GSC 111 Chapter 17: Chapter 17
13 Jan 2017
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Chapter 17: The Cretaceous World
1. Cretaceous Life
a. Marine realm
i. Modern bivalves and gastropods
ii. Enormous coiled oysters and now-extinct bivalves
iii. Diverse fishes of the modern kind
iv. Ammonoids, belemnoids, reptilian sea monsters \
b. Dinosaurs ruled the land
c. Mammals were quite small
d. Pelagic life was modernized
i. New groups of single-celled organisms
1. d of diatoms
2. Diatoms, dinoflagellates, and calcareous nanoplankton accounted
for the majority of photosynthesis in the oceans like modern times
ii. Modern planktonic foraminifera diversified greatly for the first timews3
iii. Teleost fish, subclass that today is the most common group of fish
1. Bony fish characterized by
a. Symmetrical tails
b. Overlapping scales
c. Specialized fins
d. Short jaws
e. Benthic life was also modernized
i. Decline of brachiopods
ii. Foraminifera
1. A large percentage of the families of foraminifera that exist todat
appeared during this period
iii. Bryozoans
1. Cheilostomes, the most common group of bryozoans today,
radiated
iv. Burrowing bivalve mollusks
1. Burrowers that burrowed rapidly and deep into the sediment
appeared
v. Gastropod mollusks
1. Snails began to appear
vi. Crabs
1. Much greater variety appeared
vii. Surface-dwelling bivalve mollusk
f. Modern marine predators proliferated
i. Teleost fish
ii. Modern crabs
iii. Carnivorous gastropods
iv. Efficient at penetrating shells by biting, crushing or peeling with claws,
and drilling hioles
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g. Flowering plants expanded on land
i. Included plants with flowers but also hardwood trees like maples and oaks
as well as grasses
ii. The earliest angiosperm floras
1. Earliest leaves had simple, smooth outlines
a. Supporting veins branch in irregular patterns
iii. Secrets of angiosperm success
1. Ability to provide a food supply for their seeds by a process known
as double fertilization
a. One fertilization event produces a seed and a second
produces a supply of stored food for that seed
b. Allows for quick release of a well-fortifed seed
2. Thousands of flowering plant species can grow from a seed and
then release seeds of their own in just a few weeks
3. Ability of flowers to attract insects
a. Insects carry pollen from one flower to another, fertilizing
the plants on which they feed
h. Dinosaurs dwarfed early mammals
i. Dinosaurs formed a community that has been compared with the modern
mammalian fauna of the African plains
1. Instead of antelopes, zebras, and wildebeests, there were many
species of duck-billed dinosaurs
2. Instead of rhinoceros, there were horned dinosaurs
ii. Skies were also dominated by dinosaurs
iii. Mammals appeared in the Mesozoic Era
1. They remained small until the end of the Cretaceous because
dinosaurs had originated before them and had been better poised to
take over terrestrial habitats when the terminal Triassic mass
extinction decimated the therapsides
2. Dinosaurs prevented mammals by growing in body size through
predation
2. Paleogeography of the Cretaceous World
a. Continents fragmented and narrow oceans expanded
i. Continued fragmentation of Pangaea and dispersion of daughter continents
ii. South America, Africa, and India all separated from Gondwanaland
iii. Caused narrow oceans to widen
iv. Greenland broke away from North America
v. Opening of the South Atlantic Ocean, Gulf of Mexico, Caribbean Sea
b. Sea level rose, the deep ocean stagnated, and climates warmed
i. Global sea level rose
1. Marine deposits blanketed most continents
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