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The Jurassic ( ) is a
geologic period The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other earth sciences, Earth scientists to describe t ...
and stratigraphic system that spanned from the end of the
Triassic The Triassic ( ) is a geologic period The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other earth ...

Triassic
Period million years ago (Mya) to the beginning of the
Cretaceous The Cretaceous ( ) is a geological period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of division ...

Cretaceous
Period, approximately Mya. The Jurassic constitutes the middle period of the
Mesozoic Era The Mesozoic Era ( ), also called the Age of Reptiles and the Age of Conifers, is the second-to-last era An era is a span of time defined for the purposes of chronology 222px, Joseph Scaliger's ''De emendatione temporum'' (1583) began the mo ...
and is named after the
Jura Mountains The Jura Mountains ( , , , ; french: Massif du Jura; german: Juragebirge; it, Massiccio del Giura, rm, Montagnas da Jura) are a sub-alpine mountain range a short distance north of the Western Alps and mainly demarcate a long part of the ...

Jura Mountains
, where
limestone Limestone is a common type of carbonate In chemistry, a carbonate is a salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its na ...

limestone
strata from the period were first identified. The start of the Jurassic was marked by the major
Triassic–Jurassic extinction event The Triassic–Jurassic (Tr-J) extinction event, sometimes called the end-Triassic extinction, marks the boundary between the Triassic The Triassic ( ) is a geologic period A geological period is one of the several subdivisions of geologic time ...
, associated with the eruption of the Central Atlantic Magmatic Province. The beginning of the
Toarcian The Toarcian is, in the ICS' geologic timescale The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and ot ...
Stage started around 183 million years ago, and is marked by an extinction event associated with widespread oceanic anoxia,
ocean acidification Ocean acidification is the ongoing decrease in the pH value of the Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of cont ...
, and elevated the temperatures likely caused by the eruption of the Karoo-Ferrar large igneous provinces. The end of the Jurassic, however, has no clear boundary with the Cretaceous and is the only boundary between geological periods to remain formally undefined. By the beginning of the Jurassic, the
supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the proces ...
Pangaea Pangaea or Pangea () was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology) ...

Pangaea
had begun
rift In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear Fault (geology), downfaulted depression, called a graben, or more commonly ...

rift
ing into two landmasses:
Laurasia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea Pangaea or Pangea () was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("s ...
to the north and
Gondwana Gondwana () or Gondwanaland was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (ge ...

Gondwana
to the south. The climate of the Jurassic was warmer than the present, and there were no
ice caps Image:Vatnajökull.jpeg, upright=1.35, Vatnajökull, Iceland In glaciology, an ice cap is a mass of ice that covers less than of land area (usually covering a highland area). Larger ice masses covering more than are termed ice sheets. Descript ...
. Forests grew close to the poles, with large arid expanses in the lower latitudes. On land, the fauna transitioned from the Triassic fauna, dominated jointly by dinosauromorph and
pseudosuchia Pseudosuchia is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely related to crocodilians than to birds. Pseudosuchians are also informally known as "crocodilian-line archosaurs". Prior to ...
n
archosaur Archosauria ("ruling reptiles") is a clade A clade (), also known as a monophyletic group or natural group, is a group of organism In biology, an organism () is any organic, life, living system that functions as an individual entity. ...
s, to one dominated by
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 annum, million years ago, although the exact origin and timing of the evolution ...

dinosaur
s alone. The first birds appeared during the Jurassic, evolving from a branch of
theropod Theropoda ( from Ancient Greek, Greek 'wild beast' and 'foot'), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three-toed limbs. Theropods are generally classed as a group of saurischian d ...
dinosaurs. Other major events include the appearance of the earliest lizards and the evolution of
theria Theria (; Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximatel ...
n mammals. Crocodylomorphs made the transition from a terrestrial to an aquatic life. The oceans were inhabited by
marine reptiles (top left) Sea turtle (top right) Marine iguana (bottom left) Sea snake (bottom right) Marine reptiles are reptiles which have become secondarily adaptation, adapted for an aquatic animal, aquatic or List of semiaquatic tetrapods, semiaquatic l ...
such as
ichthyosaur Ichthyosaurs (Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Myce ...
s and
plesiosaur The Plesiosauria (; Greek: πλησίος, ''plesios'', meaning "near to" and ''sauros'', meaning "lizard") or plesiosaurs are an order or clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural ...

plesiosaur
s, while
pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") were flying reptile Reptiles, as most commonly defined, are the animals in the Class (biology), class Reptilia , a paraphyletic grouping comprising all amniotes excep ...
s were the dominant flying
vertebrates Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic ma ...

vertebrates
.


Etymology and history

The chronostratigraphic term "Jurassic" is linked to the
Jura Mountains The Jura Mountains ( , , , ; french: Massif du Jura; german: Juragebirge; it, Massiccio del Giura, rm, Montagnas da Jura) are a sub-alpine mountain range a short distance north of the Western Alps and mainly demarcate a long part of the ...

Jura Mountains
, a forested
mountain range A mountain range is a series of mountains ranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure, and alignment that have arisen from the same cause, us ...

mountain range
mainly following the
France–Switzerland border The French–Swiss Swiss may refer to: * the adjectival form of Switzerland *Swiss people Places *Swiss, Missouri *Swiss, North Carolina *Swiss, West Virginia *Swiss, Wisconsin Other uses *Swiss-system tournament, in various games and sports * ...
. The name "Jura" is derived from the
Celtic The words Celt and Celtic (also Keltic) may refer to: Ethno-linguistics *Celts The Celts (, see pronunciation of ''Celt'' for different usages) are. "CELTS location: Greater Europe time period: Second millennium B.C.E. to present ancestry: ...
root ''*jor'' via
Gaulish Gaulish was an ancient Celtic language The Celtic languages ( , ) are a group of related languages descended from Proto-Celtic The Proto-Celtic language, also called Common Celtic, is the ancestral proto-language of all the known Celti ...
''*iuris'' "wooded mountain", which, borrowed into
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became ...

Latin
as a name of a place, evolved into ''Juria'' and finally ''Jura''. During a tour of the region in 1795, German naturalist
Alexander von Humboldt Friedrich Wilhelm Heinrich Alexander von Humboldt (14 September 17696 May 1859) was a , , , , and proponent of philosophy and . He was the younger brother of the Prussian minister, philosopher, and (1767–1835). Humboldt's quantitative work ...

Alexander von Humboldt
recognized
carbonate In chemistry, a carbonate is a salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crystallinity, crystalline mi ...
deposits within the Jura Mountains as geologically distinct from the
Triassic The Triassic ( ) is a geologic period The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other earth ...

Triassic
aged
Muschelkalk The Muschelkalk (German for "shell-bearing limestone"; french: calcaire coquillier) is a sequence of sedimentary Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, ...

Muschelkalk
of Southern Germany, though he erroneously concluded they were older. He then named them ('Jura limestone') in 1799. Thirty years later, in 1829, the French naturalist
Alexandre Brongniart Alexandre Brongniart (5 February 17707 October 1847) was a France, French chemist, mineralogist, geologist, paleontologist and zoologist, who collaborated with Georges Cuvier on a study of the geology of the region around Paris. He was the first t ...

Alexandre Brongniart
published a book entitled ''Description of the Terrains that Constitute the Crust of the Earth or Essay on the Structure of the Known Lands of the Earth.'' In this book, Brongniart used the phrase ''terrains jurassiques'' when correlating the "Jura-Kalkstein" of Humboldt with similarly aged in Britain, thus coining and publishing the term "Jurassic". The German geologist
Leopold von Buch Christian Leopold von Buch (April 26, 1774 – March 4, 1853), usually cited as Leopold von Buch, was a German geologist A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes the Earth and other terres ...
in 1839 established the three-fold division of the Jurassic, originally named from oldest to the youngest: the
Black Jurassic The Black Jurassic or Black Jura (german: Schwarzer Jura) in earth history refers to the lowest of the three lithostratigraphic units Unit may refer to: Arts and entertainment * UNIT Unit may refer to: Arts and entertainment * UNIT, a fictional ...
,
Brown Jurassic The Brown Jurassic or Brown Jura (german: Brauner Jura or ''Braunjura'') in earth history refers to the middle of the three lithostratigraphic group (geology), units of the South German Jurassic, the latter being understood not as a geographical, ...
, and
White Jurassic The White Jurassic or White Jura (german: Weißer Jura or ''Weißjura'') in earth history refers to the upper of the three lithostratigraphic group (geology), units of the South German Jurassic, the latter being understood not as a geographical, bu ...
. The term " Lias" had previously been used for strata of equivalent age to the Black Jurassic in England by William Conybeare and William Phillips in 1822. French
palaeontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene The Holocene ( ) is the current Geologic time scale, geological epoch. ...
Alcide d'Orbigny Alcide Charles Victor Marie Dessalines d'Orbigny (6 September 1802 – 30 June 1857) was a French Natural history, naturalist who made major contributions in many areas, including zoology (including malacology), palaeontology, geology, archaeology ...
in papers between 1842 and 1852 divided the Jurassic into ten stages based on
ammonite *Belemnoidea—an extinct group of . {{fossil cephalopods, state=collapsed Prehistoric cephalopods by classification Coleoidea ...

ammonite
and other fossil assemblages in England and France, of which seven are still used, though none retain the original definition. German geologist and palaeontologist
Friedrich August von Quenstedt Friedrich August von Quenstedt (July 10, 1809 – December 21, 1889), was a German geologist and palaeontologist. Life Von Quenstedt was born at Eisleben in Province of Saxony, Saxony, and educated at the Humboldt University of Berlin. After a ...

