"Should my Axis describe upon the lights of long,
amongst the leaf?" kap Monday, February 1, 2021
Know thyself
The Ancient Greek aphorism "know thyself" (Greek: γνῶθι σεαυτόν, transliterated: gnōthi seauton; also ... σαυτόν … sauton with the ε contracted), is one of the Delphic maxims and was the first of three maxims inscribed in the pronaos (forecourt) of the Temple of Apollo at Delphi according to the Greek writer Pausanias (10.24.1).[1] The two maxims that followed "know thyself" were "nothing to excess" and "surety brings ruin".[2] In Latin the phrase, "know thyself," is given as nosce te ipsum[3] or temet nosce.[4]
The maxim, or aphorism, "know thyself" has had a variety of meanings attributed to it in literature, and over time, as in early ancient Greek the phrase meant "know thy measure."[5]
Attribution
The Greek aphorism has been attributed to at least the following ancient Greek sages:
- Bias of Priene[6]
- Chilon of Sparta[7]
- Cleobulus of Lindus[6]
- Heraclitus[8]
- Myson of Chenae[6]
- Periander[9]
- Pittacus of Mytilene[6]
- Pythagoras[10]
- Plato[11]
- Solon of Athens[6]
- Thales of Miletus[12]
Diogenes Laërtius attributes it to Thales (Lives I.40), but also notes that Antisthenes in his Successions of Philosophers attributes it to Phemonoe, a mythical Greek poet, though admitting that it was appropriated by Chilon. In a discussion of moderation and self-awareness, the Roman poet Juvenal quotes the phrase in Greek and states that the precept descended e caelo (from heaven) (Satires 11.27). The 10th-century Byzantine encyclopedia the Suda recognized Chilon[7] and Thales[12] as the sources of the maxim "Know Thyself."
The authenticity of all such attributions is doubtful; according to Parke and Wormell (1956), "The actual authorship of the three maxims set up on the Delphian temple may be left uncertain. Most likely they were popular proverbs, which tended later to be attributed to particular sages."[13][14]
Usage
Listed chronologically:
By Aeschylus
The ancient Greek playwright Aeschylus uses the maxim "know thyself" in his play Prometheus Bound. The play about a mythological sequence, thereby places the maxim within the context of Greek mythology. In this play, the demi-god Prometheus first rails at the Olympian gods, and against what he believes to be the injustice of his having been bound to a cliffside by Zeus, king of the Olympian gods. The demi-god Oceanus comes to Prometheus to reason with him, and cautions him that he should "know thyself".[15] In this context, Oceanus is telling Prometheus that he should know better than to speak ill of the one who decides his fate and accordingly, perhaps he should better know his place in the "great order of things."
By Socrates
One of Socrates's students, the historian Xenophon, described some of the instances of Socrates's use of the Delphic maxim 'Know Thyself' in his history titled: Memorabilia. In this writing, Xenophon portrayed his teacher's use of the maxim as an organizing theme for Socrates's lengthy dialogue with Euthydemus.[16]
By Plato
Plato, another student of Socrates, employs the maxim 'Know Thyself' extensively by having the character of Socrates use it to motivate his dialogues. Benjamin Jowett's index to his translation of the Dialogues of Plato lists six dialogues which discuss or explore the Delphic maxim: 'know thyself.' These dialogues (and the Stephanus numbers indexing the pages where these discussions begin) are Charmides (164D), Protagoras (343B), Phaedrus (229E), Philebus (48C), Laws (II.923A), Alcibiades I (124A, 129A, 132C).[17]
In Plato's Charmides, Critias argues that "succeeding sages who added 'never too much,' or, 'give a pledge, and evil is nigh at hand,' would appear to have so misunderstood them; for they imagined that 'know thyself!' was a piece of advice which the god gave, and not his salutation of the worshippers at their first coming in; and they dedicated their own inscription under the idea that they too would give equally useful pieces of advice."[18] In Critias' opinion 'know thyself!' was an admonition to those entering the sacred temple to remember or know their place and that 'know thyself!' and 'be temperate!' are the same.[19] In the balance of the Charmides, Plato has Socrates lead a longer inquiry as to how we may gain knowledge of ourselves.
In Plato's Phaedrus, Socrates uses the maxim 'know thyself' as his explanation to Phaedrus to explain why he has no time for the attempts to rationally explain mythology or other far flung topics. Socrates says, "But I have no leisure for them at all; and the reason, my friend, is this: I am not yet able, as the Delphic inscription has it, to know myself; so it seems to me ridiculous, when I do not yet know that, to investigate irrelevant things."[20]
In Plato's Protagoras, Socrates lauds the authors of pithy and concise sayings delivered precisely at the right moment and says that Lacedaemon, or Sparta, educates its people to that end. Socrates lists the Seven Sages as Thales, Pittacus, Bias, Solon, Cleobulus, Myson, and Chilon, who he says are gifted in that Lacedaemonian art of concise words "twisted together, like a bowstring, where a slight effort gives great force."[21] Socrates says examples of them are, "the far-famed inscriptions, which are in all men's mouths—'Know thyself,' and 'Nothing too much'."[22] Having lauded the maxims, Socrates then spends a great deal of time getting to the bottom of what one of them means, the saying of Pittacus, 'Hard is it to be good.' The irony here is that although the sayings of Delphi bear 'great force,' it is not clear how to live life in accordance with their meanings. Although, the concise and broad nature of the sayings suggests the active partaking in the usage and personal discovery of each maxim; as if the intended nature of the saying lay not in the words but the self-reflection and self-referencing of the person thereof.
In Plato's Philebus dialogue, Socrates refers back to the same usage of 'know thyself' from Phaedrus to build an example of the ridiculous for Protarchus. Socrates says, as he did in Phaedrus, that people make themselves appear ridiculous when they are trying to know obscure things before they know themselves.[23] Plato also alluded to the fact that understanding 'thyself,' would have a greater yielded factor of understanding the nature of a human being. Syllogistically, understanding oneself would enable thyself to have an understanding of others as a result.
Later usage
The Suda, a 10th-century encyclopedia of Greek knowledge, states: "the proverb is applied to those whose boasts exceed what they are",[7] and that "know thyself" is a warning to pay no attention to the opinion of the multitude.[24]
One work by the Medieval philosopher Peter Abelard is titled Scito te ipsum (“know yourself”) or Ethica.
From 1539 onward, the phrase nosce te ipsum and its Latin variants were used in the anonymous texts written for anatomical fugitive sheets printed in Venice as well as for later anatomical atlases printed throughout Europe. The 1530s fugitive sheets are the first instances in which the phrase was applied to knowledge of the human body attained through dissection.[25]
In 1651, Thomas Hobbes used the term nosce teipsum which he translated as 'read thyself' in his famous work, The Leviathan. He was responding to a popular philosophy at the time that you can learn more by studying others than you can from reading books. He asserts that one learns more by studying oneself: particularly the feelings that influence our thoughts and motivate our actions. As Hobbes states, "but to teach us that for the similitude of the thoughts and passions of one man, to the thoughts and passions of another, whosoever looketh into himself and considereth what he doth when he does think, opine, reason, hope, fear, etc., and upon what grounds; he shall thereby read and know what are the thoughts and passions of all other men upon the like occasions."[26]
In 1734, Alexander Pope wrote a poem entitled "An Essay on Man, Epistle II", which begins "Know then thyself, presume not God to scan, The proper study of mankind is Man."[27]
In 1735, Carl Linnaeus published the first edition of Systema Naturae in which he described humans (Homo) with the simple phrase "Nosce te ipsum".[28]
In 1750, Benjamin Franklin, in his Poor Richard's Almanack, observed the great difficulty of knowing one's self, with: "There are three Things extremely hard, Steel, a Diamond, and to know one's self."[29]
In 1754, Jean-Jacques Rousseau lauded the "inscription of the Temple at Delphi" in his Discourse on the Origin of Inequality.
