Mesozoic era: Age of the dinosaurs | Live Science

During the Mesozoic, or "Middle Life" era, life diversified rapidly and giant reptiles, dinosaurs and other monstrous beasts roamed the Earth. Skiptomaincontent LiveScience LiveScience Search Subscribe RSS HowItWorksMagazineWhysubscribe?Theultimateaction-packedscienceandtechnologymagazineburstingwithexcitinginformationabouttheuniverseEngagingarticles,amazingillustrations&exclusiveinterviewsIssuesdeliveredstraighttoyourdoorordeviceFrom$3.99ViewDeal News Space&Physics Health PlanetEarth StrangeNews Animals History Forums More Forums Tech Culture Reference AboutUs Magazinesubscriptions TrendingPhysics&AstrophysicsCOVID-19FitnessUkraineinvasionupdatesPregnancytips LiveScienceissupportedbyitsaudience.Whenyoupurchasethroughlinksonoursite,wemayearnanaffiliatecommission.Learnmore Newresearchsuggeststhatreptilesthatlivedduringthedinosauragewerehard-hit.Here,thecarnivorouslizardPalaeosaniwachasesapairofyoungEdmontosauruswhilethesnakeCerberophisandthelizardObamadonlookon. (Imagecredit:CarlBuell) DuringtheMesozoic,or"MiddleLife"era,lifediversifiedrapidlyandgiantreptiles,dinosaursandothermonstrousbeastsroamedtheEarth.Theperiod,whichspansfromabout252millionyearsagotoabout66millionyearsago,wasalsoknownastheageofreptilesortheageofdinosaurs.BoundariesEnglishgeologistJohnPhillips,thefirstpersontocreatetheglobalgeologictimescale,firstcoinedthetermMesozoicinthe1800s.Phillipsfoundwaystocorrelatesedimentsfoundaroundtheworldtospecifictimeperiods,saidPaulOlsen,ageoscientistattheLamont-DohertyEarthObservatoryatColumbiaUniversityinNewYork. ThePermian-Triassicboundary,atthestartoftheMesozoic,isdefinedrelativetoaparticularsectionofsedimentinMeishan,China,whereatypeofextinct,eel-likecreatureknownasaconodontfirstappeared,accordingtothe InternationalCommissiononStratigraphy. TheendboundaryfortheMesozoicera,the Cretaceous-Paleogeneboundary,isdefinedbya20-inch(50centimeters)thicksliverofrockinElKef,Tunisia,whichcontainswell-preservedfossilsandtracesofiridiumandotherelementsfromtheasteroidimpactthatwipedoutthedinosaurs.TheMesozoiceraisdividedupintotheTriassic,Jurassic,andCretaceousperiods.LifeandclimateTheMesozoicerabeganroughlyaroundthetimeoftheend-Permianextinction,whichwipedout96percentofmarinelifeand70percentofallterrestrialspeciesontheplanet.Lifeslowlyrebounded,eventuallygivingwaytoaflourishingdiversityofanimals,frommassivelizardstomonstrousdinosaurs.The Triassicperiod,from252millionto200millionyearsago,sawtheriseofreptilesandthefirstdinosaurs.The Jurassicperiod,fromabout200millionto145millionyearsago,usheredinbirdsandmammals.Andthe Cretaceousperiod,from145millionto66millionyearsagoisknownforitsiconicdinosaurs,suchas Triceratops, andpterosaurssuchas Pteranodon.Coniferousplants,orthosethathavecone-bearingseeds,alreadyexistedatthebeginningoftheera,buttheybecamemuchmoreabundantduringtheMesozoic.FloweringplantsemergedduringthelateCretaceousperiod.ThelushplantlifeduringtheMesozoiceraprovidedplentyoffood,allowingthe biggestofthedinosaurs,suchasthe Argentinosaurus,togrowupto80tons,accordingtoa2005studyinthejournalRevistadelMuseoArgentinodeCienciasNaturales. EarthduringtheMesozoicerawasmuchwarmerthantoday,andtheplanethadnopolaricecaps.DuringtheTriassicperiod, Pangaea