User:Hemiauchenia/sandboxJurassic

Triassic
While historically ammonites were the most important index fossils used for Triassic biostratrigraphy, in recent times conodonts have become prominent.

The Induan stage is named after the Indus River, and was first used by Russian stratigraphers Kiparisova and Popov in 1956, after exposures in the Hindustan region of India. The Global Boundary Stratotype Section and Point (GSSP) for the beginning of the Induan is located Meishan, Changxing County, China. The beginning of the Induan, and thus the Triassic as a whole, is defined by the first appearance of the conodont Hindeodus parvus.

The Olenekian stage was introduced into scientific literature by Kiparisova and Popov in 1956. The stage is named after Olenëk in Siberia. Before the subdivision in Olenekian and Induan became established, both stages formed the Scythian stage, which has since disappeared from the official timescale.

Paleoceanography
At the end of the Triassic, there was a marine transgression in Europe, flooding most parts of central and western Europe transforming it into an archipelago of islands surrounded by shallow seas. The arctic arm of Panthalassa was connected to the western Tethys by the "Viking corridor", a several hundred kilometer wide passage between the Baltic Shield and Greenland. Rifting during the early Jurassic would create a seaway separating Madagascar and Antarctica from Africa.

Based on estimated sea level curves, the sea level was close to present levels during the Hettangian and Sinemurian, rising several tens of metres during the late Sinemurian-Pleinsbachian, before regressing to near present levels by the late Pleinsbachian. 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 Toacian, the sea level again drops by several tens of metres. The sea level progressively rose from the Aalenian onwards, aside from dips of a few tens of metres in the Bajocian and around the Callovian-Oxfordian boundary, culminating in a sea level 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. Sea level within the long term trend was cylical with 64 fluctuations through the Jurassic, 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, around 190 million years ago, the Pacific Plate originated at the triple junction of the Farallon, Phoenix, and Izanagi Plates, the three main oceanic plates of Panthalassa. The previously stable triple junction had converted to an unstable arrangement surrounded on all sides by transform faults, due to a kink in one of the plate boundaries, resulting in the formation of the Pacific Plate at the centre of the junction, which began to expand.

During the Toarcian-Aalenian transition, sea temperatures in the southern entrance to the Viking Passage likely dropped by 10 degrees C, possibly caused by uplift in the North Sea impeding circulation of warm equatorial waters northwards through the Viking corridor. Equatorial water temperatures during the Middle Jurassic were as high 34–35 °C, several degrees higher than present.

Toarcian Oceanic Anoxic Event
The Toarcian Oceanic Anoxic Event (TOAE) was an episode of widespread oceanic anoxia during the early part of the Toarcian period, c. 183 Mya. It is marked by a globally documented high amplitude negative carbon isotope excursion, as well as the deposition of black shales, and the extinction and collapse of carbonate producing marine organisms. The cause is often linked to the eruption of the Karoo-Ferrar large igneous provinces and the associated increase of carbon dioxide concentration in the atmosphere and the possible associated release of methane clathrates. This likely accelerated the hydrological cycle and increased silicate weathering. Groups affected include ammonites, ostracods, forams, brachiopods, bivalves and cnidarians, with the last two spire-bearing brachiopod orders Spiriferinida and Athyridida becoming extinct. While the event had significant impact on marine invertebrates, it had little effect on marine reptiles. During the TOAE, the Sichuan Basin was transformed into a giant lake, probably 3 times the size of Lake Superior, 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. 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 is what likely caused the collapse of carbonate production.

Climate
Climate during the Jurassic was warmer than at present. A 1999 analysis attempting to determine Jurassic biomes, suggested noted that there was no evidence for wet tropics or tundra, they suggested that the low latitudes were predominantly arid.

End Triassic Extinction
The preceding end-Triassic extinction would result in the decline Peltaspermaceae seed ferns, with Lepidopteris perisisting into the Early Jurassic in Patagonia. At the Triassic-Jurassic boundary in Greenland, the sporomorph diversity suggests a complete floral turnover. An analysis of macrofossil floral communites in Europe suggests no extinction over the Triassic-Jurassic boundary, and that changes were mainly due to local ecological succession. Dicroidium, a seed fern that was a dominant part of Gondwanan floral communities during the Triassic, would decline at the T-J, boundary, surviving as a relict in Antarctica into the Sinemurian.

Floral composition
Flowering plants, which make up 90% of living plant species, have no records from the Jurassic, with no claim of Jurassic representatives of the group having gained widespread acceptance.

