Transcript Life of the Paleozoic

Life of the Paleozoic
► Overview
of expansions
 Cambrian, Vast expansion of shelly marine life
forms and jawless fish
 Ordovician - most modern phyla established
 Late Paleozoic- land plants and vertebrates
(tetrapods and amniotes)
Invertebrates
► Marine
environments
 Nektic, planktic, benthic
►Adaptions:
 Epifaunal- animals living on the sea floor
 Infaunal – animals that burrow into the sea floor
 Mobile
 Review of Proterozoic fossils
►Cloudina
►Ediacaran
Early cambrian
► Small
Shelly fossils
 Rarely more than a few
millimeters long
► A-
Anabarella
► B- Camanella
► C- Aldanella
► D- Sponge Spicule
► E- Formitchella
► F- Lapworthella
Early Soft-body fossils
► The
Burgess shale:
 Most fossils reduced to shiny black impressions
► What
type of fossilization is this?
 Viewed as one of the most important finds of
the fossil record
►Altogether,
over 60,000 species have been collected
The Burgess shale
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Four Groups of
Arthropods
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Trilobites
Crustaceans
Scorpions
Insects
Sponges
Onycophorans
Crinoids
Sea Cucumbers
Chordates
Unknown species
Chordates
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Shows evolution of early notochord
► Notochord-
dorsally situated nerve cord
 Why is this important?
► Notochord
is precursor to vertebral column
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Pikaia- small animal that has notochord and also
shows evidence of v-shaped muscle bands (this
indicated sinosoidal swimming motion
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THESE ANIMALS ARE ANCESTORS TO ALL
MODERN VERTEBRATES
Other notable fossils
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Anomalocaris- fierce predator over 50cm
long (~2ft)
Opabinia- five eyes, flexible nozzle
Hallucigenia- seven pairs of legs, seven
dorsal spines, claws, cylindrical trunk.
(Considered to be a onycophoran)
Marrella- Four spines extended back from
cephalon
The most common arthropod found in the burgess shale
Protista (unicellular groups)
► Foraminifera
(Calcerous Microfossils)
 Range from Cambrian to present
 More numerous and varied by Carboniferous
 Global distribution during Pennsylvanian-Permian
► Radiolarians
(Siliceous Microfossils)
 Range early Paleozoic to present
 Most abundant in Mesozoic rocks
Cup Animals : Archaeocyathids
► Conical
of vase-shaped skeletons
► Extinct by the end of the Cambrian
► Earliest known reef builders
 Found in N. America, Siberia, Antarctia, Australia
Porifera
► Pore-bearing
animals
► Appear to evolved from
colonial flagellated
unicellular creatures
► Cambrian representatives of
all but one modern class are
known as fossils (Have not
changed much)
Fossil Porifera
Modern Sponges
Corals and Cnidarians
► Main
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Groups
Sea Anemonies
Sea Fans
Jelly Fish
Hydra
Reef-forming Corals
Body of Cnidarians
► Three
main layers
 Ectoderm: Outer layer or body wall
 Endoderm: Inner layer
► Contains:
 Primitive sensory cells
 Digestive cells
 Nutritive cells
 Mesoglea: Thin intermediate layer
Body Form
► Polyp
► Medusa
Brachiopods
► Most
abundant, diverse, and useful Paleozoic
fossil group
► Braciopods
are bivalves, however, each valve
(shell) differs in shape and size.
► Unlike
clam shell which can be considered right and left
brachiopod shells are distinguished between dorsal and
ventral.
► Most
valves are made of Calcium Carbonate.
► Ornamented
with radial ridges, grooves, spines, nodes
and growth lines.
Groups of Brachiopod
► Articulate
Brachiopods
 Valves are hinged along the
posterior margin and are
prevented by sliding sideways by
teeth and grooves
► Inarticulate
Brachiopods
 Lack a definite hinge structure
 Valves held together by muscle
► Both
are filter feeders attached
to sea floor by fleshy stalk
(pedicle)
► Lophophore:
hair like structures that
circulate water and food toward mouth
Fossil Brachiopods
Mollusks
► Gastropods
(snails)
 Earliest forms constructed small conical shells, by
late Cambrian/early Ordovician most had
developed the more recognizable coiled shell.
