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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 geochronolo ...
and stratigraphic system that spanned from the end of the
Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...
Period million years ago (Mya) to the beginning of the
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
Period, approximately 143.1 Mya. The Jurassic constitutes the second and middle period of the Mesozoic Era as well as the eighth period of the
Phanerozoic Eon The Phanerozoic is the current and the latest of the four geologic eons in the Earth's geologic time scale, covering the time period from 538.8 million years ago to the present. It is the eon during which abundant animal and plant life has ...
and is named after the
Jura Mountains The Jura Mountains ( ) are a sub-alpine mountain range a short distance north of the Western Alps and mainly demarcate a long part of the French–Swiss border. While the Jura range proper (" folded Jura", ) is located in France and Switzerla ...
, where
limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...
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 (TJME), often called the end-Triassic extinction, marks the boundary between the Triassic and Jurassic periods, . It represents one of five major extinction events during the Phanerozoic, profoundly ...
, 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 ...
(CAMP). The beginning of the
Toarcian The Toarcian is, in the International Commission on Stratigraphy, ICS' geologic timescale, an age (geology), age and stage (stratigraphy), stage in the Early Jurassic, Early or Lower Jurassic. It spans the time between 184.2 Megaannum, Ma (million ...
Age started around 183 million years ago and is marked by the
Toarcian Oceanic Anoxic Event The Toarcian extinction event, also called the Pliensbachian-Toarcian extinction event, the Early Toarcian mass extinction, the Early Toarcian palaeoenvironmental crisis, or the Jenkyns Event, was an extinction event that occurred during the early ...
, a global episode of oceanic anoxia,
ocean acidification Ocean acidification is the ongoing decrease in the pH of the Earth's ocean. Between 1950 and 2020, the average pH of the ocean surface fell from approximately 8.15 to 8.05. Carbon dioxide emissions from human activities are the primary cause of ...
, and elevated global temperatures associated with extinctions, likely caused by the eruption of the Karoo-Ferrar large igneous provinces. The end of the Jurassic, however, has no clear, definitive 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 continent, continental blocks or cratons to form a single large landmass. However, some geologists use a different definition, "a grouping of formerly dispersed continents", ...
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 period approximately 335 mi ...
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-graben ...
ing into two landmasses:
Laurasia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pa ...
to the north and
Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
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 Land, also known as dry land, ground, or earth, is the solid terrestrial surface of Earth not submerged by the ocean or another body of water. It makes up 29.2% ...
. Forests grew close to the poles, with large arid expanses in the lower latitudes. On land, the fauna transitioned from the Triassic fauna, dominated jointly by dinosauromorph and
pseudosuchia Pseudosuchia, from Ancient Greek ψεύδος (''pseúdos)'', meaning "false", and σούχος (''soúkhos''), meaning "crocodile" is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely relat ...
n
archosaur Archosauria () or archosaurs () is a clade of diapsid sauropsid tetrapods, with birds and crocodilians being the only extant taxon, extant representatives. Although broadly classified as reptiles, which traditionally exclude birds, the cladistics ...
s, to one dominated by
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...
s alone. The first
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. ...
birds appeared during the Jurassic, evolving from a branch of
theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...
dinosaurs. Other major events include the appearance of the earliest
crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...
s and modern
frog A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order (biology), order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough ski ...
s,
salamander Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All t ...
s and
lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...
s.
Mammaliaformes Mammaliaformes ("mammalian forms") is a clade of synapsid tetrapods that includes the crown group mammals and their closest extinct relatives; the group radiated from earlier probainognathian cynodonts during the Late Triassic. It is defined as ...
, one of the few
cynodont Cynodontia () is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 Megaannum, mya), and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extin ...
lineages to survive the end of the Triassic, continued to diversify throughout the period, with the Jurassic seeing the emergence of the first
crown 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 ...
mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
s. Crocodylomorphs made the transition from a terrestrial to an aquatic life. The oceans were inhabited by marine reptiles such as
ichthyosaur Ichthyosauria is an order of large extinct marine reptiles sometimes referred to as "ichthyosaurs", although the term is also used for wider clades in which the order resides. Ichthyosaurians thrived during much of the Mesozoic era; based on fo ...
s and
plesiosaur The Plesiosauria or plesiosaurs are an Order (biology), order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared in the latest Triassic Period (geology), Period, possibly in the Rhaetian st ...
s, while
pterosaur Pterosaurs are 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 million to 66 million years ago). Pterosaurs are the earli ...
s were the dominant flying
vertebrates Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...
. Modern sharks and rays first appeared and diversified during the period, while the first known crown-group
teleost Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of f ...
fish (the dominant group of modern fish) appeared near the end of the period. The flora was dominated by
fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...
s and
gymnosperm The gymnosperms ( ; ) are a group of woody, perennial Seed plant, seed-producing plants, typically lacking the protective outer covering which surrounds the seeds in flowering plants, that include Pinophyta, conifers, cycads, Ginkgo, and gnetoph ...
s, including
conifer Conifers () are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a sin ...
s, of which many modern groups made their first appearance during the period, as well as other groups like the extinct Bennettitales.


Etymology and history

The chronostratigraphic term "Jurassic" is linked to the
Jura Mountains The Jura Mountains ( ) are a sub-alpine mountain range a short distance north of the Western Alps and mainly demarcate a long part of the French–Swiss border. While the Jura range proper (" folded Jura", ) is located in France and Switzerla ...
, 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 aris ...
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 Foot ...
root via
Gaulish Gaulish is an extinct 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 languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
as a name of a place and evolved into ''Juria'' and finally ''Jura''. During a tour of the region in 1795, German
naturalist Natural history is a domain of inquiry involving organisms, including animals, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history is cal ...
Alexander von Humboldt Friedrich Wilhelm Heinrich Alexander von Humboldt (14 September 1769 – 6 May 1859) was a German polymath, geographer, natural history, naturalist, List of explorers, explorer, and proponent of Romanticism, Romantic philosophy and Romanticism ...
recognized
carbonate A carbonate is a salt of carbonic acid, (), 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 group ...
deposits within the Jura Mountains as geologically distinct from the
Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...
aged
Muschelkalk The Muschelkalk (German for "shell-bearing limestone"; ) is a sequence of sedimentary rock, sedimentary rock strata (a lithostratigraphy, lithostratigraphic unit) in the geology of central and western Europe. It has a Middle Triassic (240 to 230 m ...
of southern
Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...
, but he erroneously concluded that they were older. He then named them ('Jura limestone') in 1799. In 1829, the French naturalist
Alexandre Brongniart Alexandre Brongniart (5 February 17707 October 1847) was a French chemist, mineralogist, geologist, paleontologist, and zoologist, who collaborated with Georges Cuvier on a study of the geology of the region around Paris. Observing fossil conten ...
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 in 1839 established the three-fold division of the Jurassic, originally named from oldest to the youngest: the Black Jurassic, Brown Jurassic, and White Jurassic. The term " Lias" had previously been used for strata of equivalent age to the Black Jurassic in England by William Conybeare and William Phillips in 1822. William Phillips, the geologist, worked with William Conybeare to find out more about the Black Jurassic in England. The French
palaeontologist Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...
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 Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...
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 in 1858 divided the three series of von Buch in the
Swabian Jura The Swabian Jura ( , more rarely ), sometimes also named Swabian Alps in English, is a mountain range in Baden-Württemberg, Germany, extending from southwest to northeast and in width. It is named after the region of Swabia. It is part of th ...
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. i ...
in his studies between 1856 and 1858 altered d'Orbigny's original scheme and further subdivided the stages into biostratigraphic zones, based primarily on ammonites. Most of the modern stages of the Jurassic were formalized at the Colloque du Jurassique à Luxembourg in 1962.


Geology

The Jurassic Period is divided into three epochs: Early, Middle, and Late. Similarly, in
stratigraphy Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithost ...
, the Jurassic is divided into the Lower Jurassic,
Middle Jurassic The Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 161.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relativel ...
, 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 i ...
. 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: lithost ...
set of units called stages, 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 unofficially referred to as the International Stratigraphic Commission, is a daughter or major subcommittee grade scientific organization that concerns itself with stratigraphy, strati ...
(ICS) ratify global stages based on a
Global Boundary Stratotype Section and Point A Global Boundary Stratotype Section and Point (GSSP), sometimes referred to as a golden spike, is an internationally agreed upon reference point on a stratigraphic section which defines the lower boundary of a stage on the geologic time scale. ...
(GSSP) from a single formation (a stratotype) identifying the lower boundary of the stage. The ages of the Jurassic from youngest to oldest are as follows:


Stratigraphy

Jurassic stratigraphy is primarily based on the use of ammonites as
index fossils Biostratigraphy is the branch of stratigraphy 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 Biology ...
. 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 partic ...
of specific ammonite
taxa In biology, a taxon (back-formation from ''taxonomy''; : 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 name and ...
is used to mark the beginnings of stages, as well as smaller timespans within stages, referred to as "ammonite zones"; these, in turn, are also sometimes subdivided further into subzones. Global stratigraphy is based on standard European ammonite zones, with other regions being calibrated to the European successions.


