Editing Mesozoic

{{Short description|Second era of the Phanerozoic Eon}}
{{Use dmy dates|date=April 2021}}
{{Infobox geologic timespan
| name                         = Mesozoic Era
| color                        = Mesozoic
| top_bar                      = Phanerozoic
| time_start                   = 251.902
| time_start_uncertainty       = 0.024
| time_end                     = 66.0
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<!--Chronology-->  
| timeline                     = Mesozoic
| proposed_boundaries1         =
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| former_subdivisions          =
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<!--Etymology-->
| name_formality               = Formal
| name_accept_date             =
| alternate_spellings          =
| synonym1                     =
| synonym1_coined              =
| synonym2                     =
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| nicknames                    = Age of Reptiles, Age of Dinosaurs, Age of Conifers
| former_names                 =
| proposed_names               =
<!--Usage Information--> 
| celestial_body               = earth
| usage                        = Global ([[International Commission on Stratigraphy|ICS]])
| timescales_used              = ICS Time Scale
| formerly_used_by             =
| not_used_by                  =
<!--Definition-->
| chrono_unit                  = Era
| strat_unit                   = Erathem
| proposed_by                  =
| timespan_formality           = Formal
| lower_boundary_def           = First appearance of the Conodont ''Hindeodus parvus''.
| lower_gssp_location          = [[Meishan]], [[Zhejiang]], [[China]]
| lower_gssp_coords            = {{Coord|31.0798|N|119.7058|E|display=inline}}
| lower_gssp_accept_date       = 2001
| upper_boundary_def           = [[Iridium]] enriched layer associated with a major meteorite impact and subsequent [[Cretaceous–Paleogene extinction event|K-Pg extinction event]].
| upper_gssp_location          = El Kef Section, [[El Kef]], [[Tunisia]]
| upper_gssp_coords            = {{Coord|36.1537|N|8.6486|E|display=inline}}
| upper_gssp_accept_date       = 1991
}}
The '''Mesozoic Era'''{{refn|There are several ways of pronouncing ''Mesozoic'', including {{IPAc-en|ipa|ˌ|m|ɛ|z|ə|ˈ|z|oʊ|.|ɪ|k|,_|-|z|oʊ|-|,_|ˌ|m|ɛ|s|-|,_|ˌ|m|iː|z|-|,_|ˌ|m|iː|.|s|-}} {{respell|MEZ|ə|ZOH|ik|,_|MEZ|oh|-|,_|MESS|-|,_|MEE|z|-|,_|MEE|s-}}.{{refn|{{Citation |last=Jones |first=Daniel |author-link=Daniel Jones (phonetician) |title=English Pronouncing Dictionary |editor=Peter Roach |editor2=James Hartmann |editor3=Jane Setter |place=Cambridge |publisher=Cambridge University Press |orig-year=1917 |year=2003 |isbn=978-3-12-539683-8 }}}}{{refn|{{Dictionary.com|Mesozoic}}}}}} is the [[Era (geology)|era]] of Earth's [[Geologic time scale|geological history]], lasting from about {{ma|Mesozoic|Cenozoic|million years ago|round=0}}, comprising the [[Triassic]], [[Jurassic]] and [[Cretaceous]] [[Period (geology)|Periods]]. It is characterized by the dominance of archosaurian reptiles such as the dinosaurs, and of [[Gymnosperm|gymnosperms]] such as [[cycad]]s, [[ginkgoaceae]] and [[Araucariaceae|araucarian]] conifers; a hot [[Greenhouse and icehouse earth|greenhouse]] climate; and the [[tectonic]] break-up of [[Pangaea]]. The Mesozoic is the middle of the three eras since [[Cambrian explosion|complex life evolved]]: the [[Paleozoic]], the Mesozoic, and the [[Cenozoic]].

The era began in the wake of the [[Permian–Triassic extinction event]], the largest [[mass extinction]] in Earth's history, and ended with the [[Cretaceous–Paleogene extinction event]], another mass extinction whose victims included the [[non-avian dinosaurs]], [[Pterosaur|pterosaurs]], [[Mosasaur|mosasaurs]], and [[Plesiosaur|plesiosaurs]]. The Mesozoic was a time of significant tectonic, climatic, and evolutionary activity. The supercontinent [[Pangaea#Rifting and break-up|Pangaea began to break apart]] into separate landmasses. The climate of the Mesozoic was varied, alternating between warming and cooling periods. Overall, however, the Earth was hotter than it is today. 

Dinosaurs first appeared in the Mid-Triassic, and became the dominant terrestrial vertebrates in the Late Triassic or Early Jurassic, occupying this position for about 150 or 135&nbsp;million years until their demise at the end of the Cretaceous. [[Avialae|Archaic bird]]s appeared in the Jurassic, having [[evolution of birds|evolved]] from a branch of [[theropoda|theropod]] dinosaurs, then [[Aves|true toothless birds]] appeared in the Cretaceous. The first [[mammal]]s also appeared during the Mesozoic, but would remain small—less than 15&nbsp;kg (33&nbsp;lb)—until the Cenozoic. [[Angiosperm|Flowering plants]] appeared in the Early Cretaceous and would rapidly diversify through the end of the era, replacing [[Conifer|conifers]] and other gymnosperms (''[[sensu lato]]''), such as [[ginkgoales]], cycads and [[bennettitales]] as the dominant group of plants.

== Naming ==
The phrase "Age of Reptiles" was introduced by the 19th century [[Paleontology|paleontologist]] [[Gideon Mantell]] who viewed it as dominated by [[diapsid]]s such as ''[[Iguanodon]]'', ''[[Megalosaurus]]'', ''[[Plesiosaurus]]'', and ''[[Pterodactylus]]''.

