Life of the Paleozoic
Tuesday, November 22, 11 Life of the Paleozoic
• Overview: • Cambrian, Vast expansion of shelly marine life forms and jawless fish • Ordovician - most modern phyla established • Late Paleozoic- land plants and vertebrates (tetrapods and amniotes)
Tuesday, November 22, 11 Invertebrates
• Marine environments • Nektic, planktic, benthic • Adaptions: • Epifaunal- animals living on the sea floor • Infaunal – animals that burrow into the sea floor
Tuesday, November 22, 11 Early cambrian
• Small Shelly fossils • Rarely more than a few millimeters long • A- Anabarella • B- Camanella • C- Aldanella • D- Sponge Spicule • E- Formitchella • F- Lapworthella
Tuesday, November 22, 11 Early Soft-body fossils • The Burgess shale: • Most fossils reduced to shiny black impressions What type of fossilization is this? • Viewed as one of the most important finds of the fossil record • Altogether, over 60,000 species have been collected
Tuesday, November 22, 11 The Burgess shale • Four Groups of Arthropods • Trilobites • Crustaceans • Scorpions • Insects • Sponges • Onycophorans • Crinoids • Sea Cucumbers • Chordates
Tuesday, November 22, 11 Chordates
• Shows evolution of early notochord • Notochord- dorsally situated nerve cord Why is this important? • Pikaia- small animal that has notochord and also shows evidence of v-shaped muscle bands (this indicated sinosoidal swimming motion
THESE ANIMALS ARE ANCESTORS TO ALL MODERN VERTEBRATES
Tuesday, November 22, 11 Other Notable Fossils • Anomalocaris- fierce predator over 50cm long (~2ft) • Opabinia- five eyes, flexible nozzle • Hallucigenia- seven pairs of legs, seven dorsal spines, claws, cylindrical trunk. (Considered to be a onycophoran) • Marrella- Four spines extended back from cephalon
The most common arthropod found in the burgess shale
Tuesday, November 22, 11 Tuesday, November 22, 11 Protista (unicellular groups) • Foraminifera (Calcerous Microfossils) • Range from Cambrian to present • More numerous and varied by Carboniferous • Global distribution during Pennsylvanian-Permian
• Radiolarians (Siliceous Microfossils) • Range early Paleozoic to present • Most abundant in Mesozoic rocks
Tuesday, November 22, 11 Porifera
• Pore-bearing animals • Appear to evolved from colonial flagellated unicellular creatures • Cambrian representatives of all but one modern class are known as fossils (Have not changed much)
Tuesday, November 22, 11 Fossil Porifera
Modern Sponges
Tuesday, November 22, 11 Corals and Cnidarians
• Main Groups • Sea Anemonies • Sea Fans • Jelly Fish • Hydra • Reef-forming Corals
Tuesday, November 22, 11 Brachiopods • Most abundant, diverse, and useful Paleozoic fossil group • Braciopods are bivalves, however, each valve (shell) differs in shape and size. • Unlike clam shell which can be considered right and left brachiopod shells are distinguished between dorsal and ventral. • Most valves are made of Calcium Carbonate. • Ornamented with radial ridges, grooves, spines, nodes and growth lines.
Tuesday, November 22, 11 Groups of Brachiopod • Articulate Brachiopods • Valves are hinged along the posterior margin and are prevented by sliding sideways by teeth and grooves • Inarticulate Brachiopods • Lack a definite hinge structure • Valves held together by muscle • Both are filter feeders attached to sea floor by fleshy stalk (pedicle) • Lophophore: hair like structures that circulate water and food toward mouth
Tuesday, November 22, 11 Fossil Brachiopods
Tuesday, November 22, 11 Mollusks
• Gastropods (snails) • Earliest forms constructed small conical shells, by late Cambrian/early Ordovician most had developed the more recognizable coiled shell. • By Pennsylvanian gastropods extremely abundant and even air-breathing species had developed • Cephalopods- may be the most advanced and complex of all invertebrates
Tuesday, November 22, 11 Cephalopods
• Represented today by: • Squid • Cuttlefish • Octopods • Chambered Nautilus
Tuesday, November 22, 11 Ammonites • Goniatites, the first ammonite, appears during the Devonian
• Other Ammonites
Tuesday, November 22, 11 Arthropods
• Includes: • Lobsters • Spiders • Insects • All animals that have chitonous exterior skeletons, segmented bodies, and paired,jointed appendages
Tuesday, November 22, 11 Trilobites
Tuesday, November 22, 11 Trilobites
Tuesday, November 22, 11 Eurypterids
• Scorpion like bodies • Found in Ordovician- permian Marine and Brackish facies • Recent finds suggest that some eurypterids reached a length of 9ft.