Early Jurassic

The oldest part of the Jurassic Period has historically been referred to as the Lias or Liassic, roughly equivalent in extent to the Early Jurassic, but also including part of the preceding
Rhaetian The Rhaetian is the latest age (geology), age of the Triassic period (geology), Period (in geochronology) or the uppermost stage (stratigraphy), stage of the Triassic system (stratigraphy), System (in chronostratigraphy). It was preceded by the N ...
. The Hettangian Stage was named by Swiss palaeontologist Eugène Renevier in 1864 after Hettange-Grande in north-eastern France. The GSSP for the base of the Hettangian is located at the Kuhjoch Pass,
Karwendel Mountains The Karwendel is the largest mountain range of the Northern Limestone Alps. It is located on the Austria–Germany border. The major part belongs to the Austrian federal state of Tyrol, while the adjacent area in the north is part of Bavaria, ...
, Northern Calcareous Alps, Austria; it was ratified in 2010. The beginning of the Hettangian, and thus the Jurassic as a whole, is marked by the
first appearance In 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 interest in fir ...
of the ammonite '' Psiloceras spelae tirolicum'' in the Kendlbach Formation 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 Communes of France, commune of the Côte-d'Or Departments of France, department in eastern France. The politician François Patriat, the engineers Edmé Régnier L'Aîné (1751–1825) and Émile Dorand (1866-1922), and th ...
, near
Dijon Dijon (, ; ; in Burgundian language (Oïl), Burgundian: ''Digion'') is a city in and the Prefectures in France, prefecture of the Côte-d'Or Departments of France, department and of the Bourgogne-Franche-Comté Regions of France, region in eas ...
. 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, 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 village at Black Ball Camp are an Iron Age ...
, 6 kilometres east of Watchet,
Somerset Somerset ( , ), Archaism, archaically Somersetshire ( , , ) is a Ceremonial counties of England, ceremonial county in South West England. It is bordered by the Bristol Channel, Gloucestershire, and Bristol to the north, Wiltshire to the east ...
,
England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...
, within the
Blue Lias The Blue Lias is a formation (stratigraphy), 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 ...
, and was ratified in 2000. The beginning of the Sinemurian is defined by the first appearance of the ammonite '' Vermiceras quantoxense.'' Albert Oppel in 1858 named the Pliensbachian Stage after the hamlet of Pliensbach in the community of
Zell unter Aichelberg Zell unter Aichelberg is a municipality in the district of Göppingen (district), Göppingen in Baden-Württemberg in southern Germany. Geographical location Between Stuttgart and Ulm, on the western edge of the district Göppingen, lies the muni ...
in the
Swabian Alb The Swabian Jura ( , more rarely ), sometimes also named Swabian Alps in English, is a mountain range in Baden-Württemberg, Germany, extending from southwest to northeast and in width. It is named after the region of Swabia. It is part of th ...
, near
Stuttgart Stuttgart (; ; Swabian German, Swabian: ; Alemannic German, Alemannic: ; Italian language, Italian: ; ) is the capital city, capital and List of cities in Baden-Württemberg by population, largest city of the States of Germany, German state of ...
, Germany. The GSSP for the base of the Pliensbachian is found at the Wine Haven locality in Robin Hood's Bay,
Yorkshire Yorkshire ( ) is an area of Northern England which was History of Yorkshire, historically a county. Despite no longer being used for administration, Yorkshire retains a strong regional identity. The county was named after its county town, the ...
, England, in the Redcar Mudstone Formation, and was ratified in 2005. The beginning of the Pliensbachian is defined by the first appearance of the ammonite '' Bifericeras donovani''. The village Thouars (Latin: ''Toarcium''), just south of
Saumur Saumur () is a Communes of France, commune in the Maine-et-Loire Departments of France, department in western France. The town is located between the Loire and Thouet rivers, and is surrounded by the vineyards of Saumur itself, Chinon, Bourgu ...
in the Loire Valley of
France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...
, 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 (), officially the City of Peniche (), is a seaside municipality and a city in the Oeste region, in the historical province of Estremadura, and in the Leiria District. It has 26,431 inhabitants, in an area of 77.55 km2. The city its ...
, and was ratified in 2014. The boundary is defined by the first appearance of ammonites belonging to the subgenus '' Dactylioceras'' (''Eodactylites'')''.''


Middle Jurassic

The Aalenian is named after the city of
Aalen Aalen (; Swabian German, Swabian: ''Oole'') is a town located in the eastern part of the German state of Baden-Württemberg, about east of Stuttgart and north of Ulm. It is the seat of the Ostalbkreis district and is its largest town. It is ...
in Germany. The Aalenian was defined by Swiss geologist Karl Mayer-Eymar in 1864. The lower boundary was originally between the dark clays of the Black Jurassic and the overlying clayey sandstone and ferruginous oolite of the Brown Jurassic sequences of southwestern Germany. The GSSP for the base of the Aalenian is located at Fuentelsaz in the Iberian range 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. Guadalajara lies on the central part of the Iberian Peninsula at roughly me ...
, 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 Bayeux (, ; ) is a commune in the Calvados department in Normandy in northwestern France. Bayeux is the home of the Bayeux Tapestry, which depicts the events leading up to the Norman Conquest of England in 1066. It is also known as the fir ...
(Latin: ''Bajoce'') in Normandy, France. The GSSP for the base of the Bajocian is located in the Murtinheira section at Cabo Mondego, Portugal; it was ratified in 1997. The base of the Bajocian is defined by the first appearance of the ammonite '' Hyperlioceras mundum.'' The Bathonian is named after the city of
Bath Bath may refer to: * Bathing, immersion in a fluid ** Bathtub, a large open container for water, in which a person may wash their body ** Public bathing, a public place where people bathe * Thermae, ancient Roman public bathing facilities Plac ...
, 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 to Wilts) is a ceremonial county in South West England. It borders Gloucestershire to the north, Oxfordshire to the north-east, Berkshire to the east, Hampshire to the south-east, Dorset to the south, and Somerset to ...
, England, and was named by Alcide d'Orbigny in 1852, originally the base at the contact between the Forest Marble Formation and the Cornbrash Formation. However, this boundary was later found to be within the upper part of the Bathonian. The base of the Callovian does not yet have a certified GSSP. The working definition for the base of the Callovian is the first appearance of ammonites belonging to the genus '' Kepplerites.''


Late Jurassic

The Oxfordian is named after the city of
Oxford Oxford () is a City status in the United Kingdom, cathedral city and non-metropolitan district in Oxfordshire, England, of which it is the county town. The city is home to the University of Oxford, the List of oldest universities in continuou ...
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 and as far north as Yorkshire. The Oxford Clay Formation dates to the Jurassic, specific ...
. 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 on the coast of
Dorset Dorset ( ; Archaism, archaically: Dorsetshire , ) is a Ceremonial counties of England, ceremonial county in South West England. It is bordered by Somerset to the north-west, Wiltshire to the north and the north-east, Hampshire to the east, t ...
, 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 rock, 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 (geology), form ...
. The GSSP for the base of the Kimmeridgian is the Flodigarry section at Staffin Bay on the
Isle of Skye The Isle of Skye, or simply Skye, is the largest and northernmost of the major islands in the Inner Hebrides of Scotland. The island's peninsulas radiate from a mountainous hub dominated by the Cuillin, the rocky slopes of which provide some of ...
, Scotland, which was ratified in 2021. The boundary is defined by the first appearance of ammonites marking the boreal Bauhini Zone and the subboreal Baylei Zone. The Tithonian was introduced in scientific literature by Albert Oppel in 1865. The name Tithonian is unusual in geological stage names because it is derived from
Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...
rather than a place name.
Tithonus In Greek mythology, Tithonus ( or ; ) was the lover of Eos, Goddess of the Dawn. He was a prince of Troy, the son of King Laomedon by the Naiad Strymo (). The mythology reflected by the fifth-century vase-painters of Athens envisaged Tithonus a ...
was the son of
Laomedon In Greek mythology, Laomedon (; , ''Lāomédōn'', "ruler of the people") was a Troy, Trojan king, son of Ilus (son of Tros), Ilus and thus nephew of Ganymede (mythology), Ganymede and Assaracus. Laomedon was variously identified with differe ...
of
Troy Troy (/; ; ) or Ilion (; ) was an ancient city located in present-day Hisarlik, Turkey. It is best known as the setting for the Greek mythology, Greek myth of the Trojan War. The archaeological site is open to the public as a tourist destina ...
and fell in love with
Eos In ancient Greek mythology and Ancient Greek religion, religion, Eos (; Ionic Greek, Ionic and Homeric Greek ''Ēṓs'', Attic Greek, Attic ''Héōs'', "dawn", or ; Aeolic Greek, Aeolic ''Aúōs'', Doric Greek, Doric ''Āṓs'') is the go ...
, the Greek goddess of
dawn Dawn is the time that marks the beginning of twilight before sunrise. It is recognized by the diffuse sky radiation, appearance of indirect sunlight being Rayleigh scattering, scattered in Earth's atmosphere, when the centre of the Sun's disc ha ...
. 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 distinct nuclear species (or ''nuclides'') of the same chemical element. They have the same atomic number (number of protons in their Atomic nucleus, nuclei) and position in the periodic table (and hence belong to the same chemica ...
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 planktonic organisms with urn-shaped, calcitic t ...
s, an enigmatic group of
plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...
ic
protist A protist ( ) or protoctist is any eukaryotic organism that is not an animal, land plant, or fungus. Protists do not form a natural group, or clade, but are a paraphyletic grouping of all descendants of the last eukaryotic common ancest ...
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,'' 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 a sedimentary rock which has generated hydrocarbons or which has the potential to generate hydrocarbons. Source rocks are one of the necessary elements of a working petroleum system. They are organic-rich sedim ...
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 ...
. 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.


Impact structures

Major impact structures include the Morokweng impact structure, 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, 40 kilometres in diameter, buried beneath
Nizhny Novgorod Oblast Nizhny Novgorod Oblast () is a federal subjects of Russia, federal subject of Russia (an oblast). Its administrative center is the types of inhabited localities in Russia, city of Nizhny Novgorod. It has a population of 3,119,115 as of the 2021 Ru ...
in western Russia. The impact has been dated to the Sinemurian, 195.9 ± 1.0 Ma.