Conifers
Trees of the Jurassic were dominated by conifers and modern conifier groups would diversify throughout the period. Araucarian conifers were widespread across both hemispheres. The divergence between Araucaria and the branch containing Wollemia and Agathis is estimated to have taken place during the Mid-Jurassic, based on Araucaria mirabilis and Araucaria sphaerocarpa from the Middle Jurassic of Argentina and England respectively, which are early members of the Araucaria lineage. Representatives of Wollemia-Agathis lineage are not known until the Cretaceous. Also abundant during the Jurassic is the extinct family Cheirolepidiaceae, often recognised by their highly distinctive Classopolis pollen. Jurassic representatives include the pollen cone Classostrobus and the seed cone Pararaucaria. Both Araucarian and Cheirolepidiaceae confiers often occur in association. The oldest definitive record of Cupressaceae is Austrohamia minuta from the Early Jurassic (Pliensbachian) of Patagonia, known from several elements. Austrohamia is thought to have close affinities with Taiwania and Cunninghamia. By the Mid-Late Jurassic Cupressaceae were abundant in warm temperate-tropical regions of the Northern Hemisphere, most abundantly represented by the genus Elatides. The seed cone Scitistrobus from the Middle Jurassic (Aalenian) of Scotland displays a mosaic of traits indicative of ancestral Voltziales and derived Cupressaceae. The oldest record of the pine family (Pinaceae) is the seed cone Eathiestrobus, known from the Late Jurassic (Kimmeridgian) also of Scotland. During the Early Jurassic, the flora of the mid-latitudes of Eastern Asia were dominated by the extinct decidous broad leafed conifer Podozamites, likely of voltzialean affinities, with its range extending northwards into polar latitudes of Siberia, but its range contracted northward in the Middle-Late Jurassic corresponding to the increasing aridity of the region. The earliest record of Taxaceae is Palaeotaxus rediviva, from the Hettangian of Sweden, suggested to be closely related to 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. The Daohugou material in particular is extremely similar to living Amentotaxus, only differing in having shorter seed-bearing axes. Podocarpaceae, today largely confined to the Southern Hemisphere occurs in the Northern Hemisphere during the Jurassic, including Podocarpophyllum from the Lower-Middle Jurassic of Central Asia and Siberia. Scarburgia from the Middle Jurassic of Yorkshire, and Harrisiocarpus from the Jurassic of Poland.

Ginkgoales
Ginkgoales, which are currently represented by the single living species Ginkgo biloba, were more diverse during the Jurassic, they were among the most important components of Laurasian Jurassic floras, and were adapted to a wide variety of climatic conditions. Based on reproductive organs several lineages can be distinguished, including Yimaia, Grenana, Nagrenia and Karkenia, alongside Ginkgo. These lineages are assocated with leaf morphotaxa such as Baiera, Ginkgoites andSphenobaiera, some of which overlap with the morphological variability and growth stages of living Ginkgo biloba leaves and therefore cannot be used for reliable taxonomic identification. Umaltolepis, historically thought to be gingkoalean, and Vladimaria from the Jurassic of Asia have strap shaped ginkgo-like leaves (Pseudotorellia), with highly distinct reproductive structures with similarities to those of peltasperm and corystosperm seed ferns, and have been placed in the separate order Vladimariales, which may belong to a broader Ginkgoopsida.

Ferns
The ground cover was dominated by ferns, including members of the living families Dipteridaceae, Matoniaceae, Osmundaceae and Marattiaceae, as well as horsetails. Polypodiales ferns, which today 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 fern genus Coniopteris, historically interpreted as a close relative of tree ferns of the family Dicksoniaceae, has recently been reinterpreted as an early relative of the group. A calicfied rhizome of an Osmundaceous fern from the Early Jurassic of Sweden belongs to the stem group of the living genus Osmundastrum, with the preservation showing the remains of chromosomes during cell division. An analysis of the Osmundastrum rhizome found that it had been interacted with by numerous organisms, including Lycopsid roots growing into the rhizome, probable peronosporomycetes as well as boring and coprolites likely by orbatid mites''.  The oldest remains of modern horsetails of the genus Equisetum first appear in the Early Jurassic, represented by Equisetum dimorphum from the Early Jurassic of Patagonia and Equisetum laterale'' from the Early-Middle Jurassic of Australia. Silicified remains of Equisetum thermale from the Late Jurassic of Argentina exhibit all the morphological characters of modern members of the genus. The estimated split between Equisetum bogotense and all other living Equisetum is estimated to have occcured no later than Early Jurassic. The Cyatheales, the group containing most modern tree ferns would appear during the Late Jurassic, represented by members of the genus Cyathocaulis, which are suggested to be early members of Cyatheaceae based on cladistic analysis. Only a handful of possible records exist of the Hymenophyllaceae are known from the Jurassic, including Hymenophyllites macrosporangiatus from the Russian Jurassic.

