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Lab 12

Life of the Paleozoic

Chapters 13, 14 & 15 in Stanley

Review of Precambrian Life included.

To Begin:

A review of

Precambrian Life

(You may want to refer

to the geologic time scale.)

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Precambrian Life

Oldest fossils: 3,600

million years old

Dates are debated.

Possibly some older—

please watch the research

Stromatolites: algal mats

made by cyanobacteria

(the oldest fossils)

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Precambrian Life

Stromatolites: algal mats

made by cyanobacteria

(the oldest fossils)

El Paso: Precambrian

stromatolites in the

Castner Marble in the

Franklin Mountains.

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Cliff face of stromatolites

Precambrian Life

Australia:

Still living

cyanobacteria

creating

stromatolites

(Note the

shovel for

scale.)

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Precambrian Life

Oldest fossils: 3,600 million years old

All Archean fossils are prokaryotes—one cell

without a nucleus

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Precambrian Life

2,700 million years ago

First eukaryotes: one cell with a nucleus (a major evolutionary step)

Prokaryotes still dominate

Evidence of photosynthesizing cyanobacteria (start to release oxygen)

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Precambrian Life

1,700 million years ago

Multicellular algae

900 million years ago

Multicellular worms (China) – metazoans – multicellular animals

Don’t bother to memorize these numbers.

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Precambrian Life

Late Proterozoic animals

Ediacara Fauna (soft-bodied organisms)

Named after hills in Australia where first found

All soft-bodied animals: algae, jellyfish, worms,

strange stuff

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Precambrian Life

Some shell fragments (580 mya)

The beginning of the Phanerozoic (from Greek for

visible life)

Cambrian—542 mya: Know this date!

hard-bodied organisms (shells)

The Cambrian Explosion! – invertebrate

fossils “suddenly” become abundant worldwide

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Note:

Epeiric Sea -- Refers to shallow sea the covers

the continent (the mainland)

Also called epicontinental seas

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The Paleozoic Seven Periods—Know these

Geologic Time Scale—inside front cover of lab book

Can Oscar See Down My Pants Pocket?

Cambrian (oldest)

Ordovician

Silurian

Devonian

Mississippian

Pennsylvanian

Permian (youngest)

Trichophycus Marks the base of the Cambrian

Trace fossil: a burrow

(Do NOT memorize)

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http://www.envs.emory.edu/faculty/MARTIN/ichnology/Trichophycus.htm

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At the beginning of the Paleozoic…

Major hard shell organisms appear—The

Cambrian Explosion

Marks the end of the Precambrian

Marks the beginning of the Phanerozoic (time scale)

Many, many soft shell organisms—these still

dominate

Marine invertebrates are dominant life forms

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A Brief Overview of the

Paleozoic—The Sequence

Animals with skeletons appear abruptly and

widely (Exoskeletons—shells. The “Cambrian Explosion”)

Fish evolve (Cambrian—jawless fish)

Plants go ashore (Ordovician) before animals

From fish—first land animals: amphibians (give

birth in the water—e.g.: frogs) (Devonian)

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A Brief Overview of the Paleozoic

From amphibians—reptiles (lay hard-shelled

eggs—no need to be near water to reproduce,

e.g.: alligators and crocodiles) (Pennsylvanian)

The ending—the greatest extinction in the

history of Earth (Note: This is not the

extinction of the dinosaurs.)

Paleozoic

Epeiric Seas

Do not memorize these

sea names.

Deposition.

What is going on with

the continents?

