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CHANGES IN DIVERSITY
Summary of Events
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Order
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Fossil Record
Fossils• Most found in marine sedimentary rock• Three requirements:
1) need hard parts, e.g., shell, bone, teeth, wood2) remains escape destruction after death3) remains buried rapidly – stop decomposition –
minearlization process
Fossil Record
Fossils• Preserved as:
– Original soft parts = buried and preserved in permafrost, ice, saturated soils, amber…
– Original hard parts = shell, teeth, bones, wood = resist weathering
– Altered hard parts = mineralization
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Mammalian Evolution
Overview of Geological Time Scale(Mybp = million years before present)
1) Paleozoic EraDevonian Period (~408-360 Mybp)
- early in period = vascular plants invade land- diversification of bony fishes- 1st amphibians & insects (move onto land)
Mammalian Evolution
Overview of Geological Time Scale
1) Paleozoic EraCarboniferous Period (~360-286
Mybp)• large forests of vascular
plants• 1st seed plants• 1st reptiles (amniote egg)• late in period = 1st internal
fertilization
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Mammalian Evolution
Overview of Geological Time Scale
1) Paleozoic EraPermian Period (~286-248 Mybp)
• appearance of subclass Synapsida - synapsids
• Order Therapsida(therapsids) = mammal-like reptiles (mammalian grade of anatomical structure)
• reptilian adaptive radiation
Order
Synapsid Reptiles
Pelycosaur
Therapsid
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Mammalian Evolution
Overview of Geological Time Scale
1) Paleozoic EraPermian Period (~286-248 Mybp)
• Mass extinction event –largest?
• 90+% of marine species extinct
• Causes? – glaciation, reduction in ocean volume, volcanoes
• Expansion of terrestrial fauna• Pangea formation
Geologic Time Scale
Geologic Time Line
Triassic
Jurassic
Cretaceous
Tertiary
Quaternary
Mesozoic (245-66)
Cenozoic (66-0)
Period
Era:
37 64 78 64.8 1.6Duration
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Mammalian Evolution
Overview of Geological Time Scale
2) Mesozoic EraTriassic Period (~248-213
Mybp)“Dark Age of Mammals”
• therapsids declining in numbers; nearly extinct by end of period
• 1st dinosaurs • 1st mammals = descendants of
remaining therapsids; small body size (<120 mm)
Mammalian Evolution
Overview of Geological Time Scale
2) Mesozoic EraTriassic Period (~248-213 Mybp)• 1st birds• gymnosperms dominate landscape• land masses connected = supercontinent = Pangaea,
start dividing late
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Continental Drift – based on plate tectonicsi.e., continents floating on lithosphere via continually spreading ocean floor
Devonian Carboniferous Permian
Triassic Jurassic
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Biogeography
Mammalian Evolution
Overview of Geological Time Scale
2) Mesozoic EraJurassic Period (~213-144 Mybp)• Pangaea divides into Laurasia & Gondwanaland (N-S)• dinosaurs dominate land masses
Mammalian Evolution
Overview of Geological Time Scale
2) Mesozoic EraJurassic Period (~213-144
Mybp)• archaic mammals; 1st
adaptive radiation in mammals (pantotheres, multituberculates, symmetrodonts, triconodonts)
• adaptive radiation in birds
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Geologic Time Scale
Geologic Time LineTriassic
Jurassic
Cretaceous
Tertiary
Quaternary
Mesozoic (245-66)
Cenozoic (66-0)
Period
Era:
37 64 78 64.8 1.6Duration
Mammalian EvolutionOverview of Geological Time Scale
2) Mesozoic EraCretaceous Period (~144-65
Mybp)• dinosaurs extinct by end of
period• Early- (~135 Mybp)
– N. America dominate by marsupials, multituberculates & early placentals
– opossum-size mammals
Mammalian Evolution
Overview of Geological Time Scale
2) Mesozoic EraCretaceous Period (~144-65
Mybp)• Early- (~135 Mybp)
– angiosperms flourish (magnolias/tulip trees)
– insectivore/frugivoredentition
– coevolution of flowering plants & mammals (large attractive flowers)
