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98-708: The ocean floor of the MPM dates back to the Jurassic - Cretaceous , some of the oldest oceanic crust on Earth. The MPM is a range of guyots with a lava composition similar to those found in Iceland and the Galapagos Islands, and they probably formed similarly at or near a rift system. In the Cretaceous, they formed large tropical islands located closer to the Equator that began to sink in

196-573: A stem-group lineage , as it lacks several key morphological features that define modern crabs. Most Jurassic crabs are only known from dorsal (top half of the body) carapaces , making it difficult to determine their relationships. Crabs radiated in the Late Jurassic , corresponding with an increase in reef habitats, though they would decline at the end of the Jurassic as the result of the decline of reef ecosystems. Crabs increased in diversity through

294-632: A 70 km diameter impact structure buried beneath the Kalahari desert in northern South Africa. The impact is dated to the Tithonian, approximately 146.06 ± 0.16 Mya. Another major structure is the Puchezh-Katunki crater , 40 kilometres in diameter, buried beneath Nizhny Novgorod Oblast in western Russia. The impact has been dated to the Sinemurian, 195.9 ± 1.0 Ma. At the beginning of the Jurassic, all of

392-423: A Scottish animal welfare group, stated in 2005 that "scientific evidence ... strongly suggests that there is a potential for decapod crustaceans and cephalopods to experience pain and suffering". This is primarily due to "The likelihood that decapod crustaceans can feel pain [which] is supported by the fact that they have been shown to have opioid receptors and to respond to opioids (analgesics such as morphine) in

490-492: A dominant component of Jurassic floras. The Late Triassic and Jurassic was a major time of diversification of conifers, with most modern conifer groups appearing in the fossil record by the end of the Jurassic, having evolved from voltzialean ancestors. Araucarian conifers have their first unambiguous records during the Early Jurassic, and members of the modern genus Araucaria were widespread across both hemispheres by

588-493: A hard shell, which would otherwise prevent growth. The moult cycle is coordinated by hormones . When preparing for moult, the old shell is softened and partly eroded away, while the rudimentary beginnings of a new shell form under it. At the time of moulting, the crab takes in a lot of water to expand and crack open the old shell at a line of weakness along the back edge of the carapace . The crab must then extract all of itself – including its legs, mouthparts , eyestalks , and even

686-623: A kink in one of the plate boundaries, resulting in the formation of the Pacific Plate at the centre of the junction. During the Middle to early Late Jurassic, the Sundance Seaway , a shallow epicontinental sea , covered much of northwest North America. The eustatic sea level is estimated to have been close to present levels during the Hettangian and Sinemurian, rising several tens of metres during

784-654: A lineament that includes the Line Islands and Tuamotu archipelago, begins near the eastern part of the MPM. The formation of the MPM thus probably occurred at the Pacific-Farallon Ridge and the Easter hotspot, or where the Easter Microplate is now located. Jurassic The Jurassic ( / dʒ ʊ ˈ r æ s ɪ k / juurr- ASS -ik ) is a geologic period and stratigraphic system that spanned from

882-419: A mate through chemical ( pheromones ), visual, acoustic, or vibratory means. Pheromones are used by most fully aquatic crabs, while terrestrial and semiterrestrial crabs often use visual signals, such as fiddler crab males waving their large claws to attract females. The vast number of brachyuran crabs have internal fertilisation and mate belly-to-belly. For many aquatic species, mating takes place just after

980-453: 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. 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

1078-486: A similar way to vertebrates." Similarities between decapod and vertebrate stress systems and behavioral responses to noxious stimuli were given as additional evidence for the capacity of decapods to experience pain. In 2005 a review of the literature by the Norwegian Scientific Committee for Food Safety tentatively concluded that "it is unlikely that [lobsters] can feel pain," though they note that "there

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1176-480: A tendency that is particularly pronounced in the fiddler crabs of the genus Uca ( Ocypodidae ). In fiddler crabs, males have one greatly enlarged claw used for communication, particularly for attracting a mate. Another conspicuous difference is the form of the pleon ( abdomen ); in most male crabs, this is narrow and triangular in form, while females have a broader, rounded abdomen. This is because female crabs brood fertilised eggs on their pleopods . Crabs attract

1274-483: Is Austrohamia minuta from the Early Jurassic (Pliensbachian) of Patagonia, known from many parts of the plant. The reproductive structures of Austrohamia have strong similarities to those of the primitive living cypress genera Taiwania and Cunninghamia . By the Middle to Late Jurassic Cupressaceae were abundant in warm temperate–tropical regions of the Northern Hemisphere, most abundantly represented by

