The Jurassic ( ) is a
geologic period
The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochr ...
and
stratigraphic system that spanned from the end of the
Triassic
The Triassic ( ) is a geologic period and system (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...
Period million years ago (Mya) to the beginning of the
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
Period, approximately Mya. The Jurassic constitutes the middle period of the
Mesozoic Era and is named after the
Jura Mountains, where
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
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, often called the end-Triassic extinction, marks the boundary between the Triassic and Jurassic periods, , and is one of the top five major extinction events of the Phanerozoic eon, profoundly affect ...
, associated with the eruption of the
Central Atlantic Magmatic Province
The Central Atlantic magmatic province (CAMP) is the Earth's largest continental large igneous province, covering an area of roughly 11 million km2. It is composed mainly of basalt that formed before Pangaea broke up in the Mesozoic Era, near the ...
. The beginning of the
Toarcian
The Toarcian is, in the ICS' geologic timescale, an age and stage in the Early or Lower Jurassic. It spans the time between 182.7 Ma (million years ago) and 174.1 Ma. It follows the Pliensbachian and is followed by the Aalenian.
The Toarcian ...
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 reduction in the pH value of the Earth’s ocean. Between 1751 and 2021, the average pH value of the ocean surface has decreased from approximately 8.25 to 8.14. The root cause of ocean acidification is carbon dioxid ...
, and elevated 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, a supercontinent is the assembly of most or all of Earth's continental blocks or cratons to form a single large landmass. However, some geologists use a different definition, "a grouping of formerly dispersed continents", which leav ...
Pangaea
Pangaea or Pangea () was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 million y ...
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 downfaulted depression, called a graben, or more commonly a half-grabe ...
ing into two landmasses:
Laurasia to the north and
Gondwana to the south. The climate of the Jurassic was warmer than the present, and there were no
ice caps
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.
Description
Ice caps are not constrained by topographical featur ...
. 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
Dinosauromorpha is a clade of avemetatarsalian archosaurs (reptiles closer to birds than to crocodilians) that includes the Dinosauria (dinosaurs) and some of their close relatives. It was originally defined to include dinosauriforms and lag ...
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
archosaurs, to one dominated by
dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
s alone. The first birds appeared during the Jurassic, evolving from a branch of
theropod
Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...
dinosaurs. Other major events include the appearance of the earliest lizards and the evolution of
theria
Theria (; Greek: , wild beast) is a subclass of mammals amongst the Theriiformes. Theria includes the eutherians (including the placental mammals) and the metatherians (including the marsupials) but excludes the egg-laying monotremes.
...
n mammals.
Crocodylomorphs
Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction.
During Mesozoic and early Cenozoic times, cr ...
made the transition from a terrestrial to an aquatic life. The oceans were inhabited by
marine reptiles
Marine reptiles are reptiles which have become secondarily adapted for an aquatic or semiaquatic life in a marine environment.
The earliest marine reptile mesosaurus (not to be confused with mosasaurus), arose in the Permian period during the ...
such as
ichthyosaurs and
plesiosaurs, while
pterosaur
Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 ...
s were the dominant flying
vertebrates
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with c ...
. The first sharks, rays and crabs also first appeared during the period.
Etymology and history
![Alexandre Brongniart](https://upload.wikimedia.org/wikipedia/commons/1/1c/Alexandre_Brongniart.jpg)
The
chronostratigraphic
Chronostratigraphy is the branch of stratigraphy that studies the ages of rock strata in relation to time.
The ultimate aim of chronostratigraphy is to arrange the sequence of deposition and the time of deposition of all rocks within a geologic ...
term "Jurassic" is linked to the
Jura Mountains, a forested
mountain range
A mountain range or hill range is a series of mountains or hills arranged 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 arise ...
that mainly follows the
France–Switzerland border. The name "Jura" is derived from the
Celtic
Celtic, Celtics or Keltic may refer to:
Language and ethnicity
*pertaining to Celts, a collection of Indo-European peoples in Europe and Anatolia
**Celts (modern)
*Celtic languages
**Proto-Celtic language
* Celtic music
*Celtic nations
Sports Fo ...
root ''*jor'' via
Gaulish
Gaulish was an ancient Celtic languages, Celtic language spoken in parts of Continental Europe before and during the period of the Roman Empire. In the narrow sense, Gaulish was the language of the Celts of Gaul (now France, Luxembourg, Belgium ...
''*iuris'' "wooded mountain", which was borrowed into
Latin
Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
as a name of a place and 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 German polymath, geographer, naturalist, explorer, and proponent of Romantic philosophy and science. He was the younger brother of the Prussian minister, ...
recognized
carbonate
A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...
deposits within the Jura Mountains as geologically distinct from the
Triassic
The Triassic ( ) is a geologic period and system (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...
aged
Muschelkalk
The Muschelkalk (German for "shell-bearing limestone"; french: calcaire coquillier) is a sequence of sedimentary rock strata (a lithostratigraphic unit) in the geology of central and western Europe. It has a Middle Triassic (240 to 230 million ye ...
of Southern Germany, but he erroneously concluded that they were older. He then named them ('Jura limestone') in 1799.
In 1829, the French naturalist
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
oolitic limestones in Britain, thus coining and publishing the term "Jurassic".
The German geologist
Leopold von Buch
Christian Leopold von Buch (26 April 1774 – 4 March 1853), usually cited as Leopold von Buch, was a German geologist and paleontologist born in Stolpe an der Oder (now a part of Angermünde, Brandenburg) and is remembered as one of the most im ...
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 of the South German Jurassic, the latter being understood not as a geographical, but a geological term in the ...