In 1831, Ralph Waldo Emerson wrote a poem titled "Γνώθι Σεαυτόν", or Gnothi Seauton ('Know Thyself'), on the theme of 'God in thee.' The poem was an anthem to Emerson's belief that to "know thyself" meant knowing the God that Emerson felt existed within each person.[30]
In 1832, Samuel T. Coleridge wrote a poem titled "Self Knowledge" in which the text centers on the Delphic maxim "Know Thyself" beginning "Gnôthi seauton!--and is this the prime And heaven-sprung adage of the olden time!--" and ending with "Ignore thyself, and strive to know thy God!" Coleridge's text references JUVENAL, xi. 27.[31]
In 1857, Allan Kardec asks in The Spirits Book (question 919): "What is the most effective method for guaranteeing self-improvement and resisting the attraction of wrongdoing?" and obtains the answer from the Spirits "A philosopher of antiquity once said, "Know thyself'". [32] Acknowledging the wisdom of the maxim, he then asks about the means of acquiring self-knowledge, obtaining a detailed answer with practical instructions and philosophical-moral considerations.
In 1902, Hugo von Hofmannsthal had his 16th-century alter ego in his letter to Francis Bacon mention a book he intended to call Nosce te ipsum.
The Wachowskis used one of the Latin versions (temet nosce) of this aphorism as inscription over the Oracle's door in their movies The Matrix (1999)[33] and The Matrix Revolutions (2003).[34] The transgender character Nomi in the Netflix show Sense8, again directed by The Wachowskis, has a tattoo on her arm with the Greek version of this phrase.
"Know Thyself" is the motto of Hamilton College of Lyceum International School (Nugegoda, Sri Lanka) and of İpek University (Ankara, Turkey).[35] The Latin phrase "Nosce te ipsum" is the motto of Landmark College.
Nosce te ipsum is also the motto for the Scottish clan Thompson. It is featured on the family crest or coat of arms.[36]
In other languages
In The Art of War, the maxim 知彼知己，百战不殆 means "know others and know thyself, and you will not be endangered by innumerable battles". In this saying by Sun Zi (孙子, Sun Tze), the idea of knowing thyself is paramount.
A battle/challenge cannot be won if one does not understand his or her own strengths and weaknesses, which come into play during the preparedness and response required to avoid danger. Note, winning is not always the goal, simply not losing is the best method to avoid inciting the spirit of revenge.[citation needed]
See also
- Delphic maxims
- I know that I know nothing
- Introspection
- Jnana
- Philosophy of self
- Self-knowledge (psychology)
- The Art of War
References
- "Thompson Surname, Family Crest & Coats of Arms". House of Names. Retrieved 19 April 2017.
External links
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Wikimedia Commons has media related to Gnōthi seauton. |
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Look up know thyself in Wiktionary, the free dictionary. |
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Wikiquote has quotations related to: Know thyself |
- Gnothi sauton at Binghamton University
- "The Examined Life", BBC Radio 4 discussion with A.C. Grayling, Janet Radcliffe & Julian Baggini (In Our Time, May 9, 2002)
Languages
Evolution:
Jurassic
| Jurassic | |
|---|---|
| 201.3 ± 0.2 – ~145.0 Ma | |
| Chronology | |
Key events in the Jurassic -200 — – -195 — – -190 — – -185 — – -180 — – -175 — – -170 — – -165 — – -160 — – -155 — – -150 — – -145 — – how to approximate the timescale of key Jurassic events. Vertical axis: millions of years ago. | |
| Etymology | |
| Name formality | Formal |
| Usage Information | |
| Celestial body | Earth |
| Regional Usage | Global (ICS) |
| Time scale(s) used | ICS Time Scale |
| Definition | |
| Chronological unit | Period |
| Stratigraphic unit | System |
| Time span formality | Formal |
| Lower boundary definition | First appearance of the Ammonite Psiloceras spelae tirolicum. |
| Lower boundary GSSP | Kuhjoch section, Karwendel mountains, Northern Calcareous Alps, Austria 47.4839°N 11.5306°E |
| GSSP ratified | 2010 |
| Upper boundary definition | Not formally defined |
| Upper boundary definition candidates |
|
| Upper boundary GSSP candidate section(s) | None |
| Atmospheric and Climatic Data | |
| Mean atmospheric O 2 content | c. 26 vol % (130 % of modern) |
| Mean atmospheric CO 2 content | c. 1950 ppm (7 times pre-industrial) |
| Mean surface temperature | c. 16.5 °C (3 °C above modern) |
The Jurassic (/dʒʊˈræs.sɪk/ juu-RASS-ik[1]) is a geologic period and system that spanned 56 million years from the end of the Triassic Period 201.3 million years ago (Mya) to the beginning of the Cretaceous Period 145 Mya.[note 1] The Jurassic constitutes the middle period of the Mesozoic Era. The Jurassic is named after the Jura Mountains in the European Alps, where limestone strata from the period were first identified.
The start of the period was marked by the major Triassic–Jurassic extinction event. Two other extinction events occurred during the period: the Pliensbachian-Toarcian extinction in the Early Jurassic, and the end Jurassic transition, which is disputed in its impact.[4]
The Jurassic period 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 of rock formations.
By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses: Laurasia to the north, and Gondwana to the south. This created more coastlines and shifted the continental climate from dry to humid, and many of the arid deserts of the Triassic were replaced by lush rainforests.
On land, the fauna transitioned from the Triassic fauna, dominated by both dinosauromorph and pseudosuchian archosaurs, to one dominated by dinosaurs alone. The first birds also appeared during the Jurassic, having evolved from a branch of theropod dinosaurs. Other major events include the appearance of the earliest lizards, and the evolution of therian mammals. Crocodilians made the transition from a terrestrial to an aquatic mode of life. The oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, while pterosaurs were the dominant flying vertebrates.