The current name was proposed in 1840 by the British geologist [[John Phillips (geologist)|John Phillips]] (1800–1874). "Mesozoic" literally means 'middle life', deriving from the [[Ancient Greek|Greek]] prefix {{lang|grc-Latn|meso-}} ({{wikt-lang|grc|μεσο-}} 'between') and {{lang|grc-Latn|zōon}} ({{wikt-lang|grc|ζῷον}} 'animal, living being').<ref>See:

* {{cite book|title=Penny Cyclopaedia of the Society for the Diffusion of Useful Knowledge|last1=Phillips|first1=John|date=1840|publisher=Charles Knight and Co.|volume=17|location=London|pages=153–54|chapter=Palæozoic series|chapter-url=https://babel.hathitrust.org/cgi/pt?id=hvd.hn4zr7;view=1up;seq=163}} "As many systems or combinations of organic forms as are clearly traceable in the stratified crust of the globe, so many corresponding terms (as Palæozoic, Mesozoic, Kainozoic, &c.) may be made, … "
* {{cite book|url=https://books.google.com/books?id=my7x_PBkpm4C&pg=PA9|title=Bulletin 769: The Geologic Time Classification of the United States Geological Survey Compared With Other Classifications, accompanied by the original definitions of era, period and epoch terms|last1=Wilmarth|first1=Mary Grace|date=1925|publisher=U.S. Government Printing Office|location=Washington, D.C.|page=9}}</ref><ref name="OnlineEtDict">{{cite OEtymD|Mesozoic}}</ref> In this way, the Mesozoic is comparable to the Cenozoic ({{lit|new life}}) and Paleozoic ('old life') eras as well as the [[Proterozoic]] ('earlier life') Eon.

The Mesozoic Era was originally described as the "secondary" era, following the "primary" ([[Paleozoic]]), and preceding the [[Tertiary]].<ref name="tang">{{cite web |last1=Tang |first1=Carol Marie |title=Mesozoic Era |url=https://www.britannica.com/science/Mesozoic-Era |website=Encyclopædia Britannica |publisher=Encyclopædia Britannica |access-date=5 September 2019}}</ref>

==Geologic periods==
Following the Paleozoic, the Mesozoic extended roughly 186&nbsp;million years, from {{Ma|Mesozoic|Cenozoic}} when the [[Cenozoic]] Era began. This time frame is separated into three geologic [[Period (geology)|periods]]. From oldest to youngest:
* [[Triassic|Triassic Period]] ({{Ma|Triassic|Jurassic}})
* [[Jurassic|Jurassic Period]] ({{Ma|Jurassic|Cretaceous}})
* [[Cretaceous|Cretaceous Period]] ({{Ma|Cretaceous|Cenozoic}})

The lower boundary of the Mesozoic is set by the [[Permian–Triassic extinction event]], during which it has been estimated that up to 90–96% of marine species became [[extinction |extinct]]<ref>{{cite book|author=Benton M J|title=When life nearly died: the greatest mass extinction of all time |publisher=Thames & Hudson |location=London |date= 2005 |isbn=978-0-500-28573-2 |chapter=Chapter 8: Life's Biggest Challenge}}{{page needed|date=October 2012}}</ref> although those approximations have been brought into question with some paleontologists estimating the actual numbers as low as 81%.<ref name="stanley">{{cite journal|title=Estimates of the magnitudes of major marine mass extinctions in earth history|last=Stanley|first=Steven M.|author-link=Steven M. Stanley|journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |doi=10.1073/pnas.1613094113|date=3 October 2016|volume=113|issue=42|pages=E6325–E6334|publisher=National Academy of Sciences|pmid=27698119|pmc=5081622|bibcode= 2016PNAS..113E6325S |issn=1091-6490|doi-access=free}}</ref> It is also known as the "Great Dying" because it is considered the largest mass extinction in the Earth's history. The upper boundary of the Mesozoic is set at the [[Cretaceous–Paleogene extinction event]] (or K–Pg extinction event<ref>{{cite book |vauthors=Gradstein F, Ogg J, Smith A |title= A Geologic Time Scale 2004 |publisher = Cambridge University Press|isbn = 9780511536045|url=https://www.cambridge.org/core/books/geologic-time-scale-2004/ACED6139A9320FC9CA982E316FFF3E38 |date = 2005}}</ref>), which may have been caused by an asteroid impactor that created [[Chicxulub Crater]] on the [[Yucatán Peninsula]]. Towards the Late Cretaceous, large volcanic eruptions are also believed to have contributed to the Cretaceous–Paleogene extinction event.<ref name="PetersenEtAl2016">{{cite journal | last1 = Petersen|first1= Sierra V. |last2= Dutton|first2= Andrea|last3=Lohmann |first3=Kyger C. | year = 2016 | title = End-Cretaceous extinction in Antarctica linked to both Deccan volcanism and meteorite impact via climate change | journal = [[Nature Communications]] | volume = 7 | page = 12079 | doi = 10.1038/ncomms12079 | pmid = 27377632 | pmc = 4935969 | bibcode = 2016NatCo...712079P |url=https://www.researchgate.net/publication/304836395_ARTICLE_End-Cretaceous_extinction_in_Antarctica_linked_to_both_Deccan_volcanism_and_meteorite_impact_via_climate_change |access-date=31 July 2023}}</ref> Approximately 50% of all genera became extinct, including all of the non-[[bird|avian]] dinosaurs.

