Phylum Chordata Vertebrates, sea squirts or tunicates, lancelets such as Amphioxus. Name: "Chord" means "string," referring to the nerve cord and/or notochord.

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 Holocene. 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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Phylum Chordata Chief characteristics (some are embryonic):
Bilateral symmetry. Gill slits. These slits are a series of openings that connect the inside of the throat to the outside of the "neck." Dorsal nerve cord (sometimes called a spinal cord). The nerve cord runs down the "back," connecting the brain with the muscles and other organs. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Phylum Chordata Notochord. A stiff cartilaginous rod which supports the nerve cord. Post-anal tail. This is an extension of the body past the anal opening. Blood that circulates forward in a main ventral vessel and backward in a dorsal vessel. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Phylum Chordata Subphylum Urochordata
Primitive chordates: Sea squirts, ascidians, or tunicates. Larval forms have notochord in tail region. Chief characteristics: Adults have sac-like bodies, ranging in size from less than 1 mm to a few cm. Larval form resembles a tadpole and has a notochord, dorsal tubular nerve cord, gill slits, and post-anal tail. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Phylum Chordata Subphylum Urochordata
Geologic range: not known Mode of life: Inhabit overhangs or shaded areas in the low intertidal and subtidal zone. Most live attached as adults. Filter feeders. Behavior resembles that of a sponge. Body contracts abruptly expelling water, giving them the name "sea squirts." © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Phylum Chordata Subphylum Cephalochordata
Primitive chordates. Lancelets, Amphioxus, Branchiostoma. Small marine animals with fish-like bodies and notochord. Geologic range: Cambrian to Holocene. Mode of life: Bottom dwellers. Lancelets spend much of their time burrowing in the sand in warm, coastal, marine environments. Filter feeders. Relatively sessile but capable of swimming. Significance: An ancestor to the vertebrates resembled a lancelet-like creature (Pikaia). © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Phylum Chordata Subphylum Cephalochordata
Chief characteristics: Lancelets resemble a small, colorless anchovy fillet. No obvious eyes or lateral fins. Worm-like. Has segmented axial muscles, gill slits, a dorsal hollow nerve cord, a notochord, and a post-anal tail. No solid skeleton. Nothing resembling a vertebral column. FIGURE Branchiostoma, a fishlike member of the subphylum Cephalochordata. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

What ARE conodonts? The conodonts were previously placed in a separate phylum (Phylum Conodonta), because their affinities were unknown. The current interpretation places the conodont-bearing animal with the Chordates in Phylum Chordata. The organism from which they came is not known with certainty. Examples of various shapes of conodont elements. Photographs courtesy of K. Chauff © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Conodonts Chief characteristics: Microscopic in size
Composed of calcium fluorapatite. Shape - cone-shaped teeth, or bars with rows of tooth-like denticles, or irregular knobby plates called platforms. Each conodont element is part of a larger organism. Most fossil occurrences are of disassociated elements, but occasionally they are found arranged in specific assemblages or “apparatuses." © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Conodonts Name: Conodont means "cone" + "teeth" (dont)
Geologic range: Neoproterozoic to Late Triassic. Mode of life: Marine, free-swimming. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Conodonts Significance: Useful in biostratigraphy
Useful in marine paleoenvironmental interpretation Their color is a good indicator of the temperature to which the rock has been subjected. (This is important in determining whether oil or gas may be present in the rock). © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

What WAS the conodont animal?
Several fossils of conodont animals have been reported, but most were discredited and reinterpreted as an organism which had actually eaten the conodont animal, because the conodont elements were only in the stomach or digestive tract. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Photograph courtesy of K. Chauff Sketch of a conodont animal published in 1993 from Lower Carboniferous of Scotland. The conodont animal is found as soft-bodied impressions. The animals lack skeletal parts except for the conodonts, which occur in the mouth region. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

A fossil discovered (1995) in Ordovician Soom Shale of South Africa contains soft bodied remains of an animal with an elongated eel-like body. The animal had an eye, and had V-shaped musculature along the sides of the body, as in the amphioxus or lancelet. The organism has a longitudinal band which may mark the position of the notochord. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

