Life of Mesozoic Marine life in Mesozoic (except reptiles) are modern marine fauna Recall: Permian end extinction 90% of marine fauna extinct Gone are the: Colonies of crinoids, blastoids, horn corals, brachiopods Fusulinids 1
Mesozoic Marine Revolution Planktonic Radiation Fuels Revolution Defensive Adaptations Allow Revolution Mollusks & Gastropods Radiate Not Brachiopods Not competition - all present in Paleozoic Defenses: Burrow, swim, & thick-, spinyshells Echinoderms loose stalks Stubby crinoids, burrowing, or mobile urchins Marine Predators: Not in Kansas anymore! Mesozoic Plankton Revolution Phytoplankton diversity fueled radiation of filter feeders (and in turn, Predators)! Diatoms - Si-test, phytoplankton First in Jurassic, radiate in Cretaceous 2
Mesozoic Plankton Revolution Coccolithophores Phytoplankton - algae Calcite test (C and O isotope studies) Cretaceous Chalk! Mesozoic Plankton Revolution Foraminifera Zooplankton Calcite Test - C and O isotope studies Feed on phytoplankton 3
Mesozoic Marine Predators Adapted to Eat at the smorgasbord Teeth for crushing: Fish, Sharks, Rays, Reptiles Jurassic fish Dapedius Mesozoic Marine Predators Adapted for Eating: Crushing reptile Placodont Skull 4
Other Marine Reptiles: This is a return to the water! Survivors today: turtles, alligators Some can t return to land: Live Birth (Ichthyosaurs)! Mesozoic Marine Predators Adapted for Eating Crustaceans (lobsters & crabs) with crushing pinchers Drilling Mollusks - bore into shells and suck out prey Ammonoids develop crushing jaws & piercing beaks Reptiles 5
Mesozoic Marine Predators Adaptation for chasing prey: Fish develop swim bladders (modern fish = teleost Ammonites: Mesozoic Index Fossil Huge radiation from 2 surviving species >100 genera Suture pattern complexity increase Allows id of species 6
Belemnoids too: cephalopod Modern Corals evolve in Triassic Small reefs (Devonian reef builders are extinct!) Large Reefs develop in Mid-Triassic into Jurassic May indicate development of symbiotic relationship between coral and algae Reef Builders: 7
Cretaceous Reef Builders Strange Bivalves dominate reefs Rudistid Clams Large clams grow together and on each other Rudistid and others extinct at end of K Cretaceous Marine Fauna 8
Mesozoic Land Plants Recall: Gymnosperms (Conifers) and seed ferns evolved in Permian Triassic: Gymnosperms supplant seed ferns Cycads (palms), Gingko, and conifers This is tough on herbivores Spiny, toxic leaves & slow growing Thus, ferns likely food source Mesozoic Land Plants Triassic: Gymnosperms supplant seed ferns Cycads (palms), Ginkgo, and conifers This is tough on herbivores Spiny, toxic leaves & slow growing Thus, ferns likely food source 9
Rise of Angiosperms Flowering Plants Attract insects Fruit, nut for seed dispersal Initially small weedy things, then trees Support great numbers of Herbivore Dinos!!! Evolve in Mid- Cretaceous Co-evolve with bees and moths insures pollination & rapid transfer of mutation 100s of species in K including Families of Sycamore, magnolia, holly, palm, oak, walnut, birch Flowering Plants Attract insects Fruit, nut for seed dispersal Initially small weedy things, then trees Support great numbers of Herbivore Dinos!!! Evolve in Mid- Cretaceous Co-evolve with bees and moths insures pollination & rapid transfer of mutation Rise of Angiosperms 10
Dinosaurs: Evolve from Reptiles in Triassic First Dinos Small Bipedal - legs in line w/hips Late Triassic Radiation Saurischians & Ornithischians Lizard-snake Reptiles Pterosaurs Crocodilian Reptiles Archosaurs Dinosaurs Euparkoria (bi-pedal) Reptiles Evolution of Dinosaurs Synapsid reptiles & Amphibians going extinct Niches filled by radiating dinos Saurichians = lizard hip Sauropods -BIG, herds, nests, protect young Carnivorous Dinos Birds! 11