Friedrich August von Quenstedt
in 1858 divided the three series of von Buch in the
Swabian Jura The Swabian Jura (, more rarely: ), sometimes also named Swabian Alps in English, is a mountain range in Baden-Württemberg, Germany, extending from southwest to northeast and in width. It is named after the region of Swabia. The Swabian Jura ...
into six subdivisions defined by ammonites and other fossils. German palaeontologist Albert Oppel in his studies between 1856 and 1858 altered d'Orbigny's original scheme and further subdivided the stages into
biostratigraphic Biostratigraphy is the branch of stratigraphy through Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic period million years ago (Year, Mya ...
zones, based primarily on ammonites. Most of the modern stages of the Jurassic were formalized at the Colloque du Jurassique à Luxembourg in 1962.


Geology

The Jurassic Period is divided into three epochs: Early, Middle, and Late. Similarly, in
stratigraphy Stratigraphy is a branch of geology concerned with the study of rock (geology), rock layers (Stratum, strata) and layering (stratification). It is primarily used in the study of sedimentary rock, sedimentary and layered volcanic rocks. Stratigrap ...

stratigraphy
, the Jurassic is divided into the
Lower Jurassic The Early Jurassic epoch In chronology 222px, Joseph Scaliger's ''De emendatione temporum'' (1583) began the modern science of chronology Chronology (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, I ...
,
Middle Jurassic The Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively ...
, and
Upper Jurassic The Late Jurassic is the third epoch of the Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic period million years ago (Year, Mya) to the be ...
series Series may refer to: People with the name * Caroline Series (born 1951), English mathematician, daughter of George Series * George Series (1920–1995), English physicist Arts, entertainment, and media Music * Series, the ordered sets used i ...
. Geologists divide the rocks of the Jurassic into a
stratigraphic through Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approxi ...

stratigraphic
set of units called
stages Stage or stages may refer to: Acting * Stage (theatre) In theatre and performing arts, the stage (sometimes referred to as the deck in stagecraft) is a designated space for the performance of theatrical production, productions. The stage s ...
, each formed during corresponding time intervals called ages. Stages can be defined globally or regionally. For global stratigraphic correlation, the
International Commission on Stratigraphy The International Commission on Stratigraphy (ICS), sometimes referred to unofficially as the "International Stratigraphic Commission", is a daughter or major subcommittee grade scientific daughter organization that concerns itself with stratigr ...
(ICS) ratify global stages based on a
Global Boundary Stratotype Section and Point The 'golden spike' marking the Ediacaran GSSP A Global Boundary Stratotype Section and Point (GSSP) is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time sca ...
(GSSP) from a single
formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondary m ...
(a
stratotypeA stratotype or type section is a geological Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which i ...
) identifying the lower boundary of the stage. The ages of the Jurassic from youngest to oldest are as follows:


Stratigraphy

Jurassic stratigraphy is primarily based on the use of ammonites as
index fossils Biostratigraphy is the branch of stratigraphy through Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic period million years ago (Year, Mya ...

index fossils
. The
first appearance datumFirst appearance datum (FAD) is a term used by geologist A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes the Earth and other terrestrial planets, as well as the processes that shape them. Geologists ...
of specific ammonite
taxa In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanism ...
is used to mark the beginnings of stages, as well as smaller timespans within stages, referred to as "ammonite zones"; these, in turn, are also sometimes subdivided further into subzones. Global stratigraphy is based on standard European ammonite zones, with other regions being calibrated to the European successions.


Early Jurassic

The 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 also including part of the preceding
Rhaetian The Rhaetian is the latest age (geology), age of the Triassic period (geology), Period (in geochronology) or the uppermost stage (stratigraphy), stage of the Triassic system (stratigraphy), System (in chronostratigraphy). It was preceded by the N ...
. The Hettangian Stage was named by Swiss palaeontologist Eugène Renevier in 1864 after Hettange-Grande in north-eastern France. The GSSP for the base of the Hettangian is located at the Kuhjoch Pass,
Karwendel Mountains The Karwendel is the largest mountain range of the Northern Limestone Alps. The major part belongs to the Austrian federal state of Tyrol (state), Tyrol, while the adjacent area in the north is part of Bavaria, Germany. Four mountain chain, chains ...

Karwendel Mountains
,
Northern Calcareous Alps The Northern Limestone Alps (german: Nördliche Kalkalpen), also called the Northern Calcareous Alps, are the ranges of the Eastern Alps Eastern Alps is the name given to the eastern half of the Alps, usually defined as the area east of a line f ...

Northern Calcareous Alps
, Austria; it was ratified in 2010. The beginning of the Hettangian, and thus the Jurassic as a whole, is marked by the
first appearance In American comic books and other stories with a long history, first appearance refers to the first issue to feature a fictional character Character(s) may refer to: Arts, entertainment, and media Literature * ''Character'' (novel), a 1936 ...
of the ammonite '' Psiloceras spelae tirolicum'' in the
Kendlbach Formation The Kendlbach Formation is a Late Triassic The Late Triassic is the third and final epoch of the Triassic The Triassic ( ) is a geologic period and system A system is a group of Interaction, interacting or interrelated elements that act acco ...
exposed at Kuhjoch. The base of the Jurassic was previously defined as the first appearance of ''Psiloceras planorbis'' by Albert Oppel in 1856–58, but this was changed as the appearance was seen as too localised an event for an international boundary. The Sinemurian Stage was first defined and introduced into scientific literature by Alcide d'Orbigny in 1842. It takes its name from the French town of
Semur-en-Auxois Semur-en-Auxois () is a commune A commune is an intentional community of people sharing living spaces, interests, values, beliefs, and often property Property (''latin: Res Privata'') in the Abstract and concrete, abstract is what belon ...

Semur-en-Auxois
, near
Dijon Dijon (, , ) (dated) * it, Digione * la, Diviō or * lmo, Digion is the prefecture A prefecture (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European langua ...

Dijon
. The original definition of Sinemurian included what is now the Hettangian. The GSSP of the Sinemurian is located at a cliff face north of the hamlet of
East Quantoxhead East Quantoxhead is a village in the district of Somerset West and Taunton Somerset West and Taunton is a Districts of England, local government district in Somerset, England. It was established on 1 April 2019 by the Somerset West and Taunton ...
, 6 kilometres east of
Watchet Watchet is a harbour A harbor (American English) or harbour (British English; American and British English spelling differences#-our, -or, see spelling differences) (synonym: haven) is a sheltered body of water where ships, boats, and barg ...

Watchet
,
Somerset ( en, All The People of Somerset) , locator_map = , coordinates = , region = South West England South West England is one of nine official regions of England The regions, formerly known as the government office regions, are the ...

Somerset
,
England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest of England and the Celtic Sea to the southwest. E ...

England
, within the
Blue Lias The Blue Lias is a geological formation in southern, eastern and western England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its n ...
, and was ratified in 2000. The beginning of the Sinemurian is defined by the first appearance of the ammonite '' Vermiceras quantoxense.'' Albert Oppel in 1858 named the Pliensbachian Stage after the hamlet of Pliensbach in the community of
Zell unter Aichelberg Zell unter Aichelberg is a municipality in the district of Göppingen (district), Göppingen in Baden-Württemberg in southern Germany. Geographical location Between Stuttgart and Ulm, on the western edge of the district Göppingen, lies the munic ...
in the
Swabian Alb The Swabian Jura (, more rarely: ), sometimes also named Swabian Alps in English, is a mountain range in Baden-Württemberg Baden-Württemberg (; ) is a state (''Land'') in southwest Germany Southern Germany () as a region has no exact b ...
, near
Stuttgart Stuttgart (; Swabian: ; ) is the capital Capital most commonly refers to: * Capital letter Letter case (or just case) is the distinction between the letters that are in larger uppercase or capitals (or more formally ''majuscule'') ...

Stuttgart
, Germany. The GSSP for the base of the Pliensbachian is found at the Wine Haven locality in
Robin Hood's Bay Robin Hood's Bay is a small fishing Fishing is the activity of trying to catch fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. They form a sister gr ...
,
Yorkshire Yorkshire (; abbreviated Yorks), formally known as the County of York, is a historic county of Northern England Northern England, also known as the North of England or simply the North, is the most northern area of England England ...

Yorkshire
, England, in the Redcar Mudstone Formation, and was ratified in 2005. The beginning of the Pliensbachian is defined by the first appearance of the ammonite '' Bifericeras donovani''. The village
Thouars Thouars () is a commune A commune is an intentional community of people sharing living spaces, interests, values, beliefs, and often property Property (''latin: Res Privata'') in the Abstract and concrete, abstract is what belongs t ...

Thouars
(Latin: ''Toarcium''), just south of
Saumur Saumur () is a commune A commune is an intentional community of people sharing living spaces, interests, values, beliefs, and often property Property (''latin: Res Privata'') in the Abstract and concrete, abstract is what belongs to ...

Saumur
in the
Loire Valley The Loire Valley (french: Val de Loire, link=no, ), spanning , is a valley A valley is an elongated low area often running between hills or mountains, which will typically contain a river or stream running from one end to the other. Mos ...
of
France France (), officially the French Republic (french: link=no, République française), is a transcontinental country This is a list of countries located on more than one continent A continent is one of several large landmasses ...