What were the conodont elements used for in the conodont animal?
Internal laminated structures within conodont elements indicate that new lamellae were added on the outer surface of many elements, suggesting that they were an internal skeletal appatatus, covered with tissue, rather than being used as teeth. They may have been supports for a food-gathering apparatus. Some conodonts show evidence of having been broken and subsequently repaired. The function of the conodont apparatus is not known. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Phylum Chordata Subphylum Vertebrata
The vertebrates are animals with: Segmented backbone consisting of vertebrae Definite head with a skull that encloses a brain Ventrally-located heart Well-developed sense organs Notochord is supplemented or replaced by cartilaginous or bony vertebrae. Arches of the vertebrae encircle and protect a hollow spinal cord. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Mode of Life: Includes both water-dwelling and land-dwelling tetrapods (from the Latin, meaning four feet). Some walk on four legs and some walk only on the hind legs (bipedal). In some, forelimbs are modified into wings. In some, the limbs have been modified into flippers. Geologic range: Cambrian to Holocene. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Two major groups of vertebrates: Non-amniotic vertebrates - Egg lacks a covering and must be fertilized externally. Must be wet or in water to reproduce. Fish Amphibians Amniotic vertebrates - Amniotes. Internal fertilization and an amniotic egg (enclosed egg). Water is not required for reproduction. Reptiles Birds Mammals © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Amniotic Egg Amnion (or amniotic membrane) encloses the embryo in water (amniotic fluid). Allantois is a reservoir for waste and provides for gas diffusion. It becomes the urinary bladder in the adult. Chorion provides a protective membrane around the egg. Yolk is a storage area for fats, proteins, and other nutrients - food for the embryo. FIGURE Amniotic egg. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Significance of the Amniotic Egg
Provided freedom from dependency on water bodies. Helped the vertebrates live in diverse types of terrestrial environments. An important milestone in the evolution of vertebrates. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