,
Brown Jurassic
The Brown Jurassic or Brown Jura (german: Brauner Jura or ''Braunjura'') in earth history refers to the middle of the three lithostratigraphic units of the South German Jurassic, the latter being understood not as a geographical, but a geological ...
, 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 units of the South German Jurassic, the latter being understood not as a geographical, but a geological t ...
. The term "
Lias
Lias may refer to:
Geology
* Lias Formation, a geologic formation in France
*Lias Group, a lithostratigraphic unit in western Europe
* Early Jurassic, an epoch
People
* Godfrey Lias, British author
* Mohd Shamsudin Lias (born 1953), Malaysian ...
" had previously been used for strata of equivalent age to the Black Jurassic in England by
William Conybeare and
William Phillips William Phillips may refer to:
Entertainment
* William Phillips (editor) (1907–2002), American editor and co-founder of ''Partisan Review''
* William T. Phillips (1863–1937), American author
* William Phillips (director), Canadian film-make ...
in 1822.
The 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 epoch (roughly 11,700 years before present). It includes the study of fossi ...
Alcide d'Orbigny
Alcide Charles Victor Marie Dessalines d'Orbigny (6 September 1802 – 30 June 1857) was a French naturalist who made major contributions in many areas, including zoology (including malacology), palaeontology, geology, archaeology and anthropol ...
in papers between 1842 and 1852 divided the Jurassic into ten stages based on
ammonite and other fossil assemblages in England and France, of which seven are still used, but none has retained its original definition. The 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 Saxony, and educated at the Humboldt University of Berlin. After a period as assistant ...
in 1858 divided the three series of von Buch in the
Swabian Jura into six subdivisions defined by ammonites and other fossils.
The German palaeontologist
Albert Oppel
Carl Albert Oppel (19 December 1831 – 23 December 1865) was a German paleontologist.
History
He was born at Hohenheim in Württemberg, on 19 December 1831. He first went to the University of Tübingen, where he graduated with a Ph.D. ...
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 which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictionary of Bio ...
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
In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured.
The moment of epoch is usually decided by ...
: Early, Middle, and Late. Similarly, in
stratigraphy, the Jurassic is divided into the
Lower Jurassic
The Early Jurassic Epoch (in chronostratigraphy corresponding to the Lower Jurassic Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-Jurassic extinction event, 201.3 Ma&nb ...
,
Middle Jurassic, and
Upper Jurassic 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 in ...
. Geologists divide the rocks of the Jurassic into a
stratigraphic
Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks.
Stratigraphy has three related subfields: lithostra ...
set of units called
stages
Stage or stages may refer to:
Acting
* Stage (theatre), a space for the performance of theatrical productions
* Theatre, a branch of the performing arts, often referred to as "the stage"
* ''The Stage'', a weekly British theatre newspaper
* 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 stratigra ...
(ICS) ratify global stages based on a
Global Boundary Stratotype Section and Point
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 scale. The effort to define GSSPs is conducted b ...
(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 secondar ...
(a
stratotype A stratotype or type section in geology is the physical location or outcrop of a particular reference exposure of a stratigraphic sequence or stratigraphic boundary. If the stratigraphic unit is layered, it is called a stratotype, whereas the stan ...
) identifying the lower boundary of the stage.
The ages of the Jurassic from youngest to oldest are as follows:
Stratigraphy
![Fm Lajas Maquina Cura](https://upload.wikimedia.org/wikipedia/commons/6/60/Fm_Lajas_Maquina_Cura.jpg)
Jurassic stratigraphy is primarily based on the use of ammonites as
index fossils
Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictionary of Bio ...
. The
first appearance datum
First appearance datum (FAD) is a term used by geologists and paleontologists to designate the first appearance of a species in the geologic record. FADs are determined by identifying the geologically oldest fossil discovered, to date, of a particu ...
of specific ammonite
taxa
In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...
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 Hettangian Stage was named by Swiss palaeontologist
Eugène Renevier
Eugène Renevier (26 March 18314 May 1906) Swiss geologist, was born at Lausanne, Switzerland, as a descendant of a noble family.
After about three years of study at the polytechnical school of Stuttgart, Renevier in 1851 went to Geneva to study ...
in 1864 after
Hettange-Grande
Hettange-Grande (; ; Lorraine Franconian: ''Grouss-Hetténgen'') is a commune in the Moselle department in Grand Est in north-eastern France.
The town gives its name to the Hettangian age, the earliest age of the Jurassic period of the geologic ...
in north-eastern France.
The GSSP for the base of the Hettangian is located at the Kuhjoch Pass,
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 north of the Central Eastern Alps located in Austria and the adjacent Bavarian lands of southeastern Germany ...
, 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. These issues are often highly valued by collectors due to their rarity and iconic status.
Reader interes ...
of the ammonite ''
Psiloceras spelae tirolicum'' in the
Kendlbach Formation
The Kendlbach Formation is a Late Triassic (latest Rhaetian) to Early Jurassic (Hettangian) geological formation in Austria and Italy. It contains the Global Boundary Stratotype Section and Point (GSSP) for the Hettangian stage (the first stage o ...
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 of the Côte-d'Or department in eastern France. The politician François Patriat, the engineers Edmé Régnier L'Aîné (1751–1825) and Émile Dorand (1866-1922), and the Encyclopédiste Philippe Guéneau de ...
, near
Dijon
Dijon (, , ) (dated)
* it, Digione
* la, Diviō or
* lmo, Digion is the prefecture of the Côte-d'Or department and of the Bourgogne-Franche-Comté region in northeastern France. the commune had a population of 156,920.
The earlies ...
. 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, from West Quantoxhead, east of Williton, and west of Bridgwater, within the Quantock Hills Area of Outstanding Natural Beauty in Somerset, England.
History
Above the ...
