Chapter 97: Dinosaur period?!


    Coal beds, which can be up to 11 to 12 meters thick, characterize thete Carboniferous. The forests of seedless vascr nts that existed in the tropical swamp forests of Europe and North America provided the organic material that became coal.


    Dead nts did notpletely decay and were turned to peat in these swamp forests. When the sea covered the swamps, marine sediments covered the peat. Eventually, heat and pressure transformed these organic remains into coal. Coal balls, pockets of nt debris that were preserved as fossils and not converted to coal, are sometimes found within the coalyers.


    Multiple transgressions and regressions of the Pennsylvanian seas across the continent can be seen in the rocks, and even counted, because they leave a telltale sequence ofyers. As sea levels rise, theyers may go from sandstone (beach), to silty shale or siltstone (tidal), to freshwater limestone goon), to undery (terrestrial), to coal (terrestrial swampy forest). Then as sea levels fall, one may see a shale (nearshore tidal) grade to limestone (shallow marine) and finally to ck shale (deep marine).


    Index fossils are the remains of nts and animals that characterize a well-defined time span and ur over a wide range of geography. Fossils of marine life characterize the Mississippian, as shallow epicontinental seas covered the United States at that time.


    These fossils include solitary corals and Syringopora, tubr colonial corals. Other fossil colonial corals include Stelechophyllum and Siphonodendron. Because conodont fossils are distributed all over the world, they are utilized internationally to date Mississippian rocks.


    Index fossils used for the Pennsylvanian Subsystem are fusulinid foraminifers and the pollen and spores from the coal forests prevalent during that time.


    The Mississippian-Pennsylvanian boundary is marked by the appearance of the fusulinid Pseudostaffe antiqua. Other fossils used to identify the early Pennsylvanian are the three ammonoid cephalopod genera Gastrioceras, Daiboloceras, and Paralegoceras, all found in marine deposits.


    Afterpleting this one next on line was Permian Period. Which was a major evolutionary period in the geographical timeline of earth.


    The Permian Period was the final period of the Paleozoic Era. Lasting from 299 million to 251 million years ago, it followed the Carboniferous Period and preceded the Triassic Period.


    By the early Permian, the two great continents of the Paleozoic, Gondwana and Euramerica, had collided to form the supercontinent Pangaea. Pangaea was shaped like a thickened letter "C."


    The top curve of the "C" consisted ofndmasses that wouldter be modern Europe and Asia. North and South America formed the curved back of the "C" with Africa inside the curve.


    India, Australia and Antarctica made up the low curve. Inside the "C" was the Tethys Ocean, and most of the rest of Earth was the Panthssic Ocean. Because Pangaea was so immense, the interior portions of the continent had a much cooler, drier climate than had existed in the Carboniferous.


    Little is known about the huge Panthssic Ocean, as there is little exposed fossil evidence avable. Fossils of the shallower coastal waters around the Pangaea continental shelf indicate that reefs wererge and diverse ecosystems with numerous sponge and coral species.


    Ammonites, simr to the modern nautilus, weremon, as were brachiopods. The lobe-finned and spiny fishes that gave rise to the amphibians of the Carboniferous were being reced by true bony fish. Sharks and rays continued in abundance.


    Onnd, the giant swamp forests of the Carboniferous began to dry out. The mossy nts that depended on spores for reproduction were being reced by the first seed-bearing nts, the gymnosperms.


    Gymnosperms are vascr nts, able to transport water internally. Gymnosperms have exposed seeds that develop on the scales of cones and are fertilized when pollen sifts down andnds directly on the seed. Today''s conifers are gymnosperms, as are the short palm like cycads and the gingko.


    During this time arthropods continued to diversify during the Permian Period to fill the niches opened up by the more variable climate. True bugs, with mouthparts modified for piercing and sucking nt materials, evolved during the Permian. Other new groups included the cicadas and beetles.


    Two important groups of animals dominated the Permianndscape: Synapsids and Sauropsids. Synapsids had skulls with a single temporal opening and are thought to be the lineage that eventually led to mammals. Sauropsids had two skull openings and were the ancestors of the reptiles, including dinosaurs and birds.