The Fishes There are five classes of fishes. Agnathids or jawless fish
Acanthodians or spiny fish with jaws. Extinct. Placoderms or plate skinned fish with jaws. Extinct. Chondrichthyes or fish with cartilaginous skeletons, including sharks, rays, and skates. Osteichthyes or bony fishes. Most modern fish. Led to evolution of tetrapods. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Geologic ranges of the five classes of fishes
FIGURE Evolution of the five major categories of fishes. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Class Agnatha Jawless fishes, including the living lampreys and hagfishes as well as extinct ostracoderms Name: "A-" means "without," and "gnatha" means "jaws." Chief characteristics: Fish without jaws. Mode of life: Swimmers. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Class Agnatha Geologic range: Cambrian to Holocene. Ostracoderms were Ordovician to Devonian. Jawless fishes are present in the Harding Sandstone (Lower Ordovician) of Colorado. Also found in Lower Ordovician rocks in Australia and Bolivia. Includes Astraspis. FIGURE Ordovician agnathan Astraspis, from Harding Sandstone, Colorado. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Ostracoderms A group of armored jawless fishes called the ostracoderms (name means "shell skin") lived during Early Paleozoic. Ostracoderms were mainly small, sluggish fish that were filter feeders or "mud strainers." FIGURE Early Paleozoic ostracoderms. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Ostracoderms The armor was made of bony material, and served as protection from predators or for storing seasonally available phosphorous. Bone is made of apatite, which contains phosphorous. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Evolution of Jaws The first fish with jaws appeared in nonmarine rocks during Late Silurian. The evolution of the jaw expanded the adaptive range of vertebrates. Used for biting and grasping. Led to more varied and active ways of life, and to new sources of food. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Evolution of Jaws Origin of jaws - two hypotheses:
Modification of a front pair of bone or cartilage gill supports. More recent hypothesis: Modification of the velum, a structure used in respiration and feeding in lamprey larvae. Both hypotheses are based on anatomy and embryology of living fishes. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Class Acanthodii Acanthodians or spiny fishes.
The first fishes to have jaws. Name: "Acanthos" means "spiny." Chief characteristics: Primitive spiny fishes with jaws. Geologic range: Late Silurian to Permian. Most numerous during Devonian. Extinct. Mode of life: Swimmers. Nonmarine. FIGURE Early Devonian acanthodian fish Climatius. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Class Placodermi Placoderms or "plate-skinned" fishes.
Name: "Placo-" means plate and "derm" means "skin." Chief characteristics: Fish with jaws and armor plating. Geologic range: Late Silurian to Late Devonian. Extinct. Mode of life: Swimmers. Some were large carnivorous predators, such as Dunkleosteus, which grew to about 9 m long Dunkleosteus (top) J. Sibbick, (bottom) Courtesy of the U.S. National Museum of Natural History, Smithsonian Institution; photograph by Chip Clark) © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Class Chondrichthyes - Sharks
Sharks, rays, and skates Name: From "chondros," meaning "cartilage," and "icthyes" meaning "fish." Chief characteristics: Cartilaginous fishes. Skeleton made of cartilage not bone. Rarely preserved. Geologic range: Middle Paleozoic (Late Silurian or Devonian) to Holocene. Mode of life: Swimmers. Marine, except one Late Carboniferous freshwater genus. The genus Cladoselache, is found in Devonian shales on the southern shore of Lake Erie. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Class Osteichthyes - Bony Fishes
Name: "Osteo" means "bone" and "ichthyes" means "fish." Chief characteristics: Skeleton of bone, not cartilage. Modern bony fishes are of this type. Geologic range: Devonian to Holocene. Mode of life: Swimmers. Marine and freshwater. The earliest lived in freshwater. The most numerous, varied, and successful of all aquatic vertebrates. FIGURE 12-68 © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Class Osteichthyes - Bony Fishes
Bony fishes played a key role in the evolution of tetrapods (four-legged animals). Two types of bony fish are significant: Subclass Actinopterygii - the ray-finned fish. Subclass Sarcopterygii - the lobe-finned fish or lungfish. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Subclass Actinopterygii
Ray-finned fish Dominant fishes in the world today. No muscular base to the paired fins. Fins are thin structures supported by radiating rods or rays. First appeared during Devonian freshwater lakes and streams, and then expanded their geographic range to the sea. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Subclass Sarcopterygii - Lobe-finned fish or Lungfish
Chief Characteristics: Leg-like fins: Muscular fins used to "walk" on pond or stream bottoms. Lungs: A pair of openings in the roof of the mouth led to nostrils. Able to rise to the surface and breathe air with lungs when the water became foul or stagnant. Some had both lungs and gills. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Subclass Sarcopterygii – Lobe-finned fish or Lungfish
Geologic range: Late Devonian to Holocene Significance: This group gave rise to the amphibians and other tetrapods (four-legged animals). Types of sarcopterygians: Order Dipnoi or dipnoans Order Crossopterygii or crossopterygians – the ancestor of the amphibians © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Order Dipnoi - dipnoans
Chief characteristics: They can breathe with lungs during the dry season, and can burrow into the mud during droughts. Name: Dipnoi means "double breather" Significance: This group did not lead to tetrapods, but includes interesting freshwater lungfish living today in Australia, Africa and South America. FIGURE Dipterus, a Devonian lungfish. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Order Crossopterygii - crossopterygians
Chief characteristics: Short, muscular, paired fins. Had a single limb bone called the humerus, followed by the radius and ulna in front fins, and the tibia and fibula in hind fins. The adaptation assisted movement in shallow water, and allowed the fish to move from a stagnant or drying body of water, to another body of water. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Order Crossopterygii - crossopterygians
Significance: Considered to be ancestral to the amphibians because of the arrangement of bones in their fins, the pattern of bones of the skull, and the structure of their teeth. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Types of crossopterygian fish
Rhipidistians - This group led to the amphibians Coelacanths - Lobe-finned crossopterygian fish invaded the sea and gave rise to coelacanths. Coelacanths were long-believed to be extinct and are considered to be living fossils. One was caught in 1938 near Madagascar. More have been caught since. Latimeria, a modern coelacanth. Tail is similar to that of Dipterus, but very different from that of ray-finned fish. FIGURE 12-75 © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Similarities between Crossopterygian Fish and Amphibians
The same limb bones are present. FIGURE 12-72 Early amphibian (left). Crossopterygian fish (right). The major limb bones are coded r, u and h. r = radius u = ulna h = humurus © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Similarities between Crossopterygian Fish and Amphibians
The same skull bones are present. FIGURE 12-73 Crossopterygian fish (left) Devonian amphibian, Ichthyostega (right). © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