Etymology and history
The chronostratigraphic term "Jurassic" is directly linked to the Jura Mountains, a mountain range mainly following the course of the France–Switzerland border. The name "Jura" is derived from the Celtic root *jor via Gaulish *iuris "wooded mountain", which, borrowed into Latin as a place name, evolved into Juria and finally Jura.[5][6][7] During a tour of the region in 1795,[note 2] Alexander von Humboldt recognized the mainly limestone dominated mountain range of the Jura Mountains as a separate formation that had not been included in the established stratigraphic system defined by Abraham Gottlob Werner, and he named it "Jura-Kalkstein" ('Jura limestone') in 1799.[note 3][5][6][10]
Thirty years later, in 1829, the French naturalist Alexandre Brongniart published a survey on the different terrains that constitute the crust of the Earth. In this book, Brongniart referred to the terrains of the Jura Mountains as terrains jurassiques, thus coining and publishing the term for the first time.[11] The German geologist Leopold von Buch in 1839 established the three-fold division of the Jurassic, originally named from oldest to youngest, the Black Jurassic, Brown Jurassic and White Jurassic.[12] The term "Lias" had previously been used equivalently for strata of equivalent age to the Black Jurassic in England by Conybeare and Phillips in 1822. French palaeontologist Alcide d'Orbigny in papers between 1842 and 1852 would divide the Jurassic into ten stages “étages” based on ammonite and other fossil assemblages in England and France, of which seven are still used, though none retain the original definition. German geologist and palaeontologist Friedrich August von Quenstedt in 1858 would divide the three series of von Buch in the Swabian Jura into six subdivisions defined by ammonites and other fossils. German palaeontologist Albert Oppel in 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 á Luxembourg" in 1962.[13]
Geology
The Jurassic period 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 of rock formations, also known in Europe as Lias, Dogger and Malm.[14] The three epochs are subdivided into shorter spans of time called ages. The ages of the Jurassic from youngest to oldest are:
| Upper/Late Jurassic | Tithonian | (152.1 ± 4 – 145 ± 4 Mya) |
| Kimmeridgian | (157.3 ± 4 – 152.1 ± 4 Mya) | |
| Oxfordian | (163.5 ± 4 – 157.3 ± 4 Mya) | |
| Middle Jurassic | Callovian | (166.1 ± 4 – 163.5 ± 4 Mya) |
| Bathonian | (168.3 ± 3.5 – 166.1 ± 4 Mya) | |
| Bajocian | (170.3 ± 3 – 168.3 ± 3.5 Mya) | |
| Aalenian | (174.1 ± 2 – 170.3 ± 3 Mya) | |
| Lower/Early Jurassic | Toarcian | (182.7 ± 1.5 – 174.1 ± 2 Mya) |
| Pliensbachian | (190.8 ± 1.5 – 182.7 ± 1.5 Mya) | |
| Sinemurian | (199.3 ± 1 – 190.8 ± 1.5 Mya) | |
| Hettangian | (201.3 ± 0.6 – 199.3 ± 1 Mya) |
Stratigraphy
Jurassic stratigraphy is primarily based around of the use of ammonites as index fossils, with the First Appearance Datum of specific ammonite taxa being used to mark the beginnings of stages, and 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.[13]
The oldest part of the Jurassic period has historically been referred to as the Lias or Liassic, roughly equivalent in extent to the Early Jurassic, but also including part of the preceding Rhaetian. The Hettangian stage was named by Swiss palaeontologist Eugène Renevier in 1864 after Hettange-Grande in North-Eastern France. The Global Boundary Stratotype Section and Point (GSSP) for the base of the Hettangian is located at Kuhjoch pass, Karwendel Mountains, Northern Calcareous Alps, Austria, which was ratified in 2010. The beginning of the Hettangian, and thus the Jurassic as a whole, is marked by the first appearance of the ammonite Psiloceras spelae tirolicum in the Kendlbach Formation exposed at Kuhjoch.[15] 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.[13]
The Sinemurian stage was 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. The beginning of the Sinemurian is defined by the first appearance of the ammonite Vermiceras quantoxense.[13][16]
The Pliensbachian was named by German palaeontologist Albert Oppel in 1858 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 the Redcar Mudstone Formation. The beginning of the Pliensbachian is defined by the first appearance of the ammonite Bifericeras donovani.[17]
The Toarcian is named after the village Thouars (Latin: Toarcium), just south of Saumur in the Loire Valley of France, it was defined by Alcide d'Orbigny in 1842 originally from Vrines quarry around 2 km northwest of the village. The GSSP for the base of the Toarcian is located at Peniche, Portugal. The boundary is defined by the first appearance of ammonites belonging to the subgenus Dactylioceras (Eodactylioceras).[18]
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 the Black Jurassic and the overlying clayey sandstone and ferruginous oolite of the Brown Jurassic sequences of southwestern Germany.[13] The GSSP for the base of the Aalenian is located at Fuentelsaz in the Iberian range near Guadalajara, Spain. The base of the Aalenian is defined by the first appearance of the ammonite Leioceras opalinum.[19]
The Bajocian is named after the town of Bayeux (Latin: Bajoce) in Normandy, France, and was defined by Alcide d'Orbigny in 1842. The GSSP for the base of the Bajocian is located at Murtinheira in Portugal, and was defined in 1997. The base of the Bajocian is defined by the first appearance of the ammonite Hyperlioceras mundum.[20]
The Bathonian is named after the city of Bath, England, introduced by Belgian geologist d'Omalius d'Halloy in 1843, after an incomplete section of oolitic limestones in several quarries in the region. The GSSP for the base of the Bathonian is Ravin du Bès, Bas-Auran area, Alpes de Haute Provence, France, which was defined 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.[21]
The Callovian is derived from the Latinized name of the village of Kellaways in Wiltshire, England, and was defined by Alcide d'Orbigny in 1852, originally with base at the contact between the Forest Marble Formation and the Cornbrash Formation. However, this boundary was later found to be situated within the upper part of the Bathonian. The base of the Callovian does not yet have a certified GSSP, as of 2019.[13]
The Oxfordian 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 the first appearance of Cardioceras redcliffense as the lower boundary.[13]
The Kimmeridgian is named after the village of Kimmeridge on the coast of Dorset, England. It was named by Alcide d'Orbigny in 1842, in reference to the Kimmeridge Clay. Although not confirmed, the Flodigarry section at Staffin Bay on the Isle of Skye, Scotland has been submitted as the GSSP for the base of the Kimmeridgian.[22]
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 placename. Tithonus was the son of Laomedon of Troy and fell in love with Eos, 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.[13] The upper boundary of the Jurassic is also currently undefined. Calpionellids, an enigmatic group of pelagic protists with urn shaped calcitic tests briefly abundant during the latest Jurassic to earliest Cretaceous, have been suggested to represent the most promising candidates for fixing the J/K boundary.[23]
Mineral and hydrocarbon deposits
The Kimmeridge Clay and equivalents are the major source rock for the North Sea oil.[24] The Arabian Intrashelf Basin, deposited from the late Middle to Upper Jurassic, is the setting of the world's largest oil reserves, including the Ghawar Field, the world largest oil field.[25] The Jurassic aged Sargelu[26] and Naokelekan Formations[27] 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.[28]
Impact craters
Major impact craters include the Morokweng crater, a 70 km diameter crater buried beneath the Kalahari desert in northern South Africa. The impact is dated to the Jurassic-Cretaceous boundary, around 145 Ma. The Morokweng crater has been suggested to have had a role in the turnover at the Jurassic-Cretaceous transition.[29] Another major impact crater is the Puchezh-Katunki crater, 40-80 kilometres in diameter, buried beneath Nizhny Novgorod Oblast, Russia. The impact has been dated to the Sinemurian, around 192-196 Mya.[30]
Paleogeography and tectonics
During the early Jurassic period, the supercontinent Pangaea broke up into the northern supercontinent Laurasia and the southern supercontinent Gondwana; the Gulf of Mexico opened in the new rift between North America and what is now Mexico's Yucatán Peninsula. The Jurassic North Atlantic Ocean was relatively narrow, while the South Atlantic did not open until the following Cretaceous period.[31] 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.[32] The Boreal Ocean was connected to the western Tethys by the "Viking corridor", a several hundred kilometer wide passage between the Baltic Shield and Greenland.[33] Madagascar and Antarctica began to rift away from Africa during Early Jurassic, 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 had rifted apart, forming the Caribbean Seaway, connecting the western Tethys with eastern Panthalassa.[36] 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.[37] During the Middle to early Late Jurassic, the Sundance Seaway, a shallow epicontinental sea would cover much of northwest North America.[38]
Based on estimated sea level curves, the eustatic sea level was 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 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 cyclical 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.[39]
