Life of the Life of the MesozoicMesozoic

Mesozoic ClimatesMesozoic Climates

► Primary control is the balance Primary control is the balance between incoming/outgoing solar between incoming/outgoing solar radiationradiation

Factors affecting balance:Factors affecting balance:► Configuration and dimensions of oceans and Configuration and dimensions of oceans and

continentscontinents► Development and location of mountain Development and location of mountain

systemssystems► Changes in snow, cloud or vegetative coverChanges in snow, cloud or vegetative cover► Carbon dioxideCarbon dioxide► Location of polesLocation of poles► Amount of radiation aerosolsAmount of radiation aerosols► Astronomic factors – changes in earth’s Astronomic factors – changes in earth’s

orbital parametersorbital parameters

Factors favoring cooler Factors favoring cooler climatesclimates

Vast continental areasVast continental areas Low sea levelLow sea level Uplifting mountainsUplifting mountains Polar position of continentsPolar position of continents Lower CO2 levelsLower CO2 levels

TriassicTriassic

► Relatively coolRelatively cool► Pangaea continents still Pangaea continents still

clusteredclustered► Mountain building Mountain building

created many highlandscreated many highlands

► Paleo-equator: central Paleo-equator: central Mexico to north AfricaMexico to north Africa

► Wind shadow deserts Wind shadow deserts in continental interiorin continental interior► Red bedsRed beds► EvaporitesEvaporites

JurassicJurassic

► Relatively mildRelatively mild► No glacial depositsNo glacial deposits► Evidence of monsoons and Evidence of monsoons and

aridityaridity► Coal in many spots Coal in many spots

(including Antarctica)(including Antarctica)► Wide belts of tropical Wide belts of tropical

conditionsconditions

► Continents at current Continents at current latitudeslatitudes► Atlantic continuing to Atlantic continuing to

openingopening► TethysTethys brought warm ocean brought warm ocean

currents inlandcurrents inland

CretaceousCretaceous

► Relatively warmRelatively warm► Subtropical flora existed Subtropical flora existed

at +70o Latitudeat +70o Latitude► High and low latitude coal High and low latitude coal

swampsswamps► High sea level (maximum High sea level (maximum

inundation of Phanerozoic)inundation of Phanerozoic)

► Continents near where Continents near where they are todaythey are today► Arctic Canada near north Arctic Canada near north

polepole► Antarctica near south poleAntarctica near south pole

By the end of the CretaceousBy the end of the Cretaceous

Rapid cooling Rapid cooling Vast regressionVast regression Major mountain building Major mountain building Plankton produced CO2 shortagePlankton produced CO2 shortage Volcanic activityVolcanic activity

► Terminal Cretaceous climatic eventTerminal Cretaceous climatic event Tropical cyads sharply reducedTropical cyads sharply reduced Hardy conifers and angiosperms expandHardy conifers and angiosperms expand Drop in ocean tempDrop in ocean temp

Mesozoic invertebratesMesozoic invertebrates

► Marine invertebratesMarine invertebrates Permian extinction decimates brachiopodsPermian extinction decimates brachiopods Pelecypods bivalves take hold (mostly Pelecypods bivalves take hold (mostly

oysters)oysters)► GryphaeaGryphaea –small oyster –small oyster► ExogyraExogyra – large oyster – large oyster► RudistidsRudistids (horn-like valve, with left valve (horn-like valve, with left valve

acting as lid) – become major reef builder of acting as lid) – become major reef builder of MesozoicMesozoic

Scleractinian coralsScleractinian corals► Hermatypic (reef builders) normal salinity, less Hermatypic (reef builders) normal salinity, less

than 50 m water and 20than 50 m water and 20oo C (Algal symbionts) C (Algal symbionts)

EchinodermsEchinoderms

Starfish, sea urchins, crinoids

Regular echinoids: five-fold symmetry spherical shell numerous in European chalks

Irregular echinoids: displaced regular echinoids during cretaceous

Crinoids: both stemmed and stemless forms.

Ammonoids CephalopodsAmmonoids Cephalopods

► Mesozoic also age of ammonoidsMesozoic also age of ammonoids Suture pattern key to taxonomySuture pattern key to taxonomy

Variety due to environmental Variety due to environmental adaption; expansion follows sea-adaption; expansion follows sea-level rise and continental flooding.level rise and continental flooding.