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The Sauk Sequence

The Sauk Sea

•First major

transgression

•Late Cambrian

to Early

Ordovician

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The Sauk Sequence

The Sauk Sea

•An epeiric sea—

covered El Paso

•A period of

deposition (Bliss

Sandstone and El

Paso Group—

limestone and

dolostone

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Regression

Early to Middle Ordovician

Sauk Sea regressed

Unconformity developed--erosion

The Tippecanoe

Sequence

•Late Ordovician

•Transgression—the

Tippecanoe Sea

(note mobile belts)

•More extensive

than the Sauk Sea

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The Tippecanoe

Sequence

•Most of North

America was under

sea level

•Deposition in El

Paso of the

Montoya Group of

limestone and

dolostone (shallow

sea deposits)

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The Kaskaskia Sequence

•Regression by late

Silurian—erosion—

unconformity

•Late Devonian to

Mississippian

•The Kaskaskia Sea

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The Kaskaskia Sequence

•Mud rather than

limestone: black

shale deposits—the

Percha Shale

•Then limestone—

Las Cruces

Formation in El

Paso area

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The Kaskaskian Regressed

Late Mississippian

Clastic deposition

El Paso: interbedded sandstone and limestone

Then: erosion and unconformity—obvious in North

America, absent in rest of the world (Rest of world

speaks of Carboniferous rather than Mississippian-

Pennsylvanian)

The Absaroka Sequence

•Late Mississippian & Early Pennsylvanian

•Small scale transgressions and regressions: cyclothems—many coal deposits

in the eastern U.S.

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The Absaroka Sequence

•Regressed during the Permian

•Guadalupe Mountains: Permian reef deposits

•Late Permian rocks missing or redbeds (exposed to oxygen)

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The Absaroka Sequence

Pangea has formed—one supercontinent

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End of Review

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Life of the Paleozoic

Please open your lab book to the

geologic time scale.

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The Paleozoic (Cambrian)

The Earliest Organisms

with Hard Parts Appear

Proterozoic animals with calcareous tubes (define

calcareous)

Microscopic fossils with shells

Large animals (we can see them with our eyes)

with shells (exoskeletons) during Cambrian

Explosion

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A Quick Look at Today’s

Marine Invertebrates

Pelagic—organisms that live above the sea

floor

Plankton: floaters

Nekton: swimmers

Benthonic—organisms that live on or in the sea

floor

Sessile: stay in one place

Mobile: move about

(6 words to know)

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The Cambrian Explosion

Animals with skeletons suddenly appear (mostly

external skeletons--shells) Note: “suddenly”

occurred over millions of years

Why this occurred: still hotly debated

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The Major Players in the Early

Paleozoic—the Cambrian

Trilobites—extinct by end of Paleozoic

Brachiopods

Archaeocyathids—reef builders

(See next slides for examples.)

Life

Trilobites

•Most common

Cambrian fossil

•Extinct by end

of Paleozoic

•Declined during

the Silurian

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Brachiopods (Phylum) Still alive today. Bilateral Symmetry

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Brachiopods Still alive today.

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Invertebrates

Bilateral symmetry

Two part shell

Top

Bottom

Example: oysters

Archaeocyathids (Phylum)

(Ancient Cups) Reef Building Sponges--Extinct

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Major Phyla Marine invertebrates

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Sarcodina (Phylum)

Single celled Eukaryotes

Forams Radiolaria

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Ordovician: World-wide epeiric seas—rapid radiation

and diversification of marine invertebrates

Brachiopods--First appear during the

Cambrian——bilateral symmetry

Bryozoans—twig-like fossils

Graptolites—extinct plankton (Which means?)

Arthopods (jointed foot)—lobsters, etc.

Mollusks—Clams, snails, squid, etc.

Gastropods (stomach-foot)

Cephalopods (head-foot)—straight cone or coiled in

a plane (nautilus, etc.)

Graptolites Extinct Plankton

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Bryozoans (Moss Animals) Still Living

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Modern Bryozoans

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More Invertebrates

Tabulate corals-extinct after Permian

Rugose corals—extinct after Permian

Sponges

Echinoderms (five-way radial symmetry)—

starfish, etc.

