Mesozoic Outline Introduction to Mesozoic Tectonic Setting Life in the Water Life on Land Including infamous dinosaurs Life in the Air Not The

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1 Mesozoic Outline Introduction to Mesozoic Tectonic Setting Life in the Water Life on Land Including infamous dinosaurs Life in the Air Not The Biggest Extinction, but The Extinction of the Biggest Introduction to the Mesozoic Meso = middle + Zoic =? Triassic Named in 1834 by Friedrich Von Alberti from three distinct layers: red beds, chalk, and black shale Latin trias meaning thirds or triad Jurassic Swiss Jura Mountains Jura derived from Celtic jor, meaning forest Cretaceous Latin for chalky: chalk period Triassic Absaroka Transgression continues Sonoma Orogeny Ends Opening of Middle Atlantic begins at end Gulf of Mexico begins forming Bivalves/Echiniods expand into niches Wetter climates (local areas of aridity) Archosaurs give rise to dinos Flying and Marine Reptiles evolve Cynodonts=extinct Mammals evolve Jurassic South America, Africa Separate Nevadan Orogeny (Late J) Fault block Mountains in East Transgression=Zuni (early to mid J) Thick evaporates in Gulf of Mexico Absaroka ends (early to mid J) Mild climates Ammonites/belemnoids diversify Scleractinian Corals common Rudist bivalves Lots of Conifers, cycads

2 Giant Dinos 1st Birds-Archaeopteryx 1st Plesiosaurs Cretaceous Index fossil=ammonoid Belemnoids diversify, too Major transgression Late K (regressions & transgressions throughout) Orogenies Laramide Nevadan Sevier Greenland separates from Europe South America, Africa widely separated Appalachian region uplifted Dino climax Food chain changes Snakes/Constrictors Flowering plants Marsupials, placentals Rudists=reef builders Late K= extinction Ammonites, Rudists Most plankton Dinos, flying/marine reptiles Climate=seasonal, cooler Tectonic Setting-Triassic Beginning Global sea level = relatively low Close to modern position Rose ~100 m above present position Fell again Orogenies in Eurasia complete assembly of Pangea Large portions of central Pangea formed arid deserts like modern day Gobi and Sahara Appalachian Mountains erode Tectonic Setting=Jurassic Great tectonic change Near beginning= global sea level=lowest points in history Pangea began to slowly rift apart reshaping both both marine and terrestrial ecosystems Led to development of modern continents divergent evolution of separate biotas Tectonic Setting=Cretaceous Supercontinent breakup, rifting accelerated

3 Cooling of the poles? Oxygen isotopic ratios recorded in marine foraminifera change in land plant communities in high latitudes Life in the Water Sea level = highest levels in Cretaceous warm conditions =oceans full of life Microorganisms base of food web major contributors to marine sediments: biogenous ooze: Silaceous=diatoms single-celled chex-mix phytoplankton with ornate skeleton Composes diatomite, soft marine silicate rock Calcareous ooze =coccoliths Coccolithophorid single-celled fly-eye sphere composed of calcite plates Plates=major component of chalk=soft marine limestone Life in the Water-Extinction at end of Permian Wiped out great numbers of marine organisms: trilobites fusulinid foraminifera rugose corals lacy bryozoans leaving new world to be exploited by survivors: ammonoid cephalopods conodonts Other groups suffered substantial declines without complete loss Life in the Water-Triassic, Jurassic Reef-forming corals, sea urchins expanded End of Triassic mass extinction in marine ecosystems Evidence for arid climatic shift in terrestrial environments Large drop in sea level Reptiles First invaded sea during Triassic became top predators Plesiosaur - marine reptile with broad body and large paddle-like limbs Ichthyosaur - marine reptile with dolphin-like body Life in the Water-Jurassic Marine predator-prey systems=top of Mesozoic Marine Revolution predatory ammonoids belemnoids Cephalopods enjoyed varied diet Fishes of Mesozoic Teleost

4 carnivorous sharks and rays surviving from Paleozoic increased in number Life in the Water Other benthic or nektobenthic (bottom-dwelling) carnivores = some snails and crustaceans Dinoflagellates Brachiopods, stalked echinoderms (crinoids)=great decline non-stalked relatives proliferated Life in the Water-Cretaceous Rudist - Mesozoic clam formed reefs Many modern snails Arthropod predator= Modern crabs Break shells, skeletons of their prey with claws Yummy soft tissues inside Mosasaurs Marine reptile Life on Land=Plants Land plants not affected by extinction at end of Paleozoic Mesozoic Gymnosperms dominated landscape provided much of food for herbivorous dinosaurs, mammals Types: Ferns Conifers Cycads Ginkgos Life on Land=Plants Cretaceous Group of gymnosperms give rise to: Angiosperms flowering plants Ecological advantages: enclose seeds in ovary developed flower» Showy flowers=attractive» Animals help with fertilization process Life on Land=Animals Early Triassic Three land vertebrates: amphibian group two reptilian groups: turtles primitive archosaurs

5 crocodiles phytosaurs pterosaurs Dinosaurs» Earliest=small bipedal animals Life on Land-Mammals Appeared in Late Triassic Early mammals small Inconspicuous through entire Mesozoic Early reptiles, mammals =similar skulls Life on Land=DINOSAURS!!! characterized by upright posture carrying their legs below body having a skull with two openings behind eye (diapsid) Two major groups distinguished principally on basis of hip bone structure: Saurischian dinosaur archosaur characterized by lizard-like hip Theropods Sauropodomorphs Ornithischian dinosaur Archosaur characterized by bird-like hip most species were herbivores Both Bipeds and Quadrupeds Life on Land=Size Matters Measure foot & stride length estimate size and speed of dinosaur Theropods =long strides, could move quickly Interpretation=endothermic ( warm-blooded )? Vs. ectothermic ( cold-blooded ) Gigantotherms giant ectothermic animals with body temperature and metabolic rate similar to endotherms Life on Land=Babies Dino nests, eggs =from many areas of world nesting grounds of hadrosaur Maisaura rapidly buried under shifting desert sands Cretaceous strata of Montana most revealing discoveries Late Cretaceous, 2 modern groups of mammals Placentals, Marsupials Evolved Remained small Life in the Air Archaeopteryx ancient wing Jurassic

6 Germany Oldest known bird ancestor fossils Distinctly different from Pterosaurs Flying reptiles, birds =largest animals in air Feathers in fossils: saurischian lineage had em flying reptiles don t Extinction of the Biggest-End of Cretaceous Impact of bolide Hypothesis ~65.5 mya asteroid crashed into Yucatan Peninsula of Mexico Crippled fragile ecosystems? Impact of Chicxulub bolide felt globally: Shocked quartz - quartz showing parallel sets of welded microscopic planes Time of major volcanic activity: emitted gases, dust & blocked sunlight Less sunlight, global temperatures=declined Time of Sea level drop Ecological issues? Flowering plants Co-evolution Extreme specialization among dinosaurs