1372-403: Is apparently a paucity of exact knowledge on sentience in crustaceans, and more research is needed." This conclusion is based on the lobster 's simple nervous system. The report assumes that the violent reaction of lobsters to boiling water is a reflex response (i.e. does not involve conscious perception) to noxious stimuli. A European Food Safety Authority (EFSA) 2005 publication stated that

1470-441: Is complete, the female releases the newly hatched larvae into the water, where they are part of the plankton . The release is often timed with the tidal and light/dark diurnal cycle . The free-swimming tiny zoea larvae can float and take advantage of water currents. They have a spine, which probably reduces the rate of predation by larger animals. The zoea of most species must find food, but some crabs provide enough yolk in

1568-592: Is critical, and it must take place in a habitat that is suitable for the juvenile to survive. Most species of terrestrial crabs must migrate down to the ocean to release their larvae; in some cases, this entails very extensive migrations. After living for a short time as larvae in the ocean, the juveniles must do this migration in reverse. In many tropical areas with land crabs, these migrations often result in considerable roadkill of migrating crabs. Once crabs have become juveniles, they still have to keep moulting many more times to become adults. They are covered with

1666-487: Is divided into three epochs : Early, Middle, and Late. Similarly, in stratigraphy , the Jurassic is divided into the Lower Jurassic , Middle Jurassic , and Upper Jurassic series . Geologists divide the rocks of the Jurassic into a stratigraphic set of units called stages , each formed during corresponding time intervals called ages. Stages can be defined globally or regionally. For global stratigraphic correlation,

1764-546: Is followed by the Kimmeridgian Warm Interval (KWI) between 164 and 150 million years ago. Based on fossil wood distribution, this was one of the wettest intervals of the Jurassic. The Pangaean interior had less severe seasonal swings than in previous warm periods as the expansion of the Central Atlantic and Western Indian Ocean provided new sources of moisture. A prominent drop in temperatures occurred during

1862-463: Is fourth order, with a periodicity of approximately 410,000 years. During the Early Jurassic the world's oceans transitioned from an aragonite sea to a calcite sea chemistry, favouring the dissolution of aragonite and precipitation of calcite . The rise of calcareous plankton during the Middle Jurassic profoundly altered ocean chemistry, with the deposition of biomineralized plankton on

1960-469: 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, associated with a major rise in global temperatures. The TOAE is often attributed to the eruption of the Karoo-Ferrar large igneous provinces and the associated increase of carbon dioxide concentration in

2058-561: Is named after the city of Oxford in England and was named by Alcide d'Orbigny in 1844 in reference to the Oxford Clay . The base of the Oxfordian lacks a defined GSSP. W. J. Arkell in studies in 1939 and 1946 placed the lower boundary of the Oxfordian as the first appearance of the ammonite Quenstedtoceras mariae (then placed in the genus Vertumniceras ). Subsequent proposals have suggested

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2156-411: Is often a chief concern. Indeed, surimi is an important source of protein in most East and Southeast Asian cultures, appearing in staple ingredients such as fish balls and fish cake. Whether crustaceans as a whole experience pain or not is a scientific debate that has ethical implications for crab dish preparation. Crabs are very often boiled alive as part of the cooking process. Advocates for Animals,

2254-792: Is popular in Southeast Asian cultures, some Mediterranean and Northern European cultures, and on the East, Chesapeake , and Gulf Coasts of the United States. In some regions, spices improve the culinary experience. In Southeast Asia and the Indosphere , masala crab and chilli crab are examples of heavily spiced dishes. In the Chesapeake Bay region, blue crab is often steamed with Old Bay Seasoning . Alaskan king crab or snow crab legs are usually simply boiled and served with garlic or lemon butter. For

2352-513: Is separated into several sections, with the basal Dromiacea diverging the earliest in the evolutionary history, around the Late Triassic or Early Jurassic . The group consisting of Raninoida and Cyclodorippoida split off next, during the Jurassic period. The remaining clade Eubrachyura then divided during the Cretaceous period into Heterotremata and Thoracotremata . A summary of

2450-678: Is the setting of the world's largest oil reserves, including the Ghawar Field , the world's largest oil field. The Jurassic-aged Sargelu and Naokelekan formations are major source rocks for oil in Iraq . Over 1500 gigatons of Jurassic coal reserves are found in north-west China, primarily in the Turpan-Hami Basin and the Ordos Basin . Major impact structures include the Morokweng impact structure ,

2548-606: 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. The oldest part of the Jurassic Period has historically been referred to as the Lias or Liassic, roughly equivalent in extent to

2646-574: The France–Switzerland border . The name "Jura" is derived from the Celtic root * jor via Gaulish *iuris "wooded mountain", which was borrowed into Latin as a name of a place and evolved into Juria and finally Jura . During a tour of the region in 1795, German naturalist Alexander von Humboldt recognized carbonate deposits within the Jura Mountains as geologically distinct from

