GEOL 305 - Week 2 Notes
GEOL 305 - Week 2 Notes GEOL 305
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This 11 page Class Notes was uploaded by Alex Tucker on Friday October 7, 2016. The Class Notes belongs to GEOL 305 at University of Oregon taught by Baxter M in Fall 2016. Since its upload, it has received 118 views. For similar materials see Dinosaurs >3 in Geology at University of Oregon.
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Date Created: 10/07/16
Mesozoic Climate & Plant Life (Day 3) 10/4/16 - Pangaea formed during later part of Paleozoic Era - All during the Paleozoic Era, (from ~ 540 – 245 million years ago) the continental masses, because of tectonic plate movement, had been assembling into a mega-continent called Pangaea. - Consequences of mega-continent formation - Big continents have most of their land area far from the ocean – those interior areas experience severe weather / climate - Large scale eruptions of lava in Siberia at that time poisoned the atmosphere - These & other factors caused the largest mass extinction of life the earth has ever known - Extinction even devastated large terrestrial animal fauna (mammal-like reptiles which had dominated the Permian) - Group that developed & evolved to fill all those empty lifestyle niches were the reptilian archosaurs - One group of archosaurs were the ancestors of Dinosaurs - Triassic Period of the Mesozoic Era - Because the continental masses were all basically connected together through the Late Triassic the flora & fauna of the world were very similar (even though large mountain ranges existed which could have acted as barriers). - Early Jurassic - If oceans separate continental masses (such as now), the plants & animals on each of the isolated continents will develop into new, different species than those that develop on other continents. - More smaller continents & new ocean basins between them form in the Jurassic - Areas of shallow ocean water on top of continental land masses are called Epicontinental or Epeiric, seas. - In the Middle & Late Jurassic, epicontinental seas became more extensive. - The Southern continental fragments of Pangaea (Gondwana) & the Northern fragments (Laurasia) began to separate from each other forming the east-west trending Tethys Seaway between. Mesozoic Climate & Plant Life (Day 3) 10/4/16 - Tethys was positioned near equator, & was a warm, tropical ocean - Latest Jurassic to Early Cretaceous - By this time North America had separated from Europe & Africa, & a westward extension of the Tethys began to open the Atlantic Ocean between them. Gulf of Mexico forms. - North America continued to move west, completely breaking away from Europe. - Southern continents of Gondwana began to split apart. - Through the Cretaceous Period the continents continue to separate. - Leading (western) edge of both South & North America experience extreme episodes of mountain building. - Antarctica & Australia remain attached to each other until about 50 m. years ago - Southern tip of South America remained in relatively close proximity to an extension of Antarctica. - What was the climate like when Dinosaurs roamed Earth? - During the Mesozoic, continents go from the one extreme of all the land masses coalesced into a mega-continent, to in the Cretaceous having great separation between the continents. - Land heats & cools faster than water - It is this principle which allows large wind farms to be positioned in coastal waters of Europe & elsewhere, as air masses move from colder towards warmer areas. - When the continents were together as Pangaea, that large land mass would have experienced severe temperature extremes, especially in the interior regions. - Mesozoic Climate Change - Temperature range is less for most modern continents (which are spread around the globe) because of the moderating influence of the nearby oceans. - When Pangaea began to break apart in the Late Triassic, the strong continental effects were weakened. - Rise in sea level & development of epeiric seas further weakened the continental effects. - These large bodies of shallow water would have lessened the extremes of temperature between winter & summer. Mesozoic Climate & Plant Life (Day 3) 10/4/16 - Because of the positioning of the continents, heat & aridity dominated the Late Triassic & Early Jurassic. The Pangaea continent had marked seasonality. - In the Later Jurassic, & all the way through the Cretaceous, there was no polar glacier ice. - No glacier ice meant more water in the oceans. - Because of the moderating effect of the oceans & epeiric seas, there was less seasonality during the Late Jurassic through Cretaceous. - For the first part of the Cretaceous, the climate of Earth was about the