By the beginning of the Jurassic, thesupercontinentPangaea had begunrifting into two landmasses:Laurasia to the north andGondwana to the south. The climate of the Jurassic was warmer than the present, and there were noice caps. 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 bydinosauromorph andpseudosuchianarchosaurs, to one dominated bydinosaurs alone. The firststem-group birds appeared during the Jurassic, evolving from a branch oftheropod dinosaurs. Other major events include the appearance of the earliestcrabs and modernfrogs,salamanders andlizards.Mammaliaformes, one of the fewcynodont lineages to survive the end of the Triassic, continued to diversify throughout the period, with the Jurassic seeing the emergence of the firstcrown groupmammals.Crocodylomorphs made the transition from a terrestrial to an aquatic life. The oceans were inhabited bymarine reptiles such asichthyosaurs andplesiosaurs, whilepterosaurs were the dominant flyingvertebrates. Modern sharks and rays first appeared and diversified during the period, while the first known crown-groupteleost fish (the dominant group of modern fish) appeared near the end of the period. The flora was dominated byferns andgymnosperms, includingconifers, of which many modern groups made their first appearance during the period, as well as other groups like the extinctBennettitales.
In 1829, the French naturalistAlexandre Brongniart published a book entitledDescription 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 phraseterrains jurassiques when correlating the "Jura-Kalkstein" of Humboldt with similarly agedoolitic limestones in Britain, thus coining and publishing the term "Jurassic".[4][3]
The German geologistLeopold von Buch in 1839 established the three-fold division of the Jurassic, originally named from oldest to the youngest: theBlack Jurassic,Brown Jurassic, andWhite Jurassic.[5] The term "Lias" had previously been used for strata of equivalent age to the Black Jurassic in England byWilliam Conybeare andWilliam Phillips in 1822. William Phillips, the geologist, worked with William Conybeare to find out more about the Black Jurassic in England.
The FrenchpalaeontologistAlcide d'Orbigny in papers between 1842 and 1852 divided the Jurassic into ten stages based onammonite 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 palaeontologistFriedrich August von Quenstedt in 1858 divided the three series of von Buch in theSwabian Jura into six subdivisions defined by ammonites and other fossils.
The German palaeontologistAlbert Oppel in his studies between 1856 and 1858 altered d'Orbigny's original scheme and further subdivided the stages intobiostratigraphic zones, based primarily on ammonites. Most of the modern stages of the Jurassic were formalized at the Colloque du Jurassique à Luxembourg in 1962.[3]
Folded Lower Jurassic limestone layers of the Doldenhornnappe atGasteretal, SwitzerlandMiddle Jurassic strata inNeuquén Province, ArgentinaTidwell Member of the Morrison Formation (Upper Jurassic), Colorado
Jurassic stratigraphy is primarily based on the use of ammonites asindex fossils. Thefirst appearance datum of specific ammonitetaxa 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.[3]
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 precedingRhaetian. The Hettangian Stage was named by Swiss palaeontologistEugène Renevier in 1864 afterHettange-Grande in north-eastern France.[3] The GSSP for the base of the Hettangian is located at the Kuhjoch Pass,Karwendel Mountains,Northern Calcareous Alps, Austria; it was ratified in 2010. The beginning of the Hettangian, and thus the Jurassic as a whole, is marked by thefirst appearance of the ammonitePsiloceras spelae tirolicum in theKendlbach Formation exposed at Kuhjoch.[7] The base of the Jurassic was previously defined as the first appearance ofPsiloceras 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.[3]
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 ofSemur-en-Auxois, nearDijon. 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 ofEast Quantoxhead, 6 kilometres east ofWatchet,Somerset,England, within theBlue Lias, and was ratified in 2000. The beginning of the Sinemurian is defined by the first appearance of the ammoniteVermiceras quantoxense.[3][8]
The villageThouars (Latin:Toarcium), just south ofSaumur in theLoire Valley ofFrance, 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 atPeniche, Portugal, and was ratified in 2014. The boundary is defined by the first appearance of ammonites belonging to the subgenusDactylioceras(Eodactylites).[10]
The Aalenian is named after the city ofAalen in Germany. The Aalenian was defined by Swiss geologistKarl Mayer-Eymar in 1864. The lower boundary was originally between the dark clays of the Black Jurassic and the overlying clayey sandstone andferruginous oolite of the Brown Jurassic sequences of southwestern Germany.[3] The GSSP for the base of the Aalenian is located atFuentelsaz in theIberian range nearGuadalajara, Spain, and was ratified in 2000. The base of the Aalenian is defined by the first appearance of the ammoniteLeioceras opalinum.[11]
Alcide d'Orbigny in 1842 named the Bajocian Stage after the town ofBayeux (Latin:Bajoce) in Normandy, France. The GSSP for the base of the Bajocian is located in the Murtinheira section atCabo Mondego, Portugal; it was ratified in 1997. The base of the Bajocian is defined by the first appearance of the ammoniteHyperlioceras mundum.[12]
The Bathonian is named after the city ofBath, England, introduced by Belgian geologistd'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 ammoniteGonolkites convergens, at the base of theZigzagiceras zigzag ammonite zone.[13]
The Callovian is derived from theLatinized name of the village ofKellaways inWiltshire, England, and was named by Alcide d'Orbigny in 1852, originally the base at the contact between theForest Marble Formation and theCornbrash Formation. However, this boundary was later found to be within the upper part of the Bathonian.[3] 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 genusKepplerites.[14]
The Oxfordian is named after the city ofOxford in England and was named by Alcide d'Orbigny in 1844 in reference to theOxford Clay. 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 ammoniteQuenstedtoceras mariae (then placed in the genusVertumniceras). Subsequent proposals have suggested the first appearance ofCardioceras redcliffense as the lower boundary.[3][14]
The village ofKimmeridge on the coast ofDorset, England, is the origin of the name of the Kimmeridgian. The stage was named by Alcide d'Orbigny in 1842 in reference to theKimmeridge Clay. The GSSP for the base of the Kimmeridgian is the Flodigarry section atStaffin Bay on theIsle of Skye, Scotland,[15] 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.[14]
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 fromGreek mythology rather than a place name.Tithonus was the son ofLaomedon ofTroy and fell in love withEos, the Greek goddess ofdawn. His name was chosen by Albert Oppel for thisstratigraphical stage because the Tithonian finds itself hand in hand with the dawn of the Cretaceous. The base of the Tithonian currently lacks a GSSP.[3] The working definition for the base of the Tithonian is the first appearance of the ammonite genusGravesia.[14]