Bennettitales
Bennettitales are a group of seed plants widespread throughout the Mesozoic with foliage bearing strong similarities to those of cycads, to the point of morphologically indistinguishable. Benettitales can be distinguished from cycads by the fact they have a different arrangement of stomata, and are not thought to be closely related. Benettitales have morphologies varying from cycad-like to shubs and small trees. The Williamsoniaceae grouping is thought to have had a divaricate branching habit, similar to living Banksia, and adapted to growing in open habitats with poor soil nutrient conditions. Benettitales exhibit complex, flower like reproductive structures that are thought to have been pollinated by insects. Several groups of insects that bear long proboscis, including extinct families like Kalligrammatid lacewings and extant Acroceridae flies, are suggested to have been pollinators of benettitales, feeding on nectar produced by bennettitalean cones.

Cycads
Cycads were present during the Jurassic, the living groups of cycads have been suggested to have diverged from each other in the Early Jurassic, though a later analysis placed this divergence during the Late Permian, which placed the diversification of the Zamiineae cycads during the Jurassic. Cycads are difficult to distinguish from Bennettitales based on leaf morphology alone. Cycads are thought to have been a relatively minor component of mid-Mesozoic floras. and mostly confined to tropical and subtropical latitudes. Cycad foliage is assigned to morphogenera including Ctenis and Pterophyllum, but are not phylogenetically informative. Seeds from the late Callovian-early Oxfordian Oxford Clay are definitively assignable to the living family Cycadaceae. While seeds found in the gut of the dinosaur Isaberrysaura from the Middle Jurassic of Argentina are assigned to Zamiineae, which includes all other living cycads. The Nilssoniales, such as the leaf genus Nilssonia with leaves morphologically similar to those of cycads, have often been considered cycads or cycad relatives, but have been found to be distinct, perhaps more closely allied with Bennettitales. 

Gnetophytes
Protognetum from the Middle Jurassic of China is oldest known member of the gnetophytes and the only one known from the Jurassic. It exhibits characteristics of both Gnetum and Ephedra, and is placed in the monotypic family Protognetaceae.

Seed ferns
Seed ferns (Pteridospermatophyta) is a collective term to refer to disparate lineages of fern like plants that produce seeds, with uncertain affinities to living seed plant groups. Prominent groups of Jurassic seed ferns include Caytoniales, which includes the leaf taxon Sagenopteris, Caytonanthus pollen structures and Caytonia ovulate structures, often found close association. They have frequently been suggested to have been closely related or perhaps ancestral to flowering plants, but no definitive evidence of this has been discovered. The other prominent group is the Corystospermales, including genera like the leaf genus Pachypteris, prominent in the Jurassic of the Northern Hemisphere. As well as pollen organs belonging to Pteruchus and Umkomasia ovulate structures.

Czekanowskiales
Czekanowskiales, also known as Leptostrobales, are a group of gymnosperms of uncertain affinities with persistent 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 Mesozoic temperate and warm–temperate floras. Jurassic genera include the leaf genera Czekanowskia, Phoenicopsis and Solenites, associated with the ovulate cone Leptostrobus.

Pentoxylales
The Pentoxylales are a small group of gymnosperms of obscure affinities, known from the Jurassic and Cretaceous of Gondwana. These include the stems Pentoxylon, strap-shaped leaves Taeniopteris (more broadly used as a morphogenus representing other plant types) and Nipaniophyllum for well preserved leaves, Sahnia pollen organs, and Carnoconites seed bearing structures. The habit of the group is uncertain, but may have been small trees.

Quillworts
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.

Moss
The moss Kulindobryum from the Middle Jurassic of Russia is thought to have affinites with the Splachnaceae, while Bryokhutuliinia from the same region is thought to have affinities with Dicranales. Heinrichsiella from the Jurassic of Patagonia is thought to belong to the families Polytrichaceae or Timmiellaceae basal to Bryidae, and is the oldest representive of the grade.

Liverworts
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.