 By Pennsylvanian gastropods extremely abundant
and even air-breathing species had
developed
 Cephalopods- may be the most advanced and
complex of all invertebrates
Cephalopods
► Represented
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today by:
Squid
Cuttlefish
Octopods
Chambered Nautilus
Ammonites
► Goniatites,
the first
ammonite, appears
during the Devonian
► Other
Ammonites
Arthropods
► Includes:
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Lobsters
Spiders
Insects
All animals that have chitonous exterior
skeletons, segmented bodies, and paired,jointed
appendages
Trilobites
Trilobites
Eurypterids
► Scorpion
like bodies
► Found
in Marine
and Brackish facies
► Ordovician-permian
Echinoderms
► Spiny-skinned
animals
► Five way symmetry
► Exclusively marine- typically bottom
dwelling, either attached or mobile
 Group includes
►Starfish
►Sea
Urchins
►Crinoids
►Crystoids
Echinoderms
► Appear
to have developed during
late proterozoic
► Ediacaran,
symmetry
Arkarua, also had five way
 Stemmed or stalked echinoderms first
occur in mid cambrian (not abundant
until Ordovician)
Continental Invertebrates
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Fossil evidence is less complete
 Why?
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However as plants begin to invade continent so do
animals
► Record
begins with possible Millipede tracks in Ordovician rocks.
► Body Fossils of Centipedes and Millipedes occur in Silurian rock
► In New York, Devonian rocks have yielded fossil centipedes, spiders
and other wingless arthropods
Insects do not become common until the late Missipian
► The Pennsylvanian witnessed the arrival of flying insects
like the dragon fly
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► Coal
swamps from the Pennsylvanian yielded a dragon fly
with a wingspan of over 2 ft.
Vertebrates
► Fishes
 Dermal Plates (Upper Cambrian)
 Scales and Plates (Ordovician)
 Five Taxonomic classes:
►Agnatha
(jawless fish)
►Acanthodii (Archaic jawed fish)
►Chondrichthyes (cartilaginous fish)
►Osteichthyes (Bony fish)
Agnatha
► Earliest
known (early Cambrian)
 Myllokunminga
 Haikouichthys
Other species include Theolodus, Jamoytius,
Pteraspis (armored) and Hemicyclapsis
Acanthodii
► Arose
during Silurian
► Most numerous during Devonian
► Extinct during Permian
Chondrichthyes
► Late
Devonian to Present
► Represent shark, rays, and skates
► Cladoselache- late paleozoic shark
Osteichthyes
► Bony
Fish can be divided into two groups
 Actinoptergians
► Lack
a muscular base to their paired fins
► Also lack nasal passage to the throat
 Sarcoptergians
► Had
sturdy, fleshy lobe-fins
► A pair of openings in upper mouth that led to
external nostrils
► Were able to rise to surface to take in air that was
passed onto functional lungs (Lung Fish)
Sarcoptergians
► Two
major roups lived during the Devonian
 Dipnoans
► Dipnoans-
track does not lead to evolution of tetrapods
but does include some present day freshwater living
species of lungfish in Australia and Africa
 Crossopterygians
► Because
of the pattern of skull elements, arrangement of
bones in their fins, and the structure of their teeth,
Crossopterygians are considered to be the ancestor of
the earliest land inhabitants
Crossopterygians & Tetrapods
Tetrapods
► Tetrapods
are fourfooted vertebrates
 Amphibia, Reptilia,
Mammalia
Tetrapods
► First
to come ashore did not leave the water
completely
 Amphibians
►Return
to water to lay eggs
►From eggs come fish-like larvae that develop in
water
► Number
of changes had to accompany the
shift to land
Shift to land
►A
three chambered heart developed
► Limb and girdle bones had to be modified to
overcome gravity
► Spinal column became more sturdy but yet flexible
► To better assist hearing the Hyomandibular (fish)
transformed into an ear ossicle-the stapes
► The fish spiracle (a vestigial gill slit) became
eustacian tube and middle ear
Fossil Record of Basal Tetrapods