The Advent of Tetrapods
Tens of millions of generations passed before crossopterygian fish evolved into animals that could live entirely on land. The early tetrapods (four-legged animals) continued to return to water to lay their fish-like, naked eggs. Fish-like tadpoles hatched from these eggs, which used gills for respiration. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Anatomical changes associated with the shift from water to land:
Three-chambered heart developed and functioned to pump blood more efficiently to the lungs Limb and girdle bones altered to support the body above the ground Spinal column changed to become sturdy but flexible Fish spiracle (vestigial gill slit) became amphibian eustachian tube and middle ear © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Anatomical changes associated with the shift from water to land:
Bones of the ear changed to function better in air than in water (modification of hyomandibular bone that propped fish braincase and upper jaw together, into an ear ossicle called the stapes) Eardrum (tympanic membrane) formed across a notch in the skull © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Amphibians are interpreted to be descended from crossopterygian fishes because of:
Arrangement of bones in amphibian limbs compared with the fins of crossopterygian fish Pattern of bones of the skull Structure of the teeth - highly infolded like a maze (or labyrinth), and called labyrinthodont teeth. Bones of the spinal column in early forms. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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). © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. FIGURE Evolution of lobe-fin fishes and amphibians from Devonian fishes. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Ichthyostega – The First Amphibian
FIGURE 12-78 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). © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Ichthyostega – The First Amphibian
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 © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

The Amphibians 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). © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

The Amphibians 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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Permian pelycosaur, Dimetrodon.
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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Pelycosaurs Two well known pelycosaurs, which evolved their sails independently were the carnivorous Dimetrodon, and the plant-eating Edaphosaurus. Dimetrodon has a larger skull and teeth than does Edaphosaurus, suggesting that Dimetrodon was a meat-eater. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Therapsids Therapsids were small to moderate-sized animals with mammalian skeletal characteristics: Fewer bones in the skull than the other reptiles Mammal-like structure of the jaw Differentiated teeth (incisors, canines, and cheek teeth) Limbs in more direct alignment beneath the body Reduction of ribs in the neck and lumbar regions, allowing greater flexibility © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Therapsids Double ball-and-socket joint between the skull and neck
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. Whisker pits on the snout. Geologic range: Permian to Triassic. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Therapsids - Cynognathus
Mammal-like features are well developed in the therapsid, Cynognathus. Name: From "kynos" meaning "dog" and "gnathos" meaning "jaw" or "tooth." © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Stromatolites - A Photosynthetic Plant Ancestor
The earliest photosynthetic organisms were in the sea. Stromatolites, built by photosynthetic bacteria (cyanobacteria, sometimes called blue-green algae), were ancestral to Paleozoic plants. They were not plants themselves. Kingdom Eubacteria. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Appeared during Archean Expanded during Proterozoic Are present in Phanerozoic limestones. Most Precambrian stromatolites grew in shallow marine and intertidal environments, but some lived in freshwater. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Stromatolite reefs were widespread during Cambrian, but declined during Ordovician. They are typically found in areas lacking marine invertebrates, which feed on the cyanobacterial mats. The appearance of abundant marine invertebrates during Cambrian led to the decline of the stromatolites. Why? They ate them. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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: Chlorophytes Receptaculitids © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Chlorophytes 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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Receptaculitids 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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Land Plants Land plants include:
Bryophytes - non-vascular plants Mosses, liverworts, and hornworts. Devonian to Holocene. Tracheophytes - vascular plants Trees, ferns, and flowering plants. Silurian to Holocene © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. FIGURE 12-85 © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Major Advances in Land Plants
Three major advances in land plant history, developing more efficient reproductive systems: Seedless spore-bearing plants, appearing during Ordovician, and flourishing in Carboniferous coal swamps Seed-producing, pollinating, but non-flowering plants appearing during Late Devonian (gymnosperms, such as conifers) Flowering plants, appearing during Late Mesozoic (angiosperms) © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. FIGURE 12-87 Rhynia, a Middle Devonian vascular land plant with woody tissues called xylem. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Common plants of Carboniferous
Lycopods or Lycopsids - club mosses Sphenopsids - horsetails, scouring rushes Ferns Gymnosperms Seed ferns Cordaites Conifers Ginkgoes © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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 © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Ferns Phylum Polypodiophyta
Ferns are vascular plants that reproduce by means of spores. They live in moist habitats. Geologic range: Devonian to Holocene. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Cordaites Gymnosperms. Class Pinopsida, Order Cordaitales
Seed-bearing gymnosperms with strap-like leaves that were ancestors to the modern conifers. Tall trees (up to 50 m). Abundant in Carboniferous coal swamps. Extinct by the end Permian. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