, 6 kilometres east of
Watchet
Watchet is a harbour town, civil parish and electoral ward in the county of Somerset, England, with a population in 2011 of 3,785. It is situated west of Bridgwater, north-west of Taunton, and east of Minehead. The town lies at the mouth of ...
,
Somerset
( en, All The People of Somerset)
, locator_map =
, coordinates =
, region = South West England
, established_date = Ancient
, established_by =
, preceded_by =
, origin =
, lord_lieutenant_office =Lord Lieutenant of Somerset
, lord_ ...
,
England
England is a 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 and the Celtic Sea to the southwest. It is separated from continental Europe b ...
, within the
Blue Lias
The Blue Lias is a geological formation in southern, eastern and western England and parts of South Wales, part of the Lias Group. The Blue Lias consists of a sequence of limestone and shale layers, laid down in latest Triassic and early Jurassi ...
, 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 in Baden-Württemberg in southern Germany.
Geographical location
Between Stuttgart and Ulm, on the western edge of the district Göppingen, lies the municipality of Zell unter ...
in the
Swabian Alb, near
Stuttgart
Stuttgart (; Swabian: ; ) is the capital and largest city of the German state of Baden-Württemberg. It is located on the Neckar river in a fertile valley known as the ''Stuttgarter Kessel'' (Stuttgart Cauldron) and lies an hour from the ...
, 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 village and a bay located in the North York Moors National Park, south of Whitby and north of Scarborough on the coast of North Yorkshire, England. Bay Town, its local name, is in the ancient chapelry of ...
,
Yorkshire
Yorkshire ( ; abbreviated Yorks), formally known as the County of York, is a historic county in northern England and by far the largest in the United Kingdom. Because of its large area in comparison with other English counties, functions have ...
, England, in the
Redcar Mudstone Formation
The Redcar Mudstone Formation is a geological formation in North Yorkshire, England. Part of the Lias Group, it was deposited in the Hettangian to Pliensbachian stages of the Early Jurassic. The lithology consists of fissile mudstones and siltstone ...
, 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 in the Deux-Sèvres department in western France. On 1 January 2019, the former communes Mauzé-Thouarsais, Missé and Sainte-Radegonde were merged into Thouars.
It is on the River Thouet. Its inhabitants are known ...
(Latin: ''Toarcium''), just south of
Saumur in the
Loire Valley of
France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
, 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 Henriqu ...
, and was ratified in 2014. The boundary is defined by the first appearance of ammonites belonging to the subgenus ''
Dactylioceras
''Dactylioceras'' was a widespread genus of ammonites from the Lower Jurassic period, approximately 180 million years ago ( mya).
Etymology
The name ''Dactylioceras'' comes from the Greek ''dactyl'', meaning “finger”, and refers to the shell ...
''
(''Eodactylites'')''.''
Middle Jurassic
The Aalenian is named after the city of
Aalen in Germany. The Aalenian was defined by Swiss geologist
Karl Mayer-Eymar
Karl David Wilhelm Mayer-Eymar (29 July 1826 – 25 February 1907) was a Franco-Swiss paleontologist and geologist known for his work on classifying the stratigraphy of the Tertiary into 12 stages. He was born Karl Mayer but added the anagram Eymar ...
in 1864. The lower boundary was originally between the dark clays of the Black Jurassic and the overlying clayey sandstone and
ferruginous
The adjective ferruginous may mean:
* Containing iron, applied to water, oil, and other non-metals
* Having rust on the surface
* With the rust (color)
See also
* Ferrous, containing iron (for metals and alloys) or iron(II) cations
* Ferric, cont ...
oolite of the Brown Jurassic sequences of southwestern Germany.
The GSSP for the base of the Aalenian is located at
Fuentelsaz
Fuentelsaz is a municipality located in the province of Guadalajara, Castile-La Mancha, Spain. According to the 2004 census
A census is the procedure of systematically acquiring, recording and calculating information about the members of a g ...
in the
Iberian range
Iberian refers to Iberia. Most commonly Iberian refers to:
*Someone or something originating in the Iberian Peninsula, namely from Spain, Portugal, Gibraltar and Andorra.
The term ''Iberian'' is also used to refer to anything pertaining to the fo ...
near
Guadalajara, Spain
Guadalajara (, ) is a city and municipality in Spain, located in the autonomous community of Castilla–La Mancha. It is the capital of the Province of Guadalajara.
Lying on the central part of the Iberian Peninsula at roughly metres above sea ...
, and was ratified in 2000. The base of the Aalenian is defined by the first appearance of the ammonite ''
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
Cabo Mondego is a cape located in central western Portugal bordering the Atlantic Ocean. It is the westernmost point of the Serra da Boa Viagem and is located three kilometers north of Figueira da Foz
Figueira da Foz (), also known as Figueir ...
, Portugal; it was ratified in 1997. The base of the Bajocian is defined by the first appearance of the ammonite ''
Hyperlioceras mundum.''
The Bathonian is named after the city of
Bath, England, introduced by Belgian geologist
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, France; it was ratified in 2009. The base of the Bathonian is defined by the first appearance of the ammonite ''
Gonolkites convergens'', at the base of the
''Zigzagiceras zigzag'' ammonite zone''.''
The Callovian is derived from the
Latinized name of the village of
Kellaways in
Wiltshire
Wiltshire (; abbreviated Wilts) is a historic and ceremonial county in South West England with an area of . It is landlocked and borders the counties of Dorset to the southwest, Somerset to the west, Hampshire to the southeast, Gloucestershire ...