France
, lends its name to the Toarcian Stage. The Toarcian was named by Alcide d'Orbigny in 1842, with the original locality being Vrines quarry around 2 km northwest of Thouars. The GSSP for the base of the Toarcian is located at
Peniche, Portugal Peniche () is a seaside municipality and a city located in the Leiria District of Central Portugal. It has 26,431 inhabitants, in an area of 77.55 km2. The city itself has a population of about 15,600 inhabitants. The present mayor is Henrique ...

Peniche, Portugal
, and was ratified in 2014. The boundary is defined by the first appearance of ammonites belonging to the subgenus '' Dactylioceras'' Dactylioceras, (''Eodactylites'')''.''


Middle Jurassic

The Aalenian is named after the city of Aalen in Germany. The Aalenian was defined by Swiss geologist Karl Mayer-Eymar in 1864. The lower boundary was originally between the dark clays of the Black Jurassic and the overlying clayey sandstone and Iron, ferruginous oolite of the Brown Jurassic sequences of southwestern Germany. The GSSP for the base of the Aalenian is located at Fuentelsaz in the Sistema Ibérico, Iberian range near Guadalajara, Spain, and was ratified in 2000. The base of the Aalenian is defined by the first appearance of the ammonite ''Leioceras, Leioceras opalinum''. Alcide d'Orbigny in 1842 named the Bajocian Stage after the town of Bayeux (Latin: ''Bajoce'') in Normandy, France. The GSSP for the base of the Bajocian is located in the Murtinheira section at Cabo Mondego, Portugal; it was ratified in 1997. The base of the Bajocian is defined by the first appearance of the ammonite ''Hyperlioceras, Hyperlioceras mundum.'' The Bathonian is named after the city of Bath, Somerset, Bath, England, introduced by Belgian geologist Jean Baptiste Julien d'Omalius d'Halloy, d'Omalius d'Halloy in 1843, after an incomplete section of oolitic limestones in several quarries in the region. The GSSP for the base of the Bathonian is Ravin du Bès, Bas-Auran area, Alpes-de-Haute-Provence, Alpes de Haute Provence, France; it was ratified in 2009. The base of the Bathonian is defined by the first appearance of the ammonite ''Gonolkites, Gonolkites convergens'', at the base of the Zigzagiceras, ''Zigzagiceras zigzag'' ammonite zone''.'' The Callovian is derived from the Latinisation of names, Latinized name of the village of Kellaways in Wiltshire, England, and was named by Alcide d'Orbigny in 1852, originally the base at the contact between the Forest Marble Formation and the Cornbrash Formation. However, this boundary was later found to be within the upper part of the Bathonian. The base of the Callovian does not yet have a certified GSSP. The working definition for the base of the Callovian is the first appearance of ammonites belonging to the genus ''Kepplerites.''


Upper Jurassic

The Oxfordian is named after the city of Oxford in England and was named by Alcide d'Orbigny in 1844 in reference to the Oxford Clay. The base of the Oxfordian lacks a defined GSSP. William Joscelyn Arkell, W. J. Arkell in studies in 1939 and 1946 placed the lower boundary of the Oxfordian as the first appearance of the ammonite ''Quenstedtoceras, Quenstedtoceras mariae'' (then placed in the genus ''Vertumniceras''). Subsequent proposals have suggested the first appearance of ''Cardioceras, Cardioceras redcliffense'' as the lower boundary. The village of Kimmeridge on the coast of Dorset, England, is the origin of the name of the Kimmeridgian. The stage was named by Alcide d'Orbigny in 1842 in reference to the Kimmeridge Clay. The GSSP for the base of the Kimmeridgian is the Flodigarry section at Staffin, Staffin Bay on the Isle of Skye, Scotland, which was ratified in 2021. The boundary is defined by the first appearance of ammonites marking the boreal Bauhini Zone and the subboreal Baylei Zone. The Tithonian was introduced in scientific literature by Albert Oppel in 1865. The name Tithonian is unusual in geological stage names because it is derived from Greek mythology rather than a place name. Tithonus was the son of Laomedon of Troy and fell in love with Eos, the Greek goddess of dawn. His name was chosen by Albert Oppel for this Stratigraphy, stratigraphical stage because the Tithonian finds itself hand in hand with the dawn of the Cretaceous. The base of the Tithonian currently lacks a GSSP. The working definition for the base of the Tithonian is the first appearance of the ammonite genus ''Gravesia (ammonite), Gravesia''. The upper boundary of the Jurassic is currently undefined, and the Jurassic–Cretaceous boundary is currently the only system boundary to lack a defined GSSP. Placing a GSSP for this boundary has been difficult because of the strong regionality of most biostratigraphic markers, and lack of any Chemostratigraphy, chemostratigraphic events, such as isotope excursions (large sudden changes in Stable isotope ratio, ratios of isotopes), that could be used to define or correlate a boundary. Calpionellids, an enigmatic group of planktonic protists with urn-shaped calcitic Test (biology), tests briefly abundant during the latest Jurassic to earliest Cretaceous, have been suggested to represent the most promising candidates for fixing the Jurassic–Cretaceous boundary In particular, the first appearance ''Calpionella, Calpionella alpina,'' co-inciding with the base of the eponymous Alpina subzone, has been proposed as the definition of the base of the Cretaceous. The working definition for the boundary has often been placed as the first appearance of the ammonite ''Strambergella, Strambergella jacobi,'' formerly placed in the genus ''Berriasella'', but its use as a stratigraphic indicator has been questioned, as its first appearance does not correlate with that of ''C. alpina''.


Mineral and hydrocarbon deposits

The Kimmeridge Clay and equivalents are the major source rock for the North Sea oil. 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. The Jurassic-aged Sargelu and Naokelekan formations are major source rocks for Oil reserves in Iraq, oil in Iraq. Over 1500 gigatons of Jurassic coal reserves are found in north-west China, primarily in the Turpan Depression, Turpan-Hami Basin and the Ordos Plateau, Ordos Basin.


Impact craters

Major impact craters include the Morokweng crater, a 70 km diameter crater buried beneath the Kalahari desert in northern South Africa. The impact is dated to the Tithonian, approximately 146.06 ± 0.16 Mya. Another major impact crater is the Puchezh-Katunki crater, 40–80 kilometres in diameter, buried beneath Nizhny Novgorod Oblast, Russia. The impact has been dated to the Sinemurian, around 192–196 Mya.


Paleogeography and tectonics

At the beginning of the Jurassic, all of the worlds major landmasses were coalesced into the
supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the proces ...
Pangaea Pangaea or Pangea () was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology) ...

Pangaea
, which during the Early Jurassic began to break up into northern supercontinent
Laurasia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea Pangaea or Pangea () was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("s ...
and the southern supercontinent
Gondwana Gondwana () or Gondwanaland was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (ge ...

Gondwana
. 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. During the Jurassic, the North Atlantic Ocean remained relatively narrow, while the South Atlantic did not open until the Cretaceous. The continents were surrounded by Panthalassa, with the Tethys Ocean between Gondwana and Asia. At the end of the Triassic, there was a marine transgression in Europe, flooding most parts of central and western Europe transforming it into an archipelago of islands surrounded by shallow seas. During the Jurassic, both the North and South Pole were covered by oceans. Beginning in the Early Jurassic, the Boreal Ocean was connected to the proto-Atlantic by the "Viking corridor" or Transcontinental Laurasian Seaway, a passage between the Baltic Shield and Greenland several hundred kilometers wide. Madagascar and Antarctica began to rift away from Africa during the late Early Jurassic in association with the eruption of the Karoo-Ferrar large igneous provinces, opening the western Indian Ocean and beginning the fragmentation of Gondwana. At the beginning of the Jurassic, North and South America remained connected, but by the beginning of the Late Jurassic they had rifted apart to form the Caribbean Seaway, also known as the Hispanic Corridor, which connected the North Atlantic Ocean with eastern Panthalassa. Palaeontological data suggest that the seaway had been open since the Early Jurassic. As part of the Nevadan orogeny, which began during the Triassic, the Cache Creek Ocean closed, and various terranes including the large Wrangellia Terrane Accretion (geology), accreted onto the western margin of North America. By the Middle Jurassic the Siberia (continent), Siberian plate and the North China-Amuria block had collided, resulting in the closure of the Mongol-Okhotsk Ocean. During the Early Jurassic, around 190 million years ago, the Pacific Plate originated at the triple junction of the Farallon Plate, Farallon, Phoenix Plate, Phoenix, and Izanagi Plate, Izanagi Plate tectonics, tectonic plates, the three main Oceanic crust, oceanic plates of Panthalassa. The previously stable triple junction had converted to an unstable arrangement surrounded on all sides by transform faults because of a kink in one of the plate boundaries, resulting in the formation of the Pacific Plate at the centre of the junction. During the Middle to early Late Jurassic, the Sundance Seaway, a shallow Inland sea (geology), epicontinental sea, covered much of northwest North America.The eustatic sea level is estimated to have been close to present levels during the Hettangian and Sinemurian, rising several tens of metres during the late Sinemurian–Pliensbachian before regressing to near present levels by the late Pliensbachian. There seems to have been a gradual rise to a peak of ~75 m above present sea level during the Toarcian. During the latest part of the Toarcian, the sea level again dropped by several tens of metres. It progressively rose from the Aalenian onwards, aside from dips of a few tens of metres in the Bajocian and around the Callovian–Oxfordian boundary, peaking possibly as high as 140 metres above present sea level at the Kimmeridgian–Tithonian boundary. The sea levels falls in the late Tithonian, perhaps to around 100 metres, before rebounding to around 110 metres at the Tithonian–Berriasian boundary. The sea level within the long-term trends across the Jurassic was cyclical, with 64 fluctuations, 15 of which were over 75 metres. The most noted Stratigraphic cycles, cyclicity in Jurassic rocks is fourth order, with a periodicity of approximately 410,000 years. During the Early Jurassic the world's oceans transitioned from an aragonite sea to a calcite sea chemistry, favouring the dissolution of aragonite and precipitation of calcite. The rise of calcareous plankton during the Middle Jurassic profoundly altered ocean chemistry, with the deposition of Biomineralization, biomineralized plankton on the ocean floor acting as a Buffer solution, buffer against large CO2 emissions.