===Triassic===
The Triassic ranges roughly from 252&nbsp;million to 201&nbsp;million years ago, preceding the Jurassic Period. The period is bracketed between the Permian–Triassic extinction event and the [[Triassic–Jurassic extinction event]], two of the "[[Extinction event|big five]]", and it is divided into three major epochs: Early, Middle, and Late Triassic.<ref>{{cite encyclopedia|url=https://www.britannica.com/EBchecked/topic/604667/Triassic-Period/225842/Economic-significance-of-Triassic-deposits|title=Triassic Period |author=Alan Logan|encyclopedia=britannica.com|date = 31 January 2024}}</ref>

The Early Triassic, about 252 to 247&nbsp;million years ago, was dominated by deserts in the interior of the Pangaea supercontinent. The Earth had just witnessed a massive die-off in which 95% of all life became extinct, and the most common vertebrate life on land were ''[[Lystrosaurus]]'', [[labyrinthodont]]s, and ''[[Euparkeria]]'' along with many other creatures that managed to survive the Permian extinction. [[Temnospondyl]]s reached peak diversity during the early Triassic.<ref>{{cite journal |last1=Ruta |first1=Marcello |last2=Benton |first2=Michael J. |title=Calibrated Diversity, Tree Topology and the Mother of Mass Extinctions: The Lesson of Temnospondyls |journal=[[Palaeontology (journal)|Palaeontology]] |date=November 2008 |volume=51 |issue=6 |pages=1261–1288 |doi=10.1111/j.1475-4983.2008.00808.x|s2cid=85411546 |doi-access=free }}</ref> [[File:Sellosaurus.jpg|thumb|''[[Plateosaurus]]'' (a [[prosauropod]])]]

The Middle Triassic, from 247 to 237&nbsp;million years ago, featured the beginnings of the breakup of Pangaea and the opening of the [[Tethys Ocean]]. Ecosystems had recovered from the Permian extinction. Algae, sponge, corals, and crustaceans all had recovered, and new aquatic reptiles evolved, such as [[ichthyosaur]]s and [[nothosaur]]s. On land, pine forests flourished, as did groups of insects such as mosquitoes and fruit flies. Reptiles began to get bigger and bigger, and the first crocodilians and dinosaurs evolved, which sparked competition with the large amphibians that had previously ruled the freshwater world, respectively mammal-like reptiles on land.<ref>{{cite web|url=http://palaeos.com/mesozoic/triassic/midtrias.html|title=Middle Triassic|author=Rubidge|work=palaeos.com}}</ref>
[[File:Triassic 250.png|left|thumb|293x293px|Approximate map of Earth in the Early Triassic Period.]]
Following the bloom of the Middle Triassic, the Late Triassic, from 237 to 201&nbsp;million years ago, featured frequent heat spells and moderate precipitation (10–20 inches per year). The recent warming led to a boom of dinosaurian evolution on land as the continents began to separate from each other (Nyasasaurus from 243 to 210&nbsp;million years ago, approximately 235–30 ma, some of them separated into Sauropodomorphs, Theropods and Herrerasaurids), as well as the first [[pterosaur]]s. During the Late Triassic, some advanced [[cynodont]]s gave rise to the first [[Mammaliaformes]]. All this climatic change, however, resulted in a large die-out known as the Triassic–Jurassic extinction event, in which many [[archosaurs]] (excluding pterosaurs, dinosaurs and [[crocodylomorph]]s), most [[synapsid]]s, and almost all large amphibians became extinct, as well as 34% of marine life, in the Earth's fourth mass extinction event. The cause is debatable;<ref>{{cite encyclopedia |title=Impact Crises and Mass Extinctions: A Working Hypothesis |last1= Rampino |first1=Michael R. |author-link1=Michael R. Rampino |last2=Haggerty |first2=Bruce M.|url=https://books.google.com/books?id=kAup0TOL09gC&pg=PA19 |encyclopedia=The Cretaceous-Tertiary event and other catastrophes in earth history |editor-first1=Graham |editor-last1=Ryder |editor-first2=David |editor-last2=Fastovsky |editor-first3=Stefan |editor-last3=Gartner  |name-list-style=amp |publisher=Geological Society of America |isbn=978-0813723075|date=1996}}</ref><ref>{{cite web|url=http://www.enchantedlearning.com/subjects/dinosaurs/mesozoic/triassic/lt.shtml|title=Late Triassic life|author=Enchanted Learning|work=Enchanted Learning}}</ref> [[flood basalt eruption]]s at the [[Central Atlantic magmatic province]] is cited as one possible cause.<ref name="AnthropogenicScaleDegassing">{{cite journal |last1=Capriolo |first1=Manfredo |last2=Mills |first2=Benjamin J. W. |last3=Newton |first3=Robert J. |last4=Corso |first4=Jacobo Dal |last5=Dunhill |first5=Alexander M. |last6=Wignall |first6=Paul B. |last7=Marzoli |first7=Andrea |date=February 2022 |title=Anthropogenic-scale CO2 degassing from the Central Atlantic Magmatic Province as a driver of the end-Triassic mass extinction |url=https://www.sciencedirect.com/science/article/pii/S0921818121003167 |journal=[[Global and Planetary Change]] |volume=209 |page=103731 |doi=10.1016/j.gloplacha.2021.103731 |bibcode=2022GPC...20903731C |s2cid=245530815 |doi-access=free |access-date=23 July 2023|hdl=10852/91551 |hdl-access=free }}</ref><ref>{{cite journal |last1=Capriolo |first1=Manfredo |last2=Marzoli |first2=Andrea |last3=Aradi |first3=László E. |last4=Callegaro |first4=Sara |last5=Corso |first5=Jacopo Dal |last6=Newton |first6=Robert J. |last7=Mills |first7=Benjamin J. W. |last8=Wignall |first8=Paul B. |last9=Bartoli |first9=Omar |last10=Baker |first10=Don R. |last11=Youbi |first11=Nasrrddine |last12=Remusat |first12=Laurent |last13=Spiess |first13=Richard |last14=Szabó |first14=Csaba |date=7 April 2020 |title=Deep CO2 in the end-Triassic Central Atlantic Magmatic Province |journal=[[Nature Communications]] |volume=11 |issue=1 |page=1670 |doi=10.1038/s41467-020-15325-6 |pmid=32265448 |pmc=7138847 |bibcode=2020NatCo..11.1670C |s2cid=215404768 }}</ref><ref name="PlatinumGroupElementsCAMP">{{cite journal |last1=Tegner |first1=Christian |last2=Marzoli |first2=Andrea |last3=McDonald |first3=Iain |last4=Youbi |first4=Nasrrddine |last5=Lindström |first5=Sofie |date=26 February 2020 |title=Platinum-group elements link the end-Triassic mass extinction and the Central Atlantic Magmatic Province |journal=[[Scientific Reports]] |volume=10 |issue=1 |page=3482 |doi=10.1038/s41598-020-60483-8 |pmid=32103087 |pmc=7044291 |url=https://www.nature.com/articles/s41598-020-60483-8 |access-date=28 July 2023}}</ref>