The Jurassic was a time of calcite sea geochemistry in which low-magnesium calcite was the primary inorganic marine precipitate of calcium carbonate. Carbonate hardgrounds were thus very common, along with calcitic ooids, calcitic cements, and invertebrate faunas with dominantly calcitic skeletons.[40] The rise of calcareous plankton during the Middle Jurassic profoundly altered ocean chemistry, with the deposition of biomineralizing plankton on the ocean floor acting as a buffer against large CO2 emissions.[41]
The first of several massive batholiths were emplaced in the northern American cordillera beginning in the mid-Jurassic, marking the Nevadan orogeny.[42]
In Africa, Early Jurassic strata are distributed in a similar fashion to Late Triassic beds, with more common outcrops in the south and less common fossil beds which are predominated by tracks to the north.[43] As the Jurassic proceeded, larger and more iconic groups of dinosaurs like sauropods and ornithopods proliferated in Africa.[43] Middle Jurassic strata are neither well represented nor well studied in Africa.[43] Late Jurassic strata are also poorly represented apart from the spectacular Tendaguru fauna in Tanzania.[43] The Late Jurassic life of Tendaguru is very similar to that found in western North America's Morrison Formation.[43]
Jurassic limestones and marls (the Matmor Formation) in southern Israel
The Upper Jurassic Morrison Formation in Colorado is one of the most fertile sources of dinosaur fossils in North America
Gigandipus, a dinosaur footprint in the Lower Jurassic Moenave Formation at the St. George Dinosaur Discovery Site at Johnson Farm, southwestern Utah
The Permian through Jurassic stratigraphy of the Colorado Plateau area of southeastern Utah
Climate
The climate of Jurassic was generally warmer than at present, by around 5 °C to 10 °C. Atmospheric carbon dioxide levels were likely four times higher than present. Forests likely grew near the poles, and experienced warm summers and cold, sometimes snowy winters, and there were unlikely to have been ice sheets given the high summer temperatures, though mountain glaciers may have existed. The ocean depths were likely 8 °C warmer than present, and reefs grew 10° of latitude further north and south. The Intertropical Convergence Zone likely existed over the oceans, resulting in large areas of desert in the lower latitudes.[44]
Climatic events
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,[45] 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, foraminifera, brachiopods, bivalves and cnidarians,[46][47] with the last two spire-bearing brachiopod orders Spiriferinida and Athyridida becoming extinct.[48] While the event had significant impact on marine invertebrates, it had little effect on marine reptiles.[49] 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.[50] 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.[51] This ocean acidification is what likely caused the collapse of carbonate production.[52][53]
End-Jurassic transition
The end-Jurassic transition was originally considered one of eight mass extinctions, but is now considered to be 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.[29]
Flora
End-Triassic extinction
The preceding end-Triassic extinction would result in the decline of Peltaspermaceae seed ferns, with Lepidopteris perisisting into the Early Jurassic in Patagonia.[54] At the Triassic-Jurassic boundary in Greenland, the sporomorph diversity suggests a complete floral turnover.[55] An analysis of macrofossil floral communities in Europe suggests no extinction over the Triassic-Jurassic boundary, and that changes were mainly due to local ecological succession.[56] 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.[57]
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.[58]
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.[59][60]
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.[61]
The oldest definitive record of the cypress family (Cupressaceae) is Austrohamia minuta from the Early Jurassic (Pliensbachian) of Patagonia, known from several elements.[62] 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.[63] The seed cone Scitistrobus from the Middle Jurassic (Aalenian) of Scotland displays a mosaic of traits indicative of ancestral Voltziales and derived Cupressaceae.[64]
The oldest record of the pine family (Pinaceae) is the seed cone Eathiestrobus, known from the Late Jurassic (Kimmeridgian) also of Scotland.[65] During the Early Jurassic, the flora of the mid-latitudes of Eastern Asia were dominated by the extinct deciduous 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.[66]
The earliest record of the yew family (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.[67]
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.[68] Scarburgia from the Middle Jurassic of Yorkshire,[69] and Harrisiocarpus from the Jurassic of Poland.[70]
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 associated with leaf morphotaxa such as Baiera, Ginkgoites and Sphenobaiera, 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.[71][72] Umaltolepis, historically thought to be ginkgoalean, and Vladimaria from the Jurassic of Asia have strap shaped ginkgo-like leaves (Pseudotorellia), with highly distinct reproductive structures with similarities to those of peltasperm and corystosperm seed ferns, and have been placed in the separate order Vladimariales, which may belong to a broader Ginkgoopsida.[73]
Ferns
The ground cover was dominated by ferns, including members of the living families Dipteridaceae, Matoniaceae, Osmundaceae and Marattiaceae,[74] as well as horsetails. Polypodiales, which today make up 80% of living fern diversity, have no record from the Jurassic, and are thought to have diversified in the Cretaceous,[75] 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.[76]
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.[77] 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.[78]
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[79] and Equisetum laterale from the Early-Middle Jurassic of Australia.[80][81] Silicified remains of Equisetum thermale from the Late Jurassic of Argentina exhibit all the morphological characters of modern members of the genus.[82] The estimated split between Equisetum bogotense and all other living Equisetum is estimated to have occurred no later than the Early Jurassic.[81]
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.[83] Only a handful of possible records exist of the Hymenophyllaceae are known from the Jurassic, including Hymenophyllites macrosporangiatus from the Russian Jurassic.[84]
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.[85] 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.[86] 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[87] and extant Acroceridae flies,[88] 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,[89] though a later analysis placed this divergence during the Late Permian, which placed the diversification of the Zamiineae cycads during the Jurassic.[90] 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.[91] and mostly confined to tropical and subtropical latitudes.[92] 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.[93] 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.[94] 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.[92]
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.[95]
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 in 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.[96] 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.[97][98]
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[99]) to Cretaceous.[100] They are thought to have had a tree or shrub like habit, and formed a conspicuous component of Mesozoic temperate and warm–temperate floras.[99] Jurassic genera include the leaf genera Czekanowskia, Phoenicopsis and Solenites, associated with the ovulate cone Leptostrobus.[100]
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.[100]
Lower plants
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.[101]
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.[102] Heinrichsiella from the Jurassic of Patagonia is thought to belong to the families Polytrichaceae or Timmiellaceae basal to Bryidae, and is the oldest representative of the grade.[103]
Liverworts
The liverwort Pellites hamiensis from the Middle Jurassic Xishanyao Formation of China is the oldest record of the family Pelliaceae.[104] Pallaviciniites sandaolingensis from the same deposit is thought to belong to the subclass Pallaviciniineae within the Pallaviciniales.[105] Ricciopsis sandaolingensis also from the same deposit is the only Jurassic record of Ricciaceae.[106]
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.[74] 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.[107] 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.[108] 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.[109]
Fauna
Aquatic and marine
During the Jurassic period, the primary vertebrates living in the sea were fish and marine reptiles. The latter include ichthyosaurs, which were at the peak of their diversity, plesiosaurs, including pliosaurs, and marine thalattosuchian crocodyliformes of the families Teleosauridae, Machimosauridae and Metriorhynchidae.[110]
Calcareous sabellids (Glomerula) appeared in the Early Jurassic.[111][112] The Jurassic also had diverse encrusting and boring (sclerobiont) communities, and it saw a significant rise in the bioerosion of carbonate shells and hardgrounds. Especially common is the ichnogenus (trace fossil) Gastrochaenolites.[113] During the Jurassic period, about four or five of the twelve clades of planktonic organisms that exist in the fossil record either experienced a massive evolutionary radiation or appeared for the first time.[14]
Ichthyosaurus from lower (early) Jurassic slates in southern Germany featured a dolphin-like body shape.
