Paleozoic Invertebrates• Representatives of most major invertebrate phyla

were present during Paleozoic, including sponges, corals, bryozoans, brachiopods, mollusks, arthropods, and echinoderms.

• Almost all of the common invertebrate phyla in existence today had appeared by Ordovician.

Paleozoic Vertebrates• Vertebrates evolved during 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 Ordovician. • Vascular plants expanded across the land, forming

great forests during Devonian. • The plants progressed from seedless, spore-

bearing plants to plants with seeds but no flowers (gymnosperms).

Paleozoic Extinctions• Several mass extinctions occurred during

Paleozoic, including the largest extinction of all at the end of Permian.

• Other mass extinctions occurred at the end of Ordovician and Devonian.

Diversity during Paleozoic Red arrows mark

extinction events

Paleozoic Life Summary of

invertebrate phyla

• The first animals with shells are called small shelly fossils.

• Small shelly fossils are found at the base of Cambrian, and during Late Neoproterozoic.

• Most disappeared by at the top of the first stage within 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.

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 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.

Animals in the Burgess Shale 1. Several groups of arthropods, including trilobites and

crustaceans 2. Sponges 3. Onycophorans (velvet worms)4. Crinoids 5. Molluscs 6. Corals 7. Three phyla of worms 8. Chordates (Pikaia) 9. Many others

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.

The Chengjiang fauna • In 1984, the Lower Cambrian 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.

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 Cambrian, Ordovician

seas experienced 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 notable among trilobites, brachiopods,

bivalve molluscs, gastropods, and corals.

Late Ordovician Extinction• An extinction event at the end of 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.

Devonian Diversity • During Devonian, there was continued

diversification, but this 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 • During Early Carboniferous, diversity once again

increased. • Diversity of marine animals remained fairly

constant throughout Carboniferous and Permian. • Late Permian is marked by a catastrophic

extinction event which resulted in the total disappearance of many animal groups.

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 most primitive test. – Other forams construct tests of calcium carbonate.

Foraminifera • Geologic range: Cambrian to Holocene.• Modes of life:

– Benthic or benthonic (bottom dwellers) – Planktic or planktonic (floaters).

Fusulinid foraminifera (fusulinids) • Fusulinids were abundant during 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 during 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 Holocene. Rare during Early Paleozoic. More abundant during 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, graptolites 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 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

Holocene 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 Characteristics1. Radial symmetry2. Mouth at the center of a ring of tentacles.

Phylum Cnidaria – Chief Characteristics3. Body form may be polyp (attached to the bottom, with tentacles on

top) or medusa (free-swimming, jellyfish).

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 Devonian of Michigan).

Rugose Corals• Geologic range: Ordovician to Permian - all extinct. • Rugose corals were abundant during Devonian

and Carboniferous, but became extinct during 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 Silurian and their reef-building 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 Paleozoic • Geologic range: Triassic to Holocene.

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 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 Archimedes, from Mississippian rocks, 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 BrachiopodaMode 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:

– Early Cambrian to Holocene. – Very abundant during 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:

– Early Cambrian to Holocene

Articulate Brachiopods • Calcareous valves

attached together with a hinge consisting of teeth and sockets.

• Geologic range: Early Cambrian to Holocene

• Spiny brachiopods (called productids) are characteristic of 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.

Types of Molluscs1. 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 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 Holocene • 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 Holocene.

• 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 Holocene• 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 Holocene

Ammonoid Cephalopods• Ammonoid cephalopods have complex, wrinkled,

crenulated septa, which produce angular or dendritic sutures.

• Geologic range: Devonian to Cretaceous - all extinct.

Types of Sutures in Cephalopods

Subclass Coleoidea• Belemnoids (belemnites)

– Geologic range: Mississippian to Eocene - all extinct.

• Sepioids (cuttlefish)– Geologic range: Jurassic to Holocene

• Teuthoids (squid)– Geologic range: Jurassic to Holocene

• Octopods (octopus)– Geologic range: Cretaceous to Holocene

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 Holocene. • 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 Holocene• 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 Holocene• Eurypterids - Ordovician to Permian• Arachnids - Late Silurian to Holocene• Ostracodes - Cambrian to Holocene • Onychophorans - Cambrian to Holocene• Insects - Devonian to Holocene

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 or 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 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 Holocene.

Class Ostracoda -Ostracodes• The ostracodes are mainly

microscopic in size. • Tiny bivalved shell encasing a

shrimp-like creature. • Geologic range: Cambrian to

Holocene. • Mode of life: Both marine and

freshwater.

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

Pennsylvanian. • Geologic range: Middle Devonian to

Holocene.

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 five-part 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 Holcene. • Mode of life: Exclusively marine. Some are attached

to the sea floor by a stem with "roots" called holdfasts; others are free-moving 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 Holocene.

• Especially abundant during 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 Holocene.

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 Holocene.

Class Echninodea• Sand dollars and sea urchins• Echinoids are disk-shaped, biscuit-shaped, 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 Holocene.

Phylum Hemichordata Class Graptolithina - Graptolites

• Name: Graptolite means "write" (grapto) + "stone" (lithos), because they resemble pencil marks on rock.