Calendar of events

1
Calendar of events

• Lab schedule changes
• Nov. 26 microfossils
• Dec. 3 hominids
• Dec. 10 Lab exam 2

2
Tyrannosaurus rex
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
4
Todays outline

• Marine life of the Cretaceous
• Pelagic marine life
• Benthic marine life
• Origin of the angiosperms
• Terrestrial vertebrates

5
Marine life of the Cretaceous

• Pelagic organisms
• Expansion of diatoms (silica), planktonic
  foraminifera (calcite) and calcareous
  nannoplankton (calcite)
• Diatoms à deep sea siliceous ooze (high
  latitudes)
• Planktonic forams calcareous nannos à deep sea
  calcareous ooze (mid- and low latitudes) (chalk!!)

6
Calcareous ooze producers
7
Deep sea oozes
8
Marine life of the Cretaceous

• Pelagic organisms
• Teleost fishes originated in Cretaceous time (the
  subclass containing todays dominant freshwater
  and marine fish)
• Ammonoids and belemnoids continued to flourish

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

10
Mosasaur
11
Marine life of the Cretaceous

• Benthic marine communities began to resemble
  those of todays oceans
• Benthic forams
• Burrowing bivalves
• Marine snails
• Crabs

12
Benthic forams
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

14
Rudist reef
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!

16
Cretaceous invertebrates
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

18
Angiosperm diversification
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)

20
Cretaceous terrestrial vertebrates

• Late Cretaceous dinosaur communities resembled
  modern mammal communities of Africa

Niche Cretaceous world Modern 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
21
Maiasaur mom and pups
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

23
Dinosaur bone structure
24
Late Cretaceous scene from Alberta
25
Terrestrial crocodile
6 feet
Total length of animal was 50 feet
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

27
Mammalian evolution
28
Cretaceous mammal