Chapters 13, 14 & 15 in Stanley
Review of Precambrian Life included.
1

To Begin:
(You may want to refer to the geologic time scale.)
2

Precambrian Life


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Oldest fossils: 3,600 million years old
Dates are debated.
Possibly some older— please watch the research
S tromatolites : algal mats made by cyanobacteria
(the oldest fossils)
3

Precambrian Life

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S tromatolites : algal mats made by cyanobacteria
(the oldest fossils)
El Paso: Precambrian stromatolites in the
Castner Marble in the
Franklin Mountains.
Cliff face of stromatolites
4

Precambrian Life


Australia:
Still living cyanobacteria creating stromatolites
(Note the shovel for scale.)
5

Precambrian Life

Oldest fossils: 3,600 million years old

All Archean fossils are prokaryotes—one cell without a nucleus
6

Precambrian Life

2,700 million years ago

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First eukaryotes: one cell with a nucleus (a major evolutionary step)
Prokaryotes still dominate

Evidence of photosynthesizing cyanobacteria (start to release oxygen)
7

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.
8

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
9

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
10

Note:

Epeiric Sea -- Refers to shallow sea the covers the continent (the mainland)

Also called epicontinental seas
11

The Paleozoic
Seven Periods—Know these
Geologic Time Scale—inside front cover of lab book
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
Can Oscar See Down My Pants Pocket?
Cambrian (oldest)
Ordovician
Silurian
Devonian
Mississippian
Pennsylvanian
Permian (youngest)
12

Trichophycus
Marks the base of the Cambrian
Trace fossil: a burrow
(Do NOT memorize) http://www.envs.emory.edu/faculty/MARTIN/ichnology/Trichophycus.htm
13

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
14

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)
15

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.)
16

Paleozoic
Epeiric Seas
Do not memorize these sea names.
Deposition.
What is going on with the continents?
17

The Sauk Sequence
The Sauk Sea
•
First major transgression
•
Late Cambrian to Early
Ordovician
18

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
19

Regression

Early to Middle Ordovician

Sauk Sea regressed

Unconformity developed--erosion
20

The Tippecanoe
Sequence
•
Late Ordovician
•
Transgression—the
Tippecanoe Sea
(note mobile belts)
•
More extensive than the Sauk Sea
21

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)
22

The Kaskaskia Sequence
•
Regression by late
Silurian—erosion— unconformity
•
Late Devonian to
Mississippian
•
The Kaskaskia Sea
23

The Kaskaskia Sequence
•
Mud rather than limestone: black shale deposits—the
Percha Shale
•
Then limestone—
Las Cruces
Formation in El
Paso area
24

The Kaskaskian Regressed

Late Mississippian

Clastic deposition

El Paso: interbedded sandstone and limestone
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Then: erosion and unconformity—obvious in North
America, absent in rest of the world (Rest of world speaks of Carboniferous rather than Mississippian-
Pennsylvanian)
25

The Absaroka Sequence
•
Late Mississippian
& Early
Pennsylvanian
•
Small scale transgressions and regressions: cyclothems —many coal deposits in the eastern U.S.
26

The Absaroka Sequence
•
Regressed during the Permian
•
Guadalupe
Mountains: Permian reef deposits
•
Late Permian rocks missing or redbeds
(exposed to oxygen)
27

The Absaroka Sequence
Pangea has formed—one supercontinent
28

29

Please open your lab book to the geologic time scale.
30

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
31

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)
32

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
33

The Major Players in the Early
Paleozoic—the Cambrian
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Trilobites—extinct by end of Paleozoic
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Brachiopods
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Archaeocyathids—reef builders
(See next slides for examples.)
34

Life
Trilobites
•
Most common
Cambrian fossil
•
Extinct by end of Paleozoic
•
Declined during the Silurian
35

Brachiopods (Phylum)
Still alive today. Bilateral Symmetry
36

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Invertebrates
Brachiopods
Still alive today.
Bilateral symmetry
Two part shell


Top
Bottom
Example: oysters
37

Archaeocyathids (Phylum)
(Ancient Cups)
Reef Building Sponges--Extinct
38

Major Phyla
Marine invertebrates
39

Sarcodina (Phylum)
Single celled Eukaryotes
Forams Radiolaria
40

Ordovician: World-wide epeiric seas—rapid radiation and diversification of marine invertebrates

Brachiopods--First appear during the
Cambrian——bilateral symmetry
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Bryozoans—twig-like fossils
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Graptolites—extinct plankton
(Which means?)
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Arthopods (jointed foot)—lobsters, etc.
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Mollusks—Clams, snails, squid, etc.
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Gastropods (stomach-foot)
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Cephalopods (head-foot)—straight cone or coiled in a plane (nautilus, etc.)
41