===Jurassic===
[[File:Sericipterus NT.jpg|thumb|''[[Sericipterus]]'']]The Jurassic ranges from 200&nbsp;million years to 145&nbsp;million years ago and features three major epochs: The Early Jurassic, the Middle Jurassic, and the Late Jurassic.<ref name="Carol Marie Tang">{{cite encyclopedia|url=https://www.britannica.com/EBchecked/topic/308541/Jurassic-Period/257903/Major-subdivisions-of-the-Jurassic-System|title=Jurassic Era|author=Carol Marie Tang|encyclopedia=britannica.com|date = 7 February 2024}}</ref>

The Early Jurassic spans from 200 to 175&nbsp;million years ago.<ref name="Carol Marie Tang"/> The climate was tropical and much more humid than the Triassic, as a result of the large seas appearing between the land masses. In the oceans, [[plesiosaurs]], ichthyosaurs and [[ammonites]] were abundant. On land, dinosaurs and other archosaurs staked their claim as the dominant race, with [[theropods]] such as ''[[Dilophosaurus]]'' at the top of the food chain. The first true crocodiles evolved, pushing the large amphibians to near extinction. All-in-all, archosaurs rose to rule the world. Meanwhile, the first true mammals evolved, remaining relatively small, but spreading widely; the Jurassic ''[[Castorocauda]]'', for example, had adaptations for swimming, digging and catching fish. ''[[Fruitafossor]]'', from the late Jurassic Period about 150&nbsp;million years ago, was about the size of a chipmunk, and its teeth, forelimbs and back suggest that it dug open the nests of social insects (probably [[termite]]s, as ants had not yet appeared) ; ''[[Volaticotherium]]'' was able to glide for short distances, such as modern [[flying squirrel]]s. The first [[multituberculates]] such as ''[[Rugosodon]]'' evolved.{{Citation needed|date=June 2024}}



The Middle Jurassic spans from 175 to 163&nbsp;million years ago.<ref name="Carol Marie Tang"/> During this epoch, dinosaurs flourished as huge herds of sauropods, such as ''[[Brachiosaurus]]'' and ''[[Diplodocus]]'', filled the fern prairies, chased by many new predators such as ''[[Allosaurus]]''. [[Conifer]] forests made up a large portion of the forests. In the oceans, plesiosaurs were quite common, and ichthyosaurs flourished. This epoch was the peak of the reptiles.<ref>{{cite web|url=http://www.enchantedlearning.com/subjects/dinosaurs/mesozoic/jurassic/mj.shtml|title=Middle Jurassic|author=Enchanted Learning|work=Enchanted Learning}}</ref>{{failed verification|date=March 2022}}{{self-published source|date=March 2022}} [[File:Stegosaurus BW.jpg|thumb|''[[Stegosaurus]]'']]

The Late Jurassic spans from 163 to 145&nbsp;million years ago.<ref name="Carol Marie Tang"/> During this epoch, the first [[avialan]]s, such as ''[[Archaeopteryx]]'', evolved from small [[coelurosaurian]] dinosaurs. The increase in sea levels opened up the Atlantic seaway, which has grown continually larger until today. The further separation of the continents gave opportunity for the diversification of new dinosaurs.

===Cretaceous===
The Cretaceous is the longest period of the Mesozoic, but has only two epochs: Early and Late Cretaceous.<ref name="Carl Fred Koch">{{cite encyclopedia|url=https://www.britannica.com/EBchecked/topic/142729/Cretaceous-Period/257709/Major-subdivisions-of-the-Cretaceous-System|title=Cretaceous|author=Carl Fred Koch|encyclopedia=britannica.com}}</ref> [[File:Knight Tylosaurus.jpg|thumb|''[[Tylosaurus]]'' (a [[mosasaur]]) hunting ''[[Xiphactinus]]'']]

