Earth History, Ch. 18 1

Western U.S.orogenies

Earth History, Ch. 18 2Late Cretaceous 75 Ma

Earth History, Ch. 18 3K/T boundary 65 Ma

Earth History, Ch. 18 4

The Paleogene World

• Two-fold subdivision of Cenozoic: Paleogene, Neogene

• Previously, Cenozoic was divided into Tertiary (Paleocene-Pliocene) and Quaternary (Pleistocene-Holocene)

• Know periods and epochs!

Cen

ozoi

cPaleogene

Neogene

Paleocene

Eocene

Oligocene

Miocene

Pliocene

HolocenePleistocene

65

24

Earth History, Ch. 18 5

Paleogene life

• In marine realm, most groups that survived end-Cretaceous mass extinction recovered and diversified during Paleogene– Planktonic forams, calcareous

nannos, mollusks, arthropods

• Demise of giant marine reptiles opened the door to whales (Eocene) and giant sharks!

Earth History, Ch. 18 6

Whale evolution (Eocene-Holocene)

Terrestrial ancestor

Large, marineforms

Earth History, Ch. 18 7

Earth History, Ch. 18 8

Giant Eocene shark

Modern shark jaws

Earth History, Ch. 18 9

Paleogene life

• Other interesting newcomers to marine or marginal marine habitats:– Penguins – Pinnipeds (seals, sea lions, walruses)

Earth History, Ch. 18 10

Paleogene life

• On land…………..– Diversification and “modernization” of angiosperms

– By early Oligocene time, half of all angiosperm genera were ones that still exist today

• Origin of grasses– Earliest forms were sedge-like (discontinuous growth)

– Late Oligocene-Neogene forms capable of continuous growth (able to withstand grazing pressure)

Earth History, Ch. 18 11

Paleogene life

• Explosive adaptive radiation of mammals!– By Eocene time, most

modern orders of mammals had appeared, including primates, carnivores and horses

Cantius, climbing around inour family tree!

Earth History, Ch. 18 12

Earth History, Ch. 18 13

Earth History, Ch. 18 14

Eocene fossil bat

Earth History, Ch. 18 15

Hyracotherium (“Eohippus”)earliest horse

Dog-sized

4 toes

3 toes

Earth History, Ch. 18 16

Earth History, Ch. 18 17

Diacodexis(early even-toed ungulate)

Earth History, Ch. 18 18

Eoceneelephants

Earth History, Ch. 18 19

Diatryma(a top predator--stay away from this turkey!)

8 ft

Earth History, Ch. 18 20

Earth History, Ch. 18 21

Paleogene life

• Oligocene was noteworthy for:– Paraceratherium, largest land mammal ever

(member of rhino family)– Origin of true monkeys– Expansion of big cats

Earth History, Ch. 18 22

Paraceratherium

18 ft at shoulder

Earth History, Ch. 18 23

Aegyptopithecus(Oligocene monkey)

Earth History, Ch. 18 24

Dinictis(Oligocene saber-tooth cat)

Earth History, Ch. 18 25

Oligocene mammalian fauna of Nebraska & South Dakota

Earth History, Ch. 18 26

Paleogene life

• Many groups of mammals became extinct during Eocene time or at the Eocene—Oligocene boundary

• Climate change probably is responsible for extinctions

Earth History, Ch. 18 27

Earth History, Ch. 18 28

Paleogene paleogeography and climate

• Beginning in late Eocene, climate rapidly became cooler and drier– Relatively heavy oxygen isotope ratios

(consistent with growth of continental glaciers)– Establishment of circum-polar currents around

Antarctica

Earth History, Ch. 18 29

Evidence for climate change

Earth History, Ch. 18 30

Antarcticcircumpolarcurrent

SA

ANTAU

Earth History, Ch. 18 31

Continued break-up of Pangaea