Graptolites
Extinct Plankton
42

Bryozoans (Moss Animals)
Still Living
43

Modern Bryozoans
44

More Invertebrates
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Tabulate corals-extinct after Permian
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Rugose corals—extinct after Permian
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Sponges
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Echinoderms (five-way radial symmetry)— starfish, etc.
45

Echinoderms
(Spiny Skinned)--Living
46

Paleozoic Marine Vertebrates
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Chordate Phylum: all animals with full spinal cord
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Oldest chordates date from beginning of
Cambrian (invertebrates dominated, but vertebrates present): Jawless fish
47

Jawless Fish
Earliest Chordates (Spinal Cord)
Still living
48

Conodonts
(Teeth)
Conodonts—toothlike fossils: parts of chordates
49

More Fish
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Devonian (the age of fish): two groups
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Bony fish
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Ray finned bony fish
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Lobe finned bony fish
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Cartilaginous fish (discuss)—primitive sharks
50

Cartilaginous fish
(No bones)
51

Bony Fish
Ray finned
Lobe finned
(evolved into amphibians)
52

Tiktaalik Fossil (Late Devonian)
53

Tiktaalik (Lobe-finned fish)
54

Late Devonian
Tetrapod—a
4-footed animal
An amphibian
55

Coelacanth
Living lobe-finned fish
56

57

Foraminifera
Microscopic Floaters--Extinct
58

Stromatolites—The Structures
Created by Still-living
Cyanobacteria
59

Paleozoic Plants
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Oldest plants: Middle Ordovician fossil spores
(Algae are not plants.)
Land organisms first appeared late Ordovician
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Plants were first on land ( Why plants before animals?)

Lots of land plants by late Paleozoic
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Took a while—needed ozone layer (Why?)
60

Life Evolved
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Silurian: small multicellular plants on land
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First: rigid stems without roots or vascular system
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Then: vascular plants with roots and leaves
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Devonian: creepers, restricted to damp areas
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Late Devonian: seed plants— freedom!
(no flowers until the late Mesozoic)
61

Pennsylvanian
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Gymnosperms (naked seed) plants evolved (pine trees—pine cones)
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Forests develop
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Glossopteris— a fern in Gondwana that Wegener used to determine the extent of Gondwana
62

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)
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Amphibians: restricted to land/water habitat
(frogs, for example)—lay there eggs in water (no egg shell)
63

Early
Pennsylvanian
One group of amphibians developed the amniotic egg: hard shell and liquid sac for food
64

These are reptiles
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Lay eggs on dry land
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Move away from water
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Colonize land and become dominant terrestrial vertebrates
65

Pelycosaurs—
(Not dinosaurs)
•
Pennsylvanian: pelycosaurs evolved
•
Fin-back reptiles
(not dinosaurs)
•
Go extinct by end of Permian
Pely…--pelvis
This is Dimetrodon
66

More evolution
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Therapsids—replaced pelycosaurs—”mammallike” reptiles with some temperature regulation
(these dominated)—ancestors of mammals
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Root words: wild beast + arch of the skull
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Thecodonts—”reptile-like” reptiles
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Root words: case & teeth set in sockets
(More when we look at the Mesozoic)
67

More evolution
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End of Paleozoic: 90% of all reptiles are therapsids
(ancestors of mammals)
Decline at end of Paleozoic—survivors evolve into mammals
68

Invertebrates on Land

Arthopods (jointed foot)
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Eurypterids evolve into scorpions and spiders
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Insects (Devonian)
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Late Paleozoic: dragonflies and cockroaches
69

Extinctions
Dinosaurs
(& others) go
Greatest Extinction Ever!
70

The Really, Really Big Extinction
(Not when the dinosaurs went extinct)

End of Paleozoic (end of Permian)

Land organisms suffered most (Why land?)
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75% of amphibians extinct
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80% of reptiles extinct
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Land plants change significantly
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50% of marine invertebrates go extinct
71

The End of the Paleozoic

Pangea forms
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Biggest mass extinction ever

Lose a lot of marine life
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Trilobites

Fusilinids

Graptolites

Tabulate corals
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Rugose corals
72

 A Key Point!!

Extinctions happen due to a change in the environment
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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
73

The Reason for Extinction
(maybe…)
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Meteorite impact (ancient crater off of Australia
– much debate!)
Environmental changes occurring with the formation of Pangea
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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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