Class Amphibia –The Amphibians• Name: "Amphi" means "both" or "double," and

"bios" means "life." "Amphibios" means living a double life, referring to living in water and on the land.

• Chief characteristics and mode of life: Amphibians can live on the land as adults, but they lay their eggs in water. Young amphibians live in the water and are fish-like (tadpoles).

The Amphibians• Geologic range: Late Devonian to Holocene. • For 50 million years, from Late Devonian to

Middle Carboniferous, amphibians were the only vertebrates to the inhabit the land. Some adult amphibians reverted to an aquatic mode of life, while others retained a terrestrial lifestyle.

Ichthyostega – The First Amphibian

• The first terrestrial vertebrate, Ichthyostega, appeared in Late Devonian, about 375 m.y. ago

• Found in freshwater deposits. • "Ichthyo" means "fish" and "stega" means "roof" or

"cover" (probably referring to the bones in the roof of the skull).

• Ichthyostega retained many features of its fish ancestors, such as: – Scales – Similar skull structure, including arrangement of

nostrils – Loosely connected fish-like spinal column

• It also had a number of unique traits such as: – Five-toed limbs – Pelvic and pectoral girdles, allowing it to walk on

land

Ichthyostega – The First Amphibian

• Amphibians inhabited the Carboniferous coal swamps, and were abundant and varied.

• They had several different modes of life, including some with an aquatic lifestyle (as suggested by features such as a flattened body and skull, reduced limbs, and a slender snake-like body), and some that were clearly land dwellers (with stout limbs, short body and tail).

• Some Carboniferous amphibians were quite large, ranging up to 20 feet (about 6-7 m) long. In contrast, most living amphibians are small.

• Cacops, a small Early Permian labrynthodontic amphibian.

Class Reptilia - The Reptiles• Name: From "reptilis" meaning "creeping.“ Chief characteristics: Skull characteristics that

distinguish reptiles from amphibians:– Reptile skull is high and narrow, compared with the

low, broad amphibian skull. – In reptiles, the roof of the mouth is arched, with small

openings. In amphibians, it is flat with large openings.

Class Reptilia - The Reptiles• Mode of life: Complete colonization of land was

achieved by the reptiles, which can lay their eggs on dry land.

• Geologic range: Pennsylvanian to Holocene. • The oldest reptile fossils, genus Hylonomus, (300 m.y.

old) are found in Nova Scotia inside fossilized hollow trees filled with sediment. These reptiles were about 24 cm (1 ft) long. They resemble modern insect-eating lizards.

Class Synapsida -The Synapsids• The synapsids had diverged from the reptiles by

Late Carboniferous. • The synapsids were long considered to be a

subclass of reptile, but more recent cladistic analysis shows that they diverged from ancestors completely different than Hylonomus and other true reptiles.

The Synapsids• The synapsids were the dominant terrestrial

vertebrates during Permian. • This group was formerly called the "mammal-

like reptiles," however the name has been abandoned because they are not really reptiles.

• Synapsids include the pelycosaurs and the therapsids.

Pelycosaurs • Several species of

pelycosaurs had fins or "sails" on their backs, supported by rod-like extensions of their vertebrae. These sails may have been used as temperature regulating mechanisms.

• Pelycosaurs lived during Carboniferous and Permian. Sail-backed forms are Permian.

Permian pelycosaur, Dimetrodon.

Therapsids Therapsids were small to moderate-sized animals with mammalian

skeletal characteristics:1. Fewer bones in the skull than the other reptiles 2. Mammal-like structure of the jaw 3. Differentiated teeth (incisors, canines, and cheek teeth) 4. Limbs in more direct alignment beneath the body 5. Reduction of ribs in the neck and lumbar regions, allowing

greater flexibility

Therapsids6. Double ball-and-socket joint between the skull and neck 7. Bony palate which permitted breathing while chewing (an

important characteristic for animals evolving toward mammalian warm-bloodedness). Efficient breathing provides oxygen needed to derive heat energy from food.

8. Whisker pits on the snout.

Geologic range: Permian to Triassic.

Therapsids - Cynognathus • Mammal-like features are well developed in the therapsid,

Cynognathus. • Name: From "kynos" meaning "dog" and "gnathos" meaning

"jaw" or "tooth."

Therapsids - Cynognathus• Examination of the bone on the snout portion of the skull

reveals probable "whisker pits," suggesting that they had hair, which may have functioned to insulate the animal and slow the rate of heat loss.

Plants of Paleozoic

Marine Algae• The next step in the evolutionary path to land

plants was probably the green algae or chlorophytes. Kingdom Protista.

• Marine algae fossils are found in some Paleozoic rocks.

• Types of marine algae:1. Chlorophytes 2. Receptaculitids

Chlorophytes1. Chlorophytes - Green algae.

• Cambrian to Holocene. • A close relationship between chlorophytes and

land plants is suggested by the adaptation of some species to freshwater and moist soil.

Receptaculitids2. Receptaculitids are lower Paleozoic marine

fossils resembling sunflowers.– Produced by organisms of uncertain affinity.– Interpreted as lime-secreting algae. – Most are found in Ordovician rocks, but they are

also present in some Silurian and Devonian rocks as well.

Land Plants Land plants include:

1. Bryophytes - non-vascular plants Mosses, liverworts, and hornworts.

Devonian to Holocene. 2. Tracheophytes - vascular plants Trees, ferns, and flowering plants.

Silurian to Holocene

Tracheophytes • Tracheophytes have vascular tissues, or an internal

system of tubes and vessels, that transport water and nutrients from one part of the plant to another.

