Chapter 12
Life of the Paleozoic
Paleozoic
overview
Paleozoic Fossil Record
The Paleozoic was a time with abundant
fossils of multicellular organisms with
shells. As a result, the fossil record
improves dramatically at the beginning of
the Paleozoic Era.
Paleozoic Invertebrates
• Representatives of most major
invertebrate phyla were present during the
Paleozoic, including sponges, corals,
bryozoans, brachiopods, molluscs,
arthropods, and echinoderms.
• Almost all of the common invertebrate
phyla in existence today had appeared by
the Ordovician.
Paleozoic Vertebrates
• Vertebrates evolved during the Paleozoic,
including:
– Fishes
– Amphibians
– Reptiles
– Synapsids (“mammal-like reptiles”)
• The first vertebrates were jawless fishes,
which are found in rocks as old as
Cambrian in China.
Paleozoic Vertebrates
• An advanced lineage of fishes with
primitive lungs and stout fins gave rise to
the four-legged animals or tetrapods.
• The transition from water-dwelling
vertebrates to land-dwelling vertebrates
depended on the evolution of the amniotic
egg.
Paleozoic Plants
• The first primitive land plants appeared
near the end of the Ordovician.
• Vascular plants expanded across the land,
forming great forests in the Devonian.
• The plants progressed from seedless,
spore-bearing plants to plants with seeds
but no flowers (gymnosperms).
Paleozoic Extinctions
• Several mass extinctions occurred during
the Paleozoic, including the largest
extinction of all at the end of the Permian.
• Other mass extinctions occurred at the
end of the Ordovician and Devonian
periods.
Paleozoic Life
Summary of
invertebrate phyla
Paleozoic life includes some Precambrian
forms, which survived into the Paleozoic,
as well as more advanced forms:
– Unicellular eukaryotes
– Animals
• Invertebrates
• Vertebrates
– Plants
Adaptive Radiations
and Extinctions
• The Paleozoic was a time of several adaptive
radiations and extinctions.
• Many geologic periods began with adaptive
radiations (times of rapid evolution).
• Several periods ended with extinction events of
varying severity.
• The extinction event at the end of the Permian
Period was the worst mass extinction in the
history of life.
Diversity in the Paleozoic
Red arrows
mark extinction
events
Soft-bodied Animals
• Multicellular animals evolved in the
Precambrian. Soft-bodied Ediacaran-type
organisms ranged into the Cambrian
period.
• Soft-bodied fossils are infrequently
preserved.
• Preservation improved with the origin of
hard parts.
• The first animals with
shells are called small
shelly fossils.
• Small shelly fossils
are found at the base
of the Cambrian, and
in the late
Neoproterozoic.
• Most disappeared by
the end of the first
stage of the Lower
Cambrian.
Small Shelly Fossils
• Many had phosphatic shells, few mm in size.
• Shells and skeletal remains of primitive
molluscs, sponges, and animals of uncertain
classification, such as Cloudina, that secreted a
calcareous tube.
Cambrian Diversification
• The initial Paleozoic diversification is known as
"the Cambrian explosion“. Abrupt appearance of
many types of animals about 535 million years
ago, followed by rapid evolution.
• During that episode of explosive evolution, all
major invertebrate phyla appeared in the fossil
record (except Bryozoa).
• Sometimes this event is referred to as
"evolution's big bang".
Cambrian Substrate Revolution
• Infaunal, burrowing animals evolved
rapidly during the Cambrian, as indicated
by trace fossils and bioturbation of
sediments.
• The dramatic change in the character of
the seafloor sediments (from undisturbed
to highly burrowed) has been called the
"Cambrian substrate revolution".
Soft-Bodied Fossils in
the Burgess Shale
The extraordinarily well-preserved Middle
Cambrian Burgess Shale fauna of Canada
provides a window into the past to view
the spectacular diversity of the Middle
Cambrian.
Many soft-bodied organisms are
preserved in black shale, along with the
soft parts of animals with shells, such as
legs and gills of trilobites.