, England, and was named by Alcide d'Orbigny in 1852, originally the base at the contact between the
Forest Marble Formation
The Forest Marble is a geological formation in England. Part of the Great Oolite Group, it dates to the late Bathonian stage of the Middle Jurassic.Weishampel, David B; et al. (2004). "Dinosaur distribution (Middle Jurassic, Europe)." In: Weisha ...
and the
Cornbrash Formation
The Cornbrash Formation is a Middle Jurassic geological formation in England. It ranges in age from Bathonian to Callovian, the uppermost part of the Middle Jurassic. Dinosaur remains are among the fossils that have been recovered from the for ...
. 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
''Kepplerites'' is a moderately evolute ammonite from the lower Callovian (upper Middle Jurassic) included in the Stephanoceratoidea.
Inner whorls are finely ribbed and have a flattened or grooved venter, the outer whorl has a rounded venter wit ...
.
''
Upper Jurassic
The Oxfordian is named after the city of
Oxford
Oxford () is a city in England. It is the county town and only city of Oxfordshire. In 2020, its population was estimated at 151,584. It is north-west of London, south-east of Birmingham and north-east of Bristol. The city is home to the ...
in England and was named by Alcide d'Orbigny in 1844 in reference to the
Oxford Clay
The Oxford Clay (or Oxford Clay Formation) is a Jurassic marine sedimentary rock formation underlying much of southeast England, from as far west as Dorset
Dorset ( ; archaically: Dorsetshire , ) is a county in South West England on the ...
. The base of the Oxfordian lacks a defined GSSP.
W. J. Arkell in studies in 1939 and 1946 placed the lower boundary of the Oxfordian as the first appearance of the ammonite ''
Quenstedtoceras mariae'' (then placed in the genus ''
Vertumniceras''). Subsequent proposals have suggested the first appearance of ''
Cardioceras redcliffense'' as the lower boundary.
The village of
Kimmeridge
Kimmeridge () is a small village and civil parish on the Isle of Purbeck, a peninsula on the English Channel coast in Dorset, England. It is situated about south of Wareham and west of Swanage. In 2013 the estimated population of the civil p ...
on the coast of
Dorset
Dorset ( ; archaically: Dorsetshire , ) is a county in South West England on the English Channel coast. The ceremonial county comprises the unitary authority areas of Bournemouth, Christchurch and Poole and Dorset. Covering an area of , ...
, 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 Kimmeridge Clay is a sedimentary deposit of fossiliferous marine clay which is of Late Jurassic to lowermost Cretaceous age and occurs in southern and eastern England and in the North Sea. This rock formation is the major source rock for Nor ...
. The GSSP for the base of the Kimmeridgian is the Flodigarry section at
Staffin Bay on the
Isle of Skye,
Scotland
Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...
, 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
A major branch of classical mythology, Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the Cosmogony, origin and Cosmology#Metaphysical co ...
rather than a place name.
Tithonus
In Greek mythology, Tithonus ( or ; grc, Τιθωνός, Tithonos) was the lover of Eos, Goddess of the Dawn. He was a prince of Troy, the son of King Laomedon by the Naiad Strymo (Στρυμώ). The mythology reflected by the fifth-century va ...
was the son of
Laomedon
In Greek mythology, Laomedon (; grc, Λαομέδων means "ruler of the people") was a Trojan king, son of Ilus and thus nephew of Ganymede and Assaracus.
Family
Laomedon's mother was variously identified as Eurydice,Apollodorus3.12. ...
of
Troy
Troy ( el, Τροία and Latin: Troia, Hittite: 𒋫𒊒𒄿𒊭 ''Truwiša'') or Ilion ( el, Ίλιον and Latin: Ilium, Hittite: 𒃾𒇻𒊭 ''Wiluša'') was an ancient city located at Hisarlik in present-day Turkey, south-west of Ç ...
and fell in love with
Eos
In ancient Greek mythology and religion, Eos (; Ionic and Homeric Greek ''Ēṓs'', Attic ''Héōs'', "dawn", or ; Aeolic ''Aúōs'', Doric ''Āṓs'') is the goddess and personification of the dawn, who rose each morning from her home at ...
, the Greek goddess of
dawn
Dawn is the time that marks the beginning of twilight before sunrise. It is recognized by the appearance of indirect sunlight being scattered in Earth's atmosphere, when the centre of the Sun's disc has reached 18° below the observer's hori ...
. His name was chosen by Albert Oppel for this
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''.
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
chemostratigraphic events, such as
isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers (mass numb ...
excursions (large sudden changes in
ratios of isotopes), that could be used to define or correlate a boundary.
Calpionellid
Calpionellids are an extinct group of eukaryotic single celled organisms of uncertain affinities. Their fossils are found in marine rocks of Upper Jurassic to Lower Cretaceous age. They were planktic organisms with urn-shaped, calcitic tests t ...
s, an enigmatic group of
plankton
Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...
ic
protist
A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor), the exc ...
s with urn-shaped calcitic
tests
Test(s), testing, or TEST may refer to:
* Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities
Arts and entertainment
* ''Test'' (2013 film), an American film
* ''Test'' (2014 film), ...
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 alpina
''Calpionella'' is an extinct genus of calpionellid, a group of single celled eukaryotes. ,'' 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 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
In petroleum geology, source rock is rock which has generated hydrocarbons or which could generate hydrocarbons. Source rocks are one of the necessary elements of a working petroleum system. They are organic-rich sediments that may have been depo ...
for the
North Sea oil
North Sea oil is a mixture of hydrocarbons, comprising liquid petroleum and natural gas, produced from petroleum reservoirs beneath the North Sea.
In the petroleum industry, the term "North Sea" often includes areas such as the Norwegian Sea ...
.
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
Ghawar (Arabic: الغوار) is an oil field located in Al-Ahsa Governorate, Eastern Province, Saudi Arabia. Measuring (some ), it is by far the largest conventional oil field in the world, and accounts for roughly a third of the cumulative ...