Climate

The climate of the Jurassic was generally warmer than that of present, by around 5 °C to 10 °C, with Carbon dioxide in Earth's atmosphere, atmospheric carbon dioxide likely four times higher. Forests likely grew near the poles, where they experienced warm summers and cold, sometimes snowy winters; there were unlikely to have been ice sheets given the high summer temperatures that prevented the accumulation of snow, though there may have been mountain glaciers. Dropstones and glendonites in northeastern Siberia during the Early to Middle Jurassic indicate cold winters. The ocean depths were likely 8 °C warmer than present, and coral reefs grew 10° of latitude further north and south. The Intertropical Convergence Zone likely existed over the oceans, resulting in large areas of desert and scrubland in the lower latitudes between 40° N and S of the equator. Tropical rainforest and tundra biomes are likely to have been rare or absent. The beginning of the Jurassic was likely marked by a thermal spike corresponding to the Triassic–Jurassic extinction and eruption of the Central Atlantic magmatic province. The first part of the Jurassic was marked by the Early Jurassic cool interval between 199 and 183 million years ago. It has been proposed that glaciation was present in the Northern Hemisphere during the Pleinsbachian. There was a spike in global temperatures of around 4–8 °C during the early part of the Toarcian corresponding to the Toarcian Oceanic Anoxic Event and the eruption of the Karoo-Ferrar large igneous provinces in southern Gondwana, with the warm interval extending to the end of the Toarcian around 174 million years ago. During the Toarcian warm interval, ocean surface temperatures likely exceeded 30 °C, and equatorial and subtropical (30°N–30°S) regions are likely to have been extremely arid, with temperatures in the interior of Pangea likely in excess of 40 °C. The Toarcian warm interval is followed by the Middle Jurassic cool interval between 174 and 164 million years ago. This is followed by the Kimmeridgian warm interval between 164 and 150 million years ago. The Pangean interior had less severe seasonal swings than in previous warm periods as the expansion of the Central Atlantic and western Indian Ocean provided new sources of moisture. 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.


Climatic events


Toarcian Oceanic Anoxic Event

The Toarcian Oceanic Anoxic Event (TOAE), also known as the Jenkyns Event, was an episode of widespread oceanic anoxia during the early part of the Toarcian Age, c. 183 Mya. It is marked by a globally documented high amplitude negative Carbon isotope ratio, carbon isotope excursion, as well as the deposition of black shales and the extinction and collapse of carbonate-producing marine organisms, associated with a major rise in global temperatures. The TOAE is often attributed to the eruption of the Karoo-Ferrar large igneous provinces and the associated increase of carbon dioxide concentration in the atmosphere, as well as the possible associated release of methane clathrates. This likely accelerated the hydrological cycle and increased Carbonate–silicate cycle, silicate weathering. Groups affected include ammonites, ostracods, foraminifera, brachiopods, Bivalvia, bivalves and cnidarians, with the last two spire-bearing brachiopod orders, Spiriferinida and Athyridida, becoming extinct. While the event had significant impact on marine invertebrates, it had little effect on marine reptiles. During the TOAE, the Sichuan Basin was transformed into a giant lake, probably three times the size of modern-day Lake Superior, represented by the Da’anzhai Member of the Ziliujing Formation. The lake likely Carbon sequestration, sequestered ∼460 gigatons (Gt) of organic carbon and ∼1,200 Gt of inorganic carbon during the event. Seawater pH, which had already substantially decreased prior to the event, increased slightly during the early stages of the TOAE, before dropping to its lowest point around the middle of the event. This
ocean acidification Ocean acidification is the ongoing decrease in the pH value of the Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of cont ...
is what likely caused the collapse of carbonate production.


End-Jurassic transition

The end-Jurassic transition was originally considered one of eight mass extinctions, but is now 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.


Flora


End-Triassic extinction

There is no evidence of a mass extinction of plants at the Triassic–Jurassic boundary. At the Triassic–Jurassic boundary in Greenland, the sporomorph (pollen and spores) record suggests a complete floral turnover. An analysis of macrofossil floral communities in Europe suggests that changes were mainly due to local ecological succession. At the end of the Triassic, the Peltaspermaceae became extinct in most parts of the world, with ''Lepidopteris'' persisting into the Early Jurassic in Patagonia. ''Dicroidium'', a seed fern that was a dominant part of Gondwanan floral communities during the Triassic, also declined at the Triassic–Jurassic boundary, surviving as a relict in Antarctica into the Sinemurian.


Floral composition


Conifers

Conifers formed a dominant component of Jurassic floras. The Late Triassic and Early 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 Voltziales, voltzialean ancestors. Araucariaceae, Araucarian conifers have their first unambiguous records during the Early Jurassic, and ones closely related to the modern genus ''Araucaria'' were widespread across both hemispheres by the Middle Jurassic. Also abundant during the Jurassic is the extinct family Cheirolepidiaceae, often recognised through their highly distinctive ''Classopolis'' pollen. Jurassic representatives include the pollen cone ''Classostrobus'' and the seed cone ''Pararaucaria''. Araucarian and Cheirolepidiaceae conifers often occur in association. The oldest definitive record of the cypress family (Cupressaceae) is ''Austrohamia, Austrohamia minuta'' from the Early Jurassic (Pliensbachian) of Patagonia, known from many parts of the plant. The reproductive structures of ''Austrohamia'' have strong similarities to those of the primitive living cypress genera ''Taiwania'' and ''Cunninghamia.'' By the Middle to Late Jurassic Cupressaceae were abundant in warm temperate–tropical regions of the Northern Hemisphere, most abundantly represented by the genus ''Elatides''. Members of the extinct genus ''Schizolepidopsis'' which likely represent a stem-group to the pine family (Pinaceae), were widely distributed across Eurasia during the Jurassic. The oldest unambiguous record of Pinaceae is the Conifer cone, pine cone ''Eathiestrobus'', known from the Late Jurassic (Kimmeridgian) of Scotland, which remains the only known unequivocal fossil of the group before the Cretaceous. Despite being the earliest known member of the Pinaceae, ''Eathiestrobus'' appears to be a member of the Pinoideae, pinoid clade of the family, suggesting that the initial diversification of Pinaceae occurred earlier than has been found in the fossil record. During the Early Jurassic, the flora of the mid-latitudes of Eastern Asia were dominated by the extinct deciduous broad leafed conifer ''Podozamites,'' which appears to not be closely related to any living family of conifer. Its range extended northwards into polar latitudes of Siberia and then contracted northward in the Middle to Late Jurassic, corresponding to the increasing aridity of the region. The earliest record of the yew family (Taxaceae) is ''Palaeotaxus, Palaeotaxus rediviva'', from the Hettangian of Sweden, suggested to be closely related to the living ''Austrotaxus'', while ''Marskea, Marskea jurassica'' from the Middle Jurassic of Yorkshire, England and material from the Callovian–Oxfordian Daohugou Bed in China are thought to be closely related to ''Amentotaxus,'' with the latter material assigned to the modern genus, indicating that Taxaceae had substantially diversified by the end of the Jurassic. Podocarpaceae, today largely confined to the Southern Hemisphere, occurred in the Northern Hemisphere during the Jurassic, Examples include ''Podocarpophyllum'' from the Early to Middle Jurassic of Central Asia and Siberia, ''Scarburgia'' from the Middle Jurassic of Yorkshire, and ''Harrisiocarpus'' from the Jurassic of Poland.


Ginkgoales

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. The earliest representatives of the genus ''Ginkgo,'' represented by Ovule, ovulate and pollen organs similar to those of the modern species, are known from the Middle Jurassic in the Northern Hemisphere. Several other lineages of ginkgoaleans are known from Jurassic rocks, including ''Yimaia'', ''Grenana'', ''Nagrenia'' and Karkeniaceae, ''Karkenia''. These lineages are associated with ''Ginkgo-''like leaves, but are distinguished from living and fossil representatives of ''Ginkgo'' by having differently arranged reproductive structures. ''Umaltolepis,'' historically thought to be ginkgoalean, and ''Vladimaria'' from the Jurassic of Asia have strap-shaped ginkgo-like leaves (''Pseudotorrelia'') with highly distinct reproductive structures with similarities to those of peltasperm and corystosperm seed ferns; these have been placed in the separate order Vladimariales, which may be related to Ginkgoales.


