Chapter 22 Paleozoic Life

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Chapter 22Paleozoic Life
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Life forms in the Paleozoic

• Paleozoic begins with the appearance of marine
  skeletonized fossils of animals
  
• Contains the history of animal and plant
  diversification in the oceans and colonization
  of the land

Crinoids
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Important Paleozoic Invertebrates

• First we will examine the anatomical plans of
  Trilobites, Brachiopods, Molluscs (clams, snails
  and cephalopods), Echinoderms (starfish, sea
  urchins and especially crinoids), and
  Graptolites.
• Later we will look at corals and sponges

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Trilobite shell morphology
Arthropod jointed-leg Related to Horseshoe cr
abs
What other arthropods do you know of?
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Brachiopod morphology
Sessile benthic filter feeders related to
bryozoans
Click for source
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Articulate BrachiopodsBrachiopod life positions 1
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Brachiopod life positions 2 Inarticulate
Brachiopod
Lingula Infaunal sessile benthic filter feeders
intertidal
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Bivalve morphology
Clams, Scallops Valves are mirror images
individual valve is not
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Gastropod (snail) shapes
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Cephalopod shell morphology
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Crinoid morphology
Stalked echinoderm related to starfishes, sea
urchins, etc
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Graptolites
Related to ??? Often found in black shales,
deep shelf waters, no other fossils
Great index fossils
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What Was the Cambrian Explosion?

• The Paleozoic is marked by the abrupt appearance
  of animals with skeletons in the rock record
  
• a mechanism that would trigger this event is not
  agreed upon, but is surely due to a combination
  of geologic and biologic factors
  
• Predators prominent
• shallow water

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The Emergence of Shelly Fauna

• Organisms with hard parts have many advantages
• protection against UV rays, allowing animals to
  move into shallower water
  
• helps prevent drying out in an intertidal
  environment
  
• provides protection against predators

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Small shelly fauna
Photos Drawings
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Cambrian Marine Community

• Many body plans are observed in Cambrian fossils,
  more than in any other period
  
• trilobites - benthonic mobile sediment-deposit
  feeders that crawled or swam across the sea
  floor
  
• brachiopods - primitive benthonic sessile
  suspension feeders
  
• archaeocyathids - benthonic sessile suspension
  feeders and reef builders

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Invertebrates with hard parts
Brachiopods Note how the valves differ
Trilobites
Crinoids
Sponges
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The Burgess Shale Biota

• Consists of a rare preservation of soft-bodied
  organisms Mid Cambrian
  
• Some phyla near the basic stock from which some
  present-day invertebrates have evolved
  
• Other unique and without issue
• current debate centers around how many phyla
  arose and how many extinction events took place
  in the Cambrian

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Charles Walcotts Burgess Shale
-middle Cambrian shale in the Rockies of western
Canada
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Anomalocaris A huge predaor
Hallucigenia
Pikaia A chordate!!!
Sidneyia
Remarkable preservation of animals soft tissues,
plus the first predator, Anomalocaris
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Marella, a trilobitomorph or Lace Crab
Anomalocaris and some known prey.
Bite marks on fossils
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Leanchoilia--China
Leanchoilia--Burgess
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Opabina
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Interpreting Hallucigenia
Like the modern Peripatus, moist forests of
Cameroon, Discussion preadaptations to land if
food is present
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Pikaia
Totally unexpected find. Cartilage but no bone.
Jawless ancestor to fish, and us.
Maori legend of Pikea, the ancestor.
Lancets in comparative anatomy
Link to lancet info
Pikaia an early chordate! from the Burgess Sha
le
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Cambrian Trilobites
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Archaeocyathids (sponges?)
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Ordovician Marine Community

• Vast epeiric seas opened new marine habitats
• bryozoans, stromatoporoids, tabulate and rugose
  coral reef builders
  
• reefs with high diversity - suspension feeders
• massive extinctions end Ordovician, glaciation in
  Gondwana falling sea-level

Note large Orthoceras
Cephalopods as Index Fossils
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Bryozoans
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Halysites Tabulate Coral O-S
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Stromatoporoid - Hydrozoan coral or Sponge?
C - K
-
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Graptolite
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Silurian and Devonian Marine Communities

• Rapid diversification and recovery followed the
  Ordovician mass extinction
  
• reef building by tabulate and rugose corals
• NEW PREDATOR
• eurypterids were abundant
• ammonoids evolved quickly and are important as
  index fossils
  
• mass extinction at the end of the Devonian
  collapsed the massive reefs

Marine Scorpions Track ways in coastal sands P
robably laid eggs as horseshoe crabs do
along the foreshore
Pterygotus
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Rugose Corals individual animals
Field Trip, Stroudsburg, PA
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Devonian Tabulate Corals
Colonial
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Brachiopod
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Carboniferous and Permian Marine Communities

• Renewed diversity and recovery with adaptations
  mark the Late Paleozoic marine communities
  
• bryozoans and crinoids reach their greatest
  diversity
  
• patch reefs replace the massive reefs of the
  Devonian TEMPS?
  