Evolution of Dinosaurs Ornithischians = Bird -hip (no birds though) Herbivores Think rhinos and hippos Fast Moving Predators Likely warm blooded - high level of activity Smart: herding or stampeding of prey Hunting in packs! Examples: Tyrannosaurus, Deinonychus (evil claw) - Birds evolve from him Pterosaurs = flying dino-like, huge, albatross/condor 12
Mammal Evolution From Therapsids (reptiles) Late Triassic Small, mouse- to cat-sized Nocturnal, eat insects But, they have big brains! (complex behavior). Mammals Layed eggs initially like duckbilled platypus & spiny anteater Evolved to Two types: Marsupials (pouched) Embryo climes to pouch 3 young at different stages Placentals Advanced infant Risky, but young are well developed 13
Triassic Jurassic Cretaceous 14
Mass extinctions of Mesozoic Mass Extinctions of Mesozoic: Triassic Large M.E. of terrestrial and marine organisms 20% of all Animalia Cause: Unknown Perhaps change to Arid Climate Gymnosperms replace spore plants of Gondwanaland lowlands 15
Triassic Extinctions: Gone: Most Ammonites & mollusks Large Amphibians Some Reptiles (mammal-like) Dinos Radiate And Flourish Jurassic Extinction: Moderate Both marine and terrestrial Incomplete fossil record - incomplete information Stegosaurian & Large Sauropods (the elephants and rhinos of Dinos) Bye-bye Big Guys 16
Cretaceous Extinction: Large Third largest of Phanerozoic (P>O>K) 50% of all organisms - NOT just Dinos! Marine mostly tropical, Climate change or Regression? And Terrestrial All are gradual - begin before K/T, extend into T Fossil Record Problems? Preservation vs. gradual extinction Abrupt extinction OR unconformity? Any Hypothesis Food Web (Dinos = top of food chain) Dinos extinct b/c of angiosperms Wrong. In fact dinos radiate b/c of angios. Dinos extinct b/c competition w/mammals Wrong. They coexist for ~150 ma K extinction: Marine Predators Gone: Ammonites (only chambered Nautilus today) Reptiles (dominant predator): 17
K extinction: Plankton & Filter Feeders Gone: Forams & Coccoliths - reappear in Tertiary - C & O isotopes indicate cooling seas! Rudists (mollusks) & Brachiopods K Ext: Terrestrial Life Gone: Dinosaurs -Gradual extinction begins before K/T - <10 species just below K/T 18
K Ext: Terrestrial Life Angiosperms decline - not gone, rebound - Niches filled by Ferns K Extinction: Unaffected Birds survive. STRANGE, Not small dinos. Turtles and Crocodiles. STRANGE, they cannot hibernate Snakes, Lizards, and mammals Any Extinction Hypothesis must explain their survival! 19
Hypotheses #1: Impact W. Alvarez wanted to estimate sediment accumulation rate Using Ir and indicator of cosmic dust accumulation Clay at K/T (serendipity) too rich in Ir - must be impact! Impactor ~ 10 km diameter Site unknown - Chicxulu (?) Impact Evidence 20
Impact Problems: Can t explain gradual decline/extinctions Unless many meteorites over time Problem: won t make Ir spike! Hypothesis #2: Flood Basalt Volcanism Climate change from Volcanic gasses CO 2, (Ir) etc. Volcanic Ash Deccan Traps of India and Parana Flood Basalts of Brazil Age ~ 5 Ma of K/T Explains all restrictions best 21
Hypothesis #2: Regression One of largest regressions in Earth history at this time Reduced benthic habitat - epeiric seas gone! Shown to effect terrestrial life too. CAUSE OF K/T UNKNOWN Must explain all data Possible combination of all hypotheses? Hypothesis #3: Combination Impact effects photosynthesis (nuclear winter) and disrupts food webs dependant on primary producers (marine and terrestrial) This does not effect food webs based on detritus feeders (worms, fungi, etc.) - I.e. many mammals not effected! Regression and volcanism still operate to enhance mass extinctions. 22