Bennettitales

Bennettitales, having first become widespread during the preceeding Triassic, were diverse and abundant members of Jurassic floras across both hemispheres. The foliage of Bennettitales bears strong similarities to those of cycads, to such a degree that they cannot be reliably distinguished on the basis of morphology alone. Leaves of Bennettitales can be distinguished from those of cycads their different arrangement of stomata, and the two groups are not thought to be closely related. Most Bennettitales belong to the grouping Williamsoniaceae, which grew as shrubs and small trees. The Williamsoniaceae are thought to have had a divaricate branching habit, similar to that of living ''Banksia'', and adapted to growing in open habitats with poor soil nutrient conditions. Bennettitales exhibit complex, flower-like reproductive structures that are thought to have been pollinated by insects. Several groups of insects that bear long proboscis, including extinct families such as Kalligrammatidae, kalligrammatid lacewings and extant ones such as Acroceridae, acrocerid flies, are suggested to have been pollinators of bennettitales, feeding on nectar produced by bennettitalean cones.


Cycads

Cycads reached their apex of diversity during the Jurassic and Cretaceous Periods. Despite the Mesozoic sometimes being called the "Age of Cycads", cycads are thought to have been a relatively minor component of mid-Mesozoic floras, their foliage being confused with that of Bennettitales and other "cycadophytes". The Nilssoniales have leaves morphologically similar to those of cycads, and often been considered cycads or cycad relatives, but have been found to be distinct on chemical grounds, and perhaps more closely allied with Bennettitales.'''' Cycads are thought to have been mostly confined to tropical and subtropical latitudes throughout their evolutionary history. The relationships of most Mesozoic cycads to living groups are ambiguous. Seeds from Jurassic of England and Haida Gwaii, Canada, are early members of the Cycadaceae, one of two modern groups of cycads, indicating that the diversification of modern cycads had begun by this time. Modern cycads are pollinated by beetles, and such an association is thought to have formed by the Early Jurassic.


Other seed plants

Although there have been several claimed records, there are no widely accepted Jurassic records of flowering plants, which make up 90% of living plant species, and fossil evidence suggests that the group diversified during the following Cretaceous. The Gnetophyta, gnetophyte ''Protognetum'' from the Middle Jurassic of China exhibits characteristics of both ''Gnetum'' and Ephedra (plant), ''Ephedra'', and is placed in the Monotypic taxon, monotypic family Protognetaceae. "Seed ferns" (Pteridospermatophyta) is a collective term to refer to disparate lineages of fern like plants that produce seeds but have uncertain affinities to living Spermatophyte, seed plant groups. A prominent group of Jurassic seed ferns is the Caytoniales, which reached their zenith during the Jurassic, with widespread records in the Northern Hemisphere, though records in the Southern Hemisphere remain rare. Due to their berry-like seed-bearing capsules, they have often been suggested to have been closely related or perhaps ancestral to flowering plants, but the evidence for this is inconclusive. Records of the Corystospermaceae, corystosperms, a seed fern group primarily known from the Triassic of Gondwana, become rare after the Triassic and the decline of ''Dicroidium'', though there appear to be Jurassic records of the group from the Northern Hemisphere. Czekanowskiales, also known as Leptostrobales, are a group of seed plants uncertain affinities with persistent heavily dissected leaves borne on deciduous short shoots, subtended by scale-like leaves, known from the Late Triassic (possibly Late Permian) to Cretaceous. They are thought to have had a tree- or shrub-like habit and formed a conspicuous component of Northern Hemisphere Mesozoic temperate and warm-temperate floras. The genus ''Phoenicopsis'' was widespread in Early-Middle Jurassic floras of Eastern Asia and Siberia. The Pentoxylales, a small but clearly distinct group of seed plants of obscure affinities, first appeared during the Jurassic. Their distribution appears to have been confined to Gondwana.


Ferns and allies

Living families of ferns widespread during the Jurassic include Dipteridaceae, Matoniaceae, Gleicheniaceae, Osmundaceae and Marattiaceae. Polypodiales, which make up 80% of living fern diversity, have no record from the Jurassic and are thought to have diversified in the Cretaceous, though the widespread Jurassic Herbaceous plant, herbaceous fern genus ''Coniopteris,'' historically interpreted as a close relative of tree ferns of the family Dicksoniaceae, has recently been reinterpreted as an early relative of the group. The 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. Only a handful of possible records exist of the Hymenophyllaceae from the Jurassic, including ''Hymenophyllites macrosporangiatus'' from the Russian Jurassic. The oldest remains of modern Equisetaceae, horsetails of the genus ''Equisetum'' first appear in the Early Jurassic, represented by ''Equisetum dimorphum'' from the Early Jurassic of Patagonia and ''Equisetum laterale'' from the Early to Middle Jurassic of Australia. Petrifaction, Silicified remains of ''Equisetum thermale'' from the Late Jurassic of Argentina exhibit all the morphological characters of modern members of the genus. The estimated split between ''Equisetum bogotense'' and all other living ''Equisetum'' is estimated to have occurred no later than the Early Jurassic.


Lower plants

Isoetes, Quillworts virtually identical to modern species are known from the Jurassic onwards. ''Isoetites rolandii'' from the Middle Jurassic of Oregon is the earliest known species to represent all major morphological features of modern ''Isoetes''. More primitive forms such as ''Nathorstiana,'' which retain an elongated stem, persisted into the Early Cretaceous. The moss ''Kulindobryum'' from the Middle Jurassic of Russia, which was found associated with dinosaur bones, is thought to be related to the Splachnaceae, which grow on animal caracasses. ''Bryokhutuliinia'' from the same region is thought to be related to Dicranales. ''Heinrichsiella'' from the Jurassic of Patagonia is thought to belong to either Polytrichaceae or Timmiellaceae. The liverwort ''Pellites, Pellites hamiensis'' from the Middle Jurassic Xishanyao Formation of China is the oldest record of the family Pelliaceae. Pallaviciniites, ''Pallaviciniites sandaolingensis'' from the same deposit is thought to belong to the subclass Pallaviciniineae within the Pallaviciniales. ''Ricciopsis, Ricciopsis sandaolingensis'', also from the same deposit, is the only Jurassic record of Ricciaceae.


Fauna


Reptiles


Crocodylomorphs

The Triassic–Jurassic extinction decimated
pseudosuchia Pseudosuchia is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely related to crocodilians than to birds. Pseudosuchians are also informally known as "crocodilian-line archosaurs". Prior to ...
n diversity, with Crocodylomorpha, crocodylomorphs, which originated during the early Late Triassic, being the only group of pseudosuchians to survive, with all others, including the herbivorous aetosaurs and carnivorous "rauisuchians" becoming extinct. 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. While living crocodilians are confined to an aquatic ambush predator lifestyle, Jurassic crocodylomorphs exhibited a wide variety of life habits. An unnamed Protosuchidae, protosuchid known from teeth from the Early Jurassic of Arizona represents the earliest known herbivorous crocodylomorph, an adaptation that appeared several times during the Mesozoic. The Thalattosuchia, a clade of predominantly marine crocodylomorphs, first appeared during the Early Jurassic and became a prominent part of marine ecosystems. Within Thalattosuchia, the Metriorhynchidae became highly adapted for life in the open ocean, including the transformation of limbs into flippers, the development of a tail fluke, and smooth, scaleless skin. 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 crocodyliformes, crocodyliforms and thalattosuchians. The Neosuchia, a major group of crocodylomorphs, first appeared during the Early to Middle Jurassic. The Neosuchia represents the transition from an ancestrally terrestrial lifestyle to a freshwater aquatic ecology similar to that occupied by modern crocodilians. The timing of the origin of Neosuchia is disputed. The oldest record of Neosuchians has been suggested to be ''Calsoyasuchus,'' from the Early Jurassic of Arizona, which in many analyses has been recovered as the earliest branching member of the neosuchian family Goniopholididae, which radically alters times of diversification for crocodylomorphs. However, this placement has been disputed, with some analyses finding it outside Neosuchia, which would place the oldest records of Neosuchia in the Middle Jurassic. ''Razanandrongobe'' from the Middle Jurassic of Madagascar has been suggested the represent the oldest record of Notosuchia, a primarily Gondwanan clade of mostly terrestrial crocodylomorphs, otherwise known from the Cretaceous and Cenozoic.


Turtles

Stem-group turtles (Testudinata) diversified during the Jurassic. Jurassic stem-turtles belong to two progressively more advanced clades, the Mesochelydia and Perichelydia. It is thought that the ancestral condition for mesochelydians is aquatic, as opposed to terrestrial for testudinates. The two modern groups of turtles (Turtle, Testudines), Pleurodira and Cryptodira, diverged by the beginning of the Late Jurassic. The oldest known pleurodires, the Platychelyidae, are known from the Late Jurassic of Europe and the Americas, while the oldest unambiguous cryptodire, ''Sinaspideretes,'' an early relative of Trionychidae, softshell turtles, is known from the Late Jurassic of China. The Thalassochelydia, a diverse lineage of sea turtles, is known from the Late Jurassic of Europe and South America.


