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Introduction1. Middle Paleozoic Eraa. ~85 Ma (444-359 Ma)i. Silurian ~28 Ma (444-416 Ma)ii. Devonian ~57 Ma (416-359 Ma)b. Major orogenic events occurringc. Global eustatic changesi. Unconformity formationd. Time of “firsts” in biosphere2. Siluriana. Sea level rise/falli. Flooding: widespread marine rocks on cratonsb. Marine radiation post-Ordovician MEc. First jawed fishesd. Colonization of land habitatsi. Early plants in Siluriane. Acadian orogenyi. Tilted deposits in England3. Devoniaa. First ammonoidsb. Radiation of jawed fishc. First insectsd. First trees, forestse. First amphibiansf. Antler orogeny (W Laurentia)g. Global coolingMarine Diversification1. Rediversification of marine life after the Ordovician MEa. Brachiopods- highly diversifiedb. Bivalve mollusks- spread to non-marine habitatsc. Graptolites- 5 times diversification of species2. Reefs: coral-stromes re-flourishesa. Increasing size until end Devonian (enormous)i. Rugose (wrinkled, horned) outnumbered tabulate (tabulae internal structure)3. New nektonic (swimming) invertebratesa. Ammonoidsi. Most prominent new invert swimmersii. Evolved from coiled cephalopod mollusks (nautiloids) in the early Devonianiii. Rapid diversification and dominance: excellent index fossils1. Devonian to late-Mesozoica. Extinction at KT boundaryb. Eurypteridsi. Distant relative to modern scorpionsii. Swimming predatorsiii. Conspicuous (evolved earlier in Ordovician)iv. Arthropods, many with clawsv. Lived in brackish and freshwater4. Jawless fish diversified greatly during the Siluriana. Oldest fully-preserved and diverse specimens of fish are in the Silurian/Devonian rockb. Fragments of skeletons found in early Paleoi. Agnathans (became conspicuous in mid-Paleoc. Marined. Freshwatere. Diversificationi. Jawless fishii. Jawed fishiii. Bony skin fishiv. Cartilaginous fishv. Bony fish1. Ray-finned2. Lobe-finnedf. Ostracoderms (bony fish)i. Common1. Few survived past the Devonianii. Paired eyesiii. Lacked jawsiv. Covered with bony armorv. Various morphology1. Curved belly, elongated lower fin- swimmers2. Flattened belly, elongated upper fin- bottom dwellers5. Jawed fisha. Acanthodiansi. Elongated fish with numerous fins supported by sharp spinesii. First fist group to possess several modern features1. Paired fins2. Covered by scales (not bony platesa. Major adaptive breakthrough for predatorsb. Placodermi. Armor-like boneii. Very large fishiii. Predatory fish was at the top of the food chainiv. Primarily freshwaterv. Marine known from late Devonian1. Dunkleosteusa. 7 m long armored fish; skull 1 m longb. Armor-protected eyesc. Possessed bony teethd. Possessed an unarmored tail for easy locomotionc. Cartilaginous fishi. Mid-Devonian marine appearanceii. Primitive sharksiii. ~1 m lengthiv. An important fish group in Devonian seasd. Ray-finned fishi. First appearance in Devonian1. Dominate Mesozoic, Cenozoic2. Modern: trout, bass, herring, tunaii. Fin bones that radiate from body iii. Major difference from modern fish1. Asymmetrical tail2. Non-overlapping diamond-shaped scalese. Lobe-finned fishi. Fins are attached to the body by a single shaftii. Mainly freshwater fishiii. Originated in Devonian, but only 3 genera survive todayiv. Lungfish1. Gulp air so they can survive in stagnant evaporating pools of water during the dry seasonv. Ancestor of all terrestrial vertebratesTerrestrial Invasion1. Early Paleozoic (and Precambrian) terrestrial environments were likely populated by simple life forms (algae, cyanobacteria, fungi)a. Barren rock and soilsb. Little humus covered landc. No forests, no meadows2. One of the most important biohistory events during the mid-Paleozoic was the terrestrial invasion of plants3. Early terrestrial plant invasion is in the Siluriana. First definitive fossil evidenceb. Vascular plants- required that algae (protists) experienced two special mutationsi. Evolution of a rigid stem1. To stand upright in airii. Evolution of a root system1. To anchor the plant2. To collect water and nutrients4. Lycopodsa. Include tiny club mossesb. Some grew to the proportion of treesi. Petrified remains supply coalc. Water is essential within the spore reproductive cycled. Thus confined to aquatic habitats5. Seed plants appeared in the Devoniana. Evolved from vascular spore plantsb. The seed was an important adaptive evolutionary breakthroughc. Freed land plants to invade further inland6. Seed plants/treesa. Appeared abruptly and covered Earthb. Formed world’s first widespread inland forest7. Animals colonized land after plants expandeda. Delayed migrationi. Base of food web on land needed to be builtii. Animals needed a suitable habitat1. Protection from sun and heat8. First land animals were invertebratesa. Millipedes and flightless insects (early Devonian)i. Fed on organic detritusb. Scorpions, centipedes, and spiders (mid Devonian)i. Carnivores9. First terrestrial vertebrates- amphibiansa. Evolutionary emergence of amphibians from lobe-finned fish10. Anatomical evidence indicates amphibians (vertebrates) are most closely related to fisha. Juvenile amphibians live in waterb. Juveniles mm into air-breathing adults; but return to water to lay eggsc. Complex tooth structures of the Devonian amphibian (Labyrinthodonts) similar to Devonian lobe-finned fishd. A group of Devonian lobe-fin fish had lungs (lungfish) which adult amphibians also possess11. Tikaalika. Late Devonian “missing link” between lobe-fin fish and amphibiansb. Had traits from both lobe-finned fish and amphibiansi. Fishlike fins and scalesii. Fishlike lower jawiii. Amphibian-like flat skulliv. Lungsv. Shoulder jointsvi. Flexible wrists on finsvii. Finger-like bonesviii. Flexible neck to raise headix. Eyes and nostrils on top of head12. Ichthyostega was a common primitive amphibian during late Devoniana. Possessed true legsb. Likely fed on fishEarth-System Shift1. Plantsa. Altered landscapesi. Before “anchoring” plants, braided streams were abundant; meanders once erosion subsidedii. Late Devonian fossil root traces are abundant1. Stabilized the soil against erosionb. Provided habitatc. Provided a land-based food sourced. Paved the way for terrestrial faunal invasione. Most important adaptive breakthrough responsible for the increase inthe size of land plants was the evolution of broad leavesi. Captured sunlight; higher rate of photosynthesisf. The origin of seed plants permitted inland expansion of forests2. Widespread expansion of land plants in Devonian

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LSU GEOL 1003 - Notes

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