Tuesday, November 22, 11 Eurypterids
• Scorpion like bodies • Found in Ordovician- permian Marine and Brackish facies • Recent finds suggest that some eurypterids reached a length of 9ft.
Tuesday, November 22, 11 Echinoderms • Spiny-skinned animals • Five way symmetry • Exclusively marine- typically bottom dwelling, either attached or mobile • Group includes • Starfish • Sea Urchins • Crinoids • Crystoids
Tuesday, November 22, 11 Echinoderms
• Appear to have developed during late proterozoic • Ediacaran, also had five way symmetry • Stemmed or stalked echinoderms first occur in mid cambrian (not abundant until Ordovician)
Tuesday, November 22, 11 Echinoderms
• Appear to have developed during late proterozoic • Ediacaran, also had five way symmetry • Stemmed or stalked echinoderms first occur in mid cambrian (not abundant until Ordovician)
Tuesday, November 22, 11 Continental Invertebrates
• Fossil evidence is less complete Why? • However as plants begin to invade continent so do animals • Record begins with possible Millipede tracks in Ordovician rocks. • Body Fossils of Centipedes and Millipedes occur in Silurian rock • In New York, Devonian rocks have yielded fossil centipedes, spiders and other wingless arthropods • Insects do not become common until the late Missipian • The Pennsylvanian witnessed the arrival of flying insects like the dragon fly • Coal swamps from the Pennsylvanian yielded a dragon fly with a wingspan of over 2 ft.
Tuesday, November 22, 11 Vertebrates • Evolution of Fish • Dermal Plates (Upper Cambrian) • Scales and Plates (Ordovician) • Four Taxonomic classes: • Agnatha (jawless fish) • Acanthodii (Archaic jawed fish) • Chondrichthyes (cartilaginous fish) • Osteichthyes (Bony fish)
Tuesday, November 22, 11 Agnatha
• Earliest known (early Cambrian) species include Theolodus, Jamoytius, Pteraspis (armored) and Hemicyclapsis
Tuesday, November 22, 11 Acanthodii • Arose during Silurian • Most numerous during Devonian • Extinct during Permian
Tuesday, November 22, 11 Chondrichthyes • Late Devonian to Present • Represent shark, rays, and skates • Cladoselache- late paleozoic shark
Tuesday, November 22, 11 Osteichthyes • Bony Fish can be divided into two groups • Actinoptergians • Lack a muscular base to their paired fins • Also lack nasal passage to the throat • Sarcoptergians • Had sturdy, fleshy lobe-fins • A pair of openings in upper mouth that led to external nostrils • Were able to rise to surface to take in air that was passed onto functional lungs (Lung Fish)
Tuesday, November 22, 11 Sarcoptergians
• Two major roups lived during the Devonian • Dipnoans • Dipnoans- include some present day freshwater living species of lungfish in Australia and Africa • Crossopterygians • Because of the pattern of skull elements, arrangement of bones in their fins, and the structure of their teeth, Crossopterygians are considered to be the ancestor of the earliest land inhabitants (tetrapods).
Tuesday, November 22, 11 Sarcoptergians
• Two major roups lived during the Devonian • Dipnoans • Dipnoans- include some present day freshwater living species of lungfish in Australia and Africa • Crossopterygians • Because of the pattern of skull elements, arrangement of bones in their fins, and the structure of their teeth, Crossopterygians are considered to be the ancestor of the earliest land inhabitants (tetrapods).