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Late Devonian
 Ichthyostegids
► Retained
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many features of their fish ancestor
Tail fin
Bony gill covers
Fish-like vertrbae
Skull bones similar to crossopterygians
Labyrinthic folding of enamel
► Due to this following species are referred to as
Labyrinthodonts
During the Carboniferous large numbers of
these Labyrinthodonts wallowed in swamps and
streams
Evolution of the Tetrapods
► Among
some of the tetrapods were some
vertebrates that evolved a way of reproducing
without having to return to water
 Development of the amniotic egg
► These
animals are referred to as Amniotes
 During the Carboniferous Amniotes diverged into two
groups
► Reptilia:
anapsids, diapsids, and archosaurs
► Synapsids- Mammal-like reptiles
Synapsids
► Although
the synapsids are called “mammallike reptiles, cladistic analysis shows that
they should not be termed reptiles
 Most spectacular synapsids, Pelycosaurs
►Some
sported big sail-like structures
►Varied group
 Carnivores: Dimetrodon
 Herbivores: Edaphosaurus
Plants of the Paleozoic
► Overview
 Cambrian: Stomatolites and stromatolitic reefs
 Ordovician to SilurianReceptaculids (Green Algae)
► Four-spore tracheophytes (vascular plants) and
Bryophytes (mosses)
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 Silurian: Three spore tracheophytes
 Early Paleozoic: Chlorophytes and fungi
formed lichens
Effects of Plants
► Roots
slowed erosion
► Transpiration changes atmospheric
conditions
► Provide shelter and food for land animals
► Leaf litter and decay form early soils
Vascular Plants
► First
unquestionable vascular structures
appear during Middle Silurian
 Some fossils show plants up to 30cm tall
 Horizontal stalks (Rhizones)
 Vertical stems and spore sacs
Vascular Plants
► Although
early vascular plants were small,
evolution would soon lead to the
development of wood.
► By late Devonian lofty, well-rooted trees
appear
 One such forest stood near Gilboa, New York
►Some
of these trees stood over 7m tall (21 ft)
 Another covered the Sahara
Plants of the Carboniferous
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Lycopsids: Scale trees.
 Present day Lycopsids
consist of the Club Mosses,
such as Lycopodium
 Not so small during the
carboniferous
 Lepideodendron reached 30
meters tall
Sphenopsids
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Lived side by side with
Lepidodenrons
 Living relatives include horse
tails
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Fossil Sphenopsids posses
slender, unbranching,
longitudinally ribbed stems
with thick cores and leaves
at each joint.
Seedplants
► Seed
plants arrive in the late Paleozoic
 Most likely evolved from Devonian fern-like
plants, however, reproduced purely through
seeds
 Become the dominant plant type by the late
Paleozoic.
► Most
widely known: Glossopteris
► Ginkgo
only modern day survivor
Mass Extinctions
► Ordovician
 Two Phases
►1st
Phase – Planktonic and Nektonic organisms
 Graptolites, acritarchs, nautiloids and some trilobites,
bryozoa, coral and brachiopods
►2nd
Phase- several of the remaining trilobites
perish and corals and bryozoans severely
reduced
 Most likely caused by global cooling
associated with the growth of the
Gondwana Ice Caps
Mass Extinctions
► Devonian
 In the late Devonian we see huge decrease in
Trilobite numbers and varieties. Also large
decrease in reef building corals, brachiopods, and
placoderms.
 These extinctions occur over a 20 million yr period
so probably not due to catastrophic event
(meteor)
► What
other events are occurring that may lead to this?
Mass Extinctions
► Late
Permian
 Referred to as “the mother of mass extinctions”
 90% of all pre-existing marine species disappear
 On land, spore bearing plant give way to conifers,
cyads and othe gymnosperms.
► Vegetative
change causes chain reaction in land animals
► Many families of basal tetrapods, primitive reptiles and
synapsids disappear.