Echinoderms (Spiny Skinned)--Living

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Paleozoic Marine Vertebrates

Chordate Phylum: all animals with full spinal

cord

Oldest chordates date from beginning of

Cambrian (invertebrates dominated, but

vertebrates present): Jawless fish

Jawless Fish Earliest Chordates (Spinal Cord)

Still living

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Conodonts (Teeth)

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Conodonts—tooth-

like fossils: parts of

chordates

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More Fish

Devonian (the age of fish): two groups

Bony fish

Ray finned bony fish

Lobe finned bony fish

Cartilaginous fish (discuss)—primitive sharks

Cartilaginous fish (No bones)

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Bony Fish

Ray finned

Lobe finned

(evolved into

amphibians)

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Tiktaalik Fossil (Late Devonian)

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Tiktaalik (Lobe-finned fish)

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Late Devonian

Tetrapod—a

4-footed

animal

An amphibian

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Coelacanth Living lobe-finned fish

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Foraminifera Microscopic Floaters--Extinct

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Stromatolites—The Structures

Created by Still-living

Cyanobacteria

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Paleozoic Plants

Oldest plants: Middle Ordovician fossil spores (Algae are not plants.)

Land organisms first appeared late Ordovician

Plants were first on land (Why plants before

animals?)

Lots of land plants by late Paleozoic

Took a while—needed ozone layer (Why?)

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Life Evolved

Silurian: small multicellular plants on land

First: rigid stems without roots or vascular system

Then: vascular plants with roots and leaves

Devonian: creepers, restricted to damp areas

Late Devonian: seed plants—freedom!

(no flowers until the late Mesozoic)

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Pennsylvanian

Gymnosperms (naked seed) plants evolved (pine

trees—pine cones)

Forests develop

Glossopteris—a fern in Gondwana that Wegener

used to determine the extent of Gondwana

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Paleozoic Land Animals

Lungs, shoulder and hip bones: crosspterygians

could crawl on land. (Remember Tiktaalik)

These fish evolved into amphibians (Late

Devonian—abundant in the Mississippian and

Pennsylvanian)

Amphibians: restricted to land/water habitat

(frogs, for example)—lay there eggs in water (no

egg shell)

Early

Pennsylvanian

One group of

amphibians

developed the

amniotic egg:

hard shell and

liquid sac for

food 64

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These are reptiles

Lay eggs on dry land

Move away from water

Colonize land and become dominant

terrestrial vertebrates

Pelycosaurs—(Not dinosaurs)

•Pennsylvanian:

pelycosaurs

evolved

•Fin-back reptiles

(not dinosaurs)

•Go extinct by

end of Permian

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Pely…--pelvis

This is Dimetrodon

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More evolution

Therapsids—replaced pelycosaurs—”mammal-

like” reptiles with some temperature regulation

(these dominated)—ancestors of mammals

Root words: wild beast + arch of the skull

Thecodonts—”reptile-like” reptiles

Root words: case & teeth set in sockets

(More when we look at the Mesozoic)

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More evolution

End of Paleozoic: 90% of all reptiles are

therapsids (ancestors of mammals)

Decline at end of Paleozoic—survivors evolve

into mammals

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Invertebrates on Land

Arthopods (jointed foot)

Eurypterids evolve into scorpions and spiders

Insects (Devonian)

Late Paleozoic: dragonflies and cockroaches

Extinctions

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Greatest Extinction Ever!

Dinosaurs

(& others) go

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The Really, Really Big Extinction (Not when the dinosaurs went extinct)

End of Paleozoic (end of Permian)

Land organisms suffered most (Why land?)

75% of amphibians extinct

80% of reptiles extinct

Land plants change significantly

50% of marine invertebrates go extinct

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The End of the Paleozoic

Pangea forms

Biggest mass extinction ever

Lose a lot of marine life

Trilobites

Fusilinids

Graptolites

Tabulate corals

Rugose corals

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A Key Point!!

Extinctions happen due to a change in the

environment

Late Permian—Pangea formed: only one land

mass on earth—connected: no ocean barriers

Mountains uplifted, eroded, shed clastic

material—major regressions of epeiric seas

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The Reason for Extinction

(maybe…)

Meteorite impact (ancient crater off of Australia – much debate!)

Environmental changes occurring with the formation of Pangea

Diverse habitat disappeared

Weather patterns changed

Volcanic eruptions—A widely held view

Oxygen decrease (down to ~10%?)

(cutting edge research!—we need to watch this one)

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Any questions?

Please do lab 12.