Calendar of events

1. Calendar of events • Lab schedule changes: • Nov. 26 – microfossils • Dec. 3 – hominids • Dec. 10 – Lab exam #2 Earth History, Ch. 17

2. Tyrannosaurus rex Earth History, Ch. 17

3. 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

4. Today’s outline • Marine life of the Cretaceous • Pelagic marine life • Benthic marine life • Origin of the angiosperms • Terrestrial vertebrates Earth History, Ch. 17

5. 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

6. Calcareous ooze producers Earth History, Ch. 17

7. Deep sea oozes Earth History, Ch. 17

8. 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

9. 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

10. Mosasaur Earth History, Ch. 17

11. 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

12. Benthic forams Earth History, Ch. 17

13. 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

14. Rudist reef Earth History, Ch. 17

15. 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

16. Cretaceous invertebrates Earth History, Ch. 17

17. 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

18. Angiosperm diversification Earth History, Ch. 17

19. 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

20. 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

21. Maiasaur mom and “pups” Earth History, Ch. 17

22. 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

23. Dinosaur bone structure Earth History, Ch. 17

24. Late Cretaceous scene from Alberta Earth History, Ch. 17

25. Terrestrial crocodile 6 feet Total length of animal was 50 feet Earth History, Ch. 17

26. 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

27. Mammalian evolution Earth History, Ch. 17

28. Cretaceous mammal Earth History, Ch. 17