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 anychemostratigraphic events, such asisotope excursions (large sudden changes inratios of isotopes), that could be used to define or correlate a boundary.Calpionellids, an enigmatic group ofplanktonicprotists with urn-shaped calcitictests briefly abundant during the latest Jurassic to earliest Cretaceous, have been suggested to represent the most promising candidates for fixing the Jurassic–Cretaceous boundary[16] In particular, the first appearanceCalpionella alpina, co-inciding with the base of the eponymous Alpina subzone, has been proposed as the definition of the base of the Cretaceous.[17] The working definition for the boundary has often been placed as the first appearance of the ammoniteStrambergella jacobi, formerly placed in the genusBerriasella, but its use as a stratigraphic indicator has been questioned, as its first appearance does not correlate with that ofC. alpina.[18]
The Kimmeridge Clay and equivalents are the majorsource rock for theNorth Sea oil.[19] The Arabian Intrashelf Basin, deposited during the Middle and Late Jurassic, is the setting of the world's largest oil reserves, including theGhawar Field, the world's largest oil field.[20] The Jurassic-aged Sargelu[21] and Naokelekan formations[22] are major source rocks foroil in Iraq. Over 1500 gigatons of Jurassic coal reserves are found in north-west China, primarily in theTurpan-Hami Basin and theOrdos Basin.[23]
Major impact structures include theMorokweng 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 Ma.[24] Another major structure is thePuchezh-Katunki crater, 40 kilometres in diameter, buried beneathNizhny Novgorod Oblast in western Russia. The impact has been dated to the Sinemurian, 195.9 ± 1.0 Ma.[25]
Map of geography during the Early Jurassic, around 190 million years ago
At the beginning of the Jurassic, all of the world's major landmasses were coalesced into thesupercontinentPangaea, which during the Early Jurassic began to break up into northern supercontinentLaurasia and the southern supercontinentGondwana.[26] The rifting between North America and Africa was the first to initiate, beginning in the early Jurassic, associated with the emplacement of theCentral Atlantic Magmatic Province.[27]
Map of Europe during the Toarcian Age
During the Jurassic, the NorthAtlantic Ocean remained relatively narrow, while the South Atlantic did not open until the Cretaceous.[28][27] The continents were surrounded byPanthalassa, with theTethys Ocean between Gondwana and Asia. At the end of the Triassic, there was amarine transgression in Europe, flooding most parts of central and western Europe transforming it into an archipelago of islands surrounded by shallow seas.[29] During the Jurassic, both the North and South Pole were covered by oceans.[26] 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 theBaltic Shield andGreenland several hundred kilometers wide.[30][31][32] During the Callovian, theTurgai Epicontinental Sea formed, creating a marine barrier between Europe and Asia.[33]
Map of global geography during the Late Jurassic, around 155 million years ago
Madagascar and Antarctica began to rift away from Africa during the late Early Jurassic in association with the eruption of theKaroo-Ferrar large igneous provinces, opening the westernIndian Ocean and beginning the fragmentation of Gondwana.[34][35] 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.[36]
Formation of the Pacific Plate during the Early Jurassic
During the Early Jurassic, around 190 million years ago, thePacific Plate originated at thetriple junction of theFarallon,Phoenix, andIzanagitectonic plates, the three mainoceanic plates of Panthalassa. The previously stable triple junction had converted to an unstable arrangement surrounded on all sides bytransform faults because of a kink in one of the plate boundaries, resulting in the formation of the Pacific Plate at the centre of the junction.[40] During the Middle to early Late Jurassic, theSundance Seaway, a shallowepicontinental sea, covered much of northwest North America.[41]
Grainstone with calciticooids and sparry calcite cement;Carmel Formation, Middle Jurassic, of southern Utah, US
Theeustatic sea level is estimated to have been close to present levels during the Hettangian and Sinemurian, rising several tens of metres during the late Sinemurian–Pliensbachian before regressing to near present levels by the late Pliensbachian. There seems to have been a gradual rise to a peak of ~75 m above present sea level during the Toarcian. During the latest part of the Toarcian, the sea level again dropped by several tens of metres. It progressively rose from the Aalenian onwards, aside from dips of a few tens of metres in the Bajocian and around the Callovian–Oxfordian boundary, peaking possibly as high as 140 metres above present sea level at the Kimmeridgian–Tithonian boundary. The sea levels falls in the late Tithonian, perhaps to around 100 metres, before rebounding to around 110 metres at the Tithonian–Berriasian boundary.
The sea level within the long-term trends across the Jurassic was cyclical, with 64 fluctuations, 15 of which were over 75 metres. The most notedcyclicity in Jurassic rocks is fourth order, with a periodicity of approximately 410,000 years.[42]
During the Early Jurassic the world's oceans transitioned from anaragonite sea to acalcite sea chemistry, favouring the dissolution ofaragonite and precipitation ofcalcite.[43] The rise of calcareousplankton during the Middle Jurassic profoundly altered ocean chemistry, with the deposition ofbiomineralized plankton on the ocean floor acting as abuffer against large CO2 emissions.[44]
The climate of the Jurassic was generally warmer than that of present, by around 5–10 °C (9–18 °F), withatmospheric 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.[45] 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.[46]Dropstones andglendonites in northeasternSiberia during the Early to Middle Jurassic indicate cold winters.[47] The ocean depths were likely 8 °C (14 °F) warmer than present, andcoral reefs grew 10° of latitude further north and south. TheIntertropical Convergence Zone likely existed over the oceans, resulting in large areas of desert and scrubland in the lower latitudes between 40° N and S of the equator.Tropical rainforest andtundra biomes are likely to have been rare or absent.[46] The Jurassic also witnessed the decline of the Pangaean megamonsoon that had characterised the preceding Permian and Triassic periods.[48] Variation in the frequency ofwildfire activity in the Jurassic was governed by the 405 kyreccentricity cycle.[49] Thanks to the breakup of Pangaea, the hydrological cycle during the Jurassic was significantly enhanced.[50]
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.[47] It has been proposed that glaciation was present in the Northern Hemisphere during both the early Pliensbachian[51] and the latest Pliensbachian.[52][53] There was a spike in global temperatures of around 4–8 °C (7–14 °F) during the early part of the Toarcian corresponding to the Toarcian Oceanic Anoxic Event and the eruption of the Karoo-Ferrarlarge igneous provinces in southern Gondwana, with the warm interval extending to the end of the Toarcian around 174 million years ago.[47] During the Toarcian Warm Interval, ocean surface temperatures likely exceeded 30 °C (86 °F), and equatorial and subtropical (30°N–30°S) regions are likely to have been extremely arid, with temperatures in the interior of Pangea likely in excess of 40 °C (104 °F).The Toarcian Warm Interval is followed by the Middle Jurassic Cool Interval (MJCI) between 174 and 164 Ma,[47] which may have been punctuated by brief, ephemeral icehouse intervals.[54][55] During the Aalenian, precessionally forced climatic changes dictated peatland wildfire magnitude and frequency.[56] The European climate appears to have become noticeably more humid at the Aalenian-Bajocian boundary but then became more arid during the middle Bajocian.[57] A transient ice age possibly occurred in the late Bajocian.[58] The Callovian-Oxfordian boundary at the end of the MJCI witnessed particularly notable global cooling,[59][60] potentially even an ice age.[61] This is followed by the Kimmeridgian Warm Interval (KWI) between 164 and 150 Ma.[47] Based on fossilwood distribution, this was one of the wettest intervals of the Jurassic.[62] 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.[47] A prominent drop in temperatures occurred during the Tithonian, known as the Early Tithonian Cooling Event (ETCE).[60] The end of the Jurassic was marked by the Tithonian–early Barremian Cool Interval (TBCI), beginning 150 Ma and continuing into theEarly Cretaceous.[47]