The Early Cretaceous spans from 145 to 100&nbsp;million years ago.<ref name="Carl Fred Koch"/> The Early Cretaceous saw the expansion of seaways and a decline in diversity of sauropods, stegosaurs, and other high-browsing groups, with sauropods particularly scarce in North America.<ref name=ButlerEtal2009>{{cite journal |last1=Butler |first1=R. J. |last2=Barrett |first2=P. M. |last3=Kenrick |first3=P. |last4=Penn |first4=M. G. |title=Diversity patterns amongst herbivorous dinosaurs and plants during the Cretaceous: implications for hypotheses of dinosaur/angiosperm co-evolution |journal=[[Journal of Evolutionary Biology]] |date=March 2009 |volume=22 |issue=3 |pages=446–459 |doi=10.1111/j.1420-9101.2008.01680.x |pmid=19210589 |s2cid=26000791 |doi-access=free }}</ref> {{citation needed span|Some island-hopping dinosaurs, such as ''[[Eustreptospondylus]]'', evolved to cope with the coastal shallows and small islands of ancient Europe. Other dinosaurs rose up to fill the empty space that the Jurassic-Cretaceous extinction left behind, such as ''[[Carcharodontosaurus]]'' and ''[[Spinosaurus]]''.|date=March 2022}} Seasons came back into effect and the poles got seasonally colder, but some dinosaurs still inhabited the polar forests year round, such as ''[[Leaellynasaura]]'' and ''[[Muttaburrasaurus]]''. The poles were too cold for crocodiles, and became the last stronghold for large amphibians such as ''[[Koolasuchus]]''. Pterosaurs got larger as genera such as ''[[Tapejara (pterosaur)|Tapejara]]'' and ''[[Ornithocheirus]]'' evolved. Mammals continued to expand their range: [[eutriconodont]]s produced fairly large, [[wolverine]]-like predators such as ''[[Repenomamus]]'' and ''[[Gobiconodon]]'', early [[theria]]ns began to expand into [[metatheria]]ns and [[eutheria]]ns, and [[cimolodont]] [[multituberculate]]s went on to become common in the fossil record.

The Late Cretaceous spans from 100 to 66&nbsp;million years ago. The Late Cretaceous featured a cooling trend that would continue in the [[Cenozoic]] Era. Eventually, tropics were restricted to the equator and areas beyond the tropic lines experienced extreme seasonal changes in weather. Dinosaurs still thrived, as new taxa such as ''[[Tyrannosaurus]]'', ''[[Ankylosaurus]]'', ''[[Triceratops]]'' and [[hadrosaurs]] dominated the food web. In the oceans, [[mosasaurs]] ruled, filling the role of the ichthyosaurs, which, after declining, had disappeared in the [[Cenomanian-Turonian boundary event]]. Though [[pliosaur]]s had gone extinct in the same event, long-necked plesiosaurs such as ''[[Elasmosaurus]]'' continued to thrive. Flowering plants, possibly appearing as far back as the Triassic, became truly dominant for the first time. Pterosaurs in the Late Cretaceous declined for poorly understood reasons, though this might be due to tendencies of the fossil record, as their diversity seems to be much higher than previously thought. Birds became increasingly common and diversified into a variety of [[Enantiornithes|enantiornithe]] and [[Ornithurae|ornithurine]] forms. Though mostly small, marine [[hesperornithes]] became relatively large and flightless, adapted to life in the open sea. Metatherians and primitive eutherian also became common and even produced large and specialised genera such as ''[[Didelphodon]]'' and ''[[Schowalteria]]''. Still, the dominant mammals were multituberculates, [[cimolodont]]s in the north and [[gondwanathere]]s in the south. At the end of the Cretaceous, the [[Deccan traps]] and other volcanic eruptions were poisoning the atmosphere. As this continued, it is thought that a large meteor smashed into earth 66&nbsp;million years ago, creating the Chicxulub Crater in an event known as the [[Cretaceous–Paleogene extinction event|K-Pg Extinction]] (formerly K-T), the fifth and most recent mass extinction event, in which 75% of life became extinct, including all non-avian dinosaurs.<ref>{{cite journal |last1=Becker |first1=Luann |title=Repeated Blows|journal=[[Scientific American]] |volume=286 |issue=3 |date=2002 |pages=76–83 |doi=10.1038/scientificamerican0302-76 |pmid=11857903 |bibcode=2002SciAm.286c..76B}}</ref><ref>{{cite web|url=http://www.ucmp.berkeley.edu/mesozoic/cretaceous/cretaceous.php|title=Cretaceous|work=University of California}}</ref><ref>{{cite web|url=http://www.universetoday.com/36697/the-asteroid-that-killed-the-dinosaurs/|title=K-T Extinction event|author=Elizabeth Howell|work=Universe Today|date=3 February 2015}}</ref>

==Paleogeography and tectonics==
Compared to the vigorous convergent plate [[orogeny|mountain-building]] of the late Paleozoic, Mesozoic tectonic deformation was comparatively mild. The sole major Mesozoic orogeny occurred in what is now the [[Arctic]],{{citation needed|date=July 2022}} creating the [[Innuitian orogeny]], the [[Brooks Range]], the [[Verkhoyansk Range|Verkhoyansk]] and [[Cherskiy Range]]s in Siberia, and the [[Khingan Mountains]] in Manchuria.

This orogeny was related to the opening of the [[Arctic Ocean]] and [[Suture (geology)|suturing]] of the [[North China craton|North China]] and Siberian cratons to Asia.<ref>{{cite journal |last1=Hughes |first1=T. |title=The case for creation of the North Pacific Ocean during the Mesozoic Era |url=https://www.sciencedirect.com/science/article/abs/pii/0031018275900152 |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |date=August 1975 |volume=18 |issue=1 |pages=1–43 |doi=10.1016/0031-0182(75)90015-2 |bibcode=1975PPP....18....1H |access-date=21 July 2023}}</ref> In contrast, the era featured the dramatic [[Rift|rifting]] of the supercontinent Pangaea, which gradually split into a northern continent, [[Laurasia]], and a southern continent, [[Gondwana]]. This created the [[passive continental margin]] that characterizes most of the [[Atlantic]] coastline (such as along the [[East Coast of the United States|U.S. East Coast]]) today.<ref>Stanley, Steven M. ''Earth System History''. New York: W.H. Freeman and Company, 1999. {{ISBN|0-7167-2882-6}}</ref>