Plesiosaurs like Muraenosaurus roamed Jurassic oceans.
Terrestrial
On land, various archosaurian reptiles remained dominant. The Jurassic was a golden age for the large herbivorous dinosaurs known as the sauropods—Camarasaurus, Apatosaurus, Diplodocus, Brachiosaurus, and many others—that roamed the land late in the period; their foraging grounds were either the prairies of ferns, palm-like cycads and bennettitales, or the higher coniferous growth, according to their adaptations. The smaller Ornithischian herbivore dinosaurs, like stegosaurs and small ornithopods were less predominant, but played important roles. They were preyed upon by large theropods, such as Ceratosaurus, Megalosaurus, Torvosaurus and Allosaurus, all these belong to the 'lizard hipped' or saurischian branch of the dinosaurs.[114]
During the Late Jurassic, the first avialans, like Archaeopteryx, evolved from small coelurosaurian dinosaurs. In the air, pterosaurs were common; they ruled the skies, filling many ecological roles now taken by birds,[115] and may have already produced some of the largest flying animals of all time.[116][117] Within the undergrowth were various types of early mammals, as well as tritylodonts, lizard-like sphenodonts, and early lissamphibians. The rest of the Lissamphibia evolved in this period, introducing the first salamanders and caecilians.[118]
Diplodocus, reaching lengths over 30 m, was a common sauropod during the late Jurassic.
Allosaurus was one of the largest land predators of the Jurassic.
Stegosaurus is one of the most recognizable genera of dinosaurs and lived during the mid to late Jurassic.
Aurornis xui, which lived in the late Jurassic, may be the most primitive avialan dinosaur known to date, and is one of the earliest avialans found to date.
Reptiles
Crocodylomorphs
The T-J extinction decimated pseudosuchian diversity, with crocodylomorphs, which originated during the early Late Triassic (Norian), being the only group of pseudosuchians to survive the T-J extinction. The morphological diversity of crocodylomorphs during the Early Jurassic was around the same as those of Late Triassic pseudosuchians, but occupied different areas of morphospace, suggesting that they occupied different ecological niches to their Triassic counterparts, and that there was an extensive and rapid radiation of crocodylomorphs during this interval.[119] While living crocodilians are confined to an aquatic ambush predator lifestyle, Jurassic crocodyliformes exhibit a wide variety of life habits, with the earliest known herbivorous crocodylomorph being an unnamed species of protosuchid from the Early Jurassic of Arizona.[120] The earliest lineages of Crocodylomorpha are represented by the terrestrial small-bodied long-legged "sphenosuchians", one lineage of which, the Hallopodidae, perisisted into the Late Jurassic.[121][122] The Thalattosuchia, a clade of predominantly marine crocodylomorphs including both teleosaurioids and metriorhynchoids, first appeared during the Early Jurassic (Toarcian), and became prominent part of marine reptile communities during the Jurassic. During the Jurassic, the Neosuchia would appear, the Neosuchia are thought to be ancestrally freshwater aquatic, similar to living crocodilians.[123] The oldest record of Neosuchians has been suggested to be Calsoyasuchus, from the Early Jurassic of Arizona, which in many analyses has been recovered as the earliest branching goniopholidid, 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.[123] Razanandrongobe from the Middle Jurassic of Madagascar has been suggested the represent the oldest record of Notosuchia, a primarily Gondwanan clade of mostly terrestrial crocodylomorphs, otherwise known from the Cretaceous.[124]
Turtles
Stem-group turtles (Testudinata) would diversify during the Jurassic. Jurassic stem-turtles belong to two progressively more advanced clades, the Mesochelydia and Perichelydia.[125] It is thought that the ancestral condition for Mesochelydians is aquatic, as opposed to terrestrial for Testudinata.[126] The two modern groups of turtles (Testudines), Pleurodires and Cryptodires, would diverge by the Middle Jurassic.[127][128] Early cryptodire lineages like Xinjiangchelyidae are known from the Middle Jurassic,[129] while an early stem pleurodire lineage, the ocean-going Platychelyidae is known from the Late Jurassic.[130] The Thalassochelydia, a diverse lineage of sea-turtles, is known from the Late Jurassic (Oxfordian-Tithonian) of Europe and South America.[131]
Lepidosaurs
Lepidosaurs, which include squamates (lizards and snakes) and rhynchocephalians (which today only includes the tuatara) would diversify during the Jurassic, however little can be said for diversity trends due to the poor fossil record during this interval.[132] Rynchocephalians reached their highest morphological diversity in their evolutionary history during the Jurassic, occupying a wide range of lifestyles, including aquatic taxa such as pleurosaurids, the specialized herbivorous "eilenodontines" as well as Oenosaurus, which had broad tooth plates indicative of durophagy. Cynosphenodon from the Early Jurassic of Mexico is suggested to be among the closest known relatives of the living tuatara.[133] Rhynchocephalians disappeared from Asia after the Early Jurassic.[134] Crown group squamates first appeared during the Middle Jurassic of Asia and Europe,[132] with the estimated origin of living squamates during the Early Jurassic (~190 Mya) and the divergence of most major squamate groups during the Early-Middle Jurassic.[135] Many Jurassic squamates have unclear relationships to living groups.[136] Early members of the snake lineage (Ophidia) appear during the Middle Jurassic,[137] as well as the Paramacellodidae, a family of lizards which are diagnosed by their distinctive covering of osteoderms, and are thought to be early members of Scincomorpha.[138] Eichstaettisaurus from the Late Jurassic of Germany has been suggested to be an early relative of geckos, and displays adaptations for climbing.[139] Dorsetisaurus from the Late Jurassic of North America and Europe represents the oldest widely accepted record of Anguimorpha.[140] Marmoretta from the Middle Jurassic of Britain represents a late surviving lepidosauromorph outside both groups.[141]
Vadasaurus herzogi, a rynchocephalian from the Upper Jurassic Solnhofen Limestone of Germany
Homeosaurus maximiliani a rynchocephalian from the Solnhofen Limestone
Pleurosaurus, an aquatic rhynchocephalian from the Late Jurassic of Europe
Eichstaettisaurus schroederi, an extinct lizard from the Solnhofen Limestone.