2744-503: The International Commission on Stratigraphy (ICS) ratify global stages based on a Global Boundary Stratotype Section and Point (GSSP) from a single formation (a stratotype ) identifying the lower boundary of the stage. The ages of the Jurassic from youngest to oldest are as follows: Jurassic stratigraphy is primarily based on the use of ammonites as index fossils . The first appearance datum of specific ammonite taxa

2842-697: The Redcar Mudstone Formation , and was ratified in 2005. The beginning of the Pliensbachian is defined by the first appearance of the ammonite Bifericeras donovani . The village Thouars (Latin: Toarcium ), just south of Saumur in the Loire Valley of France , lends its name to the Toarcian Stage. The Toarcian was named by Alcide d'Orbigny in 1842, with the original locality being Vrines quarry around 2 km northwest of Thouars. The GSSP for

2940-767: The Triassic aged Muschelkalk of southern Germany , but he erroneously concluded that they were older. He then named them Jura-Kalkstein ('Jura limestone') in 1799. In 1829, the French naturalist Alexandre Brongniart published a book entitled Description of the Terrains that Constitute the Crust of the Earth or Essay on the Structure of the Known Lands of the Earth. In this book, Brongniart used

3038-642: The pea crab , a few millimeters wide, to the Japanese spider crab , with a leg span up to 4 m (13 ft). Several other groups of crustaceans with similar appearances – such as king crabs and porcelain crabs – are not true crabs, but have evolved features similar to true crabs through a process known as carcinisation . Crabs are found in all of the world's oceans, as well as in fresh water and on land , particularly in tropical regions. About 850 species are freshwater crabs . Crabs often show marked sexual dimorphism . Males often have larger claws ,

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3136-636: The thorax . They live in all the world's oceans, in freshwater , and on land . They are generally covered with a thick exoskeleton . They generally have five pairs of legs, and they have pincer claws on the ends of the frontmost pair. They first appeared during the Jurassic period, around 200 million years ago. Crabs are generally covered with a thick exoskeleton , composed primarily of highly mineralized chitin . Behind their pair of chelae (claws) are six walking legs and then two swimming legs. The crab breathes through gills on its underside; gills must be at least moist to work. Crabs vary in size from

3234-619: The Aalenian, precessionally forced climatic changes dictated peatland wildfire magnitude and frequency. The European climate appears to have become noticeably more humid at the Aalenian-Bajocian boundary but then became more arid during the middle Bajocian. A transient ice age possibly occurred in the late Bajocian. The Callovian-Oxfordian boundary at the end of the MJCI witnessed particularly notable global cooling, potentially even an ice age. This

3332-725: The Bajocian Stage after the town of Bayeux (Latin: Bajoce ) in Normandy, France. The GSSP for the base of the Bajocian is located in the Murtinheira section at Cabo Mondego , Portugal; it was ratified in 1997. The base of the Bajocian is defined by the first appearance of the ammonite Hyperlioceras mundum . The Bathonian is named after the city of Bath , England, introduced by Belgian geologist d'Omalius d'Halloy in 1843, after an incomplete section of oolitic limestones in several quarries in

3430-574: The Black Jurassic and the overlying clayey sandstone and ferruginous oolite of the Brown Jurassic sequences of southwestern Germany. The GSSP for the base of the Aalenian is located at Fuentelsaz in the Iberian range near Guadalajara, Spain , and was ratified in 2000. The base of the Aalenian is defined by the first appearance of the ammonite Leioceras opalinum . Alcide d'Orbigny in 1842 named

3528-560: The Black Jurassic in England by William Conybeare and William Phillips in 1822. William Phillips, the geologist, worked with William Conybeare to find out more about the Black Jurassic in England. The French palaeontologist Alcide d'Orbigny in papers between 1842 and 1852 divided the Jurassic into ten stages based on ammonite and other fossil assemblages in England and France, of which seven are still used, but none has retained its original definition. The German geologist and palaeontologist Friedrich August von Quenstedt in 1858 divided

3626-470: The British dish dressed crab , the crab meat is extracted and placed inside the hard shell. One American way to prepare crab meat is by extracting it and adding varying amounts of binders, such as egg white, cracker meal, mayonnaise, or mustard, creating a crab cake . Crabs can also be made into a bisque , a global dish of French origin which in its authentic form includes in the broth the pulverized shells of

3724-655: The Callovian–Oxfordian boundary, peaking possibly as high as 140 metres above present sea level at the Kimmeridgian–Tithonian boundary. The sea levels falls in the late Tithonian, perhaps to around 100 metres, before rebounding to around 110 metres at the Tithonian–Berriasian boundary. The sea level within the long-term trends across the Jurassic was cyclical, with 64 fluctuations, 15 of which were over 75 metres. The most noted cyclicity in Jurassic rocks