By the end of the era, the continents had rifted into nearly their present forms, though not their present positions. [[Laurasia]] became [[North America]] and [[Eurasia]], while [[Gondwana]] split into [[South America]], [[Africa]], [[Australia]], [[Antarctica]] and the [[South Asia|Indian subcontinent]], which collided with the [[Asia]]n plate during the Cenozoic, giving rise to the [[Himalaya]]s.{{Citation needed|date=June 2024}}

==Climate==
The Triassic was generally dry, a trend that began in the late [[Carboniferous]], and highly seasonal, especially in the interior of Pangaea. Low sea levels may have also exacerbated temperature extremes. With its high [[specific heat capacity]], water acts as a temperature-stabilizing heat reservoir, and land areas near large bodies of water—especially oceans—experience less variation in temperature. Because much of Pangaea's land was distant from its shores, temperatures fluctuated greatly, and the interior probably included expansive [[desert]]s. Abundant [[red beds]] and evaporites such as [[halite]] support these conclusions, but some evidence suggests the generally dry climate of the Triassic was punctuated by episodes of increased rainfall.<ref name=Pretoetal2010>{{cite journal |last1=Preto |first1=Nereo |last2=Kustatscher |first2=Evelyn |last3=Wignall |first3=Paul B. |date=15 April 2010 |title=Triassic climates – State of the art and perspectives | journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume = 290 |issue=1–4 |pages=1–10 |doi=10.1016/j.palaeo.2010.03.015 |bibcode=2010PPP...290....1P |url=https://www.sciencedirect.com/science/article/abs/pii/S0031018210001434 |access-date=21 July 2023}}</ref> The most important humid episodes were the [[Carnian Pluvial Event]] and one in the [[Rhaetian]], a few million years before the Triassic–Jurassic extinction event.

Sea levels began to rise during the Jurassic, probably caused by an increase in [[seafloor spreading]]. The formation of new crust beneath the surface displaced ocean waters by as much as {{convert|200|m|0|abbr=on}} above today's sea level, flooding coastal areas. Furthermore, Pangaea began to rift into smaller divisions, creating new shoreline around the Tethys Ocean. Temperatures continued to increase, then began to stabilize. [[Humidity]] also increased with the proximity of water, and deserts retreated.<ref>{{Cite journal |last=Gurung |first=Khushboo |last2=Field |first2=Katie J. |last3=Batterman |first3=Sarah A. |last4=Poulton |first4=Simon W. |last5=Mills |first5=Benjamin J. W. |date=28 February 2024 |title=Geographic range of plants drives long-term climate change |url=https://www.nature.com/articles/s41467-024-46105-1 |journal=[[Nature Communications]] |language=en |volume=15 |issue=1 |doi=10.1038/s41467-024-46105-1 |issn=2041-1723 |pmc=10901853 |pmid=38418475 |access-date=28 June 2024}}</ref>

The climate of the Cretaceous is less certain and more widely disputed. Probably, higher levels of [[carbon dioxide]] in the [[Earth's atmosphere|atmosphere]] are thought to have almost eliminated the north–south [[temperature gradient]]: temperatures were about the same across the planet, and about 10°[[Celsius|C]] higher than today.  The circulation of [[oxygen]] to the deep ocean may also have been disrupted, preventing the [[decomposition]] of large volumes of organic matter, which was eventually [[deposition (sediment)|deposited]] as "[[black shale]]".<ref>{{cite journal |last1=Leckie |first1=R. Mark |last2=Bralower |first2=Timothy J. |last3=Cashman |first3=Richard |title=Oceanic anoxic events and plankton evolution: Biotic response to tectonic forcing during the mid-Cretaceous: OCEANIC ANOXIC EVENTS AND PLANKTON EVOLUTION |journal=[[Paleoceanography and Paleoclimatology]] |date=September 2002 |volume=17 |issue=3 |pages=13–1–13–29 |doi=10.1029/2001PA000623 |doi-access=free}}</ref><ref>{{cite journal |last1=Turgeon |first1=Steven C. |last2=Creaser |first2=Robert A. |title=Cretaceous oceanic anoxic event 2 triggered by a massive magmatic episode |url=https://www.researchgate.net/publication/51407958_Cretaceous_Anoxic_Event_2_triggered_by_a_massive_magmatic_episode |journal=[[Nature (journal)|Nature]] |date=17 July 2008 |volume=454 |issue=7202 |pages=323–326 |doi=10.1038/nature07076 |pmid=18633415 |bibcode=2008Natur.454..323T |s2cid=4315155 |access-date=28 June 2024}}</ref>