same at the Equator as now, but much warmer than now at the poles. - During the Early Cretaceous Earth was under “Greenhouse” conditions - First ½ of Cretaceous was synergistic, meaning that tectonic activity such as mountain building & seafloor spreading: - caused increase in atmospheric CO 2 - caused decrease in volume of ocean basins - which caused increased volume in epeiric seas - Towards end of Cretaceous there was a withdrawal of epeiric seas, & seasonality again became prevalent. - Therefore the later part of the Cretaceous had a significantly different set of conditions that which had prevailed earlier in that period. - Earth at the end of the Age of Dinosaurs - Atlantic & Indian Oceans continued to open, while the Pacific continued to shrink. - After the Cretaceous, the Southern continents would again link to the Northern continents. - Plants & Dinosaur herbivores - Majority of Dinosaurs were herbivores (prey instead of predator) - Ate a lot of vegetation - We would thus expect them to have an effect on terrestrial plant communities - Most paleobotanists recognize 2 major plant groups during the Mesozoic Mesozoic Climate & Plant Life (Day 3) 10/4/16 - 1 Major Group = non-monophyletic grouping of ferns, lycopods (club mosses), & spheneopsids (horsetails) - low growing, & primitive in type of reproduction (spore- bearing) - 2nd Major Group = Gymnosperms & Angiosperms - seed plants - seeds are nutrient-bearing pods designed to maximize the development & dissemination of gametes - both of these 2 major plant groups were / are vascular, meaning that they possess specialized tissue for the conduction of water & nutrients throughout the plant - Gymnosperms today include - Conifers - Pines & cypresses - Other cone-bearing, needle-leafed trees - Cycads - Cycads & now extinct cycadeoids (cycadophytes) were both living during the Mesozoic - Ginkgoes are also gymnosperms (even if they look different than other gymnosperms) - Conifers - Tend to be tall - Have thick bark & cellulose-rich leaves - Neither of which are particularly nutritive - Flowering plants (Angiosperms) evolved a variety of strategies to encourage animals to eat them - Bright tasty flowers, or nectar, would reward their pollinators. - Fleshy fruits would be eaten, passing the seeds through a digestive system while being transported away from the adult plant. - Sticky, or stickery, outer coatings so the seeds will attach to passing animals, to be transported elsewhere. - Dinosaurs & Plants - Analyses have been done which compare the record of Late Triassic through Late Cretaceous plant diversity of dinosaurian herbivores during the same period. - Although abundant in the later part of the Paleozoic Era, lycopods, seed ferns, sphenopsids, & true ferns decrease in Mesozoic Climate & Plant Life (Day 3) 10/4/16 global abundance during the late Triassic (1 period of the Mesozoic Era). - Throughout the rest of the Mesozoic these primitive plants maintain a constant, although low percent, proportion of the global flora. - The gymnosperms on the other hand show a marked increase in their proportion of the total global fauna during the late Triassic. - Most of that increase was due to the development of many ancestral trees of the conifers of today. - The angiosperm reproduction system is more efficient than that of gymnosperms: - For delivery of pollen many use animal vectors - Dispersal of seeds - 1 to colonize “bare” areas - seeds mature & germinate more quickly - ability to reproduce vegetatively - Co-evolution of dinosaurs & plants - Not thought to be a coincidence that rise of tall conifer forests is accompanied by first truly tall (& thus high grazing) herbivores: prosauropods & sauropods - Co-evolution = when evolution of one group is affecting, & even effecting the evolution of another group - Problem is knowing which came first - Did the trees evolve to grow taller because the long necked dinosaurs appeared? (Predation pressure) - Or, did the long necked dinosaurs evolve longer necks to take advantage of a food source which was being under-utilized? (Advantageous adaptation) - The rise of the angiosperms coincides approximately w/ the radiation in the Cretaceous of many dinosaur groups - The ceratopsians, pachycephalosaurs, hadrosaurids, & the later forms of ankylosauria all probably took advantage of this new food source. (pictures left right) Mesozoic Climate & Plant Life (Day 3) 10/4/16 - Fossil evidence for what these dinosaurs possibly includes angiosperm material - Mummified remains of hadrosaurids from which we have found conifer fragments in the stomachs have shown only a trace of what could be angiosperm plant remains (but that was only a couple of animals, & only what was still in their digestive tract). - Coprolites large enough to be attributable to hadrosaurs or ceratopsians have been found to have conifer fragments within, but no definite angiosperms. (More easily digested?) - Mesozoic plant-herbivore interaction appears to be one in which: 1. Plants produced vast quantities of offspring to ensure survival of family line into next generation. 