic (145.0–201.3 Mya)
Late (145.0–163.5 Mya)
Middle (163.5–174.1 Mya)
Early (174.1–201.3 Mya)
Triassic (201.3–251.902 Mya)
Late (201.3–237 Mya)
Middle (237–247.2 Mya)
Early (247.2–251.902 Mya)
Permian (251.902–298.9 Mya)
Lopingian (251.902–259.8 Mya)
Guadalupian (259.8–272.3 Mya)
Cisuralian (272.3–298.9 Mya)
Carboniferous (298.9–358.9 Mya)
Pennsylvanian (298.9–323.2 Mya)
Mississippian (323.2–358.9 Mya)
Devonian (358.9–419.2 Mya)
Late (358.9–382.7 Mya)
Middle (382.7–393.3 Mya)
Early (393.3–419.2 Mya)
Silurian (419.2–443.8 Mya)
Pridoli (419.2–423.0 Mya)
Ludlow (423.0–427.4 Mya)
Wenlock (427.4–433.4 Mya)
Llandovery (433.4–443.8 Mya)
Ordovician (443.8–485.4 Mya)
Late (443.8–458.4 Mya)
Middle (458.4–470.0 Mya)
Early (470.0–485.4 Mya)
Cambrian (485.4–541.0 Mya)
Furongian (485.4–497 Mya)
Series 3 (497–509 Mya)
Series 2 (509–521 Mya)
Terreneuvian (521–541.0 Mya)
(541.0 Mya–2.5 Gya)
Neoproterozoic era (541.0 Mya–1 Gya)
Ediacaran (541.0-~635 Mya)
Cryogenian (~635-~720 Mya)
Tonian (~720 Mya-1 Gya)
Mesoproterozoic era (1–1.6 Gya)
Stenian (1-1.2 Gya)
Ectasian (1.2-1.4 Gya)
Calymmian (1.4-1.6 Gya)
Paleoproterozoic era (1.6–2.5 Gya)
Statherian (1.6-1.8 Gya)
Orosirian (1.8-2.05 Gya)
Rhyacian (2.05-2.3 Gya)
Siderian (2.3-2.5 Gya)
Archean eon² (2.5–4 Gya)
Neoarchean (2.5–2.8 Gya)
Mesoarchean (2.8–3.2 Gya)
Paleoarchean (3.2–3.6 Gya)
Eoarchean (3.6–4 Gya)
Hadean eon² (4–4.6 Gya)
kya = thousands years ago. Mya = millions years ago.
Gya = billions
years ago.¹ =
Phanerozoic eon. ² =
Source: (2017/02). International Commission on Stratigraphy. Retrieved
13 July 2015. Divisions of Geologic Time—Major Chronostratigraphic
and Geochronologic Units USGS Retrieved 10 March 2013.