Soft-Bodied Fossils in
the Burgess Shale
• The significance of the Burgess Shale is that is
records soft-bodied organisms, and the soft
parts of organisms with shells . The finely
detailed preservation reveals the extraordinary
diversity and evolutionary complexity that
existed near the beginning of the Paleozoic.
• Fossil sites containing abundant fossils with
extraordinary preservation are called
lagerstatten. Both the Burgess Shale and the
Chengjiang fauna in China are lagerstatten.
Animals in the Burgess Shale
1. Several groups of arthropods, including
trilobites and crustaceans
2. Sponges
3. Onycophorans
4. Crinoids
5. Molluscs
6. Corals
7. Three phyla of worms
8. Chordates (Pikaia)
9. Many others
Stratigraphic setting of the
Cambrian Burgess Shale
• Location of the Burgess
Shale fauna in British
Columbia, Canada
• C = Onycophoran,
Aysheaia, intermediate
in evolution between
segmented worms and
arthropods.
D = Arthropod
Leanchoila
E= Arthropod Waptia
Pikaia - One of the Oldest Chordates
• Pikaia is a fish-like lower
chordate from the
Burgess Shale.
• Modern representatives
are called lancelets, such
as the genus Amphioxus.
Chordates
• Chordates have a notochord or dorsal stiffening
rod associated with a nerve chord, at some
stage in their development.
• In vertebrates, the notochord is surrounded by
and usually replaced by a vertebral column
during embryonic development.
• Vertebrates are chordates, but Pikaia pre-dates
the evolution of vertebrae.
• It is thought that vertebrates evolved from
organisms similar to Pikaia.
Predators in the Cambrian Seas
• The giant predator of the
Cambrian seas, Anomalocaris,
up to 60 cm long.
• Predators would have caused
selective pressures on prey.
The
need to avoid being eaten probably encouraged
the evolution of hard protective shells.
• Predation probably also caused an increase in
diversity of prey, as they evolved to better
survive predation.
Other Burgess Shale Animals
• Marrella, a "lace crab“, is
common in the Burgess Shale.
• Hallucigenia, an onycophoran,
was originally interpreted to
walk on its spines, until claws
were discovered on its
“tentacles”.
The Significance of
the Burgess Shale
The significance of the Burgess Shale is
that it records soft-bodied organisms, and
the soft parts of organisms with shells.
The finely detailed preservation reveals
the extraordinary diversity and
evolutionary complexity that existed near
the beginning of the Paleozoic.
Exceptional Preservation
• Fossil sites containing abundant fossils
with extraordinary preservation are called
lagerstatten.
• Both the Burgess Shale fauna and the
Chengjiang fauna from China are
considered to be lagerstatten.
The Chengjiang fauna
• In 1984, the Lower Cambrian (535 my old)
Chengjiang fossil site was discovered in
Yunnan Province, China.
• More than 100 species of invertebrates
have been found, with extraordinary
preservation, including many soft bodied
forms
The Chengjiang fauna
•
•
•
•
•
•
•
•
•
Jelly fish
Annelid worms
Cnidaria
Porifera (sponges)
Brachiopods
Arthropods
Early chordates similar to Pikaia
The world's oldest known fish (Myllokunmingia)
Other species of unknown phyla
Oldest Known Fish
The world's oldest known
fish, Myllokunmingia, from
the Maotianshan Shale
near Chengjiang, in the
Yunnan Province of
China.
535 million years old.
Ordovician Diversity
• Following a slight dip in diversity at the end of
the Cambrian, the Ordovician was a time of
renewed diversification.
• Global diversity tripled.
• The number of genera increased rapidly, and the
number of families increased from about 160 to
530.
• The increase was particularly dramatic among
trilobites, brachiopods, bivalve molluscs,
gastropods, and corals.
Late Ordovician Extinction
• An extinction event at the end of the
Ordovician led to an abrupt decline in
diversity.