, the world's largest oil field. The Jurassic-aged Sargelu and Naokelekan formations are major source rocks for
oil in Iraq. Over 1500 gigatons of Jurassic coal reserves are found in north-west China, primarily in the
Turpan-Hami Basin and the
Ordos Basin
The Ordos Plateau, also known as the Ordos Basin or simply the Ordos, is a highland sedimentary basin in northwest China with an elevation of , and consisting mostly of land enclosed by the Ordos Loop, a large northerly rectangular bend of the Y ...
.
Impact structures
Major impact structures include the
Morokweng impact structure
The Morokweng impact structure is an impact structure buried beneath the Kalahari Desert near the town of Morokweng in South Africa's North West province, close to the border with Botswana
Botswana (, ), officially the Republic of Botsw ...
, a 70 km diameter impact structure buried beneath the Kalahari desert in northern South Africa. The impact is dated to the Tithonian, approximately 146.06 ± 0.16 Mya. Another major structure is the
Puchezh-Katunki crater
Puchezh-Katunki is a meteor crater located in the Nizhny Novgorod Oblast of the Volga Federal District, Russia. It is in diameter. Argon–argon dating has constrained the age of formation to be 195.9 ± 1.0 million years old, placing it ...
, 40 kilometres in diameter, buried beneath
Nizhny Novgorod Oblast
Nizhny Novgorod Oblast (russian: link=no, Нижегородская область, ''Nizhegorodskaya oblast''), is a federal subject of Russia (an oblast). Its administrative center is the city of Nizhny Novgorod. It has a population of 3,310,5 ...
in western Russia. The impact has been dated to the Sinemurian, 195.9 ± 1.0 Ma.
Paleogeography and tectonics
![Opening of western Indian Ocean 150 Ma](https://upload.wikimedia.org/wikipedia/commons/2/29/Opening_of_western_Indian_Ocean_150_Ma.png)
At the beginning of the Jurassic, all of the world's major landmasses were coalesced into the
supercontinent
In geology, a supercontinent is the assembly of most or all of Earth's continental blocks or cratons to form a single large landmass. However, some geologists use a different definition, "a grouping of formerly dispersed continents", which leav ...
Pangaea
Pangaea or Pangea () was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 million y ...
, which during the Early Jurassic began to break up into northern supercontinent
Laurasia and the southern supercontinent
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
The Central Atlantic magmatic province (CAMP) is the Earth's largest continental large igneous province, covering an area of roughly 11 million km2. It is composed mainly of basalt that formed before Pangaea broke up in the Mesozoic Era, near the ...
.
During the Jurassic, the North
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...
remained relatively narrow, while the South Atlantic did not open until the Cretaceous.
The continents were surrounded by
Panthalassa
Panthalassa, also known as the Panthalassic Ocean or Panthalassan Ocean (from Greek "all" and "sea"), was the superocean that surrounded the supercontinent Pangaea, the latest in a series of supercontinents in the history of Earth. During th ...
, with the
Tethys Ocean
The Tethys Ocean ( el, Τηθύς ''Tēthús''), also called the Tethys Sea or the Neo-Tethys, was a prehistoric ocean that covered most of the Earth during much of the Mesozoic Era and early Cenozoic Era, located between the ancient continents ...
between Gondwana and Asia. At the end of the Triassic, there was a
marine transgression
A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, which results in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling ...
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
Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is t ...
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
The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...
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
The Nevadan orogeny occurred along the western margin of North America during the Middle Jurassic to Early Cretaceous time which is approximately from 155 Ma to 145 Ma. Throughout the duration of this orogeny there were at least two different kin ...
, which began during the Triassic, the
Cache Creek Ocean
The Cache Creek Ocean, formerly called Anvil Ocean, is an inferred ancient ocean which existed between western North America and offshore continental terranes between the Devonian and the Middle Jurassic.
Evolution of the concept
First propo ...
closed, and various
terrane
In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust (geology), crust fragment formed on a tectonic plate (or broken off from it) and Accretion (geology), accreted or "Suture (geology), sutured" to crust lying on another pla ...
s including the large
Wrangellia Terrane accreted onto the western margin of North America. By the Middle Jurassic the
Siberian plate and the North China-Amuria block had collided, resulting in the closure of the
Mongol-Okhotsk Ocean
The Mongol-Okhotsk Ocean also known as the Khangai-Khantey Ocean was an ancient ocean, present during the Mesozoic. Oceanic rocks from the ancient ocean floor are preserved in the Mongol-Okhotsk suture zone extending through Mongolia to the Sea o ...
.
![Pacific Ocean 180Ma](https://upload.wikimedia.org/wikipedia/commons/9/95/Pacific_Ocean_180Ma.jpg)
During the Early Jurassic, around 190 million years ago, the
Pacific Plate
The Pacific Plate is an oceanic tectonic plate that lies beneath the Pacific Ocean. At , it is the largest tectonic plate.
The plate first came into existence 190 million years ago, at the triple junction between the Farallon, Phoenix, and Iza ...
originated at the
triple junction
A triple junction is the point where the boundaries of three tectonic plates meet. At the triple junction each of the three boundaries will be one of three types – a ridge (R), trench (T) or transform fault (F) – and triple junctions can ...
of the
Farallon,
Phoenix
Phoenix most often refers to:
* Phoenix (mythology), a legendary bird from ancient Greek folklore
* Phoenix, Arizona, a city in the United States
Phoenix may also refer to:
Mythology
Greek mythological figures
* Phoenix (son of Amyntor), a ...