2. Herbivores took advantage of rapidly & abundantly reproducing resource base to maintain their populations of large individuals. - Dinosaur chewing efficiency dramatically improved during the Cretaceous. - There were still some non-chewing dinosaurs alive - Even those which didn’t do much chewing, like the Pachycephalosaurs, underwent strong evolutionary bursts of radiation in the Late Cretaceous. - Especially characteristic for the Late Cretaceous increase in diversity were the hadrosaurs & ceratopsians. - Perhaps the advanced chewing systems in those 2 groups, (& in the case of ceratopsians, their ability to be very selective in their choice of diet due to their narrow parrot-like beak), allowed them to really take advantage of a food resource which was, until flowering plants appeared, unavailable to dinosaurs. Mesozoic Climate & Plant Life (Day 3) 10/4/16 - Last dinosaur group to be considered in our look at plant / dinosaur interactions are the Therizinosaurus. - called Saurischian Theropods, & yet they are thought to have an herbivorous diet - Chewing apparatus is considered primitive compared to that of many of the Ornithischians, but did the rise of angiosperms also fuel this group’s appearance & diversity gains? - Perhaps so. Who are the Dinosaurs?: Dinosaur Origins (Day 4) 10/6/16 - Recap of Tuesday’s Lecture - At end of Paleozoic Era, ~ 250 million years ago, all the continents were coalesced into a mega-continent we call Pangaea. - Interior areas of that continent experienced extremes in climate / weather. - Because of this, & several other causes, there was a mass extinction which devastated marine life & also terrestrial fauna. - Reptiles of the Later Paleozoic Era - Reptiles as a group appeared at least 60 million years before the end of the Permian. - Within that timeframe, animals had diversified into numerous forms: - some still existed which had a mix of amphibian & reptilian characteristics - some had advanced characteristics more like those of modern reptiles - some had advanced characteristics which were more mammalian in form - Reptilomorph labyrinthodonts - animals w/ mix of amphibian & reptilian characteristics - some of these animals, those that were still acquatic in lifestyle, attained large size, such as Eogyrinus, a large aquatic eel-like Embolomeri, from late Carboniferous of England. - length up to 4.5 meters - those w/ more terrestrial lifestyle had a tendency to be somewhat smaller, but even one of the smallest, Seymouria, was 2 feet long. Who are the Dinosaurs?: Dinosaur Origins (Day 4) 10/6/16 - Permian Reptilomorphs - Reptilomorphs were still relatively common in the Early Permian, even well after the first “true” reptiles have evolved. - Limnoscelis was ~ 4 feet long - In the Permian, true reptiles were also part of the terrestrial fauna, but forms w/ mammalian characteristics were becoming more numerous. - By the middle part of the Permian, there was considerable diversity of these “mammal-like” reptiles. - Pelycosaurs came in Carnivore & Herbivore lineages Dimetrodon was a carnivore - Edaphosaurus was a herbivore Notice the difference in proportion of skull to body size in the two genera. - Therapsids Who are the Dinosaurs?: Dinosaur Origins (Day 4) 10/6/16 - Pelycosaurs lasted into the late Permian, when they were replaced by the more advanced Therapsids, such as Lycaenops; carnivore of the Gorgonopsids - Top predator of late Permian - There were also herbivorous therapsids - Dicynodonts; lasted well into Triassic - Representations of the fauna present in different parts of the Northern Hemisphere in different parts of the Permian. - Early Permian; Inta Faunal Assemblage - Early Middle Permian; Golyusherma Faunal Assemblage - Middle Permian; Ocher & Beleby Faunal Assemblages - Late Middle Permian; Kotelnich Faunal Assemblage - Late Permian; Sokolki Faunal Assemblage - Terminal Late Permian; Vyazniki Faunal Assemblage - Archosauria - Sometime during the Permian-Triassic transition, one lineage of the Archosauropmorpha gained advanced characteristics that cause paleontologists to put them into their own grouping, the Archosauria. - Cladograms are a way to show the characteristics which allow paleontologists to group organisms into ever more precise, smaller, clades. Who are the Dinosaurs?: Dinosaur Origins (Day 4) 10/6/16
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