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Mammalian Evolution
Overview of Geological Time Scale
2) Mesozoic EraCretaceous Period (~144-65
Mybp)• Early- (~135 Mybp)
– trophic specializations & foraging strategies increasing in diversity
Mammalian Evolution
Overview of Geological Time Scale
2) Mesozoic EraCretaceous Period (~144-65
Mybp)• Mid- (~115-100 Mybp)
– western N. Amer. linked to Asia
– eastern N. Amer. drifting away from Europe
– Africa & India separate from Gondwanaland
Cretaceous
Mammalian Evolution
Overview of Geological Time Scale2) Mesozoic Era
Cretaceous Period (~144-65 Mybp)
• Mid- (~115-100 Mybp)– Condylarths (ungulate
ancestors) & marsupials in "Euramerica"; also in the connected S. Amer. /Antarctica/Australia land mass
– Stage set for major independent radiations of mammals during Paleocene
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CHANGES IN DIVERSITY
Geologic Time Scale
Geologic Time Line
Triassic
Jurassic
Cretaceous
Tertiary
Quaternary
Mesozoic (245-66)
Cenozoic (66-0)
Period
Era:
37 64 78 64.8 1.6Duration
Cretaceous
Tertiary
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Mammalian Evolution
Overview of Geological Time Scale3) Cenozoic Era
Tertiary Period (65-24 Mybp)
• Paleocene Epoch (~65-54 Mybp)
– major adaptive radiation of marsupials & placentals; also birds & pollinating insects
– 1st primitive primates & carnivores
Mammalian EvolutionOverview of Geological Time
Scale3) Cenozoic Era
Tertiary Period (65-24 Mybp)
– Paleocene Epoch (~65-54 Mybp)
• marsupials move from S. Amer. through unglaciated Antarctica to Australia
• marsupials restricted to S. Amer. & Aust. refugiawhen Antarctica is glaciated
Mammalian Evolution
Overview of Geological Time Scale3) Cenozoic Era
Tertiary Period (65-24 Mybp)
• Eocene Epoch (~54-38 Mybp)– modern mammalian
orders appear– further increase in
mammalian diversity– angiosperm dominance
increases
Hyracotherium
Eohippus
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Mammalian Evolution
Overview of Geological Time Scale3) Cenozoic Era
Tertiary Period (65-24 Mybp)
• Oligocene Epoch (~38-24 Mybp)
– modern mammalian families appear
– primitive horses, camels
Mesohippus
Mammalian Evolution
Overview of Geological Time Scale3) Cenozoic Era
Tertiary Period (65-24 Mybp)
• Miocene Epoch (~24-5 Mybp)
– modern mammalian subfamilies appear
– further mammalian & angiosperm radiation
– whales, apes, grazing mammals
– spread of grasslandsMerychippusMerychippus
Overview of Geological Time Scale3) Cenozoic Era
Tertiary Period (65-24 Mybp)
• Pliocene Epoch (~5-2 Mybp)– modern mammalian genera appear– apelike ancestors of humans appear– land bridge between N. Amer. & S. Amer. forms– large carnivores
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Geologic Time Scale
Geologic Time LineTriassic
Jurassic
Cretaceous
Tertiary
Quaternary
Mesozoic (245-66)
Cenozoic (66-0)
Period
Era:
37 64 78 64.8 1.6Duration
Overview of Geological Time Scale3) Cenozoic Era
Quaternary Period (~2 Mybp - present)
• Pleistocene Epoch (~2 - 0.01 Mybp)– ice ages– humans appear– large mammal extinctions
Pliocene & Pleistocene
TeleocerasTeleocerasPliohippusPliohippus
AgriotheriumAgriotheriumAmphicyonAmphicyon
AmbelodonAmbelodon
SynthetocerasSynthetoceras
EpigalusEpigalus
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MegatheriumMegatherium
GlyptodonGlyptodon
CamelopsCamelops
Mammalian Evolution
Overview of Geological Time Scale3) Cenozoic Era
Quaternary Period (~2 Mybp -present)
• Recent Epoch (~0.01 Mybp -present)
– historic time– green & industrial
revolutions– rapid loss of biodiversity
*Largest extinction event?
Fires in South American tropical forests
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Biodiversity Hotspots
Biodiversity Hotspots
Biodiversity Hotspots
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Biodiversity Hotspots
Biodiversity Hotspots
Biodiversity Hotspots
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Biodiversity Hotspots
Biodiversity Hotspots
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