Paleogeography and tectonics

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 continent, continental blocks or cratons to form a single large landmass. However, some geologists use a different definition, "a grouping of formerly dispersed continents", ...
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 period approximately 335 mi ...
, which during the Early Jurassic began to break up into northern supercontinent
Laurasia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pa ...
and the southern supercontinent
Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
. 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 borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...
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 vast superocean that encompassed planet Earth and surrounded the supercontinent Pangaea, the latest in a series of supercontinent ...
, with the
Tethys Ocean The Tethys Ocean ( ; ), also called the Tethys Sea or the Neo-Tethys, was a prehistoric ocean during much of the Mesozoic Era and early-mid Cenozoic Era. It was the predecessor to the modern Indian Ocean, the Mediterranean Sea, and the Eurasia ...
between Gondwana and Asia. At the end of the Triassic, there was a
marine transgression A marine transgression is a geologic event where sea level rises relative to the land and the shoreline moves toward higher ground, resulting in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling with water ...
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 The Baltic Shield (or Fennoscandian Shield) is a segment of the Earth's crust belonging to the East European craton, East European Craton, representing a large part of Fennoscandia, northwestern Russia and the northern Baltic Sea. It is composed ...
and
Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...
several hundred kilometers wide. During the Callovian, the Turgai Epicontinental Sea formed, creating a marine barrier between Europe and Asia. 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 approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...
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 Late Jurassic to Early Cretaceous approximately 155 Ma to 145 Ma. Throughout the duration of this orogeny there were at least two different kinds of orogenic process ...
, which began during the Triassic, the Cache Creek Ocean closed, and various
terrane In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its d ...
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. During the Early Jurassic, around 190 million years ago, the Pacific Plate originated at the triple junction of the Farallon, Phoenix, and
Izanagi Izanagi (イザナギ/伊邪那岐/伊弉諾) or Izanaki (イザナキ), formally referred to with a divine honorific as , is the creator deity (''kami'') of both creation and life in Japanese mythology. He and his sister-wife Izanami are the ...
tectonic plates Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed durin ...
, 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 (geology), fault along a plate boundary where the motion (physics), motion is predominantly Horizontal plane, horizontal. It ends abruptly where it connects to another plate boundary, either an ...
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 Seaway, a shallow epicontinental sea, covered much of northwest North America.The
eustatic sea level The eustatic sea level (from Greek εὖ ''eû'', "good" and στάσις ''stásis'', "standing") 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, inc ...
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 An aragonite sea contains aragonite and high-magnesium calcite as the primary inorganic calcium carbonate precipitates. The reason lies in the highly hydrated divalent ion, the second most abundant cation in seawater after , known to be a stron ...
to a calcite sea chemistry, favouring the dissolution of
aragonite Aragonite is a carbonate mineral and one of the three most common naturally occurring crystal forms of calcium carbonate (), the others being calcite and vaterite. It is formed by biological and physical processes, including precipitation fr ...
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 that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...
during the Middle Jurassic profoundly altered ocean chemistry, with the deposition of biomineralized plankton on the ocean floor acting as a buffer against large CO2 emissions.


Climate

The climate of the Jurassic was generally warmer than that of present, by around , with atmospheric carbon dioxide likely about four times higher. Intermittent "cold snap" intervals are known to have occurred during this time period, however, interrupting the otherwise warm greenhouse climate. 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 pyroclasts, pyroclastic beds. They range in size from small pebbles to boulders. The critical distinguishing feature is that there is eviden ...
s and glendonites in northeastern
Siberia Siberia ( ; , ) is an extensive geographical region comprising all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has formed a part of the sovereign territory of Russia and its predecessor states ...
during the Early to Middle Jurassic indicate cold winters.Alt URL
/ref> The ocean depths were likely 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 group ...
s grew 10° of latitude further north and south. The
Intertropical Convergence Zone The Intertropical Convergence Zone (ITCZ , or ICZ), known by sailors as the doldrums or the calms because of its monotonous windless weather, is the area where the northeast and the southeast trade winds converge. It encircles Earth near the t ...
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 dense and warm rainforests with high rainfall typically found between 10° north and south of the Equator. They are a subset of the tropical forest biome that occurs roughly within the 28° latitudes (in the torrid zo ...
and
tundra In physical geography, a tundra () is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. There are three regions and associated types of tundra: #Arctic, Arctic, Alpine tundra, Alpine, and #Antarctic ...
biomes are likely to have been rare or absent. The Jurassic also witnessed the decline of the Pangaean megamonsoon that had characterised the preceding Permian and Triassic periods. Variation in the frequency of
wildfire A wildfire, forest fire, or a bushfire is an unplanned and uncontrolled fire in an area of Combustibility and flammability, combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identified as a ...
activity in the Jurassic was governed by the 405 kyr
eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...
cycle. Thanks to the breakup of Pangaea, the hydrological cycle during the Jurassic was significantly enhanced. 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 both the early Pliensbachian and the latest Pliensbachian. There was a spike in global temperatures of around 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 format ...
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 , 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 .The Toarcian Warm Interval is followed by the Middle Jurassic Cool Interval (MJCI) between 174 and 164 million years ago, which may have been punctuated by brief, ephemeral icehouse intervals. During the Aalenian, precessionally forced climatic changes dictated peatland wildfire magnitude and frequency. The European climate appears to have become noticeably more humid at the Aalenian-Bajocian boundary but then became more arid during the middle Bajocian. A transient ice age possibly occurred in the late Bajocian. The Callovian-Oxfordian boundary at the end of the MJCI witnessed particularly notable global cooling, potentially even an ice age. This is followed by the Kimmeridgian Warm Interval (KWI) between 164 and 150 million years ago. Based on fossil
wood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...
distribution, this was one of the wettest intervals of the Jurassic. The Pangaean 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. A prominent drop in temperatures occurred during the Tithonian, known as the Early Tithonian Cooling Event (ETCE). The end of the Jurassic was marked by the Tithonian–early Barremian Cool Interval (TBCI), beginning 150 million years ago and continuing into the
Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...
.


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 14 known isotopes, from to as well as , of which only and are stable. The longest-lived radioisotope is , with a half-life of years. This is also the only carbon radioisotope found in nature, as trace quantities are formed ...
excursion, as well as the deposition of black
shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...
s 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 (4CH4·23H2O), 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 a ...
s. This likely accelerated the
hydrological cycle The water cycle (or hydrologic cycle or hydrological cycle) is a biogeochemical cycle that involves the continuous movement of water on, above and below the surface of the Earth across different reservoirs. The mass of water on Earth remains fai ...
and increased
silicate weathering 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 also used for ...
, 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 (biology), class of the crustacean, Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 33,000 species (only 13,000 of which are extant taxon, extant) have been identified,Brandão, S.N.; Antoni ...
s,
foraminifera Foraminifera ( ; Latin for "hole bearers"; informally called "forams") are unicellular organism, single-celled organisms, members of a phylum or class (biology), class of Rhizarian protists characterized by streaming granular Ectoplasm (cell bio ...
,
bivalves Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed by a calcified exoskeleton consis ...
,
cnidaria Cnidaria ( ) is a phylum under kingdom Animalia containing over 11,000 species of aquatic invertebrates found both in fresh water, freshwater and marine environments (predominantly the latter), including jellyfish, hydroid (zoology), hydroids, ...
ns, and especially brachiopods, 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 A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...
, probably three times the size of modern-day
Lake Superior Lake Superior is the largest freshwater lake in the world by surface areaThe Caspian Sea is the largest lake, but is saline, not freshwater. Lake Michigan–Huron has a larger combined surface area than Superior, but is normally considered tw ...
, represented by the Da'anzhai Member of the Ziliujing Formation. 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 ongoing decrease in the pH of the Earth's ocean. Between 1950 and 2020, the average pH of the ocean surface fell from approximately 8.15 to 8.05. Carbon dioxide emissions from human activities are the primary cause of ...
is the probable cause of the collapse of carbonate production. Additionally, anoxic conditions were exacerbated by enhanced recycling of
phosphorus Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...
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 Ecological succession is the process of how species compositions change in an Community (ecology), ecological community over time. The two main categories of ecological succession are primary succession and secondary succession. Primary successi ...
. At the end of the Triassic, the
Peltaspermaceae The Peltaspermales are an extinct order (biology), order of seed plants, often considered "Pteridospermatophyta, seed ferns". They span from the Late Carboniferous to the Early Jurassic or the Jurassic-Cretaceous Boundary. It includes at least on ...
became extinct in most parts of the world, with ''
Lepidopteris ''Lepidopteris'' ("scaly fern") is a form classification, form genus for leaves of Peltaspermaceae, an extinct family of seed plants, which lived from around 260 to 190 million years ago, from the Late Permian to Early Jurassic. Fossils of the ge ...
'' persisting into the Early Jurassic in Patagonia. '' Dicroidium'', a corystosperm 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 Early Jurassic.


Floral composition


Conifers

Conifer Conifers () are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a sin ...
s 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 ''Araucaria'' (; original pronunciation: .ɾawˈka. ɾja is a genus of evergreen coniferous trees in the family Araucariaceae. While today they are largely confined to the Southern Hemisphere, during the Jurassic and Cretaceous they were glo ...
'' were widespread across both hemispheres by the Middle Jurassic. Also abundant during the Jurassic is the extinct family Cheirolepidiaceae, often recognised through their highly distinctive ''Classopolis'' pollen. Jurassic representatives include the pollen cone ''Classostrobus'' and the seed cone '' Pararaucaria''. Araucarian and Cheirolepidiaceae conifers often occur in association. The oldest definitive record of the cypress family (
Cupressaceae Cupressaceae or the cypress family is a family of conifers. The family includes 27–30 genera (17 monotypic), which include the junipers and redwoods, with about 130–140 species in total. They are monoecious, subdioecious or (rarely) dioecio ...
) 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'' and '' Cunninghamia.'' By the Middle to Late Jurassic Cupressaceae were abundant in warm temperate–tropical regions of the Northern Hemisphere, most abundantly represented by the genus '' Elatides''. The Jurassic also saw the first appearances of some modern genera of cypresses, such as '' Sequoia''. 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 Cedrus, cedars, firs, Tsuga, hemlocks, Pinyon_pine, piñons, larches, pines and spruces. The family is incl ...
), were widely distributed across Eurasia during the Jurassic. The oldest unambiguous record of Pinaceae is the
pine cone A conifer cone, or in formal botanical usage a strobilus, : strobili, is a seed-bearing organ on gymnosperm plants, especially in conifers and cycads. They are usually woody and variously conic, cylindrical, ovoid, to globular, and have scal ...
'' Eathiestrobus'', known from the Late Jurassic (Kimmeridgian) of Scotland, which remains the only known unequivocal fossil of the group before the Cretaceous. Despite being the earliest known member of the Pinaceae, ''Eathiestrobus'' appears to be a member of the pinoid
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
of the family, suggesting that the initial diversification of Pinaceae occurred earlier than has been found in the fossil record. The earliest record of the yew family (
Taxaceae Taxaceae (), commonly called the yew family, is a coniferous family (biology), family which includes six Extant taxon, extant and two extinct genera, and about 30 species of plants, or in older interpretations three genera and 7 to 12 species. ...
) is '' Palaeotaxus rediviva'', from the Hettangian of Sweden, suggested to be closely related to the living '' Austrotaxus'', while '' Marskea jurassica'' from the Middle Jurassic of Yorkshire, England and material from the Callovian–Oxfordian Daohugou Bed in China are thought to be closely related to ''
Amentotaxus ''Amentotaxus'' is a genus of Pinophyta, 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 (ecology), endemic to subtr ...
,'' with the latter material assigned to the modern genus, indicating that Taxaceae had substantially diversified by the end of the Jurassic. The oldest unambiguous members of
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 Pres ...
are known from the Jurassic, found across both hemispheres, including '' Scarburgia'' and '' Harrisiocarpus'' from the Middle Jurassic of England, as well as unnamed species from the Middle-Late Jurassic of Patagonia. During the Early Jurassic, the flora of the mid-latitudes of Eastern Asia were dominated by the extinct deciduous broad leafed conifer '' Podozamites,'' which appears to not be closely related to any living family of conifer. Its range extended northwards into polar latitudes of Siberia and then contracted northward in the Middle to Late Jurassic, corresponding to the increasing aridity of the region.