• This extinction event was apparently
related to the growth of glaciers in
Gondwana, coupled with a reduction in
shallow water habitat associated with the
lowering of sea level.
Diversity in the Paleozoic
Red arrows
mark extinction
events
Silurian Diversity
Diversification of marine animals occurred
again at the beginning of the Silurian
Period.
The period ended with only a slight drop in
diversity.
Devonian Diversity
• The Devonian saw continued
diversification, but ended with another
fairly large extinction event, which
extended over about 20 million years.
• Roughly 70% of marine invertebrates
disappeared.
• Because of the long duration, the
extinction is unlikely to have been caused
by a sudden, catastrophic event.
Carboniferous-Permian Diversity
• In the early Carboniferous, diversity once
again increased.
• Diversity of marine animals remained fairly
constant throughout the Carboniferous
and Permian.
• The Late Permian is marked by a
catastrophic extinction event which
resulted in the total disappearance of
many animal groups.
Overview of Changes in
Diversity Through Time
1. Several of the periods of the Paleozoic ended
with extinction events
2. The beginning of most of the periods of
Paleozoic were marked by adaptive radiations
3. Maximum diversity in the Paleozoic seas
maintained roughly constant at between 1000
and 1500 genera
4. The largest extinction occurred at the end of
the Permian
5. Recovery of diversity in the Mesozoic was slow
(Triassic and Jurassic)
6. Diversity increased rapidly in the Cretaceous
7. Another mass extinction occurred at the end of
the Cretaceous
8. Diversity increased extremely rapidly, at
unprecedented rates, at the beginning of the
Cenozoic
9. Diversity in the Cretaceous, and Cenozoic Era
was much greater than during the Paleozoic
Diversity in the Paleozoic
Red arrows
mark extinction
events
Unicellular Organisms in the
Paleozoic Seas
• The principal groups of Paleozoic
unicellular animals with a significant fossils
record are the foraminifera and the
radiolaria, which belong to Phylum
Sarcodina.
• These organisms are unicellular
eukaryotic organisms, and belong to
Kingdom Protista.
Foraminifera
• Name: Foraminifera means "hole bearer".
• Chief characteristics:
– Unicellular.
– Related to the amoeba, with pseudopods.
– Foraminifera build tiny shells (called tests)
which grow by adding chambers.
– Some species (called agglutinated
foraminifera) construct tests of tiny particles of
sediement. This is the earliest type of foram
test.
– Other forams construct tests of calcium
carbonate.
Foraminifera
• Geologic range: Cambrian to Recent.
Modes of life:
– Benthic or benthonic (bottom dwellers)
– Planktic or planktonic (floaters).
Fusulinid foraminifera (fusulinids)
• Fusulinids were abundant in the Late Paleozoic
(primarily Pennsylvanian and Permian).
• Their tests were similar in size and shape to a
grain of rice.
• Their internal structure is complex and used to
distinguish different species.
• Important guide fossils in the Pennsylvanian and
Permian because they evolved rapidly, were
abundant, and widespread geographically.
Radiolaria
• Chief characteristics:
– Unicellular.
– Test or shell composed of opaline silica
– Ornate lattice-like skeleton
– Often spherical or radially symmetrical with
spines
• Geologic range: Precambrian or Cambrian to
Recent. Rare in Lower Paleozoic rocks. More
abundant in Mesozoic and Cenozoic.
• Mode of life: Planktonic. Marine only.
Radiolaria and the Rock Record
• Radiolarians are important constituents of
chert at certain times in geologic history.
• Their tests accumulate on the seafloor
today to form radiolarian ooze, particularly
in deep water, where any calcium
carbonate shells would be dissolved.
Marine Invertebrates in the
Paleozoic Seas
• The fossils of shell-bearing invertebrates that
inhabited shallow seas are common in Paleozoic
rocks.
• Archaeocyathids, sponges, corals, bryozoans,
trilobites, molluscs, and echinoderms.