Diversity of forms; planispiral Diversity of forms; planispiral (early cretaceous) to open spiral, (early cretaceous) to open spiral, straight conch, helicoids (late straight conch, helicoids (late cretaceous) cretaceous)

Extinction at end of cretaceousExtinction at end of cretaceous► Nautilods: sole survivorsNautilods: sole survivors

Belemnite CephalopodsBelemnite Cephalopods

► Highly successful: Jurassic- CretaceousHighly successful: Jurassic- Cretaceous► Straight pointed shellStraight pointed shell► Moved through water by jetting waterMoved through water by jetting water► Related to modern squid and octopusRelated to modern squid and octopus

Crustaceans:Crustaceans:

► barnacles, crayfish, lobsters, crabs, shrimpbarnacles, crayfish, lobsters, crabs, shrimp

Terrestrial InvertebratesTerrestrial Invertebrates

► Pulmonates – air breathing Pulmonates – air breathing snailssnails

► Fresh-water clamsFresh-water clams► Centipedes, spiders, Centipedes, spiders,

millipedes, scorpionsmillipedes, scorpions► Insects: Several groups Insects: Several groups

appeared before the end of appeared before the end of JurassicJurassic► Butterflies (Lepidoptera)Butterflies (Lepidoptera)► Ants, bees, and wasps Ants, bees, and wasps

(Hymenoptera)(Hymenoptera)► Termites (isoptera)Termites (isoptera)► Mantises (mantodea)Mantises (mantodea)► Earwigs (dermopera)Earwigs (dermopera)

AmphibiansAmphibians

TemnospondylsTemnospondyls: Surviving group of : Surviving group of tetrapods from Permian extinctiontetrapods from Permian extinction► Triassic – 17 families surviveTriassic – 17 families survive► Jurassic – 2 remainJurassic – 2 remain► Cretaceous – 1 lineage leftCretaceous – 1 lineage left

LissamphibiaLissamphibia: oldest forms known: oldest forms known► Oldest frog- Triadobatrachus (lower Triassic)Oldest frog- Triadobatrachus (lower Triassic)► Oldest salamander: Karaurus (upper Jurassic)Oldest salamander: Karaurus (upper Jurassic)

Surviving forms of Lissamphibia- frogs, Surviving forms of Lissamphibia- frogs, toads, salamanders, and newtstoads, salamanders, and newts

New reptiles groupsNew reptiles groups

First turtles (toothed turtles)First turtles (toothed turtles) Rhynchocephalians (tuartaran lizards)Rhynchocephalians (tuartaran lizards) Archosaurs: crocodiles, flying reptiles, Archosaurs: crocodiles, flying reptiles,

thecodonts, dinosaursthecodonts, dinosaurs► HesperosuchusHesperosuchus

Small, light, agile, long tail, short limbsSmall, light, agile, long tail, short limbs Walked erect (ancestor of dinosaurs)Walked erect (ancestor of dinosaurs) Caught prey with forelimbsCaught prey with forelimbs Forelimbs most likely evolved into wingsForelimbs most likely evolved into wings

PhytosaursPhytosaurs

► Reverted to four legged stance, some Reverted to four legged stance, some armoredarmored

► Example of genetic convergenceExample of genetic convergence

DinosaursDinosaurs

► Two orders: Two orders: SaurisciaSauriscia (lizard hipped) (lizard hipped) and and OrnithisciaOrnithiscia (bird hipped) (bird hipped)► Sauriscia: triradiate pelvic bones like thecodontsSauriscia: triradiate pelvic bones like thecodonts

► Ornithiscia: pubis parallel to ischium like birdsOrnithiscia: pubis parallel to ischium like birds

SaurischiansSaurischians

► First dinosaursFirst dinosaurs Eoraptor and herrerasaur: late TriassicEoraptor and herrerasaur: late Triassic CoelohysisCoelohysis OrnithomimusOrnithomimus: the bird mimic : the bird mimic

(toothless beak)(toothless beak)

Carnivorous saurischians or Carnivorous saurischians or therapodstherapods

Large hind limbs, claws on toes, smaller Large hind limbs, claws on toes, smaller forelimbs, and serrated teethforelimbs, and serrated teeth