Choristoderes
The earliest known remains of Choristodera, a group of freshwater aquatic reptiles with uncertain affinities to other reptile groups, are found in the Middle Jurassic. Only two genera of choristodere are known from the Jurassic. One is Cteniogenys, thought to be the most basal known choristodere, which is known from the Middle-Late Jurassic of Europe and Late Jurassic of North America, with similar remains also known from the upper Middle Jurassic of Kyrgyzstan, European Russia and western Siberia.[142] The other is Coeruleodraco from the Late Jurassic of China, which has close affinities to a clade of non-Neochoristodera from the Early Cretaceous of Asia as well as Lazarussuchus from the Cenozoic of Europe.[143]
Ichthyosaurs
Ichthyosaurs suffered an evolutionary bottleneck, with all non-neoichthyosaurians becoming extinct at the end of the Triassic. Ichthyosaurs would reach their apex of species diversity during the Early Jurassic, with an array of morphologies including the huge apex predator Temnodontosaurus and swordfish-like Eurhinosaurus. Jurassic ichthyosaurs were significantly less morphologically diverse than their Triassic counterparts, and would become less diverse and morphologically conservative after the Early Jurassic.[144] The fossil record of ichthyosaurs during the Middle Jurassic is poor.[145] The Ophthalmosauridae, which would represent all (with the exception of Malawania) ichthyosaurs from the late Middle Jurassic onwards, first appear in the early Middle Jurassic (Bajocian), before spreading worldwide by the Late Jurassic.[146]
Plesiosaurs
Plesiosaurs originated at the end of the Triassic (Rhaetian). By the Triassic boundary, all other sauropterygians, including placodonts and nothosaurs had become extinct. At least six lineages of plesiosaur crossed the T-J boundary.[147] Plesiosaurs were already diverse in the earliest Jurassic, with the majority of plesiosaurs in the Hettangian aged Blue Lias belonging to the Rhomaleosauridae. Early plesiosaurs were generally small-bodied forms, with body size increasing into the Toarcian.[148] The Middle Jurassic saw the evolution of short necked and large headed thalassophonean pliosaurs from ancestrally small-headed long necked forms.[149] Some thalassophonean pliosaurs, such as some species of Pliosaurus had skulls up to two metres in length with body lengths estimated around 10–12 metres, making them among the largest predators of Jurassic oceans.[150] Cryptoclididae, a family of long-necked plesiosaurs, would radiate beginning in the Middle Jurassic.[151] Plesiosaurs would invade freshwater environments during the Jurassic, with indeterminate remains of small bodied pleisosaurs known from freshwater sediments from the Jurassic of China and Australia.[152][153]
Pterosaurs
Pterosaurs first appeared in the Late Triassic. A major radiation of Jurassic pterosaurs is the Rhamphorhynchidae, which first appeared in the late Early Jurassic (Toarcian),[154] and are thought to have had piscivorous habits.[155]Anurognathids, which first appeared in the Middle Jurassic, possess short heads and densely furred bodies, and are thought to have been insectivores.[155] Derived monofenestratan pterosaurs, like wukongopterids appeared in the late Middle Jurassic. Advanced short-tailed pterodactyloids first appeared at the Middle-Late Jurassic boundary. Jurassic pterodactyloids include the ctenochasmatids like Ctenochasma, which have closely spaced needle like teeth that were presumably used for filter feeding.[155] The bizarre Late Jurassic ctenochasmatoid Cycnorhamphus possessed a jaw with teeth only at the tips, with bent jaws like those of living openbill storks, which may have been used to hold and crush hard invertebrates.[155]
Dinosaurs
Dinosaurs, which had diversified in the Late Triassic, would experience a radiation 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.[156] 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.[157]
Theropods
Advanced theropods belonging to Neotheropoda first appeared in the Late Triassic. Basal neotheropods, such as coelophysoids and "dilophosaurs", perisisted into the Early Jurassic.[158] The earliest averostrans appear during the Early Jurassic, with the earliest known member of Ceratosauria being Saltriovenator from the early Sinemurian (199.3–197.5 million years ago) of Italy.[159] The unusual ceratosaur Limusaurus from the Late Jurassic of China had a herbivorous diet with adults having edentuous beaked jaws,[160] making it the earliest known theropod to have converted from an ancestrally carnivorous diet.[161] The earliest members of the Tetanurae appeared during the early Middle Jurassic.[162] The Megalosauridae represent the oldest radiation of the Tetanurae, first appearing in Europe during the Bajocian.[163] The oldest member of Allosauroidea has been suggested to be Asfaltovenator from the Middle Jurassic of South America.[164] Coelurosaurs first appeared during the Middle Jurassic, including early tyrannosaurs such as Proceratosaurus from the Bathonian of Britain.[165] The earliest alvarezsaurs, a clade of coelurosaurs, first appeared during the Late Jurassic, represented by Shishugounykus and Haplocheirus from the Late Jurassic of China.[166] Scansoriopterygids, a group of small feathered coelurosaurs with membraneous, bat like wings for gliding, are known from the Middle-Late Jurassic of China.[167] The oldest record of troodontids is suggested to be Hesperornithoides from the Late Jurassic of North America. Tooth remains suggested to represent those of dromaeosaurs are known from the Jurassic, but no body remains are known until the Cretaceous.[168]
Skeleton of Ceratosaurus, a ceratosaurid from the Late Jurassic of North America.