• Many were benthic (bottom dwellers), but others,
such as graptolites, were planktonic. Currents
carried them over wide areas.
• As a result, they are useful index fossils for
global stratigraphic correlation.
Phylum Archaeocyatha
• Name means "ancient cup"
• Chief characteristics: Conical
or vase-shaped skeletons
made of calcium carbonate.
Double-walled structure with
partitions and pores.
• Geologic range: Cambrian
only. Extinct.
• Mode of life: Attached to the
sea floor. Reef-builders.
Phylum Porifera - The Sponges
Name means "pore-bearing". Covered by tiny
pores.
Phylum Porifera - The Sponges
Chief characteristics:
– Globular, cylindrical, conical or irregular shape.
– Basic structure is vase-like with pores and
canals.
– Interior may be hollow or filled with branching
canals.
– Solitary or colonial.
– Skeletal elements are called spicules, and they
may be separate or joined.
– Composition may be calcareous, siliceous or
organic material called spongin.
Phylum Cnidaria
• Corals, sea fans, jellyfish,
and sea anemones.
• Name: Cnidaria are named
for stinging cells called
cnidoblasts or cnidocytes.
• Many are soft-bodied but
only those which form hard
skeletal structures are readily
preservable as fossils.
Phylum Cnidaria
• Geologic range: Late Precambrian
(Proterozoic) to Recent for the phylum.
• The first corals were the tabulates.
• Mode of life: Corals live attached to the
sea floor, primarily in warm, shallow
marine environments.
Phylum Cnidaria –
Chief Characteristics
1. Radial symmetry
2. Mouth at the center of a ring of tentacles.
Phylum Cnidaria –
Chief Characteristics
3. Body form may be polyp (attached to the
bottom, with tentacles on top) or medusa (freeswimming, jellyfish).
Chief Characteristics of Corals
1. May be solitary or colonial. Colonies are
composed of many polyps living together.
2. Hard calcareous skeleton. The skeletal parts
formed by polyps are called corallites.
3. The "cup", in which an individual coral polyp
sits, is called the theca. Each theca is small,
and roughly circular or hexagonal.
4. The theca is divided internally by
vertical partitions called septae,
arranged in a radial pattern.
Chief Characteristics of Corals
5. Types of corals are distinguished by
presence or absence, and number of
septae:
– Rugose corals (or tetracorals) have
septae arranged in multiples of four.
– Tabulate corals lack septae.
– The Mesozoic and Cenozoic
scleractinian corals (or hexacorals)
have septae arranged in multiples of
six.
Rugose Corals
• Most rugose corals are
solitary and conical (shaped
like ice cream cones).
• Septae are visible in the
circular opening of the cone.
• Some rugose corals are
colonial, having hexagonal
corallites with septae (such
as Hexagonaria from the
Devonian of Michigan).
Rugose Corals
• Geologic range: Ordovician to Permian all extinct.
• Rugose corals were abundant in the
Devonian and Carboniferous, but became
extinct during the Late Permian.
Tabulate Corals
• Tabulate corals are
colonial and resemble
honeycombs or wasp
nests.
• They lack septae.
• They have horizontal
plates within the theca
called tabulae. Tabulae
are one of the main
features of the tabulate
corals.
Tabulate Corals
• Geologic range:
Ordovician to Permian all extinct.
• The principal Silurian
reef formers.
• They declined after the
Silurian and their reefbuilding role was
assumed by the rugose
corals.
Modern Corals
• Modern corals are scleractinian corals.
Scleractinian corals have septae are
arranged in multiples of six, and are
sometimes called hexacorals.
• Scleractinian corals did not appear until
after the Paleozoic
• Geologic range: Triassic to Recent.
Phylum Bryozoa
• Name: Name means "moss" (bryo) +
"animal" (zoa).
• Chief characteristics:
– Colonial (many microscopic individuals living
physically united adjacent to one another).
– The individuals are called zooids, and they
are housed in a hard "capsule" called a
zooecium.