3822-1031: The Cretaceous and represented the dominant group of decapods by the end of the period. The crab infraorder Brachyura belongs to the group Reptantia , which consists of the walking/crawling decapods ( lobsters and crabs). Brachyura is the sister clade to the infraorder Anomura , which contains the hermit crabs and relatives. The cladogram below shows Brachyura's placement within the larger order Decapoda , from analysis by Wolfe et al. , 2019. Dendrobranchiata (prawns) [REDACTED] Stenopodidea (boxer shrimp) [REDACTED] Procarididea Caridea ("true" shrimp) [REDACTED] Achelata (spiny lobsters and slipper lobsters) [REDACTED] Polychelida (benthic crustaceans) Astacidea (lobsters and crayfish) [REDACTED] Axiidea (mud shrimp, ghost shrimp, and burrowing shrimp) Gebiidea (mud lobsters and mud shrimp) [REDACTED] Anomura (hermit crabs and allies) [REDACTED] Brachyura ("true" crabs) [REDACTED] Brachyura

3920-458: The Early Jurassic, but also including part of the preceding Rhaetian . The Hettangian Stage was named by Swiss palaeontologist Eugène Renevier in 1864 after Hettange-Grande in north-eastern France. The GSSP for the base of the Hettangian is located at the Kuhjoch Pass, Karwendel Mountains , Northern Calcareous Alps , Austria; it was ratified in 2010. The beginning of the Hettangian, and thus

4018-456: The Greek goddess of dawn . His name was chosen by Albert Oppel for this stratigraphical stage because the Tithonian finds itself hand in hand with the dawn of the Cretaceous. The base of the Tithonian currently lacks a GSSP. The working definition for the base of the Tithonian is the first appearance of the ammonite genus Gravesia . The upper boundary of the Jurassic is currently undefined, and

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4116-474: The Jurassic as a whole, is marked by the first appearance of the ammonite Psiloceras spelae tirolicum in the Kendlbach Formation exposed at Kuhjoch. The base of the Jurassic was previously defined as the first appearance of Psiloceras planorbis by Albert Oppel in 1856–58, but this was changed as the appearance was seen as too localised an event for an international boundary. The Sinemurian Stage

4214-501: The Jurassic of Asia has strap-shaped ginkgo-like leaves with highly distinct reproductive structures with similarities to those of peltasperm and corystosperm seed ferns, has been suggested to be a member of Ginkgoales sensu lato. Crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tail" in Greek ), which typically have a very short projecting tail -like abdomen , usually hidden entirely under

4312-764: The Jurassic, both the North and South Pole were covered by oceans. Beginning in the Early Jurassic, the Boreal Ocean was connected to the proto-Atlantic by the "Viking corridor" or Transcontinental Laurasian Seaway, a passage between the Baltic Shield and Greenland several hundred kilometers wide. During the Callovian, the Turgai Epicontinental Sea formed, creating a marine barrier between Europe and Asia. Madagascar and Antarctica began to rift away from Africa during

4410-428: The Jurassic, however, has no clear, definitive boundary with the Cretaceous and is the only boundary between geological periods to remain formally undefined. By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses: Laurasia to the north and Gondwana to the south. The climate of the Jurassic was warmer than the present, and there were no ice caps . Forests grew close to

4508-711: The Jurassic, the North Atlantic Ocean remained relatively narrow, while the South Atlantic did not open until the Cretaceous. The continents were surrounded by Panthalassa , with the Tethys Ocean between Gondwana and Asia. At the end of the Triassic, there was a marine transgression in Europe, flooding most parts of central and western Europe transforming it into an archipelago of islands surrounded by shallow seas. During

4606-572: The Jurassic–Cretaceous boundary is currently the only system boundary to lack a defined GSSP. Placing a GSSP for this boundary has been difficult because of the strong regionality of most biostratigraphic markers, and lack of any chemostratigraphic events, such as isotope excursions (large sudden changes in ratios of isotopes ), that could be used to define or correlate a boundary. Calpionellids , an enigmatic group of planktonic protists with urn-shaped calcitic tests briefly abundant during

4704-514: The Late Jurassic (Kimmeridgian) of Scotland, which remains the only known unequivocal fossil of the group before the Cretaceous. Despite being the earliest known member of the Pinaceae, Eathiestrobus appears to be a member of the pinoid clade of the family, suggesting that the initial diversification of Pinaceae occurred earlier than has been found in the fossil record. The earliest record of