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. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Ginkgoes Gymnosperms. Class Ginkgopsida
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. Represented by a single species today, Ginkgo biloba. It is extinct in the wild, but is widely grown as an ornamental tree. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Mass Extinctions of Paleozoic
Paleozoic was a time of adaptive radiations and extinctions. Many of the geologic periods of Paleozoic began with adaptive radiations, or times of rapid evolution of organisms. Several of the Paleozoic periods ended with extinction events of varying severity. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

The three most catastrophic extinctions during Paleozoic Era were at the following times: End of Ordovician (443 m.y. ago) End of Devonian (359 m.y. ago) End of Permian (251 m.y. ago) Permian extinction was the most severe. The extinction at the end Permian is considered to be the most catastrophic mass extinction in the history of life. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Late Ordovician Extinctions
Following a slight dip in diversity at the end Cambrian, Ordovician was a time of renewed diversification. The number of genera increased rapidly, and the number of families increased from about 160 to 530. This increase was particularly dramatic among trilobites, brachiopods, bivalved molluscs, and gastropods. An extinction event at the end of Ordovician led to an abrupt decline in diversity. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

The extinction occurred in two phases. First phase - affected planktonic and nektonic (floating and swimming) organisms such as graptolites, acritarchs, many nautiloids and conodonts, as well as benthic (bottom-dwelling) organisms such as trilobites, bryozoa, corals, and brachiopods. Second phase - affected several trilobite groups, corals, conodonts, and bryozoans. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Both phases of the extinction event were related to global cooling and the growth of glaciers in Gondwana. Glaciation was coupled with the lowering of sea level and a reduction in shallow water habitat. As the climate cooled, tropical organisms showed the greatest decline. As warming occurred and the glaciers began to melt, organisms which were adapted to the cooler conditions began to suffer extinction. This was the second phase of extinctions. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Late Devonian Extinctions
Late Devonian extinctions occurred over a span of about 20 million years, and appear to have been the result of an ecological crisis in the seas, perhaps induced by changes occurring on the land. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Devonian saw the appearance of trees and spread of land plants. This would have accelerated weathering rates, leading to large volumes of nutrients being washed into the seas. Large quantities of nutrients in the water (such as phosphorus) causes algal blooms. Bacteria breaking down large quantities of dead algae uses up all of the oxygen in the water, causing anoxic conditions (= "without oxygen"). This process is called eutrophication, and it occurs today in lakes, and causes massive "fish kills." © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Extensive Devonian black shale deposits (for example, the Chattanooga Shale) suggest the widespread occurrence of anoxic conditions in the Devonian sea. Glaciation may have been an additional contributing factor. By Late Devonian, South America had drifted over the South Pole, and glaciations occurred. Overall, 70% of marine invertebrate families went extinct during Late Devonian. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Organisms most strongly affected (but not totally wiped out) by the Devonian extinction were: Tabulate corals Rugose corals Stromatoporoids Brachiopods Goniatite ammonoids (cephalopod molluscs) Trilobites Conodonts Placoderm fish © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Late Permian Extinctions
Late Permian is marked by a catastrophic extinction event which resulted in the total disappearance of many animal groups. This was the largest extinction event in the history of life, exceeding even the extinction event at the end of Cretaceous, which killed the dinosaurs. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

