Summary of Events

Fossil Record

Fossils • Most found in marine sedimentary rock• Three requirements:

1) need hard parts, e.g., shell, bone, teeth, wood

2) remains escape destruction after death

3) 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

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 Era

Carboniferous Period (~360-286

Mybp)

• large forests of vascular plants

• 1st seed plants

• 1st reptiles (amniote egg)

• late in period = 1st internal fertilization

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

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

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

Continental Drift – based on plate tectonicsi.e., continents floating on lithosphere via continually spreading ocean floor

Devonian Carboniferous Permian

Triassic Jurassic

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 Era

Jurassic Period (~213-144 Mybp)

• archaic mammals; 1st adaptive radiation in mammals (pantotheres, multituberculates, symmetrodonts, triconodonts)

• adaptive radiation in birds

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

Mammalian Evolution

Overview of Geological Time Scale

2) Mesozoic Era

Cretaceous 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 Era

Cretaceous Period (~144-65 Mybp)

• Early- (~135 Mybp)

– angiosperms flourish (magnolias/tulip trees)

– insectivore/frugivore dentition

– coevolution of flowering plants & mammals (large attractive flowers)

Mammalian Evolution

Overview of Geological Time Scale

2) Mesozoic Era

Cretaceous Period (~144-65 Mybp)

• Early- (~135 Mybp)

– trophic specializations & foraging strategies increasing in diversity

Mammalian Evolution

Overview of Geological Time Scale

2) Mesozoic Era

Cretaceous 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 Scale 2) 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

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

Mammalian Evolution

Overview of Geological Time Scale 3) 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

Scale 3) 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. refugia when Antarctica is glaciated

Mammalian Evolution

Overview of Geological Time Scale 3) 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

Mammalian Evolution

Overview of Geological Time Scale 3) 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 Scale 3) 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 Scale 3) 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

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

Overview of Geological Time Scale 3) Cenozoic Era

Quaternary Period (~2 Mybp - present)

• Pleistocene Epoch (~2 - 0.01 Mybp)– ice ages– humans appear– large mammal extinctions

Pliocene & PleistocenePliocene & Pleistocene

TeleocerasTeleocerasTeleocerasTeleocerasPliohippusPliohippusPliohippusPliohippus

AgriotheriumAgriotheriumAgriotheriumAgriotheriumAmphicyonAmphicyonAmphicyonAmphicyon

AmbelodonAmbelodonAmbelodonAmbelodon

SynthetocerasSynthetocerasSynthetocerasSynthetoceras

EpigalusEpigalus

MegatheriumMegatherium

GlyptodonGlyptodon

CamelopsCamelops

Mammalian Evolution

Overview of Geological Time Scale 3) 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

Biodiversity Hotspots

Biodiversity Hotspots

Biodiversity Hotspots

Biodiversity Hotspots

Biodiversity Hotspots

Biodiversity Hotspots

Biodiversity Hotspots

Biodiversity Hotspots