– The colony is called a zoarium.
Phylum Bryozoa
• Individual zooecia (plural of zooecium) are very
tiny (about the size of a pin-hole, a millimeter or
less in diameter). They are just large enough to
be seen with the unaided eye.
• Bryozoans may be distinguished from corals
because of the apertures in the skeleton are
much smaller.
Phylum Bryozoa
The bryozoan colony may resemble lace
or a tiny net, may be delicately branching,
finger-like, circular or dome-shaped. There
are more than 4000 living species of
bryozoans, and nearly 16,000 fossil
species.
Phylum Bryozoa
• Geologic range: Ordovician to Recent.
• Mode of life: Widespread in marine
environments. A few live in freshwater
lakes and streams.
Phylum Bryozoa
Archimedes, from the
Mississippian period, has a
cork-screw-like central axis
with a fragile net-like colony
around the outer edge.
Phylum Brachiopoda
• Name: Name means "arm" (brachio) +
"foot" (pod).
• Chief characteristics:
– Bivalved (two shells), each with bilateral
symmetry. The plane of symmetry passes
through the center of each shell or valve.
– The two valves differ in size and shape in
most. Sometimes the larger valve will have an
opening near the hinge line through which the
pedicle extended in life.
Phylum Brachiopoda
Soft parts include a lophophore consisting
of coiled tentacles with cilia. The
lophophore circulates water between the
two valves, distributing oxygen and
flushing out carbon dioxide. Water
movements caused by the lophophore
also transport food particles toward the
mouth.
Phylum Brachiopoda
Mode of life:
Shallow marine environments.
Generally attached to the sea
floor.
Inarticulate brachiopods are
known to live in burrows in the
sediment.
Brachiopods are filter feeders.
Phylum Brachiopoda
• Geologic range:
– Lower Cambrian to Recent.
– Very abundant during the Paleozoic.
– A few species (belonging to only three
families) remain today.
Inarticulate Brachiopods
• Primitive brachiopods with phosphatic or
chitinous valves.
• No hinge. Spoon-shaped valves held
together with muscles and soft parts.
• Lingula is a well known genus
• Geologic range:
– Lower Cambrian to Recent
Articulate Brachiopods
• Calcareous valves attached
together with a hinge
consisting of teeth and
sockets.
• Geologic range: Lower
Cambrian to Recent
• Spiny brachiopods (called
productids) are
characteristic of the
Carboniferous and Permian.
Phylum Mollusca
• Clams, oysters, snails, slugs, Nautilus,
squid, octopus, cuttlefish
• Name: Mollusca means " soft bodied".
Phylum Mollusca
• Chief characteristics:
– Soft body enclosed within a calcium
carbonate shell.
– A few, like slugs and the octopus, have
no shell.
– Muscular part of body of clams and
snails and some other groups of
molluscs is called the foot.
Phylum Mollusca
• Geologic range: Cambrian to Recent.
• Mode of life: Marine, freshwater, or
terrestrial.
They may: swim, float or drift, burrow into
mud or sand, bore into wood or rock,
attach themselves to rocks, or crawl.
Types of Molluscs
1. Monoplacophorans (Neopilina)
2. Polyplacophorans or amphineurans
(chitons)
3. Bivalves or pelecypods (clams, scallops)
4. Gastropods (snails and slugs)
5. Cephalopods (squid, octopus, Nautilus)
6. Scaphopods (tusk shells)
Class Monoplacophora
Chief characteristics:
– Single shell resembling a flattened cone or
cap.
– Soft part anatomy shows pseudo-segmented
arrangement of gills, muscles, and other
organs. Suggests that the primitive mollusc
was a segmented animal. Segmentation was
lost secondarily.
– Monoplacophorans are regarded as ancestral
to bivalves, gastropods, and cephalopods.
Class Monoplacophora
• Name: Monoplacophora means "single
plate-bearer".