More than 90% of all marine species that existed during Permian disappeared or were severely reduced in number. Nearly half of the known families disappeared. Tropical forms experienced the most extensive losses. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

The following marine organisms were extinct by the end Permian: Fusulinid foraminifera Rugose corals Tabulate corals Blastoids Trilobites (which had become extinct somewhat earlier during Permian) © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Other groups of organisms were severely reduced in diversity, with some surviving species: Brachiopods Crinoids Bryozoa Ammonoids Organisms which inhabited warm waters shifted their distributions toward the equator. Cool conditions prevented construction of reefs and the formation of limestones. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Permian extinction also affected land dwellers. More than 70% of land animals disappeared or were severely reduced, including: Amphibian families Reptile families Synapsids (once called "mammal-like reptiles") © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Among the plants, the spore-bearing plants that inhabited tropical coal swamps were replaced by seed-bearing gymnosperms, that could inhabit cooler, drier climatic conditions. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Contributing Factors Many factors may have contributed to the Permian mass extinction: Climatic change associated with assembly of Pangea – Global cooling and drying, along with interruption of equatorial circulation Glaciation at both north and south ends of Pangea Reduction in epicontinental seas as sea level dropped (habitat loss) © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Contributing Factors 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. Possibility of an extraterrestrial impact, as indicated by spherical carbon molecules containing an extraterrestrial helium-3 isotope © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

IMAGE CREDITS FIGURE Branchiostoma, a fishlike member of the subphylum Cephalochordata. Source: Harold Levin. FIGURE Amniotic egg. Source: Harold Levin. FIGURE Evolution of the five major categories of fishes. Source: After Romer, A., 1945, Vertebrate Paleontology, Chicago: University of Chicago Press. FIGURE Ordovician agnathan Astraspis, from Harding Sandstone, Colorado. Source: Elliot, D., 1987, A reassessment of Astraspis desiderata, the oldest North American vertebrate. Science. 237: FIGURE Early Paleozoic ostracoderms. Source: Harold Levin. FIGURE Early Devonian acanthodian fish Climatius. Source: Romer, A., 1945, Vertebrate Paleontology, Chicago: University of Chicago Press. FIGURE Cheirolepis, the ancestral bony fish that lived during the Devonian Period. Source: Harold Levin. FIGURE Dipterus, a Devonian lungfish. Source: Harold Levin. FIGURE Latimeria, a surviving coelacanth in the ocean near Madagascar. Source: Harold Levin. FIGURE Limb bones of an early amphibian (left) and crossopterygian fish (right). Source: Harold Levin. FIGURE Skulls and lower jaws of a Eusthenopteron (left) and Devonian amphibian Ichthyostega (right). Source: Harold Levin. FIGURE Evolution of lobe-fin fishes and amphibians from Devonian fishes. Source: Colbert, E. and Morales, M., 1991, Evolution of Vertebrates, 4th edition.This material is reproduced with permission of John Wiley & Sons, Inc. FIGURE The Ichthyostega skeleton retains the fishlike form of its crossopterygian ancestors. Source: Harold Levin. FIGURE Late Silurian/Early Devonian vascular plant, Cooksonia. Source: Harold Levin. FIGURE Middle Devonian vascular land plant, Rhynia. Xylem. Source: Harold Levin. © 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED.

Phylum Chordata Vertebrates, sea squirts or tunicates, lancelets such as Amphioxus. Name: "Chord" means "string," referring to the nerve cord and/or notochord.

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Phylum Chordata Vertebrates, sea squirts or tunicates, lancelets such as Amphioxus. Name: "Chord" means "string," referring to the nerve cord and/or notochord.

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Presentation on theme: "Phylum Chordata Vertebrates, sea squirts or tunicates, lancelets such as Amphioxus. Name: "Chord" means "string," referring to the nerve cord and/or notochord."— Presentation transcript:

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