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Calendar of events. Lab schedule changes: Nov. 26 – microfossils Dec. 3 – hominids Dec. 10 – Lab exam #2. Tyrannosaurus rex. Cretaceous World. 65. Cretaceous System was named in 1822 for deposits that are “ chalky ” in many parts of the world

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calendar of events
Calendar of events
  • Lab schedule changes:
    • Nov. 26 – microfossils
    • Dec. 3 – hominids
    • Dec. 10 – Lab exam #2

Earth History, Ch. 17

tyrannosaurus rex
Tyrannosaurus rex

Earth History, Ch. 17

cretaceous world
Cretaceous World

65

  • Cretaceous System was named in 1822 for deposits that are “chalky” in many parts of the world
  • Duration of Cretaceous time is longer than any other system
  • Youngest system of Mesozoic Era

Cretaceous

System

Mesozoic Era

142

Jurassic

System

206

Triassic

System

251

Earth History, Ch. 17

today s outline
Today’s outline
  • Marine life of the Cretaceous
    • Pelagic marine life
    • Benthic marine life
  • Origin of the angiosperms
  • Terrestrial vertebrates

Earth History, Ch. 17

marine life of the cretaceous
Marine life of the Cretaceous
  • Pelagic organisms
    • Expansion of diatoms (silica), planktonic foraminifera (calcite) and calcareous nannoplankton (calcite)
    • Diatomsà deep sea siliceous ooze (high latitudes)
    • Planktonic forams & calcareous nannosà deep sea calcareous ooze (mid- and low latitudes) (chalk!!)

Earth History, Ch. 17

calcareous ooze producers
Calcareous ooze producers

Earth History, Ch. 17

slide7

Deep sea oozes

Earth History, Ch. 17

marine life of the cretaceous1
Marine life of the Cretaceous
  • Pelagic organisms
    • Teleost fishes originated in Cretaceous time (the subclass containing today’s dominant freshwater and marine fish)
    • Ammonoids and belemnoids continued to flourish

Earth History, Ch. 17

marine life of the cretaceous2
Marine life of the Cretaceous
  • Pelagic organisms
    • Ichthyosaurs and marine crocodiles became rare, but…….
    • Plesiosaurs were thriving, and even bigger than before!! Up to 35 feet long.
    • Marine lizards, mosasaurs, were bigger still!! Up to 55 feet long

Earth History, Ch. 17

mosasaur
Mosasaur

Earth History, Ch. 17

marine life of the cretaceous3
Marine life of the Cretaceous
  • Benthic marine communities began to resemble those of today’s oceans
    • Benthic forams
    • Burrowing bivalves
    • Marine snails
    • Crabs

Earth History, Ch. 17

benthic forams
Benthic forams

Earth History, Ch. 17

marine life of the cretaceous4
Marine life of the Cretaceous
  • Surface-dwelling bivalves became spectacular
    • Coiled oysters reach softball size and larger
    • Rudists
      • imitated corals in ecology
      • formed large tropical reefs

Earth History, Ch. 17

rudist reef
Rudist reef

Earth History, Ch. 17

marine life of the cretaceous5
Marine life of the Cretaceous
  • By end of Mesozoic time, few immobile animals lived on seafloor (in contrast to Paleozoic time)
  • Brachiopods, stalked crinoids, bryozoans were largely replaced by mobile and predatory bivalves, snails, crustaceans
  • Teleost fishes were efficient predators, too!

Earth History, Ch. 17

cretaceous invertebrates
Cretaceous invertebrates

Earth History, Ch. 17

rise of the angiosperms
Rise of the angiosperms
  • Gymnosperms continued to dominate terrestrial floras in Cretaceous (just as in Triassic and Jurassic)
  • Angiosperms initial appearance was in middle Cretaceous time
    • Double-fertilization and enclosed seeds
    • Flowers (for attracting insects)
    • Faster reproductive cycles

Earth History, Ch. 17

angiosperm diversification
Angiosperm diversification

Earth History, Ch. 17

angiosperms and insects
Angiosperms and insects
  • Co-evolution of angiosperms and insects
    • Certain species of insects are specialized to feed only on certain flowers
    • Certain species of angiosperms are specialized to attract only certain insects
    • Result is an increase in rates of speciation (taxonomic diversification)

Earth History, Ch. 17

cretaceous terrestrial vertebrates
Cretaceous terrestrial vertebrates
  • Late Cretaceous dinosaur communities resembled modern mammal communities of Africa

NicheCretaceous worldModern world

Grazing herds duck-billed dinos wildebeests, antelopes, maiasaurs zebras

Nasty herbivores horned dinos rhinoceroses

Carnivores T. rex, terrestrial crocs lions

Flying scavengers flying reptiles vultures

Earth History, Ch. 17

maiasaur mom and pups
Maiasaur mom and “pups”

Earth History, Ch. 17

warm blooded dinosaurs
Warm-blooded Dinosaurs?
  • Evidence in support of endothermy
    • Cretaceous dinos lived in high latitudes
    • Birds are warm-blooded, and birds are highly specialized dinosaurs
    • Dinosaur bone structure resembles that in warm-blooded mammals
      • Haversian canals

Earth History, Ch. 17

dinosaur bone structure
Dinosaur bone structure

Earth History, Ch. 17

terrestrial crocodile
Terrestrial crocodile

6 feet

Total length of

animal was 50 feet

Earth History, Ch. 17

cretaceous mammals
Cretaceous mammals
  • Remained small and inconspicuous
  • Relatively well developed sense of smell and hearing
    • Enlarged brain areas associated with those senses
    • Adaptation for nocturnal activity?
  • By late Cretaceous time, placental and marsupial groups had differentiated

Earth History, Ch. 17

mammalian evolution
Mammalian evolution

Earth History, Ch. 17

cretaceous mammal
Cretaceous mammal

Earth History, Ch. 17