• Geologic range: Cambrian-Recent, but
only known as fossils from Cambrian to
Devonian. Living monoplacophorans found
in deep water off Costa Rica in 1952 and
named Neopilina. Considered to be a
"living fossil" .
Class Amphineura or
Polyplacophora – The Chitons
Chief characteristics: Chitons have 8
overlapping plates covering an ovoid,
flattened body.
Class Amphineura or
Polyplacophora – The Chitons
• Name: Polyplacophora means " many
plate-bearer" .
• Geologic range: Cambrian to Recent.
Class Bivalvia or Pelecypoda
• Clams, oysters, scallops,
mussels, rudists
• Chief characteristics:
– Skeleton consists of two
calcareous valves
connected by a hinge.
– Bilateral symmetry;
plane of symmetry
passes between the two
valves.
Class Bivalvia or Pelecypoda
• Name: Bivalvia means " two" (bi) + "
shells" (valvia).
• Geologic range: Early Cambrian to Recent
• Mode of life: Marine and freshwater. Many
species are infaunal burrowers or borers,
and others are epifaunal.
Class Gastropoda
• Snails and slugs
• Chief characteristics:
– Asymmetrical, spiral-coiled
calcareous shell.
• Name: means "stomach"
(gastro) + "foot" (pod).
• Geologic range: Early
Cambrian to Recent.
• Mode of life: Marine,
freshwater or terrestrial.
Class Cephalopoda
• Squid, octopus, Nautilus, cuttlefish
• Name: means " head" (kephale) + " foot" (pod).
• Chief characteristics:
– Symmetrical cone-shaped shell with internal
partitions called septae
– Shell may be straight or coiled in a spiral
which lies in a plane.
– Smooth or contorted sutures visible on the
outside of some fossils mark the place where
septae join the outer shell.
Class Cephalopoda
• Geologic range: Late Cambrian to Recent.
• Mode of life: Marine only; carnivorous
(meat-eating) swimmers.
• Types of Paleozoic cephalopods:
– Nautiloids
– Ammonoids
– Coleoids
Nautiloid Cephalopods
• The shells of nautiloid cephalopods have
smoothly curved septa, which produce
simple, straight or curved sutures.
• Geologic range: Cambrian to Recent.
Ammonoid Cephalopods
• Ammonoid cephalopods have complex,
wrinkled or crenulated septa, which
produce angular or dendritic sutures.
• Geologic range: Devonian to Cretaceous all extinct.
Ammonoid Cephalopods
• There are three basic types of sutures in
ammonoid shells:
– Goniatite or goniatitic (septae have relatively
simple, zig-zag undulations)
– Ceratite or ceratitic (septae have smooth
"hills" alternating with saw-toothed "valleys")
– Ammonite or ammonitic (septae are
complexly branching and tree-like or dendritic)
Types of Sutures in Cephalopods
Subclass Coleoidea
• Belemnoids (belemnites)
– Geologic range: Mississippian to Eocene - all
extinct.
• Sepioids (cuttlefish)
– Geologic range: Jurassic to Recent
• Teuthoids (squid)
– Geologic range: Jurassic to Recent
• Octopods (octopus)
– Geologic range: Cretaceous to Recent
Order Belemnoidea - Belemnoids
• The belemnoids have an internal
calcareous shell (which resembles a cigar
in size, shape, and color) called a rostrum
• The front part of this shell is chambered,
as in the nautiloids and ammonoids.
• The rostrum is made of fibrous calcite,
arranged in concentric layers.
Class Scaphopoda
• Tusk shells or tooth
shells
• Chief characteristics:
Curved tubular shells
open at both ends.
• Geologic range:
Ordovician to Recent.
• Mode of life: Marine.
Phylum Arthropoda
• Insects, spiders, shrimp, crabs, lobsters,
barnacles, ostracodes, trilobites, eurypterids
• Name: means "jointed" (arthro) + "foot" (pod).
• Chief characteristics:
– Segmented body with a hard exterior skeleton
composed of chitin (organic material).
– Paired, jointed legs.