4802-630: The MPM guyots are indeed older on the western MPM than the eastern part, but the guyots do not form chains that can be traced to any known hotspots. The MPM, nevertheless, must have originated over the South Pacific Superswell . Among the guyots in the Mid-Pacific Mountains are Allison Guyot , Horizon Guyot , Resolution Guyot and Darwin Guyot . The western half of the Easter hotspot chain,

4900-416: The Middle Jurassic. Also abundant during the Jurassic is the extinct family Cheirolepidiaceae , often recognised through their highly distinctive Classopolis pollen. Jurassic representatives include the pollen cone Classostrobus and the seed cone Pararaucaria . Araucarian and Cheirolepidiaceae conifers often occur in association. The oldest definitive record of the cypress family ( Cupressaceae )

4998-496: The Middle to Late Jurassic, corresponding to the increasing aridity of the region. Ginkgoales , of which the sole living species is Ginkgo biloba , were more diverse during the Jurassic: they were among the most important components of Eurasian Jurassic floras and were adapted to a wide variety of climatic conditions. The earliest representatives of the genus Ginkgo , represented by ovulate and pollen organs similar to those of

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5096-626: The North Atlantic Ocean with eastern Panthalassa. Palaeontological data suggest that the seaway had been open since the Early Jurassic. As part of the Nevadan orogeny , which began during the Triassic, the Cache Creek Ocean closed, and various terranes including the large Wrangellia Terrane accreted onto the western margin of North America. By the Middle Jurassic the Siberian plate and

5194-462: The North China-Amuria block had collided, resulting in the closure of the Mongol-Okhotsk Ocean . During the Early Jurassic, around 190 million years ago, the Pacific Plate originated at the triple junction of the Farallon , Phoenix , and Izanagi tectonic 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 because of

5292-502: The TOAE represented one of the most severe extinctions in their evolutionary history. While the event had significant impact on marine invertebrates, it had little effect on marine reptiles. During the TOAE, the Sichuan Basin was transformed into a giant lake , probably three times the size of modern-day Lake Superior , represented by the Da'anzhai Member of the Ziliujing Formation . The lake likely sequestered ~460 gigatons (Gt) of organic carbon and ~1,200 Gt of inorganic carbon during

5390-414: The Tithonian, known as the Early Tithonian Cooling Event (ETCE). The end of the Jurassic was marked by the Tithonian–early Barremian Cool Interval (TBCI), beginning 150 million years ago and continuing into the Early Cretaceous . The Toarcian Oceanic Anoxic Event (TOAE), also known as the Jenkyns Event, was an episode of widespread oceanic anoxia during the early part of the Toarcian Age, c. 183 Mya. It

5488-529: The Toarcian around 174 million years ago. 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 million years ago, which may have been punctuated by brief, ephemeral icehouse intervals. During

5586-428: The atmosphere, as well as the possible associated release of methane clathrates . This likely accelerated the hydrological cycle and increased silicate weathering , as evidenced by an increased amount of organic matter of terrestrial origin found in marine deposits during the TOAE. Groups affected include ammonites, ostracods , foraminifera , bivalves , cnidarians , and especially brachiopods , for which

5684-407: The base of the Toarcian is located at Peniche, Portugal , and was ratified in 2014. The boundary is defined by the first appearance of ammonites belonging to the subgenus Dactylioceras ( Eodactylites ) . The Aalenian is named after the city of Aalen in Germany. The Aalenian was defined by Swiss geologist Karl Mayer-Eymar in 1864. The lower boundary was originally between the dark clays of

5782-466: The crab may survive and regenerate the claws. Crabs are prepared and eaten as a dish in many different ways all over the world. Some species are eaten whole, including the shell, such as soft-shell crab ; with other species, just the claws or legs are eaten. The latter is particularly common for larger crabs, such as the snow crab . In many cultures, the roe of the female crab is also eaten, which usually appears orange or yellow in fertile crabs. This

5880-693: The crab species. For many crabs, a mixed diet of plant and animal matter results in the fastest growth and greatest fitness . Some species are more specialised in their diets, based in plankton, clams or fish. Crabs are known to work together to provide food and protection for their family, and during mating season to find a comfortable spot for the female to release her eggs. Crabs make up 20% of all marine crustaceans caught, farmed, and consumed worldwide, amounting to 1.5 million tonnes annually. One species, Portunus trituberculatus , accounts for one-fifth of that total. Other commercially important taxa include Portunus pelagicus , several species in

5978-426: The eggs that the larval stages can continue to live off the yolk. Each species has a particular number of zoeal stages, separated by moults , before they change into a megalopa stage, which resembles an adult crab, except for having the abdomen (tail) sticking out behind. After one more moult, the crab is a juvenile , living on the bottom rather than floating in the water. This last moult, from megalopa to juvenile,