The Toarcian Oceanic Anoxic Event (TOAE), also known as the Jenkyns Event, was an episode of widespreadoceanic anoxia during the early part of the Toarcian Age, c. 183 Ma. It is marked by a globally documented high amplitude negativecarbon isotope excursion,[63][64] as well as the deposition of blackshales[65] and the extinction and collapse of carbonate-producing marine organisms, associated with a major rise in global temperatures.[66]
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 ofmethane clathrates.[66] This likely accelerated thehydrological cycle and increasedsilicate weathering, as evidenced by an increased amount of organic matter of terrestrial origin found in marine deposits during the TOAE.[67] Groups affected include ammonites,[68]ostracods,[65][69]foraminifera,[70][71]bivalves,[65]cnidarians, and especiallybrachiopods,[72][73][74] for which the TOAE represented one of the most severe extinctions in their evolutionary history.[75] While the event had significant impact on marine invertebrates, it had little effect on marine reptiles.[76] During the TOAE, theSichuan Basin was transformed into a giantlake, probably three times the size of modern-dayLake Superior, represented by the Da'anzhai Member of theZiliujing Formation. The lake likelysequestered ~460 gigatons (Gt) of organic carbon and ~1,200 Gt of inorganic carbon during the event.[77] SeawaterpH, 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.[78] Thisocean acidification is the probable cause of the collapse of carbonate production.[79][80] Additionally, anoxic conditions were exacerbated by enhanced recycling ofphosphorus 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.[81]
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.[82]
There is no evidence of a mass extinction of plants at the Triassic–Jurassic boundary.[83] At the Triassic–Jurassic boundary in Greenland, the sporomorph (pollen and spores) record suggests a complete floral turnover.[84] An analysis of macrofossil floral communities in Europe suggests that changes were mainly due to localecological succession.[85] At the end of the Triassic, thePeltaspermaceae became extinct in most parts of the world, withLepidopteris persisting into the Early Jurassic in Patagonia.[86]Dicroidium, acorystosperm 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.[87]
Conifers formed a dominant component of Jurassic floras. The Late Triassic and Jurassic was a major time of diversification of conifers, with most modern conifer groups appearing in the fossil record by the end of the Jurassic, having evolved fromvoltzialean ancestors.[88][89]
Araucarian conifers have their first unambiguous records during the Early Jurassic, and members of the modern genusAraucaria were widespread across both hemispheres by the Middle Jurassic.[89][90][91]
Also abundant during the Jurassic is the extinct familyCheirolepidiaceae, often recognised through their highly distinctiveClassopolis pollen. Jurassic representatives include the pollen coneClassostrobus and the seed conePararaucaria. Araucarian and Cheirolepidiaceae conifers often occur in association.[92]
The oldest definitive record of the cypress family (Cupressaceae) isAustrohamia minuta from the Early Jurassic (Pliensbachian) of Patagonia, known from many parts of the plant.[93] The reproductive structures ofAustrohamia have strong similarities to those of the primitive living cypress generaTaiwania andCunninghamia. By the Middle to Late Jurassic Cupressaceae were abundant in warm temperate–tropical regions of the Northern Hemisphere, most abundantly represented by the genusElatides.[94] The Jurassic also saw the first appearances of some modern genera of cypresses, such asSequoia.[95]
Members of the extinct genusSchizolepidopsis which likely represent astem-group to the pine family (Pinaceae), were widely distributed across Eurasia during the Jurassic.[96][97] The oldest unambiguous record of Pinaceae is thepine coneEathiestrobus, known from the Late Jurassic (Kimmeridgian) of Scotland, which remains the only known unequivocal fossil of the group before the Cretaceous.[98] Despite being the earliest known member of the Pinaceae,Eathiestrobus appears to be a member of thepinoidclade of the family, suggesting that the initial diversification of Pinaceae occurred earlier than has been found in the fossil record.[99][89]
The earliest record of the yew family (Taxaceae) isPalaeotaxus rediviva, from the Hettangian of Sweden, suggested to be closely related to the livingAustrotaxus, whileMarskea jurassica from the Middle Jurassic of Yorkshire, England and material from the Callovian–OxfordianDaohugou Bed in China are thought to be closely related toAmentotaxus, with the latter material assigned to the modern genus, indicating that Taxaceae had substantially diversified by the end of the Jurassic.[100]
The oldest unambiguous members ofPodocarpaceae are known from the Jurassic, found across both hemispheres, includingScarburgia andHarrisiocarpus from the Middle Jurassic of England, as well as unnamed species from the Middle-Late Jurassic of Patagonia.[101]
During the Early Jurassic, the flora of the mid-latitudes of Eastern Asia were dominated by the extinct deciduous broad leafed coniferPodozamites, 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.[102]
Leaves ofGinkgo huttonii from the Middle Jurassic of England
Ginkgoales, of which the sole living species isGinkgo biloba, were more diverse during the Jurassic: they were among the most important components of Eurasian Jurassic floras and were adapted to a wide variety of climatic conditions.[103] The earliest representatives of the genusGinkgo, represented byovulate and pollen organs similar to those of the modern species, are known from the Middle Jurassic in the Northern Hemisphere.[103] Several other lineages of ginkgoaleans are known from Jurassic rocks, includingYimaia,Grenana,Nagrenia andKarkenia. These lineages are associated withGinkgo-like leaves, but are distinguished from living and fossil representatives ofGinkgo by having differently arranged reproductive structures.[103][104]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 Ginkgoalessensu lato.[105]
Restoration of a member ofBennettitales belonging to Williamsoniaceae.
Bennettitales, having first become widespread during the preceding Triassic, were diverse and abundant members of Jurassic floras across both hemispheres.[106] 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 ofstomata, and the two groups are not thought to be closely related.[107] Jurassic Bennettitales predominantly belong to the groupWilliamsoniaceae,[106] which grew as shrubs and small trees. The Williamsoniaceae are thought to have had adivaricate branching habit, similar to that of livingBanksia, and adapted to growing in open habitats with poor soil nutrient conditions.[108] Bennettitales exhibit complex,flower-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 askalligrammatid lacewings[109] and extant ones such asacrocerid flies,[110] are suggested to have been pollinators of bennettitales, feeding onnectar produced by bennettitalean cones.