Ginkgoales

Ginkgoales Ginkgoales are a gymnosperm Order (biology), order containing only one Neontology, extant species: ''Ginkgo biloba'', the ginkgo tree. The order has a long fossil record extending back to the Early Permian around 300 million years ago from fossi ...
, 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 gymnosperm tree native to East Asia. It is the last living species in the order Ginkgoales, which first appeared over 290 million year ...
'', 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, assigned to the gymnosperms. The scientific name is also used as the English common name. The order to which the genus belongs, Ginkgoales, first appeared in the Permian, , and ''Ginkgo'' is n ...
,'' represented by
ovulate Ovulation is an important part of the menstrual cycle in female vertebrates where the egg cells are released from the ovaries as part of the ovarian cycle. In female humans ovulation typically occurs near the midpoint in the menstrual cycle and ...
and pollen organs similar to those of the modern species, are known from the Middle Jurassic in the Northern Hemisphere. Several other lineages of ginkgoaleans are known from Jurassic rocks, including '' Yimaia'', '' Grenana'', '' Nagrenia'' and ''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'' from the Jurassic of Asia has strap-shaped ginkgo-like leaves with highly distinct reproductive structures with similarities to those of peltasperm and corystosperm seed ferns, has been suggested to be a member of Ginkgoales ''sensu lato.''


Bennettitales

Bennettitales, 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
stoma In botany, a stoma (: stomata, from Greek language, Greek ''στόμα'', "mouth"), also called a stomate (: stomates), is a pore found in the Epidermis (botany), epidermis of leaves, stems, and other organs, that controls the rate of gas exc ...
ta, and the two groups are not thought to be closely related. Jurassic Bennettitales predominantly belong to the group Williamsoniaceae, which grew as shrubs and small trees. The Williamsoniaceae are thought to have had a divaricate branching habit, similar to that of living ''
Banksia ''Banksia'' is a genus of around 170 species of flowering plants in the family Proteaceae. These Australian wildflowers and popular garden plants are easily recognised by their characteristic flower spikes, and woody fruiting "cones" and head ...
'', and adapted to growing in open habitats with poor soil nutrient conditions. Bennettitales exhibit complex,
flower Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...
-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 (biology), family of extinct insects in the order Neuroptera (lacewings) that contains twenty genera and a number of species. The family lived from the ...
lacewings and extant ones such as acrocerid flies, are suggested to have been pollinators of bennettitales, feeding on
nectar Nectar is a viscous, sugar-rich liquid produced by Plant, plants in glands called nectaries, either within the flowers with which it attracts pollination, pollinating animals, or by extrafloral nectaries, which provide a nutrient source to an ...
produced by bennettitalean cones.


Cycads

Cycad Cycads are seed plants that typically have a stout and woody (ligneous) trunk (botany), trunk with a crown (botany), crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants o ...
s 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 ''Nilssonia'' is a genus of fossil foliage traditionally assigned to the Cycadophyta either in Cycadales or their own order Nilssoniales, though the relationships of this genus with the Cycadales have been put into question on chemical grounds. ...
, 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.'''' The relationships of most Mesozoic cycads to living groups are ambiguous, with no Jurassic cycads belonging to either of the two modern groups of cycads, though some Jurassic cycads possibly represent
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. ...
relatives of modern Cycadaceae, like the leaf genus '' Paracycas'' known Europe, and Zamiaceae, like some European species of the leaf genus '' Pseudoctenis''. Also widespread during the Jurassic was the extinct '' Ctenis'' lineage, which appears to be distantly related to modern cycads. Modern cycads are pollinated by beetles, and such an association is thought to have formed by the Early Jurassic.


Other seed plants

Although there have been several claimed records, there are no widely accepted Jurassic fossil records of
flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...
s, which make up 90% of living plant species, and fossil evidence suggests that the group diversified during the following Cretaceous. The earliest known gnetophytes, one of the four main living groups of
gymnosperm The gymnosperms ( ; ) are a group of woody, perennial Seed plant, seed-producing plants, typically lacking the protective outer covering which surrounds the seeds in flowering plants, that include Pinophyta, conifers, cycads, Ginkgo, and gnetoph ...
s, appeared by the end of the Jurassic, with the oldest unequivocal gnetophyte being the seed '' Dayvaultia'' from the Late Jurassic of North America. "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
seed plant A seed plant or spermatophyte (; New Latin ''spermat-'' and Greek ' (phytón), plant), also known as a phanerogam (taxon Phanerogamae) or a phaenogam (taxon Phaenogamae), is any plant that produces seeds. It is a category of embryophyte (i.e. la ...
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 A berry is a small, pulpy, and often edible fruit. Typically, berries are juicy, rounded, brightly colored, sweet, sour or tart, and do not have a stone or pit although many pips or seeds may be present. Common examples of berries in the cul ...
-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. Corystosperm-aligned seed ferns, such as '' Pachypteris'' and '' Komlopteris'' were widespread across both hemispheres during the Jurassic. 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 A liana is a long-Plant stem, stemmed Woody plant, woody vine that is rooted in the soil at ground level and uses trees, as well as other means of vertical support, to climb up to the Canopy (biology), canopy in search of direct sunlight. T ...
-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 The Order (biology), order Polypodiales encompasses the major lineages of polypod ferns, which comprise more than 80% of today's fern species. They are found in many parts of the world including Tropics, tropical, semitropical and Temperate clima ...
, 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 Herbaceous plants are vascular plants that have no persistent woody stems above ground. This broad category of plants includes many perennials, and nearly all annuals and biennials. Definitions of "herb" and "herbaceous" The fourth edition of ...
fern genus '' Coniopteris,'' historically interpreted as a close relative of
tree fern Tree ferns are arborescent (tree-like) ferns that grow with a trunk (botany), trunk elevating the fronds above ground level, making them trees. Many extant tree ferns are members of the order Cyatheales, to which belong the families Cyatheaceae ( ...
s of the family Dicksoniaceae, has recently been reinterpreted as an early relative of the group. The
Cyatheales The order Cyatheales, which includes most tree ferns, is a Taxonomy (biology), taxonomic order of the fern class, Polypodiopsida. No clear morphology (biology), morphological features characterize all of the Cyatheales, but DNA sequence data indi ...
, 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 The Cyatheaceae are a family of ferns, the scaly tree ferns, one of eight families in the order Cyatheales in the Pteridophyte Phylogeny Group classification of 2016 (PPG I). Alternatively, the family may defined much more broadly (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 horsetails of the genus ''
Equisetum ''Equisetum'' (; horsetail) is the only living genus in Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds. ''Equisetum'' is a "living fossil", the only living genus of the entire subclass Equisetidae, which ...
'' 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.
Silicified In geology, silicification is a process in which silica-rich fluids seep into the voids of Earth materials, e.g., rocks, wood, bones, shells, and replace the original materials with silica (SiO2). Silica is a naturally existing and abundant com ...
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

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 Splachnaceae is a family (biology), family of mosses, containing around 70 species in 6 genera. Around half of those species are entomophily, entomophilous, using insects to disperse their spores, a characteristic found in no other seedless land ...
, 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 Polytrichaceae is a common family of mosses. Members of this family tend to be larger than other mosses, with the larger species occurring in particularly moist habitats. The leaves have specialized sheaths at the base and a midrib that bears pho ...
or
Timmiellaceae Timmiellaceae is a family (biology), family of Peristome#In mosses, haplolepideous mosses (Dicranidae). It contains two genera, ''Luisierella'' and ''Timmiella'', that were formerly place in family Pottiaceae. Taxonomy The genera ''Luisierella' ...
. The liverwort '' Pellites hamiensis'' from the Middle Jurassic Xishanyao Formation of China is the oldest record of the family Pelliaceae. ''Pallaviciniites sandaolingensis'' from the same deposit is thought to belong to the subclass Pallaviciniineae within the Pallaviciniales. '' Ricciopsis sandaolingensis'', also from the same deposit, is the only Jurassic record of Ricciaceae.


Fauna


Dinosaurs

Dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...
s, 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 theropods belonging to Neotheropoda first appeared in the Late Triassic. Basal neotheropods, such as coelophysoids and 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 Toothlessness or edentulism is the condition of having no teeth. In organisms that naturally have teeth, it is the result of tooth loss. Organisms that never possessed teeth can also be described as edentulous. Examples are the members of the fo ...
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 Megalosauridae is a monophyletic Family (taxonomy), family of Carnivore, carnivorous theropod dinosaurs within the group Megalosauroidea. Appearing in the Middle Jurassic, megalosaurids were among the first major radiation of large theropod dino ...
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. Coelurosaurs first appeared during the Middle Jurassic, including early 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 alvarezsaurs, however, this has been questioned. 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 troodontids is suggested to be '' Hesperornithoides'' from the Late Jurassic of North America. Tooth remains suggested to represent those of
dromaeosaurs Dromaeosauridae () is a family (biology), family of feathered coelurosaurian Theropoda, theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous period (geology), Period. The name Drom ...
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 qi'', a scansoriopterygid from the Middle to Late Jurassic of China