Different studies have come to different conclusions about the amount of oxygen in the atmosphere during different parts of the Mesozoic, with some concluding oxygen levels were lower than the current level (about 21%) throughout the Mesozoic,<ref>[[Robert Berner]], John M. VandenBrooks and Peter D. Ward, 2007, [https://www.science.org/doi/abs/10.1126/science.1140273 ''Oxygen and Evolution'']. ''Science 27 April 2007'', Vol. 316 no. 5824 pp. 557–58 . A graph showing the reconstruction from this paper can be found [http://www.oocities.org/marie.mitchell@rogers.com/climate_files/Phanerozoic_Oxygen.gif here], from the webpage [http://www.oocities.org/marie.mitchell@rogers.com/PaleoClimate.html Paleoclimate – The History of Climate Change].</ref><ref>[[Robert Berner|Berner R. A.]] 2006 ''GEOCARBSULF: a combined model for Phanerozoic atmospheric O2 and CO2''. Geochim. Cosmochim. Acta 70, 5653–64. See the dotted line in Fig. 1 of [http://rspb.royalsocietypublishing.org/content/early/2010/03/04/rspb.2010.0001.full ''Atmospheric oxygen level and the evolution of insect body size''] by Jon F. Harrison, Alexander Kaiser and John M. VandenBrooks</ref> some concluding they were lower in the Triassic and part of the Jurassic but higher in the Cretaceous,<ref>[[Robert Berner|Berner]], Robert A., 2009, [http://www.ajsonline.org/content/309/7/603.abstract ''Phanerozoic atmospheric oxygen: New results using the GEOCARBSULF model'']. ''Am. J. Sci.'' 309 no. 7, 603–06. A graph showing the reconstructed levels in this paper can be found on [https://books.google.com/books?id=GdRnFn7I38kC&pg=PA31 p. 31] of the book ''Living Dinosaurs'' by [[Gareth J. Dyke|Gareth Dyke]] and Gary Kaiser.</ref><ref>[[Robert Berner|Berner R. A.]], Canfield D. E. 1989 ''A new model for atmospheric oxygen over phanerozoic time''. ''Am. J. Sci.'' 289, 333–61. See the solid line in Fig. 1 of [http://rspb.royalsocietypublishing.org/content/early/2010/03/04/rspb.2010.0001.full ''Atmospheric oxygen level and the evolution of insect body size''] by Jon F. Harrison, Alexander Kaiser and John M. VandenBrooks</ref><ref>[[Robert Berner|Berner, R]], et al., 2003, ''Phanerozoic atmospheric oxygen'', Annu. Rev. Earth Planet. Sci., V, 31, p. 105–34. See the graph near the bottom of the webpage [http://essayweb.net/geology/timeline/phanerozoic.shtml Phanerozoic Eon] {{webarchive|url=https://web.archive.org/web/20130427055918/http://essayweb.net/geology/timeline/phanerozoic.shtml |date=27 April 2013 }}</ref> and some concluding they were higher throughout most or all of the Triassic, Jurassic and Cretaceous.<ref>Glasspool, I.J., Scott, A.C., 2010, ''Phanerozoic concentrations of atmospheric oxygen reconstructed from sedimentary charcoal'', [[Nature Geoscience]], 3, 627–30</ref><ref>Bergman N. M., Lenton T. M., Watson A. J. 2004 COPSE: a new model of biogeochemical cycling over Phanaerozoic time. ''Am. J. Sci.'' 304, 397–437. See the dashed line in Fig. 1 of [http://rspb.royalsocietypublishing.org/content/early/2010/03/04/rspb.2010.0001.full ''Atmospheric oxygen level and the evolution of insect body size''] by Jon F. Harrison, Alexander Kaiser and John M. VandenBrooks</ref>

==Life==
===Flora===
[[File:ProspectPemulwuypine.jpg|thumb|upright=1.3|Conifers were the dominant terrestrial plants for most of the Mesozoic, with [[grasses]] becoming widespread in the [[Late Cretaceous]]. [[Flowering plant]]s appeared late in the era but did not become widespread until the [[Cenozoic]].]]
The dominant land plant species of the time were [[gymnosperm]]s, which are vascular, cone-bearing, non-flowering plants such as conifers that produce seeds without a coating. This contrasts with the earth's current flora, in which the dominant land plants in terms of number of species are [[angiosperm]]s. The earliest members of the genus ''[[Ginkgo]]'' first appeared during the Middle Jurassic. This genus is represented today by a single species, ''[[Ginkgo biloba]]''.<ref name="Balducci">{{cite web | url=http://www.fossilnews.com/2000/mezplants/mezplants.html | title=Mesozoic Plants | publisher=fossilnews.com | date=2000 | access-date=28 July 2023 | last=Balducci | first=Stan | url-status=dead | archive-url=https://archive.today/20130123140455/http://www.fossilnews.com/2000/mezplants/mezplants.html | archive-date=23 January 2013}}</ref> Modern conifer groups began to radiate during the Jurassic.<ref name="Leslie-2018">{{Cite journal |last1=Leslie |first1=Andrew B. |last2=Beaulieu |first2=Jeremy |last3=Holman |first3=Garth |last4=Campbell |first4=Christopher S. |last5=Mei |first5=Wenbin |last6=Raubeson |first6=Linda R. |last7=Mathews |first7=Sarah |date=September 2018 |title=An overview of extant conifer evolution from the perspective of the fossil record |url=http://doi.wiley.com/10.1002/ajb2.1143 |journal=American Journal of Botany |language=en |volume=105 |issue=9 |pages=1531–1544 |doi=10.1002/ajb2.1143 |pmid=30157290 |s2cid=52120430|doi-access=free }}</ref> [[Bennettitales]], an extinct group of gymnosperms with foliage superficially resembling that of [[cycad]]s gained a global distribution during the Late Triassic, and represented one of the most common groups of Mesozoic seed plants.<ref>{{Cite journal |last1=Blomenkemper |first1=Patrick |last2=Bäumer |first2=Robert |last3=Backer |first3=Malte |last4=Abu Hamad |first4=Abdalla |last5=Wang |first5=Jun |last6=Kerp |first6=Hans |last7=Bomfleur |first7=Benjamin |date=26 March 2021 |title=Bennettitalean Leaves From the Permian of Equatorial Pangea—The Early Radiation of an Iconic Mesozoic Gymnosperm Group |journal=[[Frontiers in Earth Science]] |volume=9 |pages=652699 |doi=10.3389/feart.2021.652699 |bibcode=2021FrEaS...9..162B |issn=2296-6463 |doi-access=free}}</ref>