Cycads reached their apex of diversity during the Jurassic and Cretaceous Periods.[111] 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 andNilssoniales, which have cycad-like foliage, being dominant.[112] 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.[113] The relationships of most Mesozoic cycads to living groups are ambiguous,[112] with no Jurassic cycads belonging to either of the two modern groups of cycads, though some Jurassic cycads possibly representstem-group relatives of modernCycadaceae, like the leaf genusParacycas known Europe, andZamiaceae, like some European species of the leaf genusPseudoctenis. Also widespread during the Jurassic was the extinctCtenis lineage, which appears to be distantly related to modern cycads.[114] Modern cycads are pollinated by beetles, and such an association is thought to have formed by the Early Jurassic.[111]
Although there have been several claimed records, there are no widely accepted Jurassic fossil records offlowering plants, which make up 90% of living plant species, and fossil evidence suggests that the group diversified during the following Cretaceous.[115]
The earliest knowngnetophytes, one of the four main living groups ofgymnosperms, appeared by the end of the Jurassic, with the oldest unequivocal gnetophyte being the seedDayvaultia from the Late Jurassic of North America.[116]
Life restoration of the stem and leaves of a member of the extinct seed plant orderCaytoniales, a group which reached its apex of abundance during the Jurassic, and which may be closely related to livingflowering plants.
"Seed ferns" (Pteridospermatophyta) is a collective term to refer to disparate lineages of fern like plants that produce seeds but have uncertain affinities to livingseed plant groups. A prominent group of Jurassic seed ferns is theCaytoniales, which reached their zenith during the Jurassic, with widespread records in the Northern Hemisphere, though records in the Southern Hemisphere remain rare. Due to theirberry-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.[117]Corystosperm-aligned seed ferns, such asPachypteris andKomlopteris were widespread across both hemispheres during the Jurassic.[118]
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[119]) to Cretaceous.[120] 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.[119] The genusPhoenicopsis was widespread in Early-Middle Jurassic floras of Eastern Asia and Siberia.[121]
ThePentoxylales, a small but clearly distinct group ofliana-like seed plants of obscure affinities, first appeared during the Jurassic. Their distribution appears to have been confined to Eastern Gondwana.[122]
TheCyatheales, the group containing most modern tree ferns, appeared during the Late Jurassic, represented by members of the genusCyathocaulis, which are suggested to be early members ofCyatheaceae on the basis of cladistic analysis.[127] Only a handful of possible records exist of theHymenophyllaceae from the Jurassic, includingHymenophyllites macrosporangiatus from the Russian Jurassic.[128]
The oldest remains of modernhorsetails of the genusEquisetum first appear in the Early Jurassic, represented byEquisetum dimorphum from the Early Jurassic of Patagonia[129] andEquisetum laterale from the Early to Middle Jurassic of Australia.[130][131]Silicified remains ofEquisetum thermale from the Late Jurassic of Argentina exhibit all the morphological characters of modern members of the genus.[132] The estimated split betweenEquisetum bogotense and all other livingEquisetum is estimated to have occurred no later than the Early Jurassic.[131]
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 modernIsoetes. More primitive forms such asNathorstiana, which retain an elongated stem, persisted into the Early Cretaceous.[133]
Dinosaurs, which had morphologically diversified in the Late Triassic, experienced a major increase in diversity and abundance during the Early Jurassic in the aftermath of the end-Triassic extinction and the extinction of other reptile groups, becoming the dominant vertebrates in terrestrial ecosystems.[139][140]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.[141]
Advancedtheropods belonging toNeotheropoda first appeared in the Late Triassic. Basal neotheropods, such ascoelophysoids anddilophosaurs, persisted into the Early Jurassic, but became extinct by the Middle Jurassic.[142] The earliestaverostrans appear during the Early Jurassic, with the earliest known member ofCeratosauria beingSaltriovenator from the early Sinemurian (199.3–197.5 Ma) of Italy.[143] The unusual ceratosaurLimusaurus from the Late Jurassic of China had a herbivorous diet, with adults havingedentulous beaked jaws,[144] making it the earliest known theropod to have converted from an ancestrally carnivorous diet.[145] The earliest members of theTetanurae appeared during the late Early Jurassic or early Middle Jurassic.[146] TheMegalosauridae represent the oldest radiation of the Tetanurae, first appearing in Europe during the Bajocian.[147] The oldest member ofAllosauroidea has been suggested to beAsfaltovenator from the Middle Jurassic of South America.[146]Coelurosaurs first appeared during the Middle Jurassic, including earlytyrannosaurs such asProceratosaurus from the Bathonian of Britain.[148] Some coelurosaurs from the Late Jurassic of China includingShishugounykus andHaplocheirus are suggested to represent earlyalvarezsaurs,[149] however, this has been questioned.[150]Scansoriopterygids, a group of small feathered coelurosaurs with membraneous, bat-like wings for gliding, are known from the Middle to Late Jurassic of China.[151] The oldest record oftroodontids is suggested to beHesperornithoides from the Late Jurassic of North America. Tooth remains suggested to represent those ofdromaeosaurs are known from the Jurassic, but no body remains are known until the Cretaceous.[152]
Skeleton ofCeratosaurus, a ceratosaurid from the Late Jurassic of North America
Skeleton ofMonolophosaurus, a basal tetanuran from the Middle Jurassic of China
Restoration ofYi qi, a scansoriopterygid from the Middle to Late Jurassic of China
The earliestavialans, which include birds and their ancestors, appear during the Middle to Late Jurassic, definitively represented byArchaeopteryx from the Late Jurassic of Germany. Avialans belong to the cladeParaves within Coelurosauria, which also includes dromaeosaurs and troodontids. TheAnchiornithidae from the Middle-Late Jurassic of Eurasia have frequently suggested to be avialans, but have also alternatively found as a separate lineage of paravians.[153]
Skeleton ofHeterodontosaurus, a primitive ornithischian from the Early Jurassic of South Africa
Sauropods became the dominant large herbivores in terrestrial ecosystems during the Jurassic.[158] Some Jurassic sauropods reached gigantic sizes, becoming the largest organisms to have ever lived on land.[159]
Basal bipedalsauropodomorphs, such asmassospondylids, continued to exist into the Early Jurassic, but became extinct by the beginning of the Middle Jurassic.[158] Quadrupedal sauropomorphs appeared during the Late Triassic. The quadrupedalLedumahadi from the earliest Jurassic of South Africa reached an estimated weight of 12 tons, far in excess of other known basal sauropodomorphs.[160]Gravisaurian sauropods first appeared during the Early Jurassic, with the oldest definitive record beingVulcanodon from Zimbabwe, likely of Sinemurian age.[161]Eusauropods first appeared during the late Early Jurassic (Toarcian) and diversified during the Middle Jurassic;[158] these includedcetiosaurids,turiasaurs,[162] andmamenchisaurs.[163]Neosauropods such asmacronarians anddiplodocoids first appeared during the Middle Jurassic, before becoming abundant and globally distributed during the Late Jurassic.[164]