, and
Izanagi
Izanagi (イザナギ/伊邪那岐/伊弉諾) or Izanaki (イザナキ), formally known as
, is the creator deity (''kami
are the deities, divinities, spirits, phenomena or "holy powers", that are venerated in the Shinto religion. They can b ...
tectonic plates
Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large ...
, the three main
oceanic plates of Panthalassa. The previously stable triple junction had converted to an unstable arrangement surrounded on all sides by
transform fault
A transform fault or transform boundary, is a fault along a plate boundary where the motion is predominantly horizontal. It ends abruptly where it connects to another plate boundary, either another transform, a spreading ridge, or a subduct ...
s 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 Sea
The Sundance Sea was an epeiric sea that existed in North America during the mid-to-late Jurassic Period of the Mesozoic Era. It was an arm of what is now the Arctic Ocean, and extended through what is now western Canada into the central west ...
way, a shallow
epicontinental sea
An inland sea (also known as an epeiric sea or an epicontinental sea) is a continental body of water which is very large and is either completely surrounded by dry land or connected to an ocean by a river, strait, or "arm of the sea". An inland s ...
, covered much of northwest North America.
![OoidSurface01](https://upload.wikimedia.org/wikipedia/commons/c/cd/OoidSurface01.jpg)
The
eustatic sea level
The eustatic sea level is the distance from the center of the earth to the sea surface. An increase of the eustatic sea level can be generated by decreasing glaciation, increasing spreading rates of the mid-ocean ridges or more mid-oceanic ridges. ...
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
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
Aragonite is a carbonate mineral, one of the three most common naturally occurring crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and physical processes, including pre ...
and precipitation of
calcite
Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...
. The rise of calcareous
plankton
Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...
during the Middle Jurassic profoundly altered ocean chemistry, with the deposition of
biomineralized plankton on the ocean floor acting as a
buffer
Buffer may refer to:
Science
* Buffer gas, an inert or nonflammable gas
* Buffer solution, a solution used to prevent changes in pH
* Buffering agent, the weak acid or base in a buffer solution
* Lysis buffer, in cell biology
* Metal ion buffer
* ...
against large CO
2 emissions.
Climate
The climate of the Jurassic was generally warmer than that of present, by around 5 °C to 10 °C, with
atmospheric carbon dioxide
Carbon dioxide in Earth's atmosphere is a trace gas that plays an integral part in the greenhouse effect, carbon cycle, photosynthesis and oceanic carbon cycle. It is one of several greenhouse gases in Earth's atmosphere that are contributin ...
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.
Dropstone
Dropstones are isolated fragments of rock found within finer-grained water-deposited sedimentary rocks or pyroclastic beds. They range in size from small pebbles to boulders. The critical distinguishing feature is that there is evidence that the ...
s and
glendonites in northeastern Siberia during the Early to Middle Jurassic indicate cold winters.
[Alt URL]
/ref> The ocean depths were likely 8 °C warmer than present, and coral reef
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups.
C ...
s 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
Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as ''lowland equa ...
and tundra
In physical geography, tundra () is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. The term ''tundra'' comes through Russian (') from the Kildin Sámi word (') meaning "uplands", "treeless mou ...
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 Pliensbachian. 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 province
A large igneous province (LIP) is an extremely large accumulation of igneous rocks, including intrusive (sills, dikes) and extrusive (lava flows, tephra deposits), arising when magma travels through the crust towards the surface. The formation ...
s 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
Carbon (6C) has 15 known isotopes, from to , of which and are stable. The longest-lived radioisotope is , with a half-life of years. This is also the only carbon radioisotope found in nature—trace quantities are formed cosmogenically by t ...
excursion, as well as the deposition of black shales
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especiall ...
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 clathrate
Methane clathrate (CH4·5.75H2O) or (8CH4·46H2O), also called methane hydrate, hydromethane, methane ice, fire ice, natural gas hydrate, or gas hydrate, is a solid clathrate compound (more specifically, a clathrate hydrate) in which a large amo ...
s. This likely accelerated the hydrological cycle and increased silicate weathering
In chemistry, a silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is al ...
, as evidenced by an increased amount of organic matter of terrestrial origin found in marine deposits during the TOAE. Groups affected include ammonites, ostracod
Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typi ...
s, foraminifera
Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly ...
, bivalves, cnidaria
Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter.
Their distinguishing feature is cnidocytes, specialized cells that ...
ns, and especially brachiopods
Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, wh ...
, for which the TOAE represented one of the most severe extinctions in their evolutionary history. While the event had significant impact on marine invertebrates, it had little effect on marine reptiles. During the TOAE, the Sichuan Basin
The Sichuan Basin (), formerly transliterated as the Szechwan Basin, sometimes called the Red Basin, is a lowland region in southwestern China. It is surrounded by mountains on all sides and is drained by the upper Yangtze River and its tributar ...
was transformed into a giant lake, probably three times the size of modern-day Lake Superior
Lake Superior in central North America is the largest freshwater lake in the world by surface areaThe Caspian Sea is the largest lake, but is saline, not freshwater. and the third-largest by volume, holding 10% of the world's surface fresh wa ...
, represented by the Da’anzhai Member of the Ziliujing Formation
The Ziliujing Formation is a geological formation in China, It is Early Jurassic in age. It is part of the stratigraphy of the Sichuan Basin. The dinosaur ''Gongxianosaurus'' and indeterminate theropod material are known from the Dongyuemiao Mem ...
. The lake likely 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 reduction in the pH value of the Earth’s ocean. Between 1751 and 2021, the average pH value of the ocean surface has decreased from approximately 8.25 to 8.14. The root cause of ocean acidification is carbon dioxid ...
is the probable cause of the collapse of carbonate production. Additionally, anoxic conditions were exacerbated by enhanced recycling of phosphorus back into ocean water as a result of high ocean acidity and temperature inhibiting its mineralisation into apatite; the abundance of phosphorus in marine environments caused further eutrophication and consequent anoxia in a positive feedback loop.