Deinonychus and Deinonychus and velociraptorvelociraptor – Cretaceous predators – Cretaceous predators Family of Allosauridae – Family of Allosauridae – AllosaurusAllosaurus (US) (US) Giant therapods: Giant therapods: TyranosaurusTyranosaurus (13m, 4 tons, North (13m, 4 tons, North

America)America)

Herbivorous saurischians or Herbivorous saurischians or SauropodsSauropods

► (Jurassic- Cretaceous)(Jurassic- Cretaceous) Evolved from late Triassic protocerapodEvolved from late Triassic protocerapod

► Long necks, long tails, four-legged stanceLong necks, long tails, four-legged stance ApatosaurusApatosaurus (formerly Brontosaurus, Jurassic (formerly Brontosaurus, Jurassic

Colorado)Colorado) BrachiosaurusBrachiosaurus: Longer forelimbs to reach : Longer forelimbs to reach

high branches)high branches) Supersaurus: 80 – 100 tonsSupersaurus: 80 – 100 tons

► Sauropods left extensive footprint recordSauropods left extensive footprint record

OrnithischiansOrnithischians

► (late Triassic – Cretaceous)(late Triassic – Cretaceous) Characteristics: Beak for cropping Characteristics: Beak for cropping

plants, quadrupeds and bipeds, plants, quadrupeds and bipeds, primitive jawprimitive jaw► OrnithopodsOrnithopods: bipedal forms – : bipedal forms –

Iquanadon (the thumbs up dino) Herd Iquanadon (the thumbs up dino) Herd animalanimal

► HadrosaursHadrosaurs- web-footed aquatic - web-footed aquatic version (duck-billed dinosaurs)version (duck-billed dinosaurs)

Quadropedal OrnithischiansQuadropedal Ornithischians

StegosaurusStegosaurus- two paired, spike tail, heavy - two paired, spike tail, heavy platesplates

AnkylosaurAnkylosaur – bony plates over side an back – bony plates over side an back CeratopsiansCeratopsians- horn on face, bony frill on - horn on face, bony frill on

back of head (back of head (triceratopstriceratops))

Aerial ReptilesAerial Reptiles

► Adaptive radiation of Permian formsAdaptive radiation of Permian forms Gliders with skin wingsGliders with skin wings

► Coelurosauravus (Permian - Triassic)Coelurosauravus (Permian - Triassic)► Icharosaurus (Triassic)Icharosaurus (Triassic)

Gliders with modified ribs functioning as Gliders with modified ribs functioning as wings: Longisquama (Triassic)wings: Longisquama (Triassic)

Active fliersActive fliers

► PterosaursPterosaurs (late Triassic – (late Triassic – Cretaceous)Cretaceous)

Sharovipteryx – skin membrane between Sharovipteryx – skin membrane between elbows and kneeselbows and knees

Sordes pilosus “Hairy devil” wing flapping Sordes pilosus “Hairy devil” wing flapping reptilereptile► Large head and eyes, long jaw, thin slanted Large head and eyes, long jaw, thin slanted

teeth, finger bones long to support wingsteeth, finger bones long to support wings► Two groups evolved: rhamphophynchoids (long Two groups evolved: rhamphophynchoids (long

tails) and tails) and PterodactyloidsPterodactyloids (no tails) (no tails) PteranodonPteranodon – 7m wingspan example of – 7m wingspan example of

pterodactyloidpterodactyloid

Marine ReptilesMarine Reptiles

► Archosaurs: only one group invaded Archosaurs: only one group invaded Mesozoic oceans (Crocodiles)Mesozoic oceans (Crocodiles)

► Nothosaurus (paddle shaped limbs)Nothosaurus (paddle shaped limbs) Appeared during TriassicAppeared during Triassic Ancestor of PlesiosaurAncestor of Plesiosaur

PlacodontsPlacodonts

Mollusk eating reptileMollusk eating reptile Paddle-shaped flippedPaddle-shaped flipped Pavement type teeth in jaws and palatePavement type teeth in jaws and palate

PlesiosaursPlesiosaurs

► First appeared during JurassicFirst appeared during Jurassic Short broad body with flippers and small Short broad body with flippers and small

headhead► Long neck and short neck formsLong neck and short neck forms► Slender curved teethSlender curved teeth

Loch Ness Monster?Loch Ness Monster?

IchthyosaursIchthyosaurs

► Reptilian Reptilian counterpart of counterpart of modern whalesmodern whales