Regional abundance
In an analysis of the ferns of the Hettangian aged Mecsek Coal Formation found that the predominant groups of ferns by order of abundance belonged to the families Dipteridaceae (48% of collected specimens) Matoniaceae (25%), Osmundaceae (21%), Marattiaceae (6%) and 3 specimens of Coniopteris. They found that most of the ferns likely grew in monospecific thickets in disturbed areas. The Middle-Late Jurassic Daohugou flora of China was dominated by Gymnosperms and ferns, with the most abundant group of gymnosperms being Bennettitales, followed by conifers and ginkgophytes. High latitude floras of the New Zealand Jurassic were of low diversity, with only 43 species being recorded dominated by "conifers, ferns, bennettitaleans, pentoxylaleans and locally, equisetaleans" with Ginkgoales being entirely absent. The flora of the Middle Jurassic Stonesfield Slate of England was dominated by "araucariacean and cheirolepidiacean conifers, bennettitaleans, and leaves of the possible gymnosperm Pelourdea" representing a coastal environment.

Ornithischians
The oldest ornithischian dinosaurs appear in the earliest Jurassic, including basal taxa such Eocursor, Laquintasaura and Lesothosaurus and heterodontosaurids, early Neornithischians such as Lesothosaurus and early thyreophorans such as Scutellosaurus. During the Late Jurassic primitive ceratopsians belonging to the family Chaoyangsauridae appear in Asia. Iguanodontians first appear in the Late Jurassic, including Camptosaurus, which would become more prominent during the Cretaceous

Theropods
Theropods would extensively diversity during the Jurassic, the first ceratosaurians would appear during the Early Jurassic, represented by Saltriovenator from the Sinemurian of Italy. Tetanuran theropods would radiate in the Middle Jurassic, including Megalosauroids (Piatnitzkysauridae, Megalosauridae) and Allosauroids The earliest coelurosaurs would appear in the Middle Jurassic, including early tyrannosaurs belonging to the family Proceratosauridae.

Sauropods
Bipedal sauropodomorphs, including massospondylids would survive the end-Triassic extinction and would remain prominent in Early Jurassic ecological communities. The oldest remains of true sauropods are known from the Jurassic, the oldest being those of Vulcanodon from the Sinemurian-Pliensbachian of Zimbabwe. Gigantic sauropods would first appear in the Late Jurassic, becoming the largest organisms on land up to that point. the oldest Neosauropods would appear in the Middle Jurassic, represented by the dicraeosaurid Lingwulong from China, alongside other indeterminate remains, Neosauropods would become diverse and widespread in the Late Jurassic

End-Triassic extinction
During the end-Triassic extinction, 46%-72% of all marine genera would become 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 would completely collapse during the event, and would not fully recover until much later in the Jurassic. Sessile filter feeders and photosymbiotic organisms were among most severely affected.

Marine ecosystems
Having declined at the T-J boundary. Reefs would substantially expand during the Late Jurassic, including both sponge reefs and scleractinian coral reefs. Late Jurassic reefs were similar in form to modern reefs, but had more microbial carbonates and hypercalcified sponges, and had weak biogenic binding. Reefs would sharply decline at the close of the Jurassic. which caused an associated drop in diversity in decapod crustaceans. Microconchid tube worms, the last remaining order of Tentaculita, a group of animals of uncertain affinites that were convergent on Spirorbis tube worms, had become rare after the Triassic, and had become reduced to the single genus Punctaconchus, which became extinct in the late Bathonian.

Crustaceans
The Jurassic was a significant time for the evolution of decapods. The first true crabs (Brachyura) would appear during the Early Jurassic, with the earliest being Eocarcinus praecursor from the early Pliensbachian of England, which lacked the carcinisation of modern crabs. and Eoprosopon klugi from the late Pliensbachian of Germany, which possibly belongs to the living family Homolodromiidae. Most Jurassic crabs are only known from dorsal carapace pieces, which makes it difficult to determine their relationships. While rare in the Early and Middle Jurassic, crabs would become 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 helping to hide from predators Hermit crabs would also first appear 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 being known from the period.

Brachiopods
Brachiopod diversity declined during the T-J extinction. Spire bearing groups (Spiriferinida and Athyridida) would significantly decline at the T-J boundary and would not recover their biodiversity, becoming extinct in the TOAE. Rhynchonellida and Terebratulida would also decline during the T-J extincton but would rebound during the Early Jurassic, neither clade would develop any significant morphological variation. Brachiopods would substantially decline in the Late Jurassic, the causes of which are poorly understood. Proposed reasons include increased predation, competition with bivalves, enhanced bioturbation or increased grazing pressure.

Bivalves
The end Triassic extinction had a severe impact on bivalve diveristy, 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.