stillformedonemassivesupercontinent.Withoutmuchcoastlinetomoderatethecontinent'sinteriortemperature,Pangaeaexperiencedmajortemperatureswingsandwascoveredinlargeswathsofdesert.Yettheregionstillhadabeltoftropicalrainforestinregionsaroundtheequator,saidBrendanMurphy,anearthscientistatSt.FrancisXavierUniversityinAntigonish,Canada.ExtinctionsTheMesozoicerawasbookendedbytwogreatextinctions,withanothersmallerextinctionoccurringattheendoftheTriassicperiod,Olsensaid.Around252millionyearsago,theend-PermianextinctionwipedoutmostlifeonEarthoverabout60,000years,accordingtoaFebruary2014studyinthejournal ProceedingsoftheNationalAcademyofSciences (PNAS).AttheendoftheTriassicperiod,roughly201millionyearsago,mostamphibiouscreaturesandcrocodile-likecreaturesthatlivedinthetropicswerewipedout.About65millionyearsago,agiantasteroidblastedintoEarthandformedagiantcrateratChicxulubintheYucatanPeninsula. Becausethefossilrecordisincomplete,it'sdifficulttosayexactlywhatcausedtheextinctions,orevenhowrapidlytheyoccurred.Afterall,certainspeciesortracesofcatastrophiceventscouldbemissinginthefossilrecordsimplybecausethesedimentsmayhavedisappearedovertensofmillionsofyears,Olsensaid."Natureisveryefficientatgettingridofitscorpses,"OlsentoldLiveScience.However,thereareafewprimesuspectsineachoftheextinctions.AttheendofthePermian,theSiberianTrapsunderwentmassivevolcaniceruptions,whichmostgeologistsbelievecausedthe world'sbiggestextinction.Exactlyhow,however,isupfordebate.Thevolcaniceruptionscausedaspikeincarbondioxideintheatmosphere,thoughthe2014PNASstudysuggeststhatthespikewasbrief.Theeruptionsmayhaveincreasedseasurfacetemperaturesandledtooceanacidificationthatchokedoutsealife.AndanotherstudypublishedinMarch2014in PNAS proposedthattheeruptionsreleasedhugetrovesoftheelement nickel,whichfueledafeedingfrenzybynickel-munchingmicrobesknownas Methanosarcina.Thosemicrobesmayhavebelchedouthugeamountsofmethane,superheatingtheplanet.Mostscientistsagreethatan asteroidimpactwipedoutthedinosaurs attheendoftheCretaceousperiod.Theimpactwouldhavekickedupsomuchdustthatitblockedthesun,haltedphotosynthesis,andledtosuchahugedisruptioninthefoodchainthateverythingthatwasn'tascavengerorverysmalldied.Butthe DeccanTraps,inwhatisnowIndia,werespewingmassiveamountsoflavabothbeforeandaftertheasteroidimpact,andafewscientistsbelievetheseflowseitherdirectlycausedoracceleratedthedinosaurs'demise.Volcanismmayalsobetoblamefortheend-Triassicextinction.Thoughvolcanismingeneralleadstoglobalwarming,afteraninitialvolcaniceruption,hugeamountsofsulfurspewintotheairandcauseabriefperiodofglobalcooling.Suchcooling-heatingcyclesmayhaveoccurredhundredsoftimesover500,000years.Similarcoldsnapshavebeentiedtohugecropfailuresinhistoricaltimes,suchasinIcelandinthe1700s,Olsensaid. Asaresult,animalsusedtoconstant,balmytemperaturesinthetropicswerewipedout,whileanimalsthatwereinsulatedwithproto-feathers,suchaspterosaurs,orthatlivedathigherlatitudesandwerealreadyadaptedtobigtemperaturevariations,didjustfine,Olsensaid."Whenyouhavethesevolcanicwinters,wheretemperaturesmayhavedroppedevenbelowfreezinginthetropics,itwasdevastating,"Olsensaid.OriginallypublishedonLiveScience.AdditionalresourcesUniversityofCaliforniaMuseumofPaleontology:TheMesozoicEraHowardHughesMedicalInstitute:TheDaytheMesozoicDied TiaGhose ManagingEditor TiaisthemanagingeditorandwaspreviouslyaseniorwriterforLiveScience.HerworkhasappearedinScientificAmerican,Wired.comandotheroutlets.Sheholdsamaster'sdegreeinbioengineeringfromtheUniversityofWashington,agraduatecertificateinsciencewritingfromUCSantaCruzandabachelor'sdegreeinmechanicalengineeringfromtheUniversityofTexasatAustin.TiawaspartofateamattheMilwaukeeJournalSentinelthatpublishedtheEmptyCradlesseriesonpretermbirths,whichwonmultipleawards,includingthe2012CaseyMedalforMeritoriousJournalism. 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