– Highly developed nervous system and
sensory organs.
Phylum Arthropoda
• Geologic range: Cambrian to Recent.
• Mode of life: Arthropods inhabit a wide
range of environments. Most fossil forms
are found in marine or freshwater
sediments.
Paleozoic Arthropods and
Their Geologic Ranges
•
•
•
•
•
•
•
Trilobites - Cambrian to Permian
Horseshoe crabs - Silurian to Recent
Eurypterids - Ordovician to Permian
Arachnids - Late Silurian to Recent
Ostracodes - Cambrian to Recent
Onychophorans - Cambrian to Recent
Insects - Devonian to Recent
Subphylum Trilobita - Trilobites
• Chief characteristics:
– Body has three-lobes
– Skeleton composed of chitin,
with calcium carbonate
– Body is divided into three
segments:
• Rigid head segment cephalon
• Jointed, flexible middle
section - thorax
• Rigid tail piece - pygidium
Subphylum Trilobita - Trilobites
• Name: Trilobite means "three" (tri)
+ "lobed" (lobus).
• Geologic range: Cambrian to
Permian
• Mode of life: Exclusively marine.
Most were bottom dwellers living
in shallow shelf environments.
Class Eurypterida - Eurypterids
• Extinct scorpion-like or
lobster-like arthropods.
• Predators.
• Up to 10 ft long.
• Geologic range: Ordovician to
Permian. Most are Silurian
and Devonian.
• Mode of life: Inhabited
brackish estuaries.
Class Arachnida - Arachnids
• Scorpions, spiders, ticks, and mites
• Scorpions are the oldest arachnids with a fossil
record.
• Scorpions had evolved by the Late Silurian. The
earliest ones appear to have lived in the water,
because their fossils have gills.
• Scorpions, spiders, and mites are found in
Devonian rocks.
• Geologic range: Late Silurian to Recent.
Class Ostracoda -Ostracodes
• The ostracodes are mainly
microscopic in size.
• Tiny bivalved shell encasing a
shrimp-like creature.
• Geologic range: Cambrian to
Recent.
• Mode of life: Both marine and
freshwater.
Class Onychophora
• Onychophorans share many characteristics of
segmented annelid worms and arthropods, and are
considered to be intermediate in evolution between
the two groups.
• Geologic range: Cambrian to Recent
The onycophoran, Aysheaia.
Class Hexapoda - Insects
• The insects are among the most diverse
living group on Earth, but they are rarely
found as fossils.
• Body is divided into three parts, head,
thorax, and abdomen.
• Thorax has six legs.
• The earliest insects were wingless.
• Winged insects appeared by the Pennsylvanian.
• Geologic range: Middle Devonian to Recent.
Phylum Echinodermata
• Starfish, sea urchins,
sand dollars, crinoids,
blastoids, and others
• Name: Echinodermata
means "spiny"
(echinos) + "skin"
(derma).
Phylum Echinodermata
• Chief characteristics: Calcite skeleton with fivepart symmetry, superimposed on primitive
bilateral symmetry.
• Echinoderms have a water vascular system with
water in a system of tubes within the body.
• Tube feet are soft, movable parts of the water
vascular system which project from the body and
are used in locomotion, feeding, respiration, and
sensory perception.
Phylum Echinodermata
• Geologic range: Cambrian to Recent.
• Mode of life: Exclusively marine. Some are
attached to the sea floor by a stem with
"roots" called holdfasts; others are freemoving bottom dwellers.
• Similarity of embryos between echinoderms
and chordates suggests that they may be
derived from a common ancestral form.
Class Crinoidea - Crinoids
• Crinoids are animals which
resemble flowers.
• They consist of a calyx with
arms, atop a stem of calcite
disks called columnals.
• The crinoid is attached to the
sea floor by root-like holdfasts.
• Some living crinoids are
swimmers, and not attached.
• Over 1000 genera are known.
Crinoids
• Geologic range: Middle
Cambrian to Recent.