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6076-460: The end of the Triassic Period 201.4 million years ago (Mya) to the beginning of the Cretaceous Period, approximately 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era as well as the eighth period of the Phanerozoic Eon and is named after the Jura Mountains , where limestone strata from the period were first identified. The start of the Jurassic was marked by the major Triassic–Jurassic extinction event , associated with

6174-616: The end of the Jurassic. The oldest unambiguous members of Podocarpaceae are known from the Jurassic, found across both hemispheres, including Scarburgia and Harrisiocarpus from the Middle Jurassic of England, as well as unnamed species from the Middle-Late Jurassic of Patagonia. During the Early Jurassic, the flora of the mid-latitudes of Eastern Asia were dominated by the extinct deciduous broad leafed conifer Podozamites , which appears to not be closely related to any living family of conifer. Its range extended northwards into polar latitudes of Siberia and then contracted northward in

6272-413: The end of the Triassic, the Peltaspermaceae became extinct in most parts of the world, with Lepidopteris persisting into the Early Jurassic in Patagonia. Dicroidium , a corystosperm seed fern that was a dominant part of Gondwanan floral communities during the Triassic, also declined at the Triassic–Jurassic boundary, surviving as a relict in Antarctica into the Early Jurassic. Conifers formed

6370-402: The eruption of the Central Atlantic Magmatic Province (CAMP). The beginning of the Toarcian Age started around 183 million years ago and is marked by the Toarcian Oceanic Anoxic Event , a global episode of oceanic anoxia , ocean acidification , and elevated global temperatures associated with extinctions, likely caused by the eruption of the Karoo-Ferrar large igneous provinces . The end of

6468-417: 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 the probable cause of the collapse of carbonate production. Additionally, anoxic conditions were exacerbated by enhanced recycling of phosphorus back into ocean water as

6566-449: The evidence for this is primarily European, probably controlled by changes in eustatic sea level. There is no evidence of a mass extinction of plants at the Triassic–Jurassic boundary. At the Triassic–Jurassic boundary in Greenland, the sporomorph (pollen and spores) record suggests a complete floral turnover. An analysis of macrofossil floral communities in Europe suggests that changes were mainly due to local ecological succession . At

6664-436: The female has moulted and is still soft. Females can store the sperm for a long time before using it to fertilise their eggs . When fertilisation has taken place, the eggs are released onto the female's abdomen, below the tail flap, secured with a sticky material. In this location, they are protected during embryonic development. Females carrying eggs are called "berried" since the eggs resemble round berries. When development

6762-472: The few cynodont lineages to survive the end of the Triassic, continued to diversify throughout the period, with the Jurassic seeing the emergence of the first crown group mammals . Crocodylomorphs made the transition from a terrestrial to an aquatic life. The oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs , while pterosaurs were the dominant flying vertebrates . Modern sharks and rays first appeared and diversified during

6860-403: The first appearance of Cardioceras redcliffense as the lower boundary. The village of Kimmeridge on the coast of Dorset , England, is the origin of the name of the Kimmeridgian. The stage was named by Alcide d'Orbigny in 1842 in reference to the Kimmeridge Clay . The GSSP for the base of the Kimmeridgian is the Flodigarry section at Staffin Bay on the Isle of Skye , Scotland , which

6958-409: The first appearance of the ammonite Strambergella jacobi , formerly placed in the genus Berriasella , but its use as a stratigraphic indicator has been questioned, as its first appearance does not correlate with that of C. alpina . The Kimmeridge Clay and equivalents are the major source rock for the North Sea oil . The Arabian Intrashelf Basin, deposited during the Middle and Late Jurassic,

7056-454: The genus Chionoecetes , the blue crab ( Callinectes sapidus ), Charybdis spp. , Cancer pagurus , the Dungeness crab ( Metacarcinus magister ), and Scylla serrata , each of which yields more than 20,000 tonnes annually. In some crab species, meat is harvested by manually twisting and pulling off one or both claws and returning the live crab to the water in the knowledge that

7154-402: The genus Elatides . The Jurassic also saw the first appearances of some modern genera of cypresses, such as Sequoia . Members of the extinct genus Schizolepidopsis which likely represent a stem-group to the pine family ( Pinaceae ), were widely distributed across Eurasia during the Jurassic. The oldest unambiguous record of Pinaceae is the pine cone Eathiestrobus , known from

7252-514: The largest of decapod crustaceans have complex behaviour, a pain system, considerable learning abilities and appear to have some degree of awareness. Based on this evidence, they placed all decapod crustaceans into the same category of research-animal protection as vertebrates. The earliest unambiguous crab fossils date from the Early Jurassic , with the oldest being Eocarcinus from the early Pliensbachian of Britain, which likely represents