= Birds

= The earliest avialans, which include birds and their ancestors, appear during the Middle to Late Jurassic, definitively represented by ''
Archaeopteryx ''Archaeopteryx'' (; ), sometimes referred to by its German name, "" ( ''Primeval Bird'') is a genus of bird-like dinosaurs. The name derives from the ancient Greek (''archaîos''), meaning "ancient", and (''ptéryx''), meaning "feather" ...
'' from the Late Jurassic of Germany. Avialans belong to the clade Paraves within Coelurosauria, which also includes dromaeosaurs and troodontids. The
Anchiornithidae Anchiornithidae is a family of small Paraves, paravian dinosaurs. Anchiornithids have been classified at varying positions in the paravian tree, with some scientists classifying them as a distinct family, a basal subfamily of Troodontidae, membe ...
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
ornithischia Ornithischia () is an extinct clade of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek ...
ns appear during the Early Jurassic, represented by basal ornithischians like ''
Lesothosaurus ''Lesothosaurus'' is a Monotypic taxon, monospecific genus of ornithischian dinosaur that lived during the Early Jurassic in what is now South Africa and Lesotho. It was named by paleontologist Peter Galton in 1978, the name meaning "lizard from L ...
'', heterodontosaurids, and early members of
Thyreophora Thyreophora ("shield bearers", often known simply as "armored dinosaurs") is a group of armored ornithischian dinosaurs that lived from the Early Jurassic until the end of the Cretaceous. Thyreophorans are characterized by the presence of bod ...
. The earliest members of
Ankylosauria Ankylosauria is a group of herbivorous dinosaurs of the clade Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short, powerful limbs ...
and
Stegosauria Stegosauria is a group of Herbivore, herbivorous ornithischian dinosaurs that lived during the Jurassic and early Cretaceous Period (geology), periods. Stegosaurian fossils have been found mostly in the Northern Hemisphere (North America, Europe a ...
appear during the Middle Jurassic. The basal
neornithischia Neornithischia ("new ornithischians") is a clade of the dinosaur order Ornithischia. It is the sister group of the Thyreophora within the clade Genasauria. Neornithischians are united by having a thicker layer of asymmetrical enamel on the insi ...
n ''
Kulindadromeus ''Kulindadromeus'' is a genus of basal neornithischian dinosaur that lived during the Middle Jurassic. The first ''Kulindadromeus'' fossil was found in Russia. Its feather-like integument is evidence for protofeathers being basal to Ornithisch ...
'' from the Middle Jurassic of Russia indicates that at least some ornithischians were covered in protofeathers. The earliest members of Ankylopollexia, which become prominent in the Cretaceous, appeared during the Late Jurassic, represented by bipedal forms such as '' Camptosaurus''.
Ceratopsia Ceratopsia or Ceratopia ( or ; Ancient Greek, Greek: "horned faces") is a group of herbivore, herbivorous, beaked dinosaurs that thrived in what are now North America, Asia and Europe, during the Cretaceous Period (geology), Period, although ance ...
ns first appeared in the Late Jurassic of China, represented by members of Chaoyangsauridae.


Sauropodomorphs

Sauropods Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their b ...
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 bipedal sauropodomorphs, such as 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 sauropods first appeared during the Early Jurassic, with the oldest definitive record being ''
Vulcanodon ''Vulcanodon'' (meaning "volcano tooth") is an extinct genus of sauropod dinosaur from the Early Jurassic Uppermost Forest Sandstone of southern Africa. The only known species is ''V. karibaensis''. Discovered in 1969 in Zimbabwe, it was regard ...
'' from Zimbabwe, likely of Sinemurian age. Eusauropods first appeared during the late Early Jurassic (Toarcian) and diversified during the Middle Jurassic; these included cetiosaurids, turiasaurs, and mamenchisaurs. Neosauropods such as
macronaria Macronaria is a clade of sauropod dinosaurs. Macronarians are named after the large diameter of the nasal opening of their skull, known as the external naris, which exceeded the size of the orbit, the skull opening where the eye is located (hence ...
ns and diplodocoids first appeared during the Middle Jurassic, before becoming abundant and globally distributed during the Late Jurassic.


Other reptiles


Crocodylomorphs

The Triassic–Jurassic extinction decimated
pseudosuchia Pseudosuchia, from Ancient Greek ψεύδος (''pseúdos)'', meaning "false", and σούχος (''soúkhos''), meaning "crocodile" is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely relat ...
n diversity, with crocodylomorphs, which originated during the early Late Triassic, being the only group of pseudosuchians to survive. All other pseudosuchians, including the herbivorous
aetosaur Aetosaurs () are heavily armored reptiles belonging to the extinct order (biology), order Aetosauria (; from Ancient Greek, Greek, (aetos, "eagle") and (, "lizard")). They were medium- to large-sized Omnivore, omnivorous or Herbivore, herbivor ...
s and carnivorous " rauisuchians", became extinct. The morphological diversity of crocodylomorphs during the Early Jurassic was around the same as that of Late Triassic pseudosuchians, but they occupied different areas of morphospace, suggesting that they occupied different
ecological niche In ecology, a niche is the match of a species to a specific environmental condition. Three variants of ecological niche are described by It describes how an organism or population responds to the distribution of Resource (biology), resources an ...
s to their Triassic counterparts and that there was an extensive and rapid radiation of crocodylomorphs during this interval. While living
crocodilia Crocodilia () is an order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorph pseudosuchia ...
ns are mostly confined to an aquatic ambush predator lifestyle, Jurassic crocodylomorphs exhibited a wide variety of life habits. An unnamed 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 crocodyliforms and thalattosuchians. The
Neosuchia Neosuchia is a clade within Mesoeucrocodylia that includes all modern extant crocodilians and their closest fossil relatives. It is defined as the most inclusive clade containing all Crocodylomorpha, crocodylomorphs more closely related to ''Croc ...
, 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 to represent the oldest record of
Notosuchia Notosuchia is a clade of primarily Gondwanan mesoeucrocodylian Crocodylomorpha, crocodylomorphs that lived during the Jurassic and Cretaceous. Some phylogeny, phylogenies recover Sebecosuchia as a clade within Notosuchia, others as a sister group ...
, a primarily Gondwanan clade of mostly terrestrial crocodylomorphs, otherwise known from the Cretaceous and Cenozoic.


Turtles

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. ...
turtles (
Testudinata Testudinata is the group of all tetrapods with a true turtle shell. It includes both modern turtles (Testudines) and many of their extinct, shelled relatives (stem-turtles), though excluding ''Odontochelys'' and ''Eorhynchochelys,'' which are pla ...
) 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 (
Testudines Turtles are reptiles of the order (biology), order Testudines, characterized by a special turtle shell, shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Crypt ...
),
Pleurodira The Pleurodira are one of the two living suborders of turtles, the other being the Cryptodira. The division between these two suborders represents a very deep evolutionary divide between two very different types of turtles. The physical differ ...
and
Cryptodira The Cryptodira (') are a suborder of Testudines that includes most living tortoises and turtles. Cryptodira is commonly called the "Hidden-Neck Turtles" or the "Inside-Neck Turtles". Cryptodira differ from Pleurodira (side-necked turtles) in ...
, diverged by the beginning of the Late Jurassic. The oldest known pleurodires, the
Platychelyidae Platychelyidae is an extinct family of pan-pleurodiran turtles, known from the Late Jurassic and Early Cretaceous of Europe, South America, North America, and the Caribbean. It represents the oldest known clade of stem-pleurodires. All known memb ...
, are known from the Late Jurassic of Europe and the Americas, while the oldest unambiguous cryptodire, ''
Sinaspideretes ''Sinaspideretes'' is an extinct genus of turtle from the Late Jurassic of China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the ...
,'' an early relative of 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 (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerh ...
s, are known from the Late Jurassic of Europe and South America.


Lepidosaurs

Rhynchocephalians (the sole living representative being the
tuatara The tuatara (''Sphenodon punctatus'') is a species of reptile endemic to New Zealand. Despite its close resemblance to lizards, it is actually the only extant member of a distinct lineage, the previously highly diverse order Rhynchocephal ...
) had achieved a global distribution by the beginning of the Jurassic, and represented the dominant group of small reptiles during the Jurassic globally. Rhynchocephalians reached their highest morphological diversity in their evolutionary history during the Jurassic, occupying a wide range of lifestyles, including the aquatic pleurosaurs with long snake-like bodies and reduced limbs, the specialized herbivorous eilenodontines, as well as the sapheosaurs which had broad tooth plates indicative of
durophagy Durophagy is the eating behavior of animals that consume Seashell, hard-shelled or exoskeleton-bearing organisms, such as corals, shelled mollusks, or crabs. It is mostly used to describe fish, but is also used when describing reptiles, including ...
. Rhynchocephalians disappeared from Asia after the Early Jurassic. The last common ancestor of living squamates (which includes
lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...
s and
snake Snakes are elongated limbless reptiles of the suborder Serpentes (). Cladistically squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales much like other members of the group. Many species of snakes have s ...
s) 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 Scincomorpha is an infraorder and clade of lizards including skinks (Scincidae) and their close relatives. These include the living families Cordylidae (girdled lizards), Gerrhosauridae (plated lizards), and Xantusiidae (night lizards), as well a ...
, 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
gecko Geckos are small, mostly carnivorous lizards that have a wide distribution, found on every continent except Antarctica. Belonging to the infraorder Gekkota, geckos are found in warm climates. They range from . Geckos are unique among lizards ...
s and displays adaptations for climbing. '' Dorsetisaurus'' from the Late Jurassic of North America and Europe represents the oldest widely accepted record of
Anguimorpha The Anguimorpha is a suborder of Squamata, squamates. The group was named by Fürbringer in 1900 to include all autarchoglossans closer to ''Varanus'' and ''Anguis'' than ''Scincus''. These lizards, along with iguanians and snakes, constitute the ...
. '' Marmoretta'' from the Middle Jurassic of Britain has been suggested to represent a late surviving lepidosauromorph outside both Rhynchocephalia and Squamata, though some studies have recovered it as a stem-squamate. File:Vadasaurus herzogi holotype (fossil).jpg, '' 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, '' 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 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

Ichthyosaur Ichthyosauria is an order of large extinct marine reptiles sometimes referred to as "ichthyosaurs", although the term is also used for wider clades in which the order resides. Ichthyosaurians thrived during much of the Mesozoic era; based on fo ...
s suffered an
evolutionary bottleneck A population bottleneck or genetic bottleneck is a sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts; or human activities such as genocide, speciocide, wid ...
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 An apex predator, also known as a top predator or superpredator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the hig ...
'' 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