• fusulinid formanifera are important index fossils

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Types of Staked Echinoderms 1 Cystoids
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Types of Staked Echinoderms 2 Blastoids
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Fragments on Field Trip Stroudsburg PA
Types of Staked Echinoderms 3 - Crinoids
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Vertebrate Evolution

• Chordates have, during at least part of their
  life, a notochord, dorsal hollow nerve chord, and
  gill slits
  
• Vertebrates have backbones and are a sub-phylum
  of chordates
  
• ancestors were soft-bodied and left few fossils
• a close relationship exists between echinoderms
  and chordates and they may have shared a common
  ancestor

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Fish

• Fish range from the Late Cambrian to the present
  and consist of five classes
  
• Ostracoderms
• Placoderms
• Acanthodians
• Cartilaginous fish sharks and rays
• Bony fish

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Classes of fish through time
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Ostracoderms- Jawless fish
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Evolution of jaws
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Placoderms first fish w jaws
Dunkleosteous (Dinichthys) a Devonian arthrodire
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Placoderm - Bothryolepis

• Today we will examine another Placoderm
• Named Bothryolepis
• Its armor is similar to that of modern South
  American catfishes that live in shallow, fast
  moving, jungle streams in South America

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Acanthodian Placoderm a more usual body plan
Climatius, a Lower Devonian acanthodian
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Cladoselache fyleri, a 3-foot shark, was one of
the top predators in the Devonian seas.
Cartilagenous fishes Fossil Shark
http//www.exhibits.lsa.umich.edu/New/Welcome.html
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Ray-finned (Actinopterygians) and Lobe-finned
(Sarcopterygians)
Bony Fishes (Osteichthys)
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Rhipidistian fish
(Crossopterigian)
Field Trip Catskill fm. Bones of early Amphibians
Similar skulls, teeth, Bones in limbs. Fish limb
s not for walking
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Hyneria lindae from Hyner, PA
http//www.lhup.edu/jway/rdhll/RedHill.htm
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Amphibians -Vertebrates Invade the Land

• The first vertebrates to live on land, preceded
  by plants, insects, and snails
  
• Barriers they had to deal with
• desiccation
• reproduction
• effects of gravity
• extraction of oxygen by lungs rather than gills

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Early Amphibian
Late Devonian Ichthyostega Skull, teeth, backbone
and tail are Rhiphidistian-like
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Labyrinthodont amphibian
Eryops, a carnivorous amphibian,
named for folds in teeth Pennsylvania to Early P
ermian
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Middle Carboniferous - Evolution of the Reptiles
The Land is Conquered

• The evolution of the amniote egg freed reptiles
  from the constraint of returning to water to
  reproduce
  
• amnion - liquid filled sac surrounding the
  embryo
  
• allantois - waste sac
• a tough shell protects the developing fetus
• reptiles were able to colonize all parts of the
  land

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Evolution of the Reptiles
Warm

• The earliest reptiles are from the Lower
  Pennsylvanian
  
• called Captorhinomorphs, they were small, agile,
  and fed on grubs and insects
  
• success due to advanced reproductive methods,
  more advanced jaws and teeth, and speed
  
• Pelycosaurs evolved from this group and were the
  dominant reptile by Permian

Cool
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Skull structure in reptiles
Function of Temporal Openings
Early Therapsids
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Pelycosaurs
Discussion Sail function Thermoregulation Arm
or
Courtship
herbivorous Edaphosaurus
carnivorous Dimetrodon
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Evolution of the Reptiles

• Therapsids succeeded the pelycosaurs during the
  Permian
  
• mammal-like reptiles that quickly evolved into
  herbivorous and carnivorous forms
  
• they displayed fewer bones in the skull,
  enlargement of the lower jawbone, differentiation
  of the teeth, and a more vertical position of
  their legs
• therapsids may have been endothermic, which may
  help explain their distribution over wide
  latitudes
  