Lepidosaurs

Rhynchocephalians (the sole living representative being the tuatara) had achieved a global distribution by the beginning of the Jurassic. Rhynchocephalians reached their highest morphological diversity in their evolutionary history during the Jurassic, occupying a wide range of lifestyles, including the aquatic Pleurosauridae, pleurosaurs with long snake-like bodies and reduced limbs, the specialized herbivorous Eilenodontinae, eilenodontines, as well as ''Oenosaurus,'' which had broad tooth plates indicative of durophagy. Rhynchocephalians disappeared from Asia after the Early Jurassic. The last common ancestor of living Squamata, squamates (which includes lizards and snakes) is estimated to have lived around 190 million years ago during the Early Jurassic, with the major divergences between modern squamate lineages estimated to have occurred during the Early to Middle Jurassic. Squamates first appear in the fossil record during the Middle Jurassic and included early members of the snake lineage (Ophidia) and Scincomorpha, though many Jurassic squamates have unclear relationships to living groups. ''Eichstaettisaurus'' from the Late Jurassic of Germany has been suggested to be an early relative of geckos and displays adaptations for climbing. ''Dorsetisaurus'' from the Late Jurassic of North America and Europe represents the oldest widely accepted record of Anguimorpha. ''Marmoretta'' from the Middle Jurassic of Britain represents a late surviving Lepidosauromorpha, lepidosauromorph outside both Rhynchocephalia and Squamata. File:Vadasaurus herzogi holotype (fossil).jpg, ''Vadasaurus, Vadasaurus herzogi'', a rynchocephalian from the Upper Jurassic Solnhofen Limestone of Germany File:Homeosaurus maximiliani, lizard, Jurassic, Solnhofen Limestone, Eichstatt, Bavaria, Germany - Houston Museum of Natural Science - DSC01988.JPG, ''Homoeosaurus, Homeosaurus maximiliani'', a rynchocephalian from the Solnhofen Limestone File:Pleurosaurus 783534.jpg, ''Pleurosaurus,'', an aquatic rhynchocephalian from the Late Jurassic of Europe File:Eichstaettisaurus schroederi.JPG, ''Eichstaettisaurus, Eichstaettisaurus schroederi,'', an extinct lizard from the Solnhofen Limestone


Choristoderes

The earliest known remains of Choristodera, a group of freshwater aquatic reptiles with uncertain affinities to other reptile groups, are found in the Middle Jurassic. Only two genera of choristodere are known from the Jurassic. One is the small lizard-like ''Cteniogenys'', thought to be the most basal known choristodere; it is known from the Middle to Late Jurassic of Europe and Late Jurassic of North America, with similar remains also known from the upper Middle Jurassic of Kyrgyzstan and western Siberia. The other is ''Coeruleodraco'' from the Late Jurassic of China, which is a more advanced choristodere, though still small and lizard-like in morphology.


Ichthyosaurs

Ichthyosaurs suffered an evolutionary bottleneck during the end-Triassic extinction, with all non-neoichthyosaurians becoming extinct. Ichthyosaurs reached their apex of species diversity during the Early Jurassic, with an array of morphologies including the huge apex predator ''Temnodontosaurus'' and swordfish-like ''Eurhinosaurus,'' though Early Jurassic ichthyosaurs were significantly less morphologically diverse than their Triassic counterparts. At the Early–Middle Triassic boundary, between the end of the Toarcian and the beginning of the Bajocian, most lineages of ichythosaur appear to have become extinct, with the first appearance of the Ophthalmosauridae, the clade that would encompass almost all ichthyosaurs from then on, during the early Bajocian. 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.


Plesiosaurs

Plesiosauria, Plesiosaurs originated at the end of the Triassic (Rhaetian). By the end of the Triassic, all other sauropterygians, including Placodontia, placodonts and nothosaurs, had become extinct. At least six lineages of plesiosaur crossed the Triassic–Jurassic boundary. Plesiosaurs were already diverse in the earliest Jurassic, with the majority of plesiosaurs in the Hettangian-aged Blue Lias belonging to the Rhomaleosauridae. Early plesiosaurs were generally small-bodied, with body size increasing into the Toarcian. There appears to have been a strong turnover around the Early–Middle Jurassic boundary, with the extinction of the previously widespread rhomaleosaurids and Microcleididae, microcleidids after the end of the Toarcian and the first appearance of the dominant clade of plesiosaurs of the latter half of the Jurassic, the Cryptoclididae, during the Bajocian. The Middle Jurassic saw the evolution of short-necked and large-headed Thalassophonea, thalassophonean pliosaurs from ancestrally small-headed, long-necked forms''.'' Some thalassophonean pliosaurs, such as some species of ''Pliosaurus'', had skulls up to two metres in length with body lengths estimated around 10–12 metres, making them the apex predators of Late Jurassic oceans. Plesiosaurs invaded freshwater environments during the Jurassic, with indeterminate remains of small-bodied pleisosaurs known from freshwater sediments from the Jurassic of China and Australia.


Pterosaurs

Pterosaurs first appeared in the Late Triassic. A major radiation of Jurassic pterosaurs is the Rhamphorhynchidae, which first appeared in the late Early Jurassic (Toarcian); they are thought to been Piscivore, piscivorous. Anurognathidae, Anurognathids, which first appeared in the Middle Jurassic, possessed short heads and densely furred bodies, and are thought to have been insectivores. Derived monofenestratan pterosaurs such as Wukongopteridae, wukongopterids appeared in the late Middle Jurassic. Advanced short-tailed Pterodactyloidea, pterodactyloids first appeared at the Middle–Late Jurassic boundary. Jurassic pterodactyloids include the Ctenochasmatoidea, ctenochasmatids, like ''Ctenochasma'', which have closely spaced needle-like teeth that were presumably used for Filter feeder, filter feeding. The bizarre Late Jurassic Ctenochasmatoidea, ctenochasmatoid ''Cycnorhamphus'' had a jaw with teeth only at the tips, with bent jaws like those of living openbill storks that may have been used to hold and crush hard invertebrates.


Dinosaurs

Dinosaurs, which had morphologically diversified in the Late Triassic, experienced a major increase in diversity and abundance during the Early Jurassic in the aftermath of the end-Triassic extinction and the extinction of other reptile groups, becoming the dominant vertebrates in terrestrial ecosystems. ''Chilesaurus'', a morphologically aberrant herbivorous dinosaur from the Late Jurassic of South America, has uncertain relationships to the three main groups of dinosaurs, having been recovered as a member of all three in different analyses.


Theropods

Advanced Theropoda, theropods belonging to Neotheropoda first appeared in the Late Triassic. Basal neotheropods, such as Coelophysoidea, coelophysoids and Dilophosauridae, dilophosaurs, persisted into the Early Jurassic, but became extinct by the Middle Jurassic. The earliest averostrans appear during the Early Jurassic, with the earliest known member of Ceratosauria being ''Saltriovenator'' from the early Sinemurian (199.3–197.5 million years ago) of Italy. The unusual ceratosaur ''Limusaurus'' from the Late Jurassic of China had a herbivorous diet, with adults having edentulous beaked jaws, making it the earliest known theropod to have converted from an ancestrally carnivorous diet. The earliest members of the Tetanurae appeared during the late Early Jurassic or early Middle Jurassic. The Megalosauridae represent the oldest radiation of the Tetanurae, first appearing in Europe during the Bajocian. The oldest member of Allosauroidea has been suggested to be ''Asfaltovenator'' from the Middle Jurassic of South America. Coelurosauria, Coelurosaurs first appeared during the Middle Jurassic, including early Tyrannosauroidea, tyrannosaurs such as ''Proceratosaurus'' from the Bathonian of Britain. Some coelurosaurs from the Late Jurassic of China including ''Shishugounykus'' and ''Haplocheirus'' are suggested to represent early Alvarezsauroidea, alvarezsaurs, however, this has been questioned. Scansoriopterygidae, Scansoriopterygids, a group of small feathered coelurosaurs with membraneous, bat-like wings for gliding, are known from the Middle to Late Jurassic of China. The oldest record of Troodontidae, troodontids is suggested to be ''Hesperornithoides'' from the Late Jurassic of North America. Tooth remains suggested to represent those of Dromaeosauridae, dromaeosaurs are known from the Jurassic, but no body remains are known until the Cretaceous. File:Ceratosaurus mounted white background.jpg, Skeleton of ''Ceratosaurus'', a ceratosaurid from the Late Jurassic of North America File:Monolophosaurus jiangi.jpg, Skeleton of ''Monolophosaurus'', a basal tetanuran from the Middle Jurassic of China File:Yi qi restoration.jpg, Restoration of ''Yi (dinosaur), Yi qi'', a scansoriopterygid from the Middle to Late Jurassic of China


= Birds

= The earliest Avialae, avialans, which include birds and their ancestors, appear during the Middle to Late Jurassic, definitively represented by ''Archaeopteryx'' from the Late Jurassic of Germany. Avialans belong to the clade Paraves within Coelurosauria, which also includes dromaeosaurs and troodontids. The Anchiornithidae from the Middle-Late Jurassic of Eurasia have frequently suggested to be avialans, but have also alternatively found as a separate lineage of paravians.


Ornithischians

The earliest definitive ornithischians appear during the Early Jurassic, represented by basal ornithischians like ''Lesothosaurus'', Heterodontosauridae, heterodontosaurids, and early members of Thyreophora. The earliest members of Ankylosauria and Stegosauria appear during the Middle Jurassic. The basal neornithischian ''Kulindadromeus'' from the Middle Jurassic of Russia indicates that at least some ornithischians were covered in Feathered dinosaur, protofeathers. The earliest members of Ankylopollexia, which become prominent in the Cretaceous, appeared during the Late Jurassic, represented by bipedal forms such as ''Camptosaurus''. Ceratopsians first appeared in the Late Jurassic of China, represented by members of Chaoyangsauridae.