Tuesday, November 22, 11 Crossopterygians & Tetrapods
Tuesday, November 22, 11 Tetrapods
• Tetrapods are four- footed vertebrates • Amphibia, Reptilia, Mammalia
Tuesday, November 22, 11 Tetrapods
• First to come ashore did not leave the water completely • Amphibians • Return to water to lay eggs • From eggs come fish-like larvae that develop in water • Number of changes had to accompany the shift to land
Tuesday, November 22, 11 Shift to land
• A three chambered heart developed • Limb and girdle bones had to be modified to overcome gravity • Spinal column became more sturdy but yet flexible • To better assist hearing the Hyomandibular (fish) transformed into an ear ossicle-the stapes
Tuesday, November 22, 11 Fossil Record of Basal Tetrapods • Late Devonian • Ichthyostegids • Retained many features of their fish ancestor • Tail fin • Bony gill covers • Fish-like vertrbae • Skull bones similar to crossopterygians • Labyrinthic folding of enamel • Due to this following species are referred to as Labyrinthodonts
• During the Carboniferous large numbers of these Labyrinthodonts wallowed in swamps and streams Tuesday, November 22, 11 Tuesday, November 22, 11 Evolution of the Tetrapods
• Development of the amniotic egg • These animals are referred to as amniotes • During the Carboniferous Amniotes diverged into two groups • Reptilia: anapsids, diapsids, and archosaurs • Synapsids- Mammal-like reptiles
Tuesday, November 22, 11 Synapsids
• Although the synapsids are called “mammal- like reptiles, cladistic analysis shows that they are not reptiles • Some sported big sail-like structures (pelycosaurs) • Varied group • Carnivores: Dimetrodon • Herbivores: Edaphosaurus
Tuesday, November 22, 11 Synapsids
• Although the synapsids are called “mammal- like reptiles, cladistic analysis shows that they are not reptiles • Some sported big sail-like structures (pelycosaurs) • Varied group • Carnivores: Dimetrodon • Herbivores: Edaphosaurus
Tuesday, November 22, 11 Synapsids
• Although the synapsids are called “mammal- like reptiles, cladistic analysis shows that they are not reptiles • Some sported big sail-like structures (pelycosaurs) • Varied group • Carnivores: Dimetrodon • Herbivores: Edaphosaurus
Tuesday, November 22, 11 Plants of the Paleozoic
• Overview • Cambrian: Stomatolites and stromatolitic reefs • Ordovician to Silurian- • Receptaculids (Green Algae) • Four-spore tracheophytes (vascular plants) and Bryophytes (mosses) • Silurian: Three spore tracheophytes • Early Paleozoic: Chlorophytes and fungi formed lichens
Tuesday, November 22, 11 Effects of Plants
• Roots slowed erosion • Transpiration changes atmospheric conditions • Provide shelter and food for land animals • Leaf litter and decay form early soils
Tuesday, November 22, 11 Vascular Plants • First unquestionable vascular structures appear during Middle Silurian • Some fossils show plants up to 30cm tall • Horizontal stalks (Rhizones) • Vertical stems and spore sacs
Tuesday, November 22, 11 Vascular Plants
• Although early vascular plants were small, evolution would soon lead to the development of wood. • By late Devonian lofty, well-rooted trees appear • One such forest stood near Gilboa, New York • Some of these trees stood over 7m tall (21 ft) • Another covered the Sahara
Tuesday, November 22, 11 Plants of the Carboniferous
• Lycopsids: Scale trees. • Present day Lycopsids consist of the Club Mosses, such as Lycopodium • Not so small during the carboniferous • Lepideodendron reached 30 meters tall
Tuesday, November 22, 11 Sphenopsids • Lived side by side with Lepidodenrons • Living relatives include horse tails • Fossil Sphenopsids posses slender, unbranching, longitudinally ribbed stems with thick cores and leaves at each joint.
Tuesday, November 22, 11 Seed Plants
• Seed plants arrive in the late Paleozoic • Most likely evolved from Devonian fern-like plants, however, reproduced purely through seeds • Become the dominant plant type by the late Paleozoic. • Most widely known: Glossopteris • Ginkgo only modern day survivor
Tuesday, November 22, 11 Mass Extinctions
• Ordovician • Two Phases • 1st Phase – Planktonic and Nektonic organisms • Graptolites, acritarchs, nautiloids and some trilobites, bryozoa, coral and brachiopods • 2nd Phase- several of the remaining trilobites perish and corals and bryozoans severely reduced
Tuesday, November 22, 11 Mass Extinctions
• Devonian • In the late Devonian we see huge decrease in Trilobite numbers and varieties. Also large decrease in reef building corals, brachiopods, and placoderms.
• These extinctions occur over a 20 million yr period so probably not due to catastrophic event (meteor) • What other events are occurring that may lead to this?
Tuesday, November 22, 11 Mass Extinctions
• Late Permian • Referred to as “the mother of mass extinctions”
• 90% of all pre-existing marine species disappear
• On land, spore bearing plant give way to conifers, cyads and othe gymnosperms. • Vegetative change causes chain reaction in land animals • Many families of basal tetrapods, primitive reptiles and synapsids disappear.
Tuesday, November 22, 11