Plesiosaurs The Plesiosauria or plesiosaurs are an Order (biology), order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared in the latest Triassic Period (geology), Period, possibly in the Rhaetian st ...
originated at the end of the Triassic (Rhaetian). By the end of the Triassic, all other
sauropterygia Sauropterygia ("lizard flippers") is an extinct taxon of diverse, aquatic diapsid reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosau ...
ns, including
placodonts Placodonts ("Tablet (pharmacy), tablet tooth, teeth") are an Extinction, extinct order (biology), order of marine reptiles that lived during the Triassic period, becoming extinct at the end of the period. They were part of Sauropterygia, the gro ...
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 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 Cryptoclididae is a family of medium-sized plesiosaurs that existed from the Middle Jurassic to the Early Cretaceous. They had long necks, broad and short skulls and densely packed teeth. They fed on small soft-bodied preys such as small fish and ...
during the Bajocian. The Middle Jurassic saw the evolution of short-necked and large-headed 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 , 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

Pterosaur Pterosaurs are 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 million to 66 million years ago). Pterosaurs are the earli ...
s first appeared in the Late Triassic. A major radiation of Jurassic pterosaurs is the
Rhamphorhynchidae Rhamphorhynchidae is a group of early pterosaurs named after '' Rhamphorhynchus'', that lived in the Late Jurassic. The family Rhamphorhynchidae was named in 1870 by Harry Govier Seeley.Seeley, H.G. (1870). "The Orithosauria: An Elementary Study ...
, which first appeared in the late Early Jurassic (Toarcian); they are thought to been
piscivorous A piscivore () is a carnivorous animal that primarily eats fish. Fish were the diet of early tetrapod evolution (via water-bound amphibians during the Devonian period); insectivory came next; then in time, the more terrestrially adapted rept ...
. 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 wukongopterids appeared in the late Middle Jurassic. Advanced short-tailed pterodactyloids first appeared at the Middle–Late Jurassic boundary. Jurassic pterodactyloids include the ctenochasmatids, like '' Ctenochasma'', which have closely spaced needle-like teeth that were presumably used for
filter feeding Filter feeders are aquatic animals that acquire nutrients by feeding on organic matters, food particles or smaller organisms (bacteria, microalgae and zooplanktons) suspended in water, typically by having the water pass over or through a spe ...
. The bizarre Late Jurassic 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.


Amphibians

The diversity of temnospondyls had progressively declined through the Late Triassic, with only brachyopoids surviving into the Jurassic and beyond. Members of the family Brachyopidae are known from Jurassic deposits in Asia, while the chigutisaurid '' Siderops'' is known from the Early Jurassic of Australia. Modern
lissamphibia The Lissamphibia (from Greek λισσός (lissós, "smooth") + ἀμφίβια (amphíbia), meaning "smooth amphibians") is a group of tetrapods that includes all modern amphibians. Lissamphibians consist of three living groups: the Salientia ( ...
ns 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 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 ...
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 neotenic. Early representatives of crown group salamanders include '' Chunerpeton, Pangerpeton'' and '' Linglongtriton'' from the Middle to Late Jurassic Yanliao Biota of China. Some of these are suggested to belong to Cryptobranchoidea, which contains living Asiatic and
giant salamander The Cryptobranchidae (commonly known as giant salamanders) are a family of large salamanders that are fully aquatic. The family includes some of the largest living amphibians. They are native to China, Japan, and the eastern United States. Giant ...
s. '' Beiyanerpeton'', and ''
Qinglongtriton ''Qinglongtriton'' is an extinct genus of salamanders from the Late Jurassic ( Oxfordian age) of what is now Hebei, China. It contains one species, ''Q. gangouensis'', which is known from numerous adult and juvenile specimens collected from the T ...
'' from the same biota are thought to be early members of
Salamandroidea The Salamandroidea are a suborder of salamanders, referred to as advanced salamanders. The members of the suborder are found worldwide except for Antarctica, sub-Saharan Africa, and Oceania. They differ from suborder Cryptobranchoidea as the Angu ...
, 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 Morrison Formation is a distinctive sequence of Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltston ...
. The stem-
caecilian Caecilians (; ) are a group of limbless, vermiform (worm-shaped) or serpentine (snake-shaped) amphibians with small or sometimes nonexistent eyes. They mostly live hidden in soil or in streambeds, and this cryptic lifestyle renders caecilians ...
'' Eocaecilia'' is known from the Early Jurassic of Arizona. The fourth group of lissamphibians, the extinct salamander-like albanerpetontids, first appeared in the Middle Jurassic, represented by '' Anoualerpeton priscus'' from the Bathonian of Britain, as well as indeterminate remains from equivalently aged sediments in France and the Anoual Formation of Morocco.


Mammaliaformes

Mammaliaformes Mammaliaformes ("mammalian forms") is a clade of synapsid tetrapods that includes the crown group mammals and their closest extinct relatives; the group radiated from earlier probainognathian cynodonts during the Late Triassic. It is defined as ...
, including
mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
s, having originated from
cynodont Cynodontia () is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 Megaannum, mya), and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extin ...
s at the end of the Triassic, diversified extensively during the Jurassic. While most Jurassic mammalaliaforms are solely known from isolated teeth and jaw fragments, exceptionally preserved remains have revealed a variety of lifestyles. The
docodonta Docodonta is an Order (biology), order of extinct Mesozoic Mammaliaformes, mammaliaforms (advanced cynodonts closely related to true Crown group, crown-group mammals). They were among the most common mammaliaforms of their time, persisting from t ...
n ''
Castorocauda ''Castorocauda'' is an extinct, semi-aquatic, superficially otter-like genus of docodont mammaliaforms with one species, ''C. lutrasimilis''. It is part of the Yanliao Biota, found in the Daohugou Beds of Inner Mongolia, China dating to the ...
'' was adapted to aquatic life, similarly to the
platypus The platypus (''Ornithorhynchus anatinus''), sometimes referred to as the duck-billed platypus, is a semiaquatic, egg-laying mammal endemic to eastern Australia, including Tasmania. The platypus is the sole living representative or monotypi ...
and
otter Otters are carnivorous mammals in the subfamily Lutrinae. The 13 extant otter species are all semiaquatic, aquatic, or marine. Lutrinae is a branch of the Mustelidae family, which includes weasels, badgers, mink, and wolverines, among ...
s. Some members of
Haramiyida Haramiyida is a possibly Paraphyly, paraphyletic order of Mammaliaformes, mammaliaform cynodonts or mammals of controversial taxonomic affinites. Their teeth, which are by far the most common remains, resemble those of the multituberculates. Howe ...
and the
eutriconodonta Eutriconodonta is an order (biology), order of early mammals. Eutriconodonts existed in Asia (including Insular India, pre-contact India), Africa, Europe, North America, North and South America during the Jurassic and the Cretaceous periods. The ...
n tribe VolaticotheriniMeng, J.; Hu, Y.-M.; Wang, Y.-Q.; Wang, X.-L.; Li, C.-K. (2007). "Corrigendum: A Mesozoic gliding mammal from northeastern China". Nature 446 (7131): 102. . . had a
patagium The patagium (: patagia) is a membranous body part that assists an animal in obtaining lift when gliding or flying. The structure is found in extant and extinct groups of flying and gliding animals including bats, theropod dinosaurs (inclu ...
akin to those of
flying squirrel Flying squirrels (scientifically known as Pteromyini or Petauristini) are a tribe (biology), tribe of 50 species of squirrels in the family (biology), family Squirrel, Sciuridae. Despite their name, they are not in fact capable of full flight i ...
s, allowing them to glide through the air. The
aardvark Aardvarks ( ; ''Orycteropus afer'') are medium-sized, burrowing, nocturnal mammals native to Africa. Aardvarks are the only living species of the family Orycteropodidae and the order Tubulidentata. They have a long proboscis, similar to a pi ...
-like mammal '' Fruitafossor'', of uncertain taxonomy, was likely a specialist on colonial insects, similarly to living
anteater Anteaters are the four extant mammal species in the suborder Vermilingua (meaning "worm tongue"), commonly known for eating ants and termites. The individual species have other names in English and other languages. Together with sloths, they ar ...
s.
Australosphenida The Australosphenida are a clade of mammals, containing mammals with tribosphenic molars, known from the Jurassic to Mid-Cretaceous of Gondwana. Although they have often been suggested to have acquired tribosphenic molars independently from those ...
, a group of mammals possibly related to living
monotreme Monotremes () are mammals of the order Monotremata. They are the only group of living mammals that lay eggs, rather than bearing live young. The extant monotreme species are the platypus and the four species of echidnas. Monotremes are typified ...
s, first appeared in the Middle Jurassic of Gondwana. The earliest records of multituberculates, one of the longest lasting and most successful orders of mammals, are known from the Middle Jurassic.
Theria Theria ( or ; ) is a scientific classification, subclass of mammals amongst the Theriiformes. Theria includes the eutherians (including the Placentalia, placental mammals) and the metatherians (including the marsupials) but excludes the egg-lay ...
n mammals, represented today by living placentals and
marsupial Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a r ...
s, diversified meteorically during the Middle Jurassic. They have their earliest records during the early Late Jurassic, represented by ''
Juramaia ''Juramaia'' is an extinct genus of a therian mammal, possibly a very basal eutherian mammal, known from the Late Jurassic ( Oxfordian stage) or Early Cretaceous deposits of western Liaoning, China. It is a small shrew-like mammal weighing aro ...
,'' a
eutheria Eutheria (from Greek , 'good, right' and , 'beast'; ), also called Pan-Placentalia, is the clade consisting of Placentalia, placental mammals and all therian mammals that are more closely related to placentals than to marsupials. Eutherians ...
n 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, and it has been suggested that ''Juramaia'' may also originate from the Early Cretaceous instead. Two groups of non-mammaliaform cynodonts persisted beyond the end of the Triassic. The insectiviorous
Tritheledontidae Tritheledontidae, the tritheledontids or ictidosaurs, is an extinct family of small to medium-sized (about 10 to 20 cm long) cynodonts. They were highly mammal-like, specialized cynodonts, although they still retained a few reptile-like ...
has a few records from the Early Jurassic. The
Tritylodontidae Tritylodontidae ("three-knob teeth", named after the shape of their cheek teeth) is an extinct family of small to medium-sized, highly specialized mammal-like cynodonts, with several mammalian traits including erect limbs, endothermy, and some d ...
, a herbiviorous group of cynodonts that first appeared during the Rhaetian, has abundant records from the Jurassic, overwhelmingly from the Northern Hemisphere.