Sauropodomorphs

Sauropoda, Sauropods became the dominant large herbivores in terrestrial ecosystems during the Jurassic. Some Jurassic sauropods reached gigantic sizes, becoming the largest organisms to have ever lived on land. Basal (phylogenetics), Basal bipedal Sauropodomorpha, sauropodomorphs, such as Massospondylidae, massospondylids, continued to exist into the Early Jurassic, but became extinct by the beginning of the Middle Jurassic. Quadrupedal sauropomorphs appeared during the Late Triassic. The quadrupedal ''Ledumahadi'' from the earliest Jurassic of South Africa reached an estimated weight of 12 tons, far in excess of other known basal sauropodomorphs. Gravisaurian Sauropoda, sauropods first appeared during the Early Jurassic, with the oldest definitive record being ''Vulcanodon'' from Zimbabwe, likely of Sinemurian age. Eusauropoda, Eusauropods first appeared during the late Early Jurassic (Toarcian) and diversified during the Middle Jurassic; these included Cetiosauridae, cetiosaurids, Turiasauria, turiasaurs, and Mamenchisauridae, mamenchisaurs. The earliest known member of Neosauropoda is ''Lingwulong'', a Dicraeosauridae, dicraeosaurid Diplodocoidea, diplodocoid from the Early to Middle Jurassic of China. Neosauropods dispersed worldwide during the Late Jurassic. The Middle-Late Jurassic saw the first appearance of Synapomorphy and apomorphy, derived neosauropod groups, including BrachiosauridaePhilip D. Mannion, Ronan Allain & Olivier Moine, 2017, "The earliest known titanosauriform sauropod dinosaur and the evolution of Brachiosauridae", ''PeerJ'' 5: e3217 https://doi.org/10.7717/peerj.3217 and Diplodocidae.


Amphibians

The diversity of Temnospondyli, temnospondyls had progressively declined through the Late Triassic, with only Brachyopoidea, brachyopoids surviving into the Jurassic and beyond. Members of the family Brachyopidae are known from Jurassic deposits in Asia, while the Chigutisauridae, chigutisaurid ''Siderops'' is known from the Early Jurassic of Australia. Modern lissamphibians began to diversify during the Jurassic. The Early Jurassic ''Prosalirus'' thought to represent the first frog relative with a morphology capable of hopping like living frogs. Morphologically recognisable stem-frogs like the South American ''Notobatrachus'' are known from the Middle Jurassic. While the earliest salamander-line amphibians are known from the Triassic, crown group salamanders first appear during the Middle to Late Jurassic in Eurasia, alongside stem-group relatives. Many Jurassic stem-group salamanders, such as ''Marmorerpeton'' and ''Kokartus'', are thought to have been Neoteny, neotenic. Early representatives of crown group salamanders include ''Chunerpeton, Pangerpeton'' and ''Linglongtriton'' from the Middle to Late Jurassic Yanliao Biota of China. These belong to the Cryptobranchoidea, which contains living Asiatic salamander, Asiatic and giant salamanders. ''Beiyanerpeton'', and ''Qinglongtriton'' from the same biota are thought to be early members of Salamandroidea, the group which contains all other living salamanders. Salamanders dispersed into North America by the end of the Jurassic, as evidenced by ''Iridotriton'', found in the Late Jurassic Morrison Formation. The oldest undisputed stem-caecilian is the Early Jurassic ''Eocaecilia'' from Arizona. The fourth group of lissamphibians, the extinct Albanerpetontidae, albanerpetontids, first appeared in the Middle Jurassic, represented by ''Anoualerpeton, Anoualerpeton priscus'' from the Bathonian of Britain, as well as indeterminate remains from equivalently aged sediments in France and the Anoual Formation of Morocco.


Mammals

Mammals, having originated from cynodonts at the end of the Triassic, diversified extensively during the Jurassic. Important groups of Jurassic mammals include Morganucodonta, Docodonta, Eutriconodonta, Dryolestida, Haramiyida and Multituberculata. While most Jurassic mammals are solely known from isolated teeth and jaw fragments, exceptionally preserved remains have revealed a variety of lifestyles. The docodontan ''Castorocauda'' was adapted to aquatic life, similarly to the platypus and otters. Some members of Haramiyida and the eutriconodontan tribe VolaticotheriniMeng, J.; Hu, Y.-M.; Wang, Y.-Q.; Wang, X.-L.; Li, C.-K. (2007). "Corrigendum: A Mesozoic gliding mammal from northeastern China". Nature 446 (7131): 102. . . had a patagium akin to those of flying squirrels, allowing them to glide through the air. The aardvark-like mammal ''Fruitafossor'', of uncertain taxonomy, was likely a specialist on colonial insects, similarly to living anteaters. Australosphenida, the group which contains modern monotremes, first appeared in the Middle Jurassic of Gondwana. Therian mammals, represented today by living Placentalia, placentals and marsupials, appear during the early Late Jurassic, represented by ''Juramaia,'' a eutherian mammal closer to the ancestry of placentals than marsupials.Electronic supplementary material
/ref> ''Juramaia'' is much more advanced than expected for its age, as other therian mammals are not known until the Early Cretaceous. Two groups of non-mammalian cynodonts persisted beyond the end of the Triassic. The insectiviorous Tritheledontidae has a few records from the Early Jurassic. The Tritylodontidae, a herbiviorous group of cynodonts that first appeared during the Rhaetian, has abundant records from the Jurassic, overwhelmingly from the Northern Hemisphere.


Fish


Conodonts

The last known species of conodont, a class of Agnatha, jawless fish whose hard tooth-like elements are key index fossils, finally became extinct during the earliest Jurassic after over 300 million years of evolutionary history, with an asynchronous extinction occurring first in the Tethys and eastern Panthalassa and survivors persisting into the earliest Hettangian of Hungary and central Panthalassa. End-Triassic conodonts were represented by only a handful of species and had been progressively declining through the Middle and Late Triassic.


Sarcopterygii

Lungfish (Dipnoi) were present in freshwater environments of both hemispheres during the Jurassic. Genera include ''Ceratodus'' and ''Ptychoceratodus'', which are more closely related to living South American lungfish, South American and Protopterus, African lungfish than Australian lungfish, Queensland lungfish, and ''Ferganoceratodus'' from the Jurassic of Asia, which is not closely related to either group of living lungfish. Mawsoniidae, Mawsoniids, a marine and freshwater/brackish group of coelacanths, which first appeared in North America during the Triassic, expanded into Europe and South America by the end of the Jurassic. The marine Latimeriidae, which contains the living coelacanths of the genus ''Latimeria'', were also present in the Jurassic, having originated in the Triassic.


Actinopterygii

Bony fish (Actinopterygii) were major components of Jurassic freshwater and marine ecosystems. Archaic "palaeoniscoid" fish, such as Coccolepididae, coccolepidids, which were common in both marine and freshwater habitats during the preceeding Triassic declined during the Jurassic, being largely replaced by modern actinopterygian lineages. The oldest known Acipenseriformes, the group that contains living sturgeon and paddlefish, are from the Early Jurassic. Amiiformes, Amiiform fish (which today only includes the bowfin) 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. Pycnodontiformes, which first appeared in the western Tethys during the Late Triassic, expanded to South America and Southeast Asia by the end of the Jurassic, having a high diversity in Europe during the Late Jurassic. During the Jurassic, the Ginglymodi, the only living representatives being gars (Lepisosteidae) were diverse in both freshwater and marine environments. The oldest known representatives of anatomically modern gars appeared during the Upper Jurassic. Teleosts, which make up over 99% of living Actinopterygii, had first appeared during the Triassic in the western Tethys; they underwent a major diversification beginning in the Late Jurassic, with early representatives of modern teleost clades such as Elopomorpha and Osteoglossoidei appearing during this time. The Pachycormiformes, a group of fish closely allied to 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.Liston, J., Newbrey, M., Challands, T., and Adams, C., 2013, "Growth, age and size of the Jurassic pachycormid ''Leedsichthys problematicus'' (Osteichthyes: Actinopterygii) in: Arratia, G., Schultze, H. and Wilson, M. (eds.) ''Mesozoic Fishes 5 – Global Diversity and Evolution''. Verlag Dr. Friedrich Pfeil, München, Germany, pp. 145–175


Chondrichthyes

During the Early Jurassic, Hybodontiformes, Hybodonts, such as ''Hybodus'', were common in both marine and freshwater settings; however, by the Late Jurassic, hybodonts had become minor components of most marine communities, having been largely replaced by modern Neoselachii, neoselachians, but remained common in freshwater and restricted marine environments. The Neoselachii, which contains all living sharks and rays, radiated beginning in the Early Jurassic. The oldest known Hexanchiformes are from the Early Jurassic (Pliensbachian) of Europe. The oldest known ray (Batoidea) is ''Antiquaobatis'' from the Pliensbachian of Germany. Jurassic batoids known from complete remains retain a conservative, guitarfish-like morphology. The oldest known relatives of the bullhead shark (''Heterodontus'') in the order Heterodontiformes first appeared in the Early Jurassic, with representatives of the living genus appearing during the Late Jurassic. Carpet sharks (Orectolobiformes) first appeared during the Toarcian, represented by ''Folipistrix'' and ''Annea (fish), Annea'' from Europe. The oldest known Lamniformes, mackerel sharks (Lamniformes) 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. The oldest record of angelsharks (Squatiniformes) is ''Pseudorhina'' from the Oxfordian–Tithonian of Europe. The oldest known remains of Carcharhiniformes, the largest order of living sharks, first appear in the late Middle Jurassic (Bathonian) of the western Tethys (England and Morocco). Known dental and exceptionally preserved body remains of Jurassic Carchariniformes are similar to those of living catsharks. Synechodontiformes, an extinct group of sharks closely related to Neoselachii, were also widespread during the Jurassic. The oldest remains of chimaeras are from the Early Jurassic of Europe, with members of the living family Callorhinchidae appearing during the Middle Jurassic. Unlike living chimaeras, these were found in shallow water settings. The closely related ''Squaloraja'' and Myriacanthoidei, myriacanthoids are also known from the Jurassic of Europe.