• End Permian extinction eliminated about 66 of
  all amphibians and reptiles

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Late Permian therapsids
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Land Plant Evolution - Silurian
Back to the early Paleozoic to consider plant
evolution

• Plants had the same water-to-land transition
  problems that animals did
  
• vascular land plants have a tissue system to move
  water
  
• nonvascular plants do not have this system, and
  are usually small and live in moist environments
  
• seedless vascular plants such as ferns closely
  resemble green algae in their pigmentation,
  metabolism, and reproductive cycle
  
• green algae have also been able to make the
  transition from salt water to fresh water,
  leading some to believe that modern terrestrial
  land plants evolved from them

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Silurian and Devonian Floras

• The earliest land plants are from the Silurian
• small, simple leafless stalks with a
  spore-producing structure at the tip (Rhynia
  drawing and modern Psilotum pictured)
  
• a rhizome (the underground part of the stem)
  transferred water from the soil to the plant and
  anchored it
  
• leaves, roots, and secondary growth all followed
  during the Devonian
  
• The evolution of the first seed allowed land
  plants (Seed Ferns) to spread over all parts of
  the land

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Lepidodendron L Dev. Penn.A lycopod tree 90
100 feet tall
An important coal-former
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Calamites, a huge horsetail rush 10-14 meters
tall (Pennsylvanian)
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L. Dev E. Penns. Floras
Spenopsid (Horsetail Rush) Calamites shown
Lycopsid (club moss) Lepidodendron shown

• Source of coal
• Seedless vascular Need moisture to reproduce,
  vulnerable to insect attack
  
• Lycopsids to 30m branches at top leaves similar
  to palm
  
• Sphenopsids jointed stem underground rhizomes
• First Seed Ferns Late Devonian West Virginia
• seed ferns

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L. Pennsylvanian M. Permian Floras

• Seed-bearing vascular
• Gymnosperm trees - Cordaites, Glossopteris, and
  others were able to colonize large areas of land
  
• many of these became extinct in the Late Permian
  those that survived were able to tolerate the
  warmer and drier climates

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Insects and other land arthropods

• Have a strong exoskeleton, impervious to water so
  good for osmoregulation.
  
• Predation on plant spores probably a strong
  selective pressure for seed coatings.

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Permian Marine Extinction Event

• The greatest recorded mass extinction to affect
  Earth occurred at the end of the Permian
  
• about 90 of all marine invertebrate species
• fusulinids, rugose and tabulate corals, many
  bryozoan and brachiopod orders, and trilobites
  did not survive the end of the Permian
  
• causes for this have been speculated to be
• reduction in marine shelf as Pangaea formed
• global drop in sea level due to glaciation
• reduction in marine shelf due to regression
• climatic changes

Fusilinids, large forams
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Permian Extinctions

• S. A. Bowring, et. al. (1998) U/Pb Zircon
  Geochronology and Tempo of the End-Permian Mass
  Extinction. SCIENCE 280 1039-1045
  
• The mass extinction at the end of the Permian was
  the most profound in the history of life.
  
• U/Pb zircon data from south China place the
  Permian-Triassic boundary at 251 mya.
  
• Strata intercalated with ash beds below the
  boundary Changhsingian pulse of the end-Permian
  extinction (loss of 85 percent of marine species)
  lasted less than 1 my.
• At Meishan, a negative excursion in d13C at the
  boundary had a duration of 165,000 years or less,
  suggesting a catastrophic addition of light
  carbon. GLOBAL FIRE!

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d13C

• 12C and 13C are stable isotopes of Carbon
• 12C 98.89
• 13C 1.11 in todays atmosphere

Negative excursions mean 13C down or 12C up.
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d13C

• Standard carbon in calcite from belemnites Pee
  Dee Formation (abbreviated as PDB).
  
• The process of photosynthesis favors the lighter
  form of carbon
  
• If you recall from the above brief discussion of
  the soot found in the K/T clay layer, it appears
  that a significant portion of the land plants
  burned this would have released a great deal of
  light carbon into the atmosphere
• http//www.acad.carleton.edu/curricular/GEOL/DaveS
  TELLA/Carbon/c_isotope_models.htm
  

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Extinctions aligned
Extinction
Extinction
Extinction
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Major mass-extinction events
Asteroid Impact
Asteroid Impact
Asteroid Impact
Asteroid Impact
Supposedly due to glaciation but it doesnt line
up with low water
Mention 26-30 my cycle of extinctions
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End of Chapter 22