Skeleton of Monolophosaurus, a basal tetanuran from the Middle Jurassic of China
Restoration of Yi qi, a scansoriopterygid from the Middle-Late Jurassic of China
Birds
The earliest avialans, which include birds and their ancestors, appear during the Middle-Late Jurassic, definitively represented by Archaeopteryx from the Late Jurassic of Germany. Avialans belong to the clade Paraves within Coelurosuria, which also includes dromaeosaurs and troodontids. The Anchiornithidae from the Middle-Late Jurassic of China have frequently suggested to be avialans, but have also been found as a separate lineage of paravians.[162]
Ornithischians
The earliest definitive ornithischians appear during the Early Jurassic, represented by basal ornithischians like Lesothosaurus, heterodontosaurids, and early members of Thyreophora. The earliest members of Ankylosauria and Stegosauria appear during the Middle Jurassic.[169] The basal neornithischian Kulindadromeus from the Middle Jurassic of Russia indicates that at least some ornithischians were covered in protofeathers.[170] The earliest members of Ankylopollexia, which would become prominent in the Cretaceous, appeared during the Late Jurassic, represented by bipedal forms such as Camptosaurus.[171] Ceratopsians first appeared in the Late Jurassic of China, represented by members of Chaoyangsauridae.[172]
Sauropodomorphs
Bipedal basal sauropodomorphs, such as massospondylids, continued to exist into the Early Jurassic. Quadrupedal sauropomorphs appeared during the Late Triassic. The quadupedal Ledumahadi from the earliest Jurassic of South Africa reached an estimated weight of 12 tons, far in excess of other known basal sauropodomorphs.[173] Gravisaurian sauropods first appeared during the Early Jurassic, with the oldest definitive record being Vulcanodon from Zimbabwe, likely of Sinemurian age.[174] Eusauropodan sauropods diverisfied during the Middle Jurassic, including cetiosaurids, turiasaurs,[175] and mamenchisaurs.[176] The earliest known member of Neosauropoda is Lingwulong, a dicraeosaurid diplodocoid from the Middle Jurassic of China. Neosauropods dispersed worldwide during the Late Jurassic.[177] The Late Jurassic saw the first appearance of several derived neosauropod groups, including Brachiosauridae[178] and Diplodocidae.[179] Jurassic sauropods would reach gigantic sizes, becoming the largest organisms to have ever lived on land up to that point.[180]
Amphibians
The vast majority of temnospondyls went extinct at the end of the Triassic, with only brachyopoids surviving into the Jurassic and beyond. Members of the family Brachyopidae are known from Jurassic deposits in Asia,[181] while the chigutisaurid Siderops is known from the Early Jurassic of Australia.[182] Modern lissamphibians would also begin to diversify during the Jurassic. The Early Jurassic Prosalirus thought to represent the first frog relative with a morphology capable of hopping like living frogs.[183] Morphogically recognisable stem-frogs like Notobatrachus are known from the Middle Jurassic.[184] While the earliest salamander-line amphibians are known from the Triassic.[185] Crown group salamanders first appear during the Middle-Late Jurassic of Eurasia, alongside stem-group relatives. Many Jurassic stem-group salamanders, like Marmorerpeton and Kokartus are thought to have been neotenic.[186] Early representatives of crown group salamanders include Chunerpeton, Pangerpeton and Linglongtriton from the Middle-Late Jurassic Yanliao Biota of China, which belong to the Cryptobranchoidea, which contains living Asiatic and giant salamanders.[187] While Beiyanerpeton, also from the same biota is thought to be an early member of Salamandroidea, the group which contains all other living salamanders.[188] Salamanders would disperse into North America by the end of the Jurassic, as evidenced by Iridotriton found in the Late Jurassic Morrison Formation.[189] The oldest undisputed stem-caecilian is the Early Jurassic Eocaecilia from Arizona.[190] The fourth group of lissamphibians, the extinct albanerpetontids, would first appear in the Middle Jurassic, represented by Anoualerpeton priscus from the Bathonian of Britain, as well as indeterminate remains from equivalently aged sediments in France and the Anoual Formation of Morocco.[191]
Mammals
Mammals, having originated from cynodonts at the end of the Triassic, diversified extensively during the Jurassic. Important groups of Jurassic mammals include Morganucodonta, Docodonta, Eutriconodonta, Dryolestida, Haramiyida and Multituberculata. While most Jurassic mammals are solely known from isolated teeth and jaw fragments, exceptionally preserved remains have revealed a variety of lifestyles.[192] The docodontan Castorocauda was adapted for aquatic life, similar to the platypus and otters.[193] Some members of Haramiyida[194] and the eutriconodontan tribe Volaticotherini[195] possessed a patagium akin to those of flying squirrels, allowing them to glide through the air. The aardvark like mammal Fruitafossor of uncertain affinities was likely a specialist on colonial insects, similar to living anteaters.[196] Early relatives of monotremes, the Australosphenida, first appear in the Middle Jurassic of Gondwana.[197] Theriiform mammals, represented today by living placentals and marsupials, would also appear during the early Late Jurassic, represented by Juramaia, a eutherian mammal closer to the ancestry of placentals than marsupials.[198] Juramaia is much more advanced than expected for its age, as other theriiform mammals do not appear until the Early Cretaceous.[199] Non-mammalian cynodonts of the families Tritheledontidae and Tritylodontidae survived the T-J extinction, and continued to exist into the Early Jurassic and Early Cretaceous, respectively.[200]
Fish
Conodonts
The last known species of conodont, a class of jawless fish-like animals whose hard teeth like elements are key index fossils, would finally become extinct during the earliest Jurassic after over 300 million years of evolutionary history, with an asynchronous extinction occurring first in the Tethys and eastern Panthalassia, with late survivors in the earliest Hettangian of Hungary and central Panthalassa.[201] End-Triassic conodonts were only represented by a handful of species, and had been progressively declining though the Middle and Late Triassic.[202]
Sarcopterygii
Lungfish (Dipnoi) were present in freshwater environments of both hemispheres during the Jurassic. Genera include Ceratodus and Ptychoceratodus which are more closely related to living South American and African lungfish than Queensland lungfish and Ferganoceratodus from the Jurassic of Asia, which is not closely related to either group of living lungfish.[203] Mawsoniids, a marine and freshwater/brackish group of coelacanths, which first appeared in North America during the Triassic, would expand into Europe and South America by the end of the Jurassic.[204] The marine Latimeriidae, which contains the living coelacanths of the genus Latimeria, were also present in the Jurassic, having originated in the Triassic.[205]
Actinopterygii
Bony fish (Actinopterygii) were major components of Jurassic freshwater and marine ecosystems. Amiiform fish (which today only includes the bowfin) would first appear during the Early Jurassic, represented by Caturus from the Pliensbachian of Britain, after their first appearance in western Tethys, they would expand to Africa, North America and Southeast and East Asia by the end of the Jurassic. Pycnodontiformes, which first appeared in the western Tethys during the Late Triassic, would expand to South America and Southeast Asia by the end of the Jurassic, having a high diversity in Europe during the Late Jurassic.[206] Teleosts, which make up over 99% of living Actinopterygii, had first appeared during the Triassic in the western Tethys, underwent a major diversification beginning in the Late Jurassic, with early representatives of modern teleost clades such as Elopomorpha and Osteoglossoidei appearing during this time.[207][208] The Pachycormiformes, a group of fish closely allied to teleosts, first appeared in the Early Jurassic, and included both tuna-like predatory and filter feeding forms, the latter including 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.[209]
Chondrichthyes