Fish


Jawless fish

The last known species of
conodont Conodonts, are an extinct group of marine jawless vertebrates belonging to the class Conodonta (from Ancient Greek κῶνος (''kōnos''), meaning " cone", and ὀδούς (''odoús''), meaning "tooth"). They are primarily known from their hard ...
, a class of
jawless fish Agnatha (; ) or jawless fish is a paraphyletic infraphylum of animals in the subphylum Vertebrata of the phylum Chordata, characterized by the lack of jaws. The group consists of both extant taxon, living (Cyclostomi, cyclostomes such as hagfish ...
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. '' Yanliaomyzon'' from the Middle Jurassic of China represents the oldest post Paleozoic
lamprey Lampreys (sometimes inaccurately called lamprey eels) are a group of Agnatha, jawless fish comprising the order (biology), order Petromyzontiformes , sole order in the Class (biology), class Petromyzontida. The adult lamprey is characterize ...
, and the oldest lamprey to have the toothed feeding apparatus and likely the three stage life cycle typical of modern members of the group.


Sarcopterygii

Lungfish Lungfish are freshwater vertebrates belonging to the class Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, inc ...
(Dipnoi) were present in freshwater environments of both hemispheres during the Jurassic. Some studies have proposed that the last common ancestor of all living lungfish lived during the Jurassic. Mawsoniids, a marine and freshwater/brackish group of
coelacanth Coelacanths ( ) are an ancient group of lobe-finned fish (Sarcopterygii) in the class Actinistia. As sarcopterygians, they are more closely related to lungfish and tetrapods (the terrestrial vertebrates including living amphibians, reptiles, bi ...
s, 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 ''Latimeria'' is a rare genus of fish which contains the two only living species of coelacanth. It includes two Extant taxon, extant species: the West Indian Ocean coelacanth (''Latimeria chalumnae'') and the Indonesian coelacanth (''Latimeria me ...
'', were also present in the Jurassic, having originated in the Triassic, with a number of records from the Jurassic of Europe including '' Swenzia'', thought to be the closest known relative of living coelacanths.


Actinopterygii

Ray-finned fish (
Actinopterygii Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class (biology), class of Osteichthyes, bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built ...
) were major components of Jurassic freshwater and marine ecosystems. Archaic " palaeoniscoid" fish, which were common in both marine and freshwater habitats during the preceding Triassic declined during the Jurassic, being largely replaced by more derived actinopterygian lineages. The oldest known
Acipenseriformes Acipenseriformes is an order (biology), order of basal (phylogenetics), basal Actinopterygii, ray-finned fishes that includes living and fossil sturgeons and paddlefishes (Acipenseroidei), as well as the extinct family (biology), families C ...
, the group that contains living
sturgeon Sturgeon (from Old English ultimately from Proto-Indo-European language, Proto-Indo-European *''str̥(Hx)yón''-) is the common name for the 27 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the ...
and
paddlefish Paddlefish (family Polyodontidae) are a family of ray-finned fish belonging to order Acipenseriformes, and one of two living groups of the order alongside sturgeons (Acipenseridae). They are distinguished from other fish by their elongated rost ...
, are from the Early Jurassic. 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, with the modern family Amiidae appearing during the Late Jurassic.
Pycnodontiformes Pycnodontiformes is an extinct order of primarily marine bony fish. The group first appeared during the Late Triassic and disappeared during the Eocene. The group has been found in rock formations in Africa, Asia, Europe, North and South America. ...
, 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 Late Jurassic. Stem-group
teleost Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of f ...
s, 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 A tuna (: tunas or tuna) is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae ( mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bul ...
-like predatory and filter-feeding forms, the latter included the largest bony fish known to have existed: ''
Leedsichthys ''Leedsichthys'' is an extinct genus of pachycormid fish that lived in the oceans of the Middle to Late Jurassic.Liston, JJ (2004). An overview of the pachycormiform ''Leedsichthys''. In: Arratia G and Tintori A (eds) Mesozoic Fishes 3 - Systema ...
'', 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
hybodonts Hybodontiformes, commonly called hybodonts, are an extinct group of shark-like cartilaginous fish (chondrichthyans) which existed from the late Devonian to the Late Cretaceous. Hybodonts share a close common ancestry with modern sharks and Batoide ...
, which represented the dominant group of chondrichthyans 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 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 Batomorphi is a Division (taxonomy), division of Chondrichthyes, cartilaginous fishes, commonly known as rays, this taxon is also known as the Order (biology), superorder Batoidea, but the 5th edition of ''Fishes of the World'' classifies it as ...
) is '' Antiquaobatis'' from the Pliensbachian of Germany. Jurassic batoids known from complete remains retain a conservative, guitarfish-like morphology. The oldest known
Hexanchiformes The Hexanchiformes Help:IPA/English, /hɛkˈsæŋkɪfɔːrmiːz/ are a primitive Order (biology), order of sharks, numbering just five extant species in two Family (biology), families, Chlamydoselachidae and Cow shark, Hexanchidae. Chlamydoselach ...
and
carpet shark Carpet sharks are sharks classified in the order (biology), order Orectolobiformes . Sometimes the common name "carpet shark" (given because many species resemble ornately patterned carpets) is used interchangeably with "wobbegong", which is the ...
s (Orectolobiformes) are from the Early Jurassic (Pliensbachian and Toarcian, respectively) of Europe. The oldest known members of the Heterodontiformes, the only living members of which are the bullhead shark (''Heterodontus''), first appeared in the Early Jurassic, with representatives of the living genus appearing during the Late Jurassic. The oldest record of angelsharks ( Squatiniformes) is '' Pseudorhina'' from the Late Jurassic (Oxfordian–Tithonian) of Europe, which already has a bodyform similar to members of the only living genus of the order, '' Squatina''. 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
chimaera Chimaeras are Chondrichthyes, cartilaginous fish in the order (biology), order Chimaeriformes (), known informally as ghost sharks, rat fish (not to be confused with rattails), spookfish, or rabbit fish; the last two names are also applied to B ...
s are from the Early Jurassic of Europe, with members of the living family Callorhinchidae appearing during the Middle Jurassic. Unlike most living chimaeras, Jurassic chimeras are often found in shallow water environments. The closely related myriacanthids and the flattened '' Squaloraja'' 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 Insects have arthropod mouthparts, mouthparts that may vary greatly across insect species, as they are adapted to particular modes of feeding. The earliest insects had chewing mouthparts. Most specialisation of mouthparts are for piercing and su ...
. The Middle to Late Jurassic was a time of major diversification for
beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...
s, particularly for the suborder
Polyphaga Polyphaga is the largest and most diverse suborder of beetles. It comprises 144 families in 16 superfamilies, and displays an enormous variety of specialization and adaptation, with over 350,000 described species, or approximately 90% of the b ...
, which represents 90% of living beetle species but which was rare during the preceding Triassic.
Weevil Weevils are beetles belonging to the superfamily Curculionoidea, known for their elongated snouts. They are usually small – less than in length – and herbivorous. Approximately 97,000 species of weevils are known. They belong to several fa ...
s 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.
Orthoptera Orthoptera () is an order of insects that comprises the grasshoppers, locusts, and crickets, including closely related insects, such as the bush crickets or katydids and wētā. The order is subdivided into two suborders: Caelifera – gras ...
n diversity had declined during the Late Triassic, but recovered during the Early Jurassic, with the Hagloidea, a superfamily of
ensifera Ensifera is a Order (biology), suborder of insects that includes the various types of crickets and their allies, including cricket (insect), true crickets, Rhaphidophoridae, camel crickets, Tettigoniidae, bush crickets or katydids, Prophalangops ...
n orthopterans today confined to a few living species, being particularly diverse during the Jurassic. The oldest known
lepidoptera Lepidoptera ( ) or lepidopterans is an order (biology), order of winged insects which includes butterflies and moths. About 180,000 species of the Lepidoptera have been described, representing 10% of the total described species of living organ ...
ns (the group containing butterflies and moths) are known from the Triassic–Jurassic boundary, with wing scales belonging to the suborder
Glossata Glossata ( Fabricius, 1775) is a suborder of the Lepidoptera, containing all members that have a coilable proboscis; i.e., it includes all butterflies and the vast majority of moth species. The only non-Glossatan moths are in the suborders Aglo ...
and Micropterigidae-grade moths from the deposits of this age in Germany. Modern representatives of both
dragonflies A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of dragonflies are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threate ...
and
damselflies Damselflies are flying insects of the suborder Zygoptera in the order Odonata. They are similar to dragonflies (which constitute the other odonatan suborder, Epiprocta) but are usually smaller and have slimmer bodies. Most species fold the win ...
also first appeared during the Jurassic. Although modern representatives are not known until the Cenozoic, ectoparasitic insects thought to represent primitive
flea Flea, the common name for the order (biology), order Siphonaptera, includes 2,500 species of small flightless insects that live as external parasites of mammals and birds. Fleas live by hematophagy, ingesting the blood of their hosts. Adult f ...
s, 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 are a large group of hymenopteran Superfamily (zoology), superfamilies, with all but the wood wasps (Orussoidea) being in the wasp-waisted Apocrita. As parasitoids, they lay their eggs on or in the bodies of other arthropods, ...
s (
Apocrita Apocrita is a suborder of insects in the order Hymenoptera. It includes wasps, bees, and ants, and consists of many families. It contains the most advanced hymenopterans and is distinguished from Symphyta by the narrow "waist" ( petiole) formed ...
) 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 The Phasmatodea (also known as Phasmida or Phasmatoptera) are an Order (biology), order of insects whose members are variously known as stick insects, stick bugs, walkingsticks, stick animals, or bug sticks. They are also occasionally referred ...
(stick insects), Mantophasmatidae (gladiators),
Embioptera The order Embioptera, commonly known as webspinners or footspinners, are a small group of mostly tropical and subtropical insects, classified under the subclass Pterygota. The order has also been called Embiodea or Embiidina. More than 400 spe ...
(webspinners), and
Raphidioptera Snakeflies are a group of predatory insects comprising the order (biology), order Raphidioptera with two extant families: Raphidiidae and Inocelliidae, consisting of roughly 260 species. In the past, the group had a much wider distribution than i ...
(snakeflies). The earliest
scale insect Scale insects are small insects of the Order (biology), order Hemiptera, suborder Sternorrhyncha. Of dramatically variable appearance and extreme sexual dimorphism, they comprise the infraorder Coccomorpha which is considered a more convenient g ...
(Coccomorpha) is known from amber dating to the Late Jurassic, though the group probably originated earlier during the Triassic. Only a handful of records of mites are known from the Jurassic, including '' Jureremus'', an 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 Synspermiata is a clade of araneomorph spiders, comprising most of the former " haplogynes". They are united by having simpler genitalia than other araneomorph spiders, lacking a cribellum, and sharing an evolutionary history of synspermia – a ...
. 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 The Eupnoi are a suborder of harvestmen, with more than 200 genera, and about 1,700 described species. They consist of two superfamilies, the Phalangioidea with many long-legged species common to northern temperate regions, and the small group ...
harvestmen (
Opiliones The Opiliones (formerly Phalangida) are an Order (biology), order of arachnids, Common name, colloquially known as harvestmen, harvesters, harvest spiders, or daddy longlegs (see below). , over 6,650 species of harvestmen have been discovered w ...
) are known from the Middle Jurassic of China, including members of the family
Sclerosomatidae The Sclerosomatidae are a family (taxonomy), family of Opiliones, harvestmen with about 1,300 known species. One former subfamily has been recently removed to form a new family, Globipedidae.Kury, A.B. & J.C. Cokendolpher (2020) Chapter 9. A new ...
.