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
''Lepidopteris'' ("scaly fern") is a form genus for leaves of Late Permian to Late Triassic Period Pteridospermatophyta, or seed ferns, which lived from around 260 to 200 million years ago in what is now Australia, Antarctica, India, South Amer ...
'' persisting into the Early Jurassic in Patagonia. ''Dicroidium
''Dicroidium'' is an extinct genus of fork-leaved seed ferns that were widely distributed over Gondwana during the Triassic (). Their fossils are known from South Africa, the Arabian Peninsula, Australia, New Zealand, South America, Madagascar ...
'', 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 Jurassic was a major time of diversification of conifers, with most modern conifer groups appearing in the fossil record by the end of the Jurassic, having evolved from voltzialean ancestors.
Araucarian conifers have their first unambiguous records during the Early Jurassic, and members of the modern genus '' Araucaria'' were widespread across both hemispheres by the Middle Jurassic.
Also abundant during the Jurassic is the extinct family Cheirolepidiaceae
Cheirolepidiaceae is an extinct family of conifers. They first appeared in the Triassic, and were widespread during most of the Mesozoic era. They are united by the possession of a distinctive pollen type assigned to the form genus '' Classopolli ...
, 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 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
''Taiwania'', with the single living species ''Taiwania cryptomerioides'', is a large coniferous tree in the cypress family Cupressaceae.
Etymology
''Taiwania'' means 'from Taiwan', while ''Cryptomerioides'' means 'resembling ''Cryptomeria''.G ...
'' and ''Cunninghamia
''Cunninghamia'' is a genus of one or two living species of evergreen coniferous trees in the cypress family Cupressaceae. They are native to China, northern Vietnam and Laos, and perhaps also Cambodia. They may reach in height. In vernacular ...
.'' 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
In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...
to the pine family (Pinaceae
The Pinaceae, or pine family, are conifer trees or shrubs, including many of the well-known conifers of commercial importance such as cedars, firs, hemlocks, larches, pines and spruces. The family is included in the order Pinales, formerly kn ...
), were widely distributed across Eurasia during the Jurassic. The oldest unambiguous record of Pinaceae is the pine cone
A conifer cone (in formal botanical usage: strobilus, plural strobili) is a seed-bearing organ on gymnosperm plants. It is usually woody, ovoid to globular, including scales and bracts arranged around a central axis, especially in conifers an ...
''Eathiestrobus
''Eathiestrobus mackenziei'' is a fossil pine cone found in the Kimmeridge Clay Formation (Upper Jurassic) near Eathie, on the Black Isle in Scotland. It is the oldest fossil pine currently known.
Etymology
The genus name ''Eathiestrobus'' refers ...
'', 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 pinoid clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
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
''Podozamites'' is an extinct genus of fossil conifer leaves. In its broader sense, it has been used as a morphogenus ( form taxon) to refer to any broad leaved multi-veined conifer leaves. Modern broad-leaved conifers with a similar form include ...
,'' 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
Taxaceae (), commonly called the yew family, is a coniferous family which includes six extant and two extinct genera, and about 30 species of plants, or in older interpretations three genera and 7 to 12 species.
Description
They are many-bran ...
) is '' Palaeotaxus rediviva'', from the Hettangian of Sweden, suggested to be closely related to the living ''Austrotaxus
''Austrotaxus spicata'', the New Caledonia yew or southern yew, is a species of yew, the sole species in the genus ''Austrotaxus''. It is related to the other yews in the genera ''Taxus'' and '' Pseudotaxus''.
It is endemic to New Caledonia, o ...
'', while '' Marskea jurassica'' from the Middle Jurassic of Yorkshire, England and material from the Callovian–Oxfordian Daohugou Bed
The Haifanggou Formation (), also known as the Jiulongshan Formation (), is a fossil-bearing rock deposit located near Daohugou () village of Ningcheng County, in Inner Mongolia, northeastern China.
The formation consists of coarse conglomerates ...
in China are thought to be closely related to ''Amentotaxus
''Amentotaxus'' is a genus of conifers (catkin-yews) comprising five species, treated in either the Cephalotaxaceae, or in the Taxaceae when that family is considered in a broad sense. The genus is endemic to subtropical Southeast Asia, from ...
,'' with the latter material assigned to the modern genus, indicating that Taxaceae had substantially diversified by the end of the Jurassic.
Podocarpaceae
Podocarpaceae is a large family of mainly Southern Hemisphere conifers, known in English as podocarps, comprising about 156 species of evergreen trees and shrubs.James E. Eckenwalder. 2009. ''Conifers of the World''. Portland, Oregon: Timber Pr ...
, 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
''Ginkgo biloba'', commonly known as ginkgo or gingko ( ), also known as the maidenhair tree, is a species of tree native to China. It is the last living species in the order Ginkgoales, which first appeared over 290 million years ago. Fossil ...
'', 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
''Ginkgo'' is a genus of non-flowering seed plants. The scientific name is also used as the English name. The order to which it belongs, Ginkgoales, first appeared in the Permian, 270 million years ago, and is now the only living genus with ...
,'' represented by ovulate
Ovulation is the release of eggs from the ovaries. In women, this event occurs when the ovarian follicles rupture and release the secondary oocyte ovarian cells. After ovulation, during the luteal phase, the egg will be available to be fertilized ...
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
''Yimaia'' is a extinct genus of Ginkgoalean tree, and the only member of the family Yimaiaceae. In botanical form classification, its a form taxon for ginkgoalean ovulate organs. ''Yimaia'' species are distinguished from other Ginkgoales by ...