The Triassic–Jurassic extinction decimatedpseudosuchian diversity, withcrocodylomorphs, which originated during the early Late Triassic, being the only group of pseudosuchians to survive. All other pseudosuchians, including the herbivorousaetosaurs and carnivorous "rauisuchians", became extinct.[165] 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 differentecological niches to their Triassic counterparts and that there was an extensive and rapid radiation of crocodylomorphs during this interval.[166] While livingcrocodilians are mostly confined to an aquatic ambush predator lifestyle, Jurassic crocodylomorphs exhibited a wide variety of life habits. An unnamedprotosuchid known from teeth from the Early Jurassic of Arizona represents the earliest known herbivorous crocodylomorph, an adaptation that appeared several times during the Mesozoic.[167]
TheThalattosuchia, a clade of predominantly marine crocodylomorphs, first appeared during the Early Jurassic and became a prominent part of marine ecosystems.[168] Within Thalattosuchia, theMetriorhynchidae 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.[169] 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-leggedsphenosuchians, earlycrocodyliforms and thalattosuchians.[170][168] TheNeosuchia, 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.[171] The timing of the origin of Neosuchia is disputed. The oldest record of Neosuchians has been suggested to beCalsoyasuchus, from the Early Jurassic of Arizona, which in many analyses has been recovered as the earliest branching member of the neosuchian familyGoniopholididae, 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.[171]Razanandrongobe from the Middle Jurassic of Madagascar has been suggested to represent the oldest record ofNotosuchia, a primarily Gondwanan clade of mostly terrestrial crocodylomorphs, otherwise known from the Cretaceous and Cenozoic.[172]
Stem-group turtles (Testudinata) diversified during the Jurassic. Jurassic stem-turtles belong to two progressively more advanced clades, theMesochelydia andPerichelydia.[173] It is thought that the ancestral condition for mesochelydians is aquatic, as opposed to terrestrial for testudinates.[174] The two modern groups of turtles (Testudines),Pleurodira andCryptodira, diverged by the beginning of the Late Jurassic.[173] The oldest known pleurodires, thePlatychelyidae, are known from the Late Jurassic of Europe and the Americas,[175] while the oldest unambiguous cryptodire,Sinaspideretes, an early relative ofsoftshell turtles, is known from the Late Jurassic of China.[176] TheThalassochelydia, a diverse lineage of marine turtles unrelated to modernsea turtles, are known from the Late Jurassic of Europe and South America.[177]
Rhynchocephalians (the sole living representative being thetuatara) had achieved a global distribution by the beginning of the Jurassic,[178] and represented the dominant group of small reptiles during the Jurassic globally.[179] Rhynchocephalians reached their highest morphological diversity in their evolutionary history during the Jurassic, occupying a wide range of lifestyles, including the aquaticpleurosaurs with long snake-like bodies and reduced limbs, the specialized herbivorouseilenodontines, as well as thesapheosaurs which had broad tooth plates indicative ofdurophagy.[180] Rhynchocephalians disappeared from Asia after the Early Jurassic.[178] The last common ancestor of livingsquamates (which includeslizards andsnakes) 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.[181] Squamates first appear in the fossil record during the Middle Jurassic[182] including members of modern clades such asScincomorpha,[183] though many Jurassic squamates have unclear relationships to living groups.[184]Eichstaettisaurus from the Late Jurassic of Germany has been suggested to be an early relative ofgeckos and displays adaptations for climbing.[185]Dorsetisaurus from the Late Jurassic of North America and Europe represents the oldest widely accepted record ofAnguimorpha.[186]Marmoretta from the Middle Jurassic of Britain has been suggested to represent a late survivinglepidosauromorph outside both Rhynchocephalia and Squamata, though some studies have recovered it as a stem-squamate.[187]
The earliest known remains ofChoristodera, 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-likeCteniogenys, 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.[188] The other isCoeruleodraco from the Late Jurassic of China, which is a more advanced choristodere, though still small and lizard-like in morphology.[189]
Ichthyosaurs suffered anevolutionary bottleneck during the end-Triassic extinction, with all non-neoichthyosaurians becoming extinct. Ichthyosaurs reached their apex of species diversity during the Early Jurassic, with an array of morphologies including the hugeapex predatorTemnodontosaurus and swordfish-likeEurhinosaurus, though Early Jurassic ichthyosaurs were significantly less morphologically diverse than their Triassic counterparts.[190][191] 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 theOphthalmosauridae, the clade that would encompass almost all ichthyosaurs from then on, during the early Bajocian.[192] 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.[192][190][191]
Plesiosaurs originated at the end of the Triassic (Rhaetian). By the end of the Triassic, all othersauropterygians, includingplacodonts andnothosaurs, had become extinct. At least six lineages of plesiosaur crossed the Triassic–Jurassic boundary.[193] Plesiosaurs were already diverse in the earliest Jurassic, with the majority of plesiosaurs in the Hettangian-aged Blue Lias belonging to theRhomaleosauridae. Early plesiosaurs were generally small-bodied, with body size increasing into the Toarcian.[194] There appears to have been a strong turnover around the Early–Middle Jurassic boundary, withmicrocleidids 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, theCryptoclididae during the Bajocian.[192] The Middle Jurassic saw the evolution of short-necked and large-headedthalassophonean pliosaurs from ancestrally small-headed, long-necked forms.[195][192] Some thalassophonean pliosaurs, such as some species ofPliosaurus, had skulls up to two metres in length with body lengths estimated around 10–12 meters (33–39 ft), making them the apex predators of Late Jurassic oceans.[196][192] 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.[197][198]
Pterosaurs first appeared in the Late Triassic. A major radiation of Jurassic pterosaurs is theRhamphorhynchidae, which first appeared in the late Early Jurassic (Toarcian);[199] they are thought to beenpiscivorous.[200]Anurognathids, which first appeared in the Middle Jurassic, possessed short heads and densely furred bodies, and are thought to have been insectivores.[200] Derivedmonofenestratan pterosaurs such aswukongopterids appeared in the late Middle Jurassic. Advanced short-tailedpterodactyloids first appeared at the Middle–Late Jurassic boundary. Jurassic pterodactyloids include thectenochasmatids, likeCtenochasma, which have closely spaced needle-like teeth that were presumably used forfilter feeding.[200] The bizarre Late JurassicctenochasmatoidCycnorhamphus had a jaw with teeth only at the tips, with bent jaws like those of livingopenbill storks that may have been used to hold and crush hard invertebrates.[200]