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. Sessile
filter feeder Filter feeders are aquatic animals that acquire nutrients by feeding on organic matters, food particles or smaller organisms (bacteria, microalgae and zooplanktons) suspended in water, typically by having the water pass over or through a s ...
s and photosymbiotic organisms were among those most severely affected.


Marine ecosystems

Having declined at the Triassic–Jurassic boundary, reefs substantially expanded during the Late Jurassic, including both
sponge reef Sponge reefs are reefs produced by sea sponges. All modern sponge reefs are formed by hexactinellid sponges, which have an endoskeleton made of silica spicules and are often referred to as "glass sponges", while historically the non-spicule ...
s and
scleractinia Scleractinia, also called stony corals or hard corals, are marine animals in the phylum Cnidaria that build themselves a hard skeleton. The individual animals are known as polyps and have a cylindrical body crowned by an oral disc in which a mo ...
n
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 group ...
s. Late Jurassic reefs were similar in form to modern reefs but had more microbial carbonates and hypercalcified
sponge Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a basal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and a ...
s, and had weak biogenic binding. Reefs sharply declined at the close of the Jurassic, which caused an associated drop in diversity in
decapod The Decapoda or decapods, from Ancient Greek δεκάς (''dekás''), meaning "ten", and πούς (''poús''), meaning "foot", is a large order of crustaceans within the class Malacostraca, and includes crabs, lobsters, crayfish, shrimp, and p ...
crustaceans. The earliest planktonic foraminifera, which constitute the suborder
Globigerinina The Globigerinina is a suborder of foraminiferans that are found as marine plankton. They produce hyaline calcareous Test (biology), tests, and are known as fossils from the Jurassic period onwards. The group has included more than 100 genera a ...
, 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.
Coccolithophore Coccolithophores, or coccolithophorids, are single-celled organisms which are part of the phytoplankton, the autotrophic (self-feeding) component of the plankton community. They form a group of about 200 species, and belong either to the kingdom ...
s and
dinoflagellate The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also commo ...
s, which had first appeared during the Triassic, radiated during the Early to Middle Jurassic, becoming prominent members of the
phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater Aquatic ecosystem, ecosystems. The name comes from the Greek language, Greek words (), meaning 'plant', and (), mea ...
. Microconchid tube worms, the last remaining order of Tentaculita, a group of animals of uncertain affinities that were convergent on ''
Spirorbis ''Spirorbis'' is a genus of very small () polychaete worms, usually with a white coiled shell. Members of the genus live in the littoral, lower littoral and Sublittoral zone, sublittoral zones of rocky shores. ''Spirorbis'' worms usually live att ...
'' 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 A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...
is from Late Jurassic–aged amber from Thailand, assigned to the living genus '' Hemiaulus.''


Echinoderms

Crinoid Crinoids are marine invertebrates that make up the class Crinoidea. Crinoids that remain attached to the sea floor by a stalk in their adult form are commonly called sea lilies, while the unstalked forms, called feather stars or comatulids, are ...
s 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.
Echinoids Sea urchins or urchins () are echinoderms in the class (biology), class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal zone to deep seas of . They typically have a globular body cove ...
(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
decapods The Decapoda or decapods, from Ancient Greek δεκάς (''dekás''), meaning "ten", and πούς (''poús''), meaning "foot", is a large order (biology), order of crustaceans within the class Malacostraca, and includes crabs, lobsters, crayfis ...
. The first true crabs ( Brachyura) are known from the Early Jurassic, with the earliest being '' Eocarcinus praecursor'' from the early Pliensbachian of England, which lacked the crab-like morphology ( carcinisation) of modern crabs, and ''Eoprosopon klugi'' from the late Pliensbachian of Germany, which may belong to the living family Homolodromiidae. Most Jurassic crabs are known only from
carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the unde ...
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 crab Hermit crabs are anomuran Decapoda, decapod crustaceans of the superfamily (taxonomy), superfamily Paguroidea that have adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit c ...
s also first appeared during the Jurassic, with the earliest known being '' Schobertella hoelderi'' from the late Hettangian of Germany. Early hermit crabs are associated with ammonite shells rather than those of gastropods. 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 Brachiopods (), phylum (biology), phylum Brachiopoda, are a phylum of 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 e ...
diversity declined during the Triassic–Jurassic extinction. Spire-bearing brachiopods ( Spiriferinida and Athyridida) did not recover their biodiversity, becoming extinct in the TOAE. Rhynchonellida and
Terebratulida Terebratulids are one of only three living orders of articulate brachiopods, the others being the Rhynchonellida and the Thecideida. Craniida and Lingulida include living brachiopods, but are inarticulates. The name, Terebratula, may be der ...
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 Bioturbation is defined as the reworking of soils and sediments by animals or plants. It includes burrowing, ingestion, and defecation of sediment grains. Bioturbating activities have a profound effect on the environment and are thought to be a ...
or increased grazing pressure.


Bryozoans

Like the preceding Triassic,
bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic animal, aquatic invertebrate animals, nearly all living in sedentary Colony (biology), colonies. Typically about long, they have a spe ...
n diversity was relatively low compared to the Paleozoic. The vast majority of Jurassic bryozoans are members of
Cyclostomatida Cyclostomatida, or cyclostomata (also known as cyclostomes), are an ancient order of stenolaemate bryozoans which first appeared in the Lower Ordovician. It consists of 7+ suborders, 59+ families, 373+ genera, and 666+ species. The cyclostome ...
, which experienced a radiation during the Middle Jurassic, with all Jurassic representatives belonging to the suborders Tubuliporina and Cerioporina.
Cheilostomata Cheilostomatida, also called Cheilostomata, is an order of Bryozoa in the class Gymnolaemata. They are exclusively marine, colonial invertebrate animals. Cheilostome colonies are composed of calcium carbonate and grow on a variety of surfaces, ...
, the dominant group of modern bryozoans, first appeared during the Late Jurassic.


Molluscs


= Gastropods

= Marine gastropods were significantly affected by the T-J extinction, with around 56% of genera going extinct, with
Neritimorpha Neritimorpha is a clade of gastropod molluscs that contains around 2,000 extant species of sea snails, limpets, freshwater snails, land snails and slugs. This clade used to be known as the superorder Neritopsina. Etymology The clade’s name, N ...
being particularly strongly effected, while
Heterobranchia Heterobranchia, the heterobranchs (meaning "different gill"), is a taxonomic clade of snails and slugs, which includes marine, aquatic, and terrestrial gastropod molluscs. Heterobranchia is one of the main clades of gastropods. Currently Het ...
suffered much lower losses than other groups. While present, the diversity of
freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...
and
land snail A land snail is any of the numerous species of snail that live on land, as opposed to the sea snails and freshwater snails. ''Land snail'' is the common name for terrestrial molluscs, terrestrial gastropod mollusks that have gastropod shell, shel ...
s was much lower during the Jurassic than in contemporary ecosystems, with the diversity of these groups not reaching levels comparable to modern times until the following Cretaceous.


= 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 Rudists are a group of extinct box-, tube- or ring-shaped Marine (ocean), marine Heterodonta, heterodont bivalves belonging to the order Hippuritida that arose during the Late Jurassic and became so diverse during the Cretaceous that they were m ...
, 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 The Phylloceratina comprise a suborder (biology), suborder of Ammonoidea, ammonoid cephalopods, belonging to the Ammonitida, whose range extends from the Lower Triassic to the Upper Cretaceous. Shells of the Phylloceratina are generally smooth w ...
surviving and becoming ancestral to all later Jurassic and Cretaceous ammonites. Ammonites explosively diversified during the Early Jurassic, with the orders Psiloceratina, Ammonitina, Lytoceratina, Haploceratina, Perisphinctina and
Ancyloceratina The Ancyloceratina were a diverse suborder of ammonite most closely related to the ammonites of order Lytoceratina. They evolved during the Late Jurassic but were not very common until the Cretaceous period, when they rapidly diversified and beca ...
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. Ammonite diversifications occurred coevally with
marine transgression A marine transgression is a geologic event where sea level rises relative to the land and the shoreline moves toward higher ground, resulting in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling with water ...
s, while their diversity nadirs occurred during
marine regression A marine regression is a geological process occurring when areas of submerged seafloor are exposed during a drop in sea level. The opposite event, marine transgression, occurs when flooding from the sea covers previously-exposed land. Descript ...
s. The oldest definitive records of the squid-like 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 shelves A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...
and in the
littoral zone The littoral zone, also called litoral or nearshore, is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely flood ...
. 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 vampyromorphs, of which the only living member is the vampire squid, first appeared during the Early Jurassic. The earliest
octopus An octopus (: octopuses or octopodes) is a soft-bodied, eight-limbed mollusc of the order Octopoda (, ). The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like oth ...
es 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 ''Gladius'' () is a Latin word properly referring to the type of sword that was used by Ancient Rome, ancient Roman foot soldiers starting from the 3rd century BC and until the 3rd century AD. Linguistically, within Latin, the word also came t ...
. Octopuses likely originated from bottom-dwelling (
benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from the Ancient Greek word (), meaning "the depths". ...
) ancestors which lived in shallow environments. '' Proteroctopus'' from the late Middle Jurassic 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 Geological periods