'', '' Grenana'', '' Nagrenia'' and ''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 ('' Pseudotorellia'') 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
Bennettitales (also known as cycadeoids) is an extinct order of seed plants that first appeared in the Permian period and became extinct in most areas toward the end of the Cretaceous. Bennettitales are among the most common Mesozoic seed plants ...
, having first become widespread during the preceding 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. Jurassic Bennettitales predominantly belong to the group Williamsoniaceae
''Williamsoniaceae'' is a family within the Bennettitales, an extinct group of seed plants within the Cycadophyta subdivision. Members of this family are believed to have been around two meters tall and with widely serrate leaves along a central ...
, which grew as shrubs and small trees. The Williamsoniaceae are thought to have had a divaricate
Divaricate means branching, or having separation or a degree of separation. The angle between branches is wide.
In botany
In botany, the term is often used to describe the branching pattern of plants. Plants are said to be divaricating when the ...
branching habit, similar to that of living ''Banksia
''Banksia'' is a genus of around 170 species in the plant family Proteaceae. These Australian wildflowers and popular garden plants are easily recognised by their characteristic flower spikes, and fruiting "cones" and heads. ''Banksias'' range ...
'', and adapted to growing in open habitats with poor soil nutrient conditions. Bennettitales exhibit complex, flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...
-like reproductive structures some of which are thought to have been pollinated by insects. Several groups of insects that bear long proboscis, including extinct families such as kalligrammatid
Kalligrammatidae, sometimes known as kalligrammatids or kalligrammatid lacewings, is a family of extinct insects in the order Neuroptera (lacewings) that contains twenty genera and a number of species. The family lived from the Middle Jurassic t ...
lacewings and extant ones such as 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, with the Bennettitales and Nilssoniales, which have cycad-like foliage, being dominant. The Nilssoniales have 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. 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 and phylogenetic stem group age estimates for individual early diverging angiosperm orders, there are no widely accepted Jurassic fossil 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 earliest known Gnetophytes appeared by the end of the Jurassic.
"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. A variety of other Jurassic seed ferns of uncertain placement are known, including ''Pachypteris'' from Europe, which has sometimes been allied with the corystosperms.
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 liana-like seed plants of obscure affinities, first appeared during the Jurassic. Their distribution appears to have been confined to Eastern 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 marine turtles unrelated to modern Sea turtle, sea turtles, are 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 including members of modern clades such as 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. ''Tamaulipasaurus'' from Early Jurassic of Mexico and ''Marmoretta'' from the Middle Jurassic of Britain represents late surviving Lepidosauromorpha, lepidosauromorphs 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 Jurassic 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 Microcleididae, microcleidids and rhomaleosaurids becoming extinct and nearly extinct respectively after the end of the Toarcian with 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. Neosauropoda, Neosauropods such as Macronaria, macronarians and Diplodocoidea, diplodocoids first appeared during the Middle Jurassic, before becoming abundant and globally distributed during the Late Jurassic.
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, with modern crown-group frogs like ''Enneabatrachus'' and ''Rhadinosteus'' appearing by the Late 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.
Mammaliaformes
Mammaliaformes, having originated from cynodonts at the end of the Triassic, diversified extensively during the Jurassic. Important groups of Jurassic Mammaliaformes include Morganucodonta, Docodonta, Eutriconodonta, Dryolestida, Haramiyida and Multituberculata. While most Jurassic mammalaliaformes 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 Volaticotherini[Meng, 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, a group of mammals possibly related to 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
Ray-finned fish (Actinopterygii) were major components of Jurassic freshwater and marine ecosystems. Archaic "Palaeonisciformes, palaeoniscoid" fish, which were common in both marine and freshwater habitats during the preceding Triassic declined during the Jurassic, being largely replaced by more Derived (phylogenetics), derived 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. Stem-group 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 marine stem-teleosts, first appeared in the Early Jurassic and included both tuna-like predatory and filter-feeding forms, the latter included the largest bony fish known to have existed: ''Leedsichthys'', with an estimated maximum length of over 15 metres, known from the late Middle to Late Jurassic.[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, the shark-like Hybodontiformes, hybodonts, which represented the dominant group of Chondrichthyes, chondrichthyians during the preceding Triassic, 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 ray (Batoidea) is ''Antiquaobatis'' from the Pliensbachian of Germany. Jurassic batoids known from complete remains retain a conservative, guitarfish-like morphology. The oldest known Hexanchiformes and carpet sharks (Orectolobiformes) are from the Early Jurassic (Pliensbachian & Toarcian, respectively) of Europe. The oldest known members of the Heterodontiformes, the only living member of which is the bullhead shark (''Heterodontus''), first appeared in the Early Jurassic, with representatives of the living genus appearing during the Late Jurassic. 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 Late Jurassic (Oxfordian–Tithonian) of Europe, which already has a bodyform similar to living members of the order. 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 modern 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, Parasitoid wasps (Apocrita) 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, Embioptera (webspinners), and Raphidioptera (snakeflies).
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 reef
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups.
C ...
s. 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, which constitute the suborder 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.
Bryozoans
Like the preceding Triassic, bryozoan diversity was relatively low compared to the Paleozoic. The vast majority of Jurassic bryozoans are members of Cyclostomatida, which experienced a radiation during the Middle Jurassic, with all Jurassic representatives belonging to the suborders Tubuliporina and List of Cyclostomatida families, Cerioporina. Cheilostomata, the dominant group of modern bryozoans, first appeared during the Late Jurassic.
Molluscs
= 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.
= Cephalopods
=
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.
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.
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. Octopuses likely originated from bottom-dwelling (Benthic zone, benthic) ancestors which lived in shallow environments. ''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.
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