7350-583: The late Early Jurassic in association with the eruption of the Karoo-Ferrar large igneous provinces , opening the western Indian Ocean and beginning the fragmentation of Gondwana. At the beginning of the Jurassic, North and South America remained connected, but by the beginning of the Late Jurassic they had rifted apart to form the Caribbean Seaway, also known as the Hispanic Corridor, which connected

7448-536: The late Mesozoic. The MPM formed in the Early Cretaceous (at c. 110 Ma) over a hotspot that uplifted the ocean floor of the still young Pacific Plate. Reefs developed on the subsiding islands and renewed volcanism in the Late Cretaceous helped maintain some of eastern islands but inevitably the guyots sank to their present depth. It has been proposed that the MPM has crossed over several hotspots, and

7546-467: 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

7644-403: The latest Jurassic to earliest Cretaceous, have been suggested to represent the most promising candidates for fixing the Jurassic–Cretaceous boundary In particular, the first appearance Calpionella alpina , co-inciding with the base of the eponymous Alpina subzone, has been proposed as the definition of the base of the Cretaceous. The working definition for the boundary has often been placed as

7742-436: The lining of the front and back of the digestive tract – from the old shell. This is a difficult process that takes many hours, and if a crab gets stuck, it will die. After freeing itself from the old shell (now called an exuvia ), the crab is extremely soft and hides until its new shell has hardened. While the new shell is still soft, the crab can expand it to make room for future growth. Crabs typically walk sideways (hence

7840-428: The modern species, are known from the Middle Jurassic in the Northern Hemisphere. Several other lineages of ginkgoaleans are known from Jurassic rocks, including Yimaia , Grenana , Nagrenia and Karkenia . These lineages are associated with Ginkgo- like leaves, but are distinguished from living and fossil representatives of Ginkgo by having differently arranged reproductive structures. Umaltolepis from

7938-422: The ocean floor acting as a buffer against large CO 2 emissions. The climate of the Jurassic was generally warmer than that of present, by around 5–10 °C (9–18 °F), with atmospheric carbon dioxide likely about four times higher. Intermittent "cold snap" intervals are known to have occurred during this time period, however, interrupting the otherwise warm greenhouse climate. Forests likely grew near

8036-455: The oceans, resulting in large areas of desert and scrubland in the lower latitudes between 40° N and S of the equator. Tropical rainforest and tundra biomes are likely to have been rare or absent. The Jurassic also witnessed the decline of the Pangaean megamonsoon that had characterised the preceding Permian and Triassic periods. Variation in the frequency of wildfire activity in the Jurassic

8134-490: The period, while the first known crown-group teleost fish appeared near the end of the period. The flora was dominated by ferns and gymnosperms , including conifers , of which many modern groups made their first appearance during the period, as well as other groups like the extinct Bennettitales . The chronostratigraphic term "Jurassic" is linked to the Jura Mountains , a forested mountain range that mainly follows

8232-580: The phrase terrains jurassiques when correlating the "Jura-Kalkstein" of Humboldt with similarly aged oolitic limestones in Britain, thus coining and publishing the term "Jurassic". The German geologist Leopold von Buch in 1839 established the three-fold division of the Jurassic, originally named from oldest to the youngest: the Black Jurassic , Brown Jurassic , and White Jurassic . The term " Lias " had previously been used for strata of equivalent age to

8330-607: The poles, where they experienced warm summers and cold, sometimes snowy winters; there were unlikely to have been ice sheets given the high summer temperatures that prevented the accumulation of snow, though there may have been mountain glaciers. Dropstones and glendonites in northeastern Siberia during the Early to Middle Jurassic indicate cold winters. The ocean depths were likely 8 °C (14 °F) warmer than present, and coral reefs grew 10° of latitude further north and south. The Intertropical Convergence Zone likely existed over

8428-476: The poles, with large arid expanses in the lower latitudes. On land, the fauna transitioned from the Triassic fauna, dominated jointly by dinosauromorph and pseudosuchian archosaurs , to one dominated by dinosaurs alone. The first stem-group birds appeared during the Jurassic, evolving from a branch of theropod dinosaurs. Other major events include the appearance of the earliest crabs and modern frogs , salamanders and lizards . Mammaliaformes , one of

8526-627: The region. The GSSP for the base of the Bathonian is Ravin du Bès, Bas-Auran area, Alpes de Haute Provence , France; it was ratified in 2009. The base of the Bathonian is defined by the first appearance of the ammonite Gonolkites convergens , at the base of the Zigzagiceras zigzag ammonite zone . The Callovian is derived from the Latinized name of the village of Kellaways in Wiltshire , England, and