• Especially abundant
during the Mississippian.
Class Blastoidea - Blastoids
• Blastoids are extinct animals
with an armless bud-like
calyx on a stem.
• About 95 genera are known.
• A common genus is
Pentremites.
• Geologic range: Ordovician
to Permian - all extinct.
Class Asteroidea - Starfish
• Starfish are star-shaped echinoderms with
five arms.
• About 430 genera are known.
• Geologic range: Ordovician to Recent.
Class Ophiuroidea – Brittle Stars
• Brittle stars have 5 arms, like starfish, but
the arms are thin and serpent-like.
• About 325 genera are known.
• Geologic range: Ordovician to Recent.
Class Echninodea
• Sand dollars and sea urchins
• Echinoids are disk-shaped, biscuitshaped, or globular.
• Viewed from above, they may be
circular or somewhat irregular in
shape, but with a five-part
symmetry.
• About 765 genera are known.
• Geologic range: Ordovician to
Recent.
Class Holothuroidea
• Sea cucumbers
• Soft-bodied echinoderms resembling
cucumbers.
• They have microscopic hard parts called
sclerites in various shapes resembling
hooks, wheels and anchors.
• About 200 genera are known.
• Geologic range: Middle Cambrian?, Middle
Ordovician to Recent
Class Edrioasteroidea
• Edrioasteroids
• A group that was probably
ancestral to starfish and sea
urchins.
• Globular, discoidal, or cylindrical
tests (shells), many of which had
concave surfaces.
• Geologic range: Early Cambrian to
Middle Pennsylvanian.
Class Cystoidea
• Cystoids
• This primitive group had a calyx attached
to the seafloor by a stem (like crinoids and
blastoids).
• Distinctive patterns of pores on the plates
of the calyx.
• Geologic range: Cambrian to Late
Devonian. Most common in Ordovician
and Silurian.
The Echinoderm-Backbone
Connection
• Echinoderms are closely related to chordates
(the group that includes the vertebrates).
• The early cell division, embryonic development,
and larvae of echinoderms resemble those of
chordates, and are different from those of other
invertebrates.
• Biochemistry of echinoderms is also similar to
that of chordates (chemical similarities
associated with muscle activity and chemistry of
oxygen-carrying pigments in the blood).
Phylum Hemichordata
Class Graptolithina - Graptolites
• Name: Graptolite means "write" (grapto) +
"stone" (lithos), because they resemble
pencil marks on rock.
Graptolites
• Chief characteristics:
– Organic (chitinous) skeletons consisting of
rows or lines of small tubes or cups, called
thecae.
– Tubes or cups branch off a main cord or tube
called a stem or stipe.
– Stipes may consist of one, two, or many
branches.
– Entire colony called a rhabdosome.
– A filament at the lower end of the rhabdosome
is called a nema.
Graptolites
• Most graptolites are found flattened and
carbonized in black shales and mudstones.
• Geologic range: Cambrian to Mississippian.
(Most abundant in Ordovician and Silurian.)
• Some living organisms which may be surviving
descendants (living fossils) have been
recovered in 1989 in the South Pacific and later
in Bermuda.
• Mode of Life: Planktonic (colonies attached to
floats).
Phylum Chordata
• Vertebrates, sea squirts or tunicates, lancelets
such as Amphioxus.
• Name: "Chord" means "string", referring to the
nerve cord and/or notochord.
• Geologic range: Cambrian to Recent.
• Mode of life: Varied. Among the vertebrates
alone, various members are land dwellers,
swimmers, or fliers. Paleozoic vertebrates were
initially in the sea, but later colonized freshwater
and land.
Phylum Chordata
Chief characteristics (some are embryonic):
1. Bilateral symmetry.
2. Gill slits. These slits are a series of openings
that connect the inside of the throat to the
outside of the "neck".
3. Dorsal nerve cord (sometimes called a spinal
cord). The nerve cord runs down the "back",
connecting the brain with the muscles and
other organs.