Skeleton ofKaraurus sharovi, a stem-group salamander from the Middle to Late Jurassic of Kazakhstan
The diversity oftemnospondyls had progressively declined through the Late Triassic, with onlybrachyopoids surviving into the Jurassic and beyond.[201] Members of the familyBrachyopidae are known from Jurassic deposits in Asia,[202] while thechigutisauridSiderops is known from the Early Jurassic of Australia.[203] Modernlissamphibians began to diversify during the Jurassic. The Early JurassicProsalirus thought to represent the first frog relative with a morphology capable of hopping like living frogs.[204] Morphologically recognisable stem-frogs like the South AmericanNotobatrachus are known from the Middle Jurassic,[205] with modern crown-group frogs likeEnneabatrachus andRhadinosteus appearing by the Late Jurassic.[206] While the earliest salamander-line amphibians are known from the Triassic,[207]crown group salamanders first appear during the Middle to Late Jurassic in Eurasia, alongside stem-group relatives. Many Jurassic stem-group salamanders, such asMarmorerpeton andKokartus, are thought to have beenneotenic.[208] Early representatives of crown group salamanders includeChunerpeton,Pangerpeton andLinglongtriton from the Middle to Late JurassicYanliao Biota of China. Some of these are suggested to belong toCryptobranchoidea, which contains livingAsiatic andgiant salamanders.[209]Beiyanerpeton, andQinglongtriton from the same biota are thought to be early members ofSalamandroidea, the group which contains all other living salamanders.[210][211] Salamanders dispersed into North America by the end of the Jurassic, as evidenced byIridotriton, found in the Late JurassicMorrison Formation.[212] The stem-caecilianEocaecilia is known from the Early Jurassic of Arizona.[213] The fourth group of lissamphibians, the extinct salamander-likealbanerpetontids, first appeared in the Middle Jurassic, represented byAnoualerpeton priscus from the Bathonian of Britain, as well as indeterminate remains from equivalently aged sediments in France and theAnoual Formation of Morocco.[214]
Henkelotherium, a likely arboreal dyolestoid from the Late Jurassic of Portugal
Mammaliaformes, includingmammals, having originated fromcynodonts at the end of the Triassic, diversified extensively during the Jurassic.[215] While most Jurassic mammalaliaforms are solely known from isolated teeth and jaw fragments, exceptionally preserved remains have revealed a variety of lifestyles.[215] ThedocodontanCastorocauda was adapted to aquatic life, similarly to theplatypus andotters.[216] Some members ofHaramiyida[217] and theeutriconodontan tribeVolaticotherini[218] had apatagium akin to those offlying squirrels, allowing them to glide through the air. Theaardvark-like mammalFruitafossor, of uncertain taxonomy, was likely a specialist on colonial insects, similarly to livinganteaters.[219]Australosphenida, a group of mammals possibly related to livingmonotremes, first appeared in the Middle Jurassic of Gondwana.[220] The earliest records ofmultituberculates, one of the longest lasting and most successful orders of mammals, are known from the Middle Jurassic.[221]Therian mammals, represented today by livingplacentals andmarsupials, diversified meteorically during the Middle Jurassic.[222] They have their earliest records during the early Late Jurassic, represented byJuramaia, aeutherian mammal closer to the ancestry of placentals than marsupials.[223]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 thatJuramaia may also originate from the Early Cretaceous instead.[224] Two groups of non-mammaliaform cynodonts persisted beyond the end of the Triassic. The insectiviorousTritheledontidae has a few records from the Early Jurassic. TheTritylodontidae, a herbiviorous group of cynodonts that first appeared during the Rhaetian, has abundant records from the Jurassic, overwhelmingly from the Northern Hemisphere.[225][226]
Fossils and life restorations of the two species ofYanliaomyzon , alamprey known from the Middle Jurassic of China
The last known species ofconodont, a class ofjawless fish whose hard, tooth-like elements are key index fossils, finally became extinct during the earliest Jurassic after over 300 million years of evolutionary history, with an asynchronous extinction occurring first in the Tethys and eastern Panthalassa and survivors persisting into the earliest Hettangian of Hungary and central Panthalassa.[227] End-Triassic conodonts were represented by only a handful of species and had been progressively declining through the Middle and Late Triassic.[228]Yanliaomyzon from the Middle Jurassic of China represents the oldest post Paleozoiclamprey, and the oldest lamprey to have the toothed feeding apparatus and likely the three stage life cycle typical of modern members of the group.[229]
Lungfish (Dipnoi) were present in freshwater environments of both hemispheres during the Jurassic.[230] Some studies have proposed that the last common ancestor of all living lungfish lived during the Jurassic.[231]Mawsoniids, a marine and freshwater/brackish group ofcoelacanths, which first appeared in North America during the Triassic, expanded into Europe and South America by the end of the Jurassic.[232] The marineLatimeriidae, which contains the living coelacanths of the genusLatimeria, were also present in the Jurassic, having originated in the Triassic, with a number of records from the Jurassic of Europe includingSwenzia, thought to be the closest known relative of living coelacanths.[233]
Fossil ofThrissops, anichthyodectid stem-group teleost from the Late Jurassic Solnhofen Limestone of Germany, showing preserved colouration
Ray-finned fish (Actinopterygii) 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 morederived actinopterygian lineages.[234] The oldest knownAcipenseriformes, the group that contains livingsturgeon andpaddlefish, are from the Early Jurassic.[235]Amiiform fish (which today only includes thebowfin) first appeared during the Early Jurassic, represented byCaturus 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,[236] with the modern familyAmiidae appearing during the Late Jurassic.[237]Pycnodontiformes, which first appeared in the western Tethys during the Late Triassic, expanded to South America and Southeast Asia by the end of the Jurassic, having a high diversity in Europe during the Late Jurassic.[236] During the Jurassic, theGinglymodi, the only living representatives beinggars (Lepisosteidae) were diverse in both freshwater and marine environments. The oldest known representatives of anatomically modern gars appeared during the Late Jurassic.[238] Stem-groupteleosts, 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 asElopomorpha andOsteoglossoidei appearing during this time.[239][240] ThePachycormiformes, a group of marine stem-teleosts, first appeared in the Early Jurassic and included bothtuna-like predatory and filter-feeding forms, the latter included the largest bony fish known to have existed:Leedsichthys, with an estimated maximum length of over 15 metres, known from the late Middle to Late Jurassic.[241]
Fossil ofPseudorhina from the Late Jurassic of Germany, a close relative of modernangelsharks.