A water transport system is important, because plants generally withdraw water from below the ground. Below the ground there is water but no light. Above the ground there is sunlight but there may not be water. The vascular system allows the plant to take advantage of both places.

Tracheophytes• The oldest unquestioned vascular plant fossils occur

in Silurian rocks.• Small, leafless plants with thin branching stems. • These plants are called psilophytes. • Spore bodies are present on the ends of the stems in

fossils of Cooksonia.

Cooksonia, an early vascular plant of Late Silurian - Early Devonian. Height about 4 cm.

Major Advances in Land Plants Three major advances in land plant history, developing

more efficient reproductive systems:1. Seedless spore-bearing plants, appearing during

Ordovician, and flourishing in Carboniferous coal swamps

2. Seed-producing, pollinating, but non-flowering plants appearing during Late Devonian (gymnosperms, such as conifers)

3. Flowering plants, appearing during Late Mesozoic (angiosperms)

Spore-bearing Plants• The first plants to invade the land were

spore-bearing plants. • In fact, the first evidence of land plants is the

presence of spores in Ordovician rocks. • Spores are plant reproductive structures.

Familiar spore-bearing plants include mosses and ferns.

Life Cycle of Spore-bearing Plants• The life cycle of spore-bearing plants differs from

that of the more familiar seed-bearing plants. • Alternation of generations between diploid

(double set of chromosomes) and haploid (single set of chromosomes) forms.

• Water is required for fertilization.

The First Seeds• Seeds appeared during Late Devonian, although it is

not known which plant produced them.• Seed-bearing plants became more abundant during

Carboniferous. • The seed is significant because it freed plants from

their dependence on moist environments and allowed them to inhabit dry land, much as the amniotic egg freed animals from their dependence on wet environments.

Invasion of the Land by Plants The invasion of the land by plants profoundly

altered the landscape. – Plant roots slowed erosion. – Decaying vegetation led to soil formation.– Plants also provided a food source for animals, which

invaded the land after the appearance of land plants. Animals could not have survived on land without a food source (plants) in place.

Evolution of Wood• As plants evolved wood, they

were able to withstand the pull of gravity and grow taller.

• During Middle Devonian, the first wood appeared in plants of the genus Rhynia.

Rhynia, a Middle Devonian vascular land plant with woody tissues called xylem.

The First Trees• The first trees were present by Late Devonian. • By Carboniferous, trees reached 30 m tall or

more, with trunks 1 m in diameter.

Carboniferous Coal• There are more plant fossils in Carboniferous strata

than in any other geologic interval. • Plants gave Carboniferous its name, because of the

vast coal deposits which formed from plant remains in lowland swamps. Coal is dominated by the element carbon.

• Coal represents an enormous biomass of plants because it takes several cubic meters of wood to make one cubic meter of coal.

Common plants of Carboniferous 1. Lycopods or Lycopsids - club mosses2. Sphenopsids - horsetails, scouring rushes 3. Ferns 4. Gymnosperms

a. Seed fernsb. Cordaitesc. Conifersd. Ginkgoes

Lycopods or Lycopsids • Phylum Lycopodophyta or

Lycopsida • Club mosses, scale trees • Spore-bearing plants were

confined to swamps because spores require moisture to germinate.

• Some grew to be 30 m tall and 1 m diameter.

• Geologic range: Silurian to Holocene. (Only a few species persisted after Permian.)

• Common genera = Lepidodendron and Sigillaria.

Sphenopsids • Phylum Equisetaphyta or

Sphenopsida • Spore-bearing and similar to

living horsetails or scouring rushes.

• Interpreted as living in moist areas or standing water.

• Geologic range: Devonian to Holocene. (But only a few persisted after Permian.)

• Common genus = Calamites

Ferns • Phylum Polypodiophyta • Ferns are vascular plants that reproduce by

means of spores. • They live in moist habitats. • Geologic range: Devonian to Holocene.

Gymnosperms • Phylum Pinophyta or Gymnospermophyta • Conifers, cycads, ginkgoes, and various evergreen plants

without flowers • The word "gymnosperm" means "naked seed."• Seed-bearing plants. No flowers. • Seed-bearing plants no longer require moist habitats. This

led to the expansion of plants into drier areas. • Geologic range: Middle Paleozoic to Holocene.

Seed ferns • Gymnosperms. Class

Pteridospermophyta • Fernlike leaves, but reproduced

with seeds instead of spores. • Geologic range: Devonian to

Holocene. • Common genera = Neuropteris

and Glossopteris. • One of the best-known is

Glossopteris, which lived in Gondwana during Carboniferous and Permian. They were sometimes associated with glacial deposits, suggesting that they were adapted to cool climates.

Conifers • Gymnosperms. Class Pinopsida, Order Coniferales • The word "conifer" means "cone bearing." • Trees with cones which contain seeds.• Today conifers are represented by trees such as pines,

cedars, hemlocks, spruces, firs, etc.• Conifers spread widely during Permian, perhaps as a

result of the drier conditions which led to the demise of the coal swamps.

Ginkgoes • Gymnosperms.

Deciduous trees (they drop their leaves)

• Fan-shaped leaves. • They produce a

fleshy fruit but have no flowers.

• Geologic range: Early Permian to Holocene. Maximum diversity during Jurassic.

• single species today.

Late Permian Extinctions• Late Permian is marked by a catastrophic

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

• More than 90% of all marine species that existed during Permian disappeared or were severely reduced in number.

• Unusually active volcanism releasing CO2 (flood basalts in Siberia), leading to global warming, which may have triggered release of large stores of methane gas frozen in sediments on the sea floor, causing increased global warming.