Post on 12-Jan-2016
transcript
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
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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