During the Early Jurassic, the shark-likehybodonts, which represented the dominant group ofchondrichthyans 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 modernneoselachians, but remained common in freshwater and restricted marine environments.[242][243] The Neoselachii, which contains all living sharks and rays, radiated beginning in the Early Jurassic.[244] The oldest known ray (Batoidea) isAntiquaobatis from the Pliensbachian of Germany.[245] Jurassic batoids known from complete remains retain a conservative,guitarfish-like morphology.[246] The oldest knownHexanchiformes andcarpet sharks (Orectolobiformes) are from the Early Jurassic (Pliensbachian and Toarcian, respectively) of Europe.[247][248] The oldest known members of theHeterodontiformes, the only living members of which are thebullhead shark (Heterodontus), first appeared in the Early Jurassic, with representatives of the living genus appearing during the Late Jurassic.[249] The oldest record of angelsharks (Squatiniformes) isPseudorhina 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.[250] The oldest known remains ofCarcharhiniformes, 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 livingcatsharks.[251]Synechodontiformes, an extinct group of sharks closely related to Neoselachii, were also widespread during the Jurassic.[252] The oldest remains of modernchimaeras are from the Early Jurassic of Europe, with members of the living familyCallorhinchidae appearing during the Middle Jurassic. Unlike most living chimaeras, Jurassic chimeras are often found in shallow water environments.[253] The closely relatedmyriacanthids and the flattenedSqualoraja are also known from the Jurassic of Europe.[254]
There appears to have been no major extinction of insects at the Triassic–Jurassic boundary.[83] Many important insect fossil localities are known from the Jurassic of Eurasia, the most important being theKarabastau 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.[255] The increasing diversity of insects in the Middle–Late Jurassic corresponds with a substantial increase in the diversity ofinsect mouthparts.[256] The Middle to Late Jurassic was a time of major diversification forbeetles,[257] particularly for the suborderPolyphaga, which represents 90% of living beetle species but which was rare during the preceding Triassic.[258]Weevils first appear in the fossil record during the Middle to Late Jurassic, but are suspected to have originated during the Late Triassic to Early Jurassic.[259]Orthopteran diversity had declined during the Late Triassic, but recovered during the Early Jurassic,[260] with theHagloidea, a superfamily ofensiferan orthopterans today confined to a few living species, being particularly diverse during the Jurassic.[261] The oldest knownlepidopterans (the group containing butterflies and moths) are known from the Triassic–Jurassic boundary, with wing scales belonging to the suborderGlossata andMicropterigidae-grade moths from the deposits of this age in Germany.[262] Modern representatives of bothdragonflies anddamselflies also first appeared during the Jurassic.[263] Although modern representatives are not known until the Cenozoic,ectoparasitic insects thought to represent primitivefleas, belonging to the familyPseudopulicidae, 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.[264][265]Parasitoid wasps (Apocrita) first appeared during the Early Jurassic and subsequently became widespread, reshaping terrestrial food webs.[266] The Jurassic saw also saw the first appearances of several other groups of insects, includingPhasmatodea (stick insects),[267]Mantophasmatidae (gladiators),[268]Embioptera (webspinners),[269] andRaphidioptera (snakeflies).[270] The earliestscale insect (Coccomorpha)is known from amber dating to the Late Jurassic, though the group probably originated earlier during the Triassic.[271]
Only a handful of records of mites are known from the Jurassic, includingJureremus, anoribatid mite belonging to the familyCymbaeremaeidae known from the Late Jurassic of Britain and Russia,[272] and a member of the still living orbatid genusHydrozetes from the Early Jurassic of Sweden.[273] Spiders diversified through the Jurassic.[274] The Early JurassicSeppo koponeni may represent a stem group toPalpimanoidea.[275]Eoplectreurys from the Middle Jurassic of China is considered a stem lineage ofSynspermiata. The oldest member of the familyArchaeidae,Patarchaea, is known from the Middle Jurassic of China.[274]Mongolarachne from the Middle Jurassic of China is among the largest known fossil spiders, with legs over 5 centimetres long.[276] The only scorpion known from the Jurassic isLiassoscorpionides from the Early Jurassic of Germany, of uncertain placement.[277]Eupnoi harvestmen (Opiliones) are known from the Middle Jurassic of China, including members of the familySclerosomatidae.[278][279]
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.Sessilefilter feeders andphotosymbiotic organisms were among those most severely affected.[280]
Having declined at the Triassic–Jurassic boundary, reefs substantially expanded during the Late Jurassic, including bothsponge reefs andscleractiniancoral reefs. Late Jurassic reefs were similar in form to modern reefs but had more microbial carbonates and hypercalcifiedsponges, and had weak biogenic binding. Reefs sharply declined at the close of the Jurassic,[281] which caused an associated drop in diversity indecapod crustaceans.[282] The earliest planktonic foraminifera, which constitute the suborderGlobigerinina, 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.[283]Coccolithophores anddinoflagellates, which had first appeared during the Triassic, radiated during the Early to Middle Jurassic, becoming prominent members of thephytoplankton.[284]Microconchid tube worms, the last remaining order ofTentaculita, a group of animals of uncertain affinities that were convergent onSpirorbis tube worms, were rare after the Triassic and had become reduced to the single genusPunctaconchus, which became extinct in the late Bathonian.[285] The oldest knowndiatom is from Late Jurassic–aged amber from Thailand, assigned to the living genusHemiaulus.[286]
Crinoids diversified throughout the Jurassic, reaching their peak Mesozoic diversity during the Late Jurassic, primarily due to the radiation of sessile forms belonging to the ordersCyrtocrinida andMillericrinida.[287]Echinoids (sea urchins) underwent substantial diversification beginning in the Early Jurassic, primarily driven by the radiation of irregular (asymmetrical) forms, which were adapting to deposit feeding. Rates of diversification sharply dropped during the Late Jurassic.[288]
Eryon, apolychelidan decapod crustacean from the Late Jurassic of Germany.
The Jurassic was a significant time for the evolution ofdecapods.[282] The first true crabs (Brachyura) are known from the Early Jurassic, with the earliest beingEocarcinus praecursor from the early Pliensbachian of England, which lacked the crab-like morphology (carcinisation) of modern crabs,[289] andEoprosopon klugi from the late Pliensbachian of Germany, which may belong to the living familyHomolodromiidae.[290] Most Jurassic crabs are known only fromcarapace pieces, which makes it difficult to determine their relationships.[291] 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.[291][282]Hermit crabs also first appeared during the Jurassic, with the earliest known beingSchobertella hoelderi from the late Hettangian of Germany.[292] Early hermit crabs are associated with ammonite shells rather than those of gastropods.[293]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.[294] Jurassic barnacles were of low diversity compared to present,[295] but several important evolutionary innovations are known, including the first appearances of calcite shelled forms and species with an epiplanktonic mode of life.[296]
Brachiopod diversity declined during the Triassic–Jurassic extinction. Spire-bearing brachiopods (Spiriferinida andAthyridida) did not recover their biodiversity, becoming extinct in the TOAE.[297]Rhynchonellida andTerebratulida also declined during the Triassic–Jurassic extinction but rebounded during the Early Jurassic; neither clade underwent much morphological variation.[298] Brachiopods substantially declined in the Late Jurassic; the causes are poorly understood. Proposed reasons include increased predation, competition with bivalves, enhancedbioturbation or increasedgrazing pressure.[299]
Like the preceding Triassic,bryozoan diversity was relatively low compared to the Paleozoic. The vast majority of Jurassic bryozoans are members ofCyclostomatida, which experienced a radiation during the Middle Jurassic, with all Jurassic representatives belonging to the subordersTubuliporina andCerioporina.Cheilostomata, the dominant group of modern bryozoans, first appeared during the Late Jurassic.[300]
Marine gastropods were significantly affected by the T-J extinction, with around 56% of genera going extinct, withNeritimorpha being particularly strongly effected, whileHeterobranchia suffered much lower losses than other groups.[301] While present, the diversity offreshwater andland snails 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.[302]
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.[303] Bivalve family level diversity after the Early Jurassic was static, though genus diversity experienced a gradual increase throughout the period.[304]Rudists, the dominant reef-building organisms of the Cretaceous, first appeared in the Late Jurassic (mid-Oxfordian) in the northern margin of the western Tethys, expanding to the eastern Tethys by the end of the Jurassic.[305]
Fossil specimen ofProteroctopus from the Middle Jurassic of France, formerly thought to be world's oldest known octopus
Ammonites were devastated by the end-Triassic extinction, with only a handful of genera belonging to the familyPsiloceratidae of the suborderPhylloceratina surviving and becoming ancestral to all later Jurassic and Cretaceous ammonites. Ammonites explosively diversified during the Early Jurassic, with the ordersPsiloceratina,Ammonitina,Lytoceratina,Haploceratina,Perisphinctina andAncyloceratina 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.[306] Ammonite diversifications occurred coevally withmarine transgressions, while their diversity nadirs occurred duringmarine regressions.[307]
The oldest definitive records of the squid-likebelemnites are from the earliest Jurassic (Hettangian–Sinemurian) of Europe and Japan; they expanded worldwide during the Jurassic.[308] Belemnites were shallow-water dwellers, inhabiting the upper 200 metres of the water column on thecontinental shelves and in thelittoral zone. They were key components of Jurassic ecosystems, both as predators and prey, as evidenced by the abundance of belemnite guards in Jurassic rocks.[309]
The earliestvampyromorphs, of which the only living member is thevampire squid, first appeared during the Early Jurassic.[310] The earliestoctopuses appeared during the Middle Jurassic, having split from their closest living relatives, the vampyromorphs, during the Triassic to Early Jurassic.[311] All Jurassic octopuses are solely known from the hardgladius.[311][312] Octopuses likely originated from bottom-dwelling (benthic) ancestors which lived in shallow environments.[311]Proteroctopus from the late Middle JurassicLa 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.[313]
^Brongniart, Alexandre (1829).Tableau des terrains qui composent l'écorce du globe ou essai sur la structure de la partie connue de la terre [Description of the Terrains that Constitute the Crust of the Earth or Essay on the Structure of the Known Lands of the Earth] (in French). Strasbourg, France: F.G. Levrault – via Gallica. From p. 221, footnote 2:"Souvent aussi calcaire oolithique moyen ou principal (great oolithe); mais le nom de terrains jurassiques nous paroît préférable […] analogue à celle de la chaîne du Jura." (Often also middle or principal oolitic limestone (great oolithe); but the name of "Jurassic terrains" seems to us preferable, because it is more general, because it indicates a terrain composed of different rocks, being in a geognostic position analogous to that of the Jura chain.)