8624-469: The shellfish from which it is made. Imitation crab , also called surimi , is made from minced fish meat that is crafted and colored to resemble crab meat. While it is sometimes disdained among some elements of the culinary industry as an unacceptably low-quality substitute for real crab, this does not hinder its popularity, especially as a sushi ingredient in Japan and South Korea, and in home cooking, where cost

8722-1147: The term crabwise ), because of the articulation of the legs which makes a sidelong gait more efficient. Some crabs walk forward or backward, including raninids , Libinia emarginata and Mictyris platycheles . Some crabs, like the Portunidae and Matutidae , are also capable of swimming, the Portunidae especially so as their last pair of walking legs are flattened into swimming paddles. Crabs are mostly active animals with complex behaviour patterns such as communicating by drumming or waving their pincers . Crabs tend to be aggressive toward one another, and males often fight to gain access to females. On rocky seashores , where nearly all caves and crevices are occupied, crabs may also fight over hiding holes. Fiddler crabs (genus Uca ) dig burrows in sand or mud, which they use for resting, hiding, and mating, and to defend against intruders. Crabs are omnivores , feeding primarily on algae , and taking any other food, including molluscs , worms , other crustaceans , fungi , bacteria , and detritus , depending on their availability and

8820-562: The three series of von Buch in the Swabian Jura into six subdivisions defined by ammonites and other fossils. The German palaeontologist Albert Oppel in his studies between 1856 and 1858 altered d'Orbigny's original scheme and further subdivided the stages into biostratigraphic zones, based primarily on ammonites. Most of the modern stages of the Jurassic were formalized at the Colloque du Jurassique à Luxembourg in 1962. The Jurassic Period

8918-483: The world's major landmasses were coalesced into the supercontinent Pangaea , which during the Early Jurassic began to break up into northern supercontinent Laurasia and the southern supercontinent Gondwana . The rifting between North America and Africa was the first to initiate, beginning in the early Jurassic, associated with the emplacement of the Central Atlantic Magmatic Province . During

9016-581: The yew family ( Taxaceae ) is Palaeotaxus rediviva , from the Hettangian of Sweden, suggested to be closely related to the living Austrotaxus , while Marskea jurassica from the Middle Jurassic of Yorkshire, England and material from the Callovian–Oxfordian Daohugou Bed in China are thought to be closely related to Amentotaxus , with the latter material assigned to the modern genus, indicating that Taxaceae had substantially diversified by

9114-469: Was first defined and introduced into scientific literature by Alcide d'Orbigny in 1842. It takes its name from the French town of Semur-en-Auxois , near Dijon . The original definition of Sinemurian included what is now the Hettangian. The GSSP of the Sinemurian is located at a cliff face north of the hamlet of East Quantoxhead , 6 kilometres east of Watchet , Somerset , England , within the Blue Lias , and

9212-617: Was governed by the 405 kyr eccentricity cycle. Thanks to the breakup of Pangaea, the hydrological cycle during the Jurassic was significantly enhanced. The beginning of the Jurassic was likely marked by a thermal spike corresponding to the Triassic–Jurassic extinction and eruption of the Central Atlantic magmatic province. The first part of the Jurassic was marked by the Early Jurassic Cool Interval between 199 and 183 million years ago. It has been proposed that glaciation

9310-563: Was named by Alcide d'Orbigny in 1852, originally the base at the contact between the Forest Marble Formation and the Cornbrash Formation . However, this boundary was later found to be within the upper part of the Bathonian. The base of the Callovian does not yet have a certified GSSP. The working definition for the base of the Callovian is the first appearance of ammonites belonging to the genus Kepplerites . The Oxfordian

9408-478: Was present in the Northern Hemisphere during both the early Pliensbachian and the latest Pliensbachian. 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-Ferrar large igneous provinces in southern Gondwana, with the warm interval extending to the end of

9506-660: Was ratified in 2000. The beginning of the Sinemurian is defined by the first appearance of the ammonite Vermiceras quantoxense . Albert Oppel in 1858 named the Pliensbachian Stage after the hamlet of Pliensbach in the community of Zell unter Aichelberg in the Swabian Alb , near Stuttgart , Germany. The GSSP for the base of the Pliensbachian is found at the Wine Haven locality in Robin Hood's Bay , Yorkshire , England, in

9604-430: Was ratified in 2021. The boundary is defined by the first appearance of ammonites marking the boreal Bauhini Zone and the subboreal Baylei Zone. The Tithonian was introduced in scientific literature by Albert Oppel in 1865. The name Tithonian is unusual in geological stage names because it is derived from Greek mythology rather than a place name. Tithonus was the son of Laomedon of Troy and fell in love with Eos ,

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