Insects and arachnids

There appears to have been no major extinction of insects at the Triassic–Jurassic boundary. Many important insect fossil localities are known from the Jurassic of Eurasia, the most important being the Karabastau Formation of Kazakhstan and the various Yanliao Biota deposits in Inner Mongolia, China, such as the Daohugou Bed, dating to the Callovian–Oxfordian. The diversity of insects stagnated throughout the Early and Middle Jurassic, but during the latter third of the Jurassic origination rates increased substantially while extinction rates remained flat. The increasing diversity of insects in the Middle–Late Jurassic corresponds with a substantial increase in the diversity of insect mouthparts. The Middle to Late Jurassic was a time of major diversification for beetles. 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. The oldest known lepidopterans (the group containing butterflies and moths) are known from the Triassic–Jurassic boundary, with wing scales belonging to the suborder Glossata and Micropterigidae-grade moths from the deposits of this age in Germany. Modern representatives of both Dragonfly, dragonflies and Damselfly, damselflies also first appeared during the Jurassic. Although modern representatives are not known until the Cenozoic, ectoparasitic insects thought to represent primitive fleas, belonging to the family Pseudopulicidae, are known from the Middle Jurassic of Asia. These insects are substantially different from modern fleas, lacking the specialised morphology of the latter and being larger. Parasitoid wasp, Parasitic wasps (Aculeata) first appeared during the Early Jurassic and subsequently became widespread, reshaping terrestrial food webs. The Jurassic saw also saw the first appearances of several other groups of insects, including Phasmatodea (stick insects), Mantophasmatidae, and Embioptera (webspinners). Only a handful of records of mites are known from the Jurassic, including ''Jureremus'', an Oribatida, oribatid mite belonging to the family Cymbaeremaeidae known from the Late Jurassic of Britain and Russia, and a member of the still living orbatid genus ''Hydrozetes'' from the Early Jurassic of Sweden. Spiders diversified through the Jurassic. The Early Jurassic ''Seppo koponeni'' may represent a stem group to Palpimanoidea. ''Eoplectreurys'' from the Middle Jurassic of China is considered a stem lineage of Synspermiata. The oldest member of the family Archaeidae, ''Patarchaea'', is known from the Middle Jurassic of China. ''Mongolarachne'' from the Middle Jurassic of China is among the largest known fossil spiders, with legs over 5 centimetres long. The only scorpion known from the Jurassic is ''Liassoscorpionides'' from the Early Jurassic of Germany, of uncertain placement. Eupnoi harvestmen (Opiliones) are known from the Middle Jurassic of China, including members of the family Sclerosomatidae.


Marine invertebrates


End-Triassic extinction

During the end-Triassic extinction, 46%–72% of all marine genera became extinct. The effects of the end Triassic extinction were greatest at tropical latitudes and were more severe in Panthalassa than the Tethys or Boreal oceans. Tropical reef ecosystems collapsed during the event, and would not fully recover until much later in the Jurassic. Sessility (motility), Sessile filter feeders and photosymbiotic organisms were among most severely affected.


Marine ecosystems

Having declined at the Triassic–Jurassic boundary, reefs substantially expanded during the Late Jurassic, including both sponge reefs and scleractinian coral reefs. Late Jurassic reefs were similar in form to modern reefs but had more microbial carbonates and hypercalcified sponges, and had weak biogenic binding. Reefs sharply declined at the close of the Jurassic, which caused an associated drop in diversity in Decapoda, decapod crustaceans. The earliest planktonic foraminifera, Globigerinina, are known from the late Early Jurassic (mid-Toarcian) of the western Tethys, expanding across the whole Tethys by the Middle Jurassic and becoming globally distributed in tropical latitudes by the Late Jurassic. Coccolithophores and dinoflagellates, which had first appeared during the Triassic, radiated during the Early to Middle Jurassic, becoming prominent members of the phytoplankton. Microconchida, Microconchid tube worms, the last remaining order of Tentaculita, a group of animals of uncertain affinities that were convergent on ''Spirorbis'' tube worms, were rare after the Triassic and had become reduced to the single genus ''Punctaconchus,'' which became extinct in the late Bathonian. The oldest known diatom is from Late Jurassic–aged amber from Thailand, assigned to the living genus ''Hemiaulus.''


Echinoderms

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. Sea urchin, Echinoids (sea urchins) underwent substantial diversification beginning in the Early Jurassic, primarily driven by the radiation of irregular (asymmetrical) forms, which were adapting to deposit feeding. Rates of diversification sharply dropped during the Late Jurassic.


Crustaceans

The Jurassic was a significant time for the evolution of Decapoda, decapods. The first true crabs (Crab, Brachyura) are known from the Early Jurassic, with the earliest being ''Eocarcinus, Eocarcinus praecursor'' from the early Pliensbachian of England, which lacked the crab-like morphology (carcinisation) of modern crabs, and Eoprosopon, ''Eoprosopon klugi'' from the late Pliensbachian of Germany, which may belong to the living family Homolodromiidae. Most Jurassic crabs are known only from carapace pieces, which makes it difficult to determine their relationships. While rare in the Early and Middle Jurassic, crabs became abundant during the Late Jurassic as they expanded from their ancestral silty sea floor habitat into hard substrate habitats like reefs, with crevices in reefs providing refuge from predators. Hermit crabs also first appeared during the Jurassic, with the earliest known being ''Schobertella, Schobertella hoelderi'' from the late Hettangian of Germany. Early hermit crabs are associated with ammonite shells rather than those of gastropods. Glypheidea, Glypheids, which today are only known from two species, reached their peak diversity during the Jurassic, with around 150 species out of a total fossil record of 250 known from the period. 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.


Brachiopods

Brachiopod diversity declined during the Triassic–Jurassic extinction. Spire-bearing groups (Spiriferinida and Athyridida) declined at the Triassic–Jurassic boundary and did not recover their biodiversity, becoming extinct in the TOAE. Rhynchonellida and Terebratulida also declined during the Triassic–Jurassic extinction but rebounded during the Early Jurassic; neither clade underwent much morphological variation. Brachiopods substantially declined in the Late Jurassic; the causes are poorly understood. Proposed reasons include increased predation, competition with bivalves, enhanced bioturbation or increased grazing pressure.


Molluscs


= Ammonites

= Ammonites were devastated by the end-Triassic extinction, with only a handful of genera belonging to the family Psiloceratidae of the suborder Phylloceratina surviving and becoming ancestral to all later Jurassic and Cretaceous ammonites. Ammonites explosively diversified during the Early Jurassic, with the orders Psiloceratina, Ammonitina, Lytoceratina, Haploceratoidea, Haploceratina, Perisphinctoidea, Perisphinctina and Ancyloceratina all appearing during the Jurassic. 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.


= Bivalves

= The end-Triassic extinction had a severe impact on bivalve diversity, though it had little impact on bivalve ecological diversity. The extinction was selective, having less of an impact on deep burrowers, but there is no evidence of a differential impact between surface-living (epifaunal) and burrowing (infaunal) bivalves. Bivalve family level diversity after the Early Jurassic was static, though genus diversity experienced a gradual increase throughout the period. Rudists, the dominant reef-building organisms of the Cretaceous, first appeared in the Late Jurassic (mid-Oxfordian) in the northern margin of the western Tethys, expanding to the eastern Tethys by the end of the Jurassic.


= Belemnites

= The oldest definitive records of the squid-like Belemnitida, belemnites are from the earliest Jurassic (Hettangian–Sinemurian) of Europe and Japan; they expanded worldwide during the Jurassic. Belemnites were shallow-water dwellers, inhabiting the upper 200 metres of the water column on the Continental shelf, continental shelves and in the littoral zone. They were key components of Jurassic ecosystems, both as predators and prey, as evidenced by the abundance of belemnite guards in Jurassic rocks.


= Octopodiformes

= The earliest Vampyromorphida, vampyromorphs, of which the only living member is the vampire squid, first appeared during the Early Jurassic. The earliest octopuses appeared during the Middle Jurassic, having split from their closest living relatives, the vampyromorphs, during the Triassic to Early Jurassic. All Jurassic octopuses are solely known from the hard Gladius (cephalopod), gladius. ''Proteroctopus'' from the late Middle Jurassic La Voulte-sur-Rhône (lagerstätte), La Voulte-sur-Rhône lagerstätte, previously interpreted as an early octopus, is now thought to be a basal taxon outside the clade containing vampyromorphs and octopuses. Octopuses likely originated from bottom-dwelling (Benthic zone, benthic) ancestors which lived in shallow environments.


References


Citations


External links


Examples of Jurassic Fossils



Jurassic fossils in Harbury, Warwickshire

Jurassic Microfossils: 65+ images of Foraminifera
* With map and table. {{Authority control Jurassic, Geological periods