^von Buch, L., 1839. Über den Jura in Deutschland. Der Königlich Preussischen Akademie der Wissenschaften, Berlin, p. 87.
^BARSKI, Marcin (2018-09-06). "Dinoflagellate cyst assemblages across the Oxfordian/Kimmeridgian boundary (Upper Jurassic) at Flodigarry, Staffin Bay, Isle of Skye, Scotland – a proposed GSSP for the base of the Kimmeridgian".Volumina Jurassica.XV (1):51–62.doi:10.5604/01.3001.0012.4594 (inactive 20 August 2025).ISSN1731-3708.S2CID133861564.{{cite journal}}: CS1 maint: DOI inactive as of August 2025 (link)
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^Rothwell, Gar W.; Mapes, Gene; Stockey, Ruth A.; Hilton, Jason (April 2012). "The seed cone Eathiestrobus gen. nov.: Fossil evidence for a Jurassic origin of Pinaceae".American Journal of Botany.99 (4):708–720.Bibcode:2012AmJB...99..708R.doi:10.3732/ajb.1100595.PMID22491001.
^Tian, Ning; Wang, Yong-Dong; Zhang, Wu; Zheng, Shao-Lin; Zhu, Zhi-Peng; Liu, Zhong-Jian (2018-03-01). "Permineralized osmundaceous and gleicheniaceous ferns from the Jurassic of Inner Mongolia, NE China".Palaeobiodiversity and Palaeoenvironments.98 (1):165–176.Bibcode:2018PdPe...98..165T.doi:10.1007/s12549-017-0313-0.ISSN1867-1608.S2CID134149095.
^Gould, R. E. 1968. Morphology ofEquisetum laterale Phillips, 1829, andE. bryanii sp. nov. from the Mesozoic of south‐eastern Queensland. Australian Journal of Botany 16: 153–176.
^Bippus, Alexander C.; Savoretti, Adolfina; Escapa, Ignacio H.; Garcia-Massini, Juan; Guido, Diego (October 2019). "Heinrichsiella patagonica gen. et sp. nov.: A Permineralized Acrocarpous Moss from the Jurassic of Patagonia".International Journal of Plant Sciences.180 (8):882–891.Bibcode:2019IJPlS.180..882B.doi:10.1086/704832.ISSN1058-5893.S2CID202859471.
^Qin, Z., Clark, J., Choiniere, J., & Xu, X. (2019). A new alvarezsaurian theropod from the Upper Jurassic Shishugou Formation of western China. Scientific Reports, 9: 11727.doi:10.1038/s41598-019-48148-7
^Rauhut, Oliver W. M.; Foth, Christian (2020), Foth, Christian; Rauhut, Oliver W. M. (eds.), "The Origin of Birds: Current Consensus, Controversy, and the Occurrence of Feathers",The Evolution of Feathers: From Their Origin to the Present, Fascinating Life Sciences, Cham: Springer International Publishing, pp. 27–45,doi:10.1007/978-3-030-27223-4_3,ISBN978-3-030-27223-4,S2CID216372010
^Godefroit, Pascal; Sinitsa, Sofia M.; Cincotta, Aude; McNamara, Maria E.; Reshetova, Svetlana A.; Dhouailly, Danielle (2020), Foth, Christian; Rauhut, Oliver W. M. (eds.), "Integumentary Structures in Kulindadromeus zabaikalicus, a Basal Neornithischian Dinosaur from the Jurassic of Siberia",The Evolution of Feathers: From Their Origin to the Present, Fascinating Life Sciences, Cham: Springer International Publishing, pp. 47–65,doi:10.1007/978-3-030-27223-4_4,ISBN978-3-030-27223-4,S2CID216261986
^Simões, Tiago R.; Caldwell, Michael W.; Nydam, Randall L.; Jiménez-Huidobro, Paulina (September 2016). "Osteology, phylogeny, and functional morphology of two Jurassic lizard species and the early evolution of scansoriality in geckoes".Zoological Journal of the Linnean Society.doi:10.1111/zoj.12487.
^Reilly, Stephen M.; Jorgensen, Michael E. (February 2011). "The evolution of jumping in frogs: Morphological evidence for the basal anuran locomotor condition and the radiation of locomotor systems in crown group anurans".Journal of Morphology.272 (2):149–168.Bibcode:2011JMorp.272..149R.doi:10.1002/jmor.10902.PMID21210487.S2CID14217777.
^Cavin, Lionel; Cupello, Camila; Yabumoto, Yoshitaka; Léo, Fragoso; Deersi, Uthumporn; Brito, Paul M. (2019)."Phylogeny and evolutionary history of mawsoniid coelacanths"(PDF).Bulletin of the Kitakyushu Museum of Natural History and Human History, Series A.17:3–13.
^Arratia G. Mesozoic halecostomes and the early radiation of teleosts. In: Arratia G, Tintori A, editors. Mesozoic Fishes 3 – Systematics, Paleoenvironments and Biodiversity. München: Verlag Dr. Friedrich Pfeil; 2004. p. 279–315.
^Liston, J., Newbrey, M., Challands, T., and Adams, C., 2013, "Growth, age and size of the Jurassic pachycormidLeedsichthys 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
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