The Jurassic was a major time in the evolution of Chondrichthyes. Hybodonts, such as Hybodus were common in the Early Jurassic in both marine and freshwater settings, however by the Late Jurassic, hybodonts had become minor components of most marine communities, having been largely replaced by modern neoselachians, but would remain common in freshwater and restricted marine environments.[210] The Neoselachii, which contains all living sharks and rays, would radiate beginning in the Early Jurassic.[211] The oldest known Hexanchiformes are from the Early Jurassic (Pliensbachian) of Europe.[212] The oldest known ray (Batoidea) is Antiquaobatis from the Pliensbachian of Germany.[213] Jurassic batoids known from complete remains retain a conservative, guitarfish-like morphology.[214] The oldest known relatives of the Bullhead shark (Heterodontus) in the order Heterodontiformes first appear in the Early Jurassic, with representatives of the living genus appearing during the Late Jurassic.[215] Carpet sharks (Orectolobiformes) first appear during the Toarcian, represented by Folipistrix and Annea from Europe.[216] The oldest known mackerel sharks (Lamniformes) are known from the Middle Jurassic, represented by the genus Palaeocarcharias., which has an orectolobiform-like bodyform, but shares key similarities in tooth histology with lamniformes, including the absence of orthodentine.[217] The oldest record of Angelsharks (Squatiniformes) is Pseudorhina from the Oxfordian-Tithonian of Europe.[218] The oldest known remains of Carcharhiniformes, the largest order of living sharks, first appear in the late Middle Jurassic (Bathonian) of the western Tethys (England and Morocco). Known dental and exceptionally preserved body remains of Jurassic Carchariniformes are similar to those of living catsharks.[219] The oldest remains of chimaeras are known from the Early Jurassic of Europe, with members of the living family Callorhinchidae appearing during the Middle Jurassic. Unlike living chimaeras, these were found in shallow water settings.[220] The closely related Squaloraja and myriacanthoids are also known from the Jurassic of Europe.[221]
Insects and arachnids
Numerous important insect fossil localities are known from the Jurassic of Eurasia, the most important being the Karabastau Formation of Kazakhstan, and the various Yanliao Biota deposits in Inner Mongolia, China, such as the Daohugou Bed, dating to the Callovian-Oxfordian. The diversity of insects was stagnant throughout the Early and Middle Jurassic, but during the latter third of the Jurassic origination rates increased substantially while extinction rates remained flat.[222] The Middle-Late Jurassic was a time of major diverisification for beetles.[223] Weevils first appear in the fossil record during the Middle-Upper Jurassic, but are suspected to have originated during the Late Triassic-Early Jurassic.[224] The oldest known lepidopterans (the group containing butterflies and moths) are known from the Triassic-Jurassic boundary, with wing scales belonging to the suborder Glossata and Micropterigidae-grade moths from the deposits of this age in Germany.[225] Although modern representatives are not known until the Cenozoic, ectoparasitic insects thought to represent a stem-group to fleas first appear during the Jurassic, such as Pseudopulex jurassicus. These insects are substantially different from modern fleas, lacking the specialised morphology of modern fleas and being larger in size.[226][227] The earliest group of Phasmatodea (stick insects), the winged Susumanioidea, an outgroup to living Phasmatodeans, first appear during the Middle Jurassic.[228] The oldest member of the Mantophasmatidae (gladiators) also appeared during this time.[229]
Only a handful of records of mites are known from the Jurassic, including Jureremus, an Oribatid mite belonging to the family Cymbaeremaeidae known from the Upper Jurassic of Britain and Russia.[230] Spiders would diversify through the Jurassic.[231] The Early Jurassic Seppo koponeni thought to possibly represent a stem-group to Palpimanoidea.[232] Eoplectreurys from the Middle Jurassic of China is considered a stem lineage of Synspermiata. The oldest member of the family Archaeidae, Patarchaea, is known from the Middle Jurassic.[231] Mongolarachne from the Middle Jurassic of China is among the largest known fossil spiders, with legs over 5 centimetres in length.[233] The only scorpion known from the Jurassic is Liassoscorpionides from the Lower Jurassic of Germany, of uncertain placement.[234] Eupnoi Opiliones are known from the Middle Jurassic, including members of the family Sclerosomatidae.[235][236]
Marine invertebrates
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.[237]
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.[238] which caused an associated drop in diversity in decapod crustaceans.[239] The earliest planktonic foraminifera are known from the late Early Jurassic (mid Toarcian) of the western Tethys, expanding across the whole Tethys by the Middle Jurassic, before being globally distributed in tropical latitudes by the Late Jurassic.[240] Coccolithophores and dinoflagellates, which had first appeared during the Triassic, would radiate during the Early-Middle Jurassic, becoming prominent members of the phytoplankton.[241] 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.[242] The oldest known diatom is known from amber found in the Late Jurassic of Thailand, assigned to the living genus Hemiaulus.[243]
Crustaceans
The Jurassic was a significant time for the evolution of decapods.[239] 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.[244] and Eoprosopon klugi from the late Pliensbachian of Germany, which possibly belongs to the living family Homolodromiidae.[245] Most Jurassic crabs are only known from dorsal carapace pieces, which makes it difficult to determine their relationships.[246] 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[246][239] Hermit crabs would also first appear during the Jurassic, with the earliest known being Schobertella hoelderi from the late Hettangian of Germany.[247] Early hermit crabs are associated with ammonite shells rather than those of gastropods.[248] 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.[249] Thylacocephalans are an enigmatic group of arthropods known from the Silurian to the Cretaceous, with probable crustacean affinities. Remains of Jurassic thylacocephalans are among the best preserved members of the group.[250]
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.[48] 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.[251] 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.[252]
Molluscs
Ammonites
Ammonites were devastated by the end-Triassic extinction, with only the family Psiloceratidae of the suborder Phylloceratina surviving, and becoming ancestral to all later Jurassic and Cretaceous ammonites. Ammonites explosively diversified during the Early Jurassic, with the orders Psiloceratina, Ammonitina, Lytoceratina, Haploceratina, Perisphinctina and Ancyloceratina all appearing during the Jurassic. Ammonite faunas during the Jurassic were regional, being divided into around 20 distinguishable provinces and subprovinces in two realms, the northern high latitude Pan-Boreal realm, consisting of the Arctic, northern Panthalassa and northern Atlantic regions, and the equatorial-southern Pan-Tethyan realm, which included the Tethys and most of Panthalassa.[253]
Bivalves
The end Triassic extinction had a severe impact on bivalve diversity, though it had little impact on bivalve ecological diversity. The extinction was selective, having less of an impact on deep burrowers, but there is no evidence of a differential impact between surface living (epifaunal) and burrowing (infaunal) bivalves.[254] Rudists, the dominant reef building organisms of the Cretaceous, would first appear in the Late Jurassic (mid Oxfordian) in the northern margin of the western Tethys region, expanding to the eastern Tethys by the end of the Jurassic.[255]
Belemnites
The oldest definitive records of the squid-like belemnites are from the earliest Jurassic (Hettangian-Sinemurian) of Europe and Japan, and would expand worldwide during the Jurassic.[256] Belemnites were shallow water dwellers, inhabiting the upper 200 metres of the water column on the continental shelves and in the littoral zone. They were key components of Jurassic ecosystems, both as predators and prey, as evidenced by the abundance of belemnite guards in Jurassic rocks.[257]
References
Notes
- "[…] die ausgebreitete Formation, welche zwischen dem alten Gips und neueren Sandstein liegt, und welchen ich vorläufig mit dem Nahmen Jura-Kalkstein bezeichne." '… the widespread formation which lies between the old gypsum and the more recent sandstone and which I provisionally designate with the name "Jura limestone".'[9]
Citations
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Si logramos publicar esos nuevos resultados, sería el primer paso para cambiar formalmente la edad del Jurásico-Cretácico. A partir de ahí, la Unión Internacional de la Ciencias Geológicas y la Comisión Internacional de Estratigrafía certificaría o no, depende de los resultados, ese cambio.
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- Witton, Mark P. (23 June 2016). "Why the giant azhdarchid Arambourgiania philadelphiae needs a fanclub". markwitton-com.blogspot.com.
Further reading
- Mader, Sylvia (2004). Biology (eighth ed.).
- Ogg, Jim (June 2004). Overview of Global Boundary Stratotype Sections and Points (GSSP's). International Commission on Stratigraphy. p. 17.
- Stanley, S.M.; Hardie, L.A. (1999). "Hypercalcification; paleontology links plate tectonics and geochemistry to sedimentology". GSA Today. 9: 1–7.
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- Examples of Jurassic Fossils
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- Jurassic Microfossils: 65+ images of Foraminifera
- . Encyclopædia Britannica. 15 (11th ed.). 1911. With map and table.
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In the extant species G. biloba, leaves from the same tree on different shoots or from shoots at different developmental stages may be referrable to the different leaf types (morphogenera) established for fossil ginkgoaleans.
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