[[Flowering plant]]s radiated during the early Cretaceous, first in the [[tropics]], but the even temperature gradient allowed them to spread toward the poles throughout the period. By the end of the Cretaceous, angiosperms dominated tree floras in many areas, although some evidence suggests that [[Biomass (ecology)|biomass]] was still dominated by cycads and [[fern]]s until after the Cretaceous–Paleogene extinction. Some plant species had distributions that were markedly different from succeeding periods; for example, the [[Schizeales]], a fern order, were skewed to the Northern Hemisphere in the Mesozoic, but are now better represented in the Southern Hemisphere.<ref>C.Michael Hogan. 2010. [http://www.eoearth.org/article/Fern ''Fern''. Encyclopedia of Earth. National council for Science and the Environment] {{webarchive|url=https://web.archive.org/web/20111109071540/http://www.eoearth.org/article/Fern |date=9 November 2011 }}. Washington, DC</ref>

===Fauna===
[[File:Europasaurus holgeri Scene 2.jpg|thumb|[[Dinosaur]]s were the dominant terrestrial vertebrates throughout much of the Mesozoic.]]
The extinction of nearly all animal species at the end of the [[Permian]] Period allowed for the [[adaptive radiation|radiation]] of many new lifeforms.  In particular, the extinction of the large [[herbivore|herbivorous]] [[pareiasaur]]s and [[carnivore|carnivorous]] [[gorgonopsia]]ns left those [[ecological niche]]s empty. Some were filled by the surviving [[cynodont]]s and [[dicynodont]]s, the latter of which subsequently became extinct.

Recent research indicates that it took much longer for the reestablishment of complex ecosystems with high biodiversity, complex food webs, and specialized animals in a variety of niches, beginning in the mid-Triassic 4 million to 6 million years after the extinction,<ref name="LehrmannRamezanBowring2006TimingOfRecovery">{{cite journal | title=Timing of recovery from the end-Permian extinction: Geochronologic and biostratigraphic constraints from south China | last1=Lehrmann |first1=D. J. |last2=Ramezan |first2=J. |last3=Bowring |first3=S.A. | display-authors=etal |
journal=[[Geology (journal)|Geology]] |date=December 2006 | volume=34 | pages=1053–56 | doi=10.1130/G22827A.1 | issue=12 |bibcode = 2006Geo....34.1053L }}</ref> and not fully proliferated until 30 million years after the extinction.<ref name="SahneyBenton2008RecoveryFromProfoundExtinction">{{cite journal |author1=Sahney, S. |author2=Benton, M. J. |name-list-style=amp | date=2008 | title=Recovery from the most profound mass extinction of all time | journal=[[Proceedings of the Royal Society B: Biological Sciences]] | doi=10.1098/rspb.2007.1370 | volume = 275 | pages = 759–65| pmid=18198148 | issue=1636 | pmc=2596898}}</ref> During the Triassic, terrestrial herbivores avoided competition through significant niche partitioning by generally occupying highly distinct guilds.<ref>{{Cite journal |last=Singh |first=Suresh A. |last2=Elsler |first2=Armin |last3=Stubbs |first3=Thomas L. |last4=Bond |first4=Russell |last5=Rayfield |first5=Emily J. |last6=Benton |first6=Michael James |date=14 May 2021 |title=Niche partitioning shaped herbivore macroevolution through the early Mesozoic |url=https://www.nature.com/articles/s41467-021-23169-x |journal=[[Nature Communications]] |language=en |volume=12 |issue=1 |pages=2796 |doi=10.1038/s41467-021-23169-x |issn=2041-1723 |access-date=7 April 2025}}</ref> Animal life was then dominated by various archosaurs: [[dinosaur]]s, pterosaurs, and aquatic reptiles such as ichthyosaurs, plesiosaurs, and [[mosasaur]]s.

The climatic changes of the late Jurassic and Cretaceous favored further adaptive radiation. The Jurassic was the height of archosaur diversity, and the first [[bird]]s and [[eutheria]]n mammals also appeared. Some have argued that [[insect]]s diversified in [[symbiosis]] with angiosperms, because insect [[anatomy]], especially the mouth parts, seems particularly well-suited for flowering plants. However, all major insect mouth parts preceded angiosperms, and insect diversification actually slowed when they arrived, so their anatomy originally must have been suited for some other purpose.{{Citation needed|reason=Molecular clock data for at least some genera are consistent with insect/angiosperm co-evolution. While also potentially plausible, this counter-claim should be supported with a citation.|date=October 2021}}
{{clear}}

===Microbiota===
At the dawn of the Mesozoic, ocean plankton communities transitioned from ones dominated by green [[Archaeplastida|archaeplastidans]] to ones dominated by endosymbiotic algae with red-algal-derived plastids. This transition is speculated to have been caused by an increasing paucity of many trace metals in the Mesozoic ocean.<ref>{{cite journal |last1=Zhang |first1=Qiong |last2=Bendif |first2=El Mahdi |last3=Zhou |first3=Yu |last4=Nevado |first4=Bruno |last5=Shafiee |first5=Roxana |last6=Rickaby |first6=Rosalind E. M. |date=31 October 2022 |title=Declining metal availability in the Mesozoic seawater reflected in phytoplankton succession |url=https://www.nature.com/articles/s41561-022-01053-7 |journal=[[Nature Geoscience]] |volume=15 |issue=1 |pages=932–941 |doi=10.1038/s41561-022-01053-7 |access-date=21 July 2023|hdl=10451/55860 |hdl-access=free }}</ref>

==See also==
*[[Paleozoic|Paleozoic Era]]
*[[Cenozoic|Cenozoic Era]]
*[[Phanerozoic|Phanerozoic Eon]]

==References==
{{Reflist}}
{{refbegin}}
*''British Mesozoic Fossils'', 1983, The Natural History Museum, London.
{{refend}}

==External links==
* [https://ghkclass.com/ghkC.html?mesozoic Mesozoic (chronostratigraphy scale)]

{{Wikisource portal|Mesozoic}}
{{Commons category|Mesozoic}}

{{Geological history|p|m|state=collapsed}}
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[[Category:Geological eras]]
[[Category:Mesozoic| ]]