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Life of the Mesozoic

Life of the Mesozoic. Mesozoic Climates. Primary control is the balance between incoming/outgoing solar radiation Factors affecting balance: Configuration and dimensions of oceans and continents Development and location of mountain systems Changes in snow, cloud or vegetative cover

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Life of the Mesozoic

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  1. Life of the Mesozoic

  2. Mesozoic Climates • Primary control is the balance between incoming/outgoing solar radiation • Factors affecting balance: • Configuration and dimensions of oceans and continents • Development and location of mountain systems • Changes in snow, cloud or vegetative cover • Carbon dioxide • Location of poles • Amount of radiation aerosols • Astronomic factors – changes in earth’s orbital parameters

  3. Factors favoring cooler climates • Vast continental areas • Low sea level • Uplifting mountains • Polar position of continents • Lower CO2 levels

  4. Triassic • Relatively cool • Pangaea continents still clustered • Mountain building created many highlands • Paleo-equator: central Mexico to north Africa • Wind shadow deserts in continental interior • Red beds • Evaporites

  5. Jurassic • Relatively mild • No glacial deposits • Evidence of monsoons and aridity • Coal in many spots (including Antarctica) • Wide belts of tropical conditions • Continents at current latitudes • Atlantic continuing to opening • Tethys brought warm ocean currents inland

  6. Cretaceous • Relatively warm • Subtropical flora existed at +70o Latitude • High and low latitude coal swamps • High sea level (maximum inundation of Phanerozoic) • Continents near where they are today • Arctic Canada near north pole • Antarctica near south pole

  7. By the end of the Cretaceous • Rapid cooling • Vast regression • Major mountain building • Plankton produced CO2 shortage • Volcanic activity • Terminal Cretaceous climatic event • Tropical cyads sharply reduced • Hardy conifers and angiosperms expand • Drop in ocean temp

  8. Mesozoic invertebrates • Marine invertebrates • Permian extinction decimates brachiopods • Pelecypods bivalves take hold (mostly oysters) • Gryphaea –small oyster • Exogyra – large oyster • Rudistids (horn-like valve, with left valve acting as lid) – become major reef builder of Mesozoic • Scleractinian corals • Hermatypic (reef builders) normal salinity, less than 50 m water and 20o C (Algal symbionts)

  9. Echinoderms • 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.

  10. Ammonoids Cephalopods • Mesozoic also age of ammonoids • Suture pattern key to taxonomy • Variety due to environmental adaption; expansion follows sea-level rise and continental flooding. • Diversity of forms; planispiral (early cretaceous) to open spiral, straight conch, helicoids (late cretaceous) • Extinction at end of cretaceous • Nautilods: sole survivors

  11. Belemnite Cephalopods • Highly successful: Jurassic- Cretaceous • Straight pointed shell • Moved through water by jetting water • Related to modern squid and octopus

  12. Crustaceans: • barnacles, crayfish, lobsters, crabs, shrimp

  13. Terrestrial Invertebrates • Pulmonates – air breathing snails • Fresh-water clams • Centipedes, spiders, millipedes, scorpions • Insects: Several groups appeared before the end of Jurassic • Butterflies (Lepidoptera) • Ants, bees, and wasps (Hymenoptera) • Termites (isoptera) • Mantises (mantodea) • Earwigs (dermopera)

  14. Amphibians • Temnospondyls: Surviving group of tetrapods from Permian extinction • Triassic – 17 families survive • Jurassic – 2 remain • Cretaceous – 1 lineage left • Lissamphibia: oldest forms known • Oldest frog- Triadobatrachus (lower Triassic) • Oldest salamander: Karaurus (upper Jurassic) • Surviving forms of Lissamphibia- frogs, toads, salamanders, and newts

  15. New reptiles groups • First turtles (toothed turtles) • Rhynchocephalians (tuartaran lizards) • Archosaurs: crocodiles, flying reptiles, thecodonts, dinosaurs • Hesperosuchus • Small, light, agile, long tail, short limbs • Walked erect (ancestor of dinosaurs) • Caught prey with forelimbs • Forelimbs most likely evolved into wings

  16. Phytosaurs • Reverted to four legged stance, some armored • Example of genetic convergence

  17. Dinosaurs • Two orders: Sauriscia (lizard hipped) and Ornithiscia (bird hipped) • Sauriscia: triradiate pelvic bones like thecodonts • Ornithiscia: pubis parallel to ischium like birds

  18. Saurischians • First dinosaurs • Eoraptor and herrerasaur: late Triassic • Coelohysis • Ornithomimus: the bird mimic (toothless beak)

  19. Carnivorous saurischians or therapods • Large hind limbs, claws on toes, smaller forelimbs, and serrated teeth • Deinonychus and velociraptor – Cretaceous predators • Family of Allosauridae – Allosaurus (US) • Giant therapods: Tyranosaurus (13m, 4 tons, North America)

  20. Herbivorous saurischians or Sauropods • (Jurassic- Cretaceous) • Evolved from late Triassic protocerapod • Long necks, long tails, four-legged stance • Apatosaurus(formerly Brontosaurus, Jurassic Colorado) • Brachiosaurus: Longer forelimbs to reach high branches) • Supersaurus: 80 – 100 tons • Sauropods left extensive footprint record

  21. Ornithischians • (late Triassic – Cretaceous) • Characteristics: Beak for cropping plants, quadrupeds and bipeds, primitive jaw • Ornithopods: bipedal forms – Iquanadon (the thumbs up dino) Herd animal • Hadrosaurs- web-footed aquatic version (duck-billed dinosaurs)

  22. Quadropedal Ornithischians • Stegosaurus- two paired, spike tail, heavy plates • Ankylosaur – bony plates over side an back • Ceratopsians- horn on face, bony frill on back of head (triceratops)

  23. Aerial Reptiles • Adaptive radiation of Permian forms • Gliders with skin wings • Coelurosauravus (Permian - Triassic) • Icharosaurus (Triassic) • Gliders with modified ribs functioning as wings: Longisquama (Triassic)

  24. Active fliers • Pterosaurs (late Triassic – Cretaceous) • Sharovipteryx – skin membrane between elbows and knees • Sordes pilosus “Hairy devil” wing flapping reptile • Large head and eyes, long jaw, thin slanted teeth, finger bones long to support wings • Two groups evolved: rhamphophynchoids (long tails) and Pterodactyloids (no tails) • Pteranodon – 7m wingspan example of pterodactyloid

  25. Marine Reptiles • Archosaurs: only one group invaded Mesozoic oceans (Crocodiles) • Nothosaurus (paddle shaped limbs) • Appeared during Triassic • Ancestor of Plesiosaur

  26. Placodonts • Mollusk eating reptile • Paddle-shaped flipped • Pavement type teeth in jaws and palate

  27. Plesiosaurs • First appeared during Jurassic • Short broad body with flippers and small head • Long neck and short neck forms • Slender curved teeth • Loch Ness Monster?

  28. Ichthyosaurs • Reptilian counterpart of modern whales

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