    In the early Permian, it appeared that the Synapsids were to be the dominant group ofnd animals. The group was highly diversified. The earliest, most primitive Synapsids were the Pelycosaurs, which included an apex predator, a genus known as Dimetrodon.


    This animal had a lizard-like body and arge bony "sail" fin on its back that was probably used for thermoregtion.


    Despite its lizard-like appearance, recent discoveries have concluded that Dimetrodon skulls, jaws and teeth are closer to mammal skulls than to reptiles.


    Another genus of Synapsids, Lystrosaurus, was a small herbivore  about 3 feet long (almost 1 meter)  that looked something like a cross between a lizard and a hippopotamus. It had a t face with two tusks and the typical reptilian stance with legs angled away from the body.


    In thete Permian, Pelycosaurs were seeded by a new lineage known as Therapsids. These animals were much closer to mammals. Their legs were under their bodies, giving them the more upright stance typical of quadruped mammals.


    They had more powerful jaws and more tooth differentiation. Fossil skulls show evidence of whiskers, which indicates that some species had fur and were endothermic. The Cynodont ("dog-toothed") group included species that hunted in organized packs. Cynodonts are considered to be the ancestors of all modern mammals.


    At the end of the Permian, thergest Synapsids became extinct, leaving many ecological niches open. The second group ofnd animals, the Sauropsid group, weathered the Permian Extinction more sessfully and rapidly diversified to fill them. The Sauropsid lineage gave rise to the dinosaurs that would dominate the Mesozoic Era.


    The Permian Period ended with the greatest mass extinction event in Earth''s history. In a blink of Geologic Time  in as little as 100,000 years  the majority of living species on the were wiped out of existence. Scientists estimate that more than 95 percent of marine species became extinct and more than 70 percent ofnd animals. Fossil beds in the Italian Alps show that nts were hit just as hard as animal species. Fossils from thete Permian show that huge conifer forests nketed the region. These strata are followed by early Triassic fossils that show few signs of nts being present but instead are filled with fossil remnants of fungi that probably proliferated on a glut of decaying trees.


    Scientists are unclear about what caused the mass extinction. Some point to evidence of catastrophic volcanic activity in Siberia and China (areas in the northern part of the "C" shaped Pangaea).


    This series of massive eruptions would have initially caused a rapid cooling of global temperatures leading to increased ciations.


    This "nuclear winter" would have led to the demise of photosynthetic organisms, the basis of most food chains.


    Lowered sea levels and volcanic fallout would ount for the evidence of much higher levels of carbon dioxide in the oceans, which may have led to the copse of marine ecosystems.


    Other scientists point to indications of a massive asteroid impacting the southernmost tip of the "C" in what is now Australia. Whatever the cause, the Great Dying closed the Paleozoic Era.


    After the great extinction it was the time of a new beginning, the Mesozoic era. During the Mesozoic, or "Middle Life" era, life diversified rapidly and giant reptiles, dinosaurs and other monstrous beasts roamed the Earth. The period, which spans from about 252 million years ago to about 66 million years ago, was also known as the age of reptiles or the age of dinosaurs.


    The Mesozoic era began roughly around the time of the end-Permian extinction, which wiped out 96 percent of marine life and 70 percent of all terrestrial species on the. Life slowly rebounded, eventually giving way to a flourishing diversity of animals, from massive lizards to monstrous dinosaurs.


    The Triassic period, from 252 million to 200 million years ago, saw the rise of reptiles and the first dinosaurs. The Jurassic period, from about 200 million to 145 million years ago, ushered in birds and mammals. And the Cretaceous period, from 145 million to 66 million years ago is known for its iconic dinosaurs, such as Triceratops, and pterosaurs such as Pteranodon.


    Coniferous nts, or those that have cone-bearing seeds, already existed at the beginning of the era, but they became much more abundant during the Mesozoic. Flowering nts emerged during thete Cretaceous period. The lush nt life during the Mesozoic era provided plenty of food, allowing the biggest of the dinosaurs, such as the Argentinosaurus, to grow up to 80 tons, ording to a 2005 study in the journal Revista del Museo Argentino de Ciencias Naturales.


    Earth during the Mesozoic era was much warmer than today, and the had no pr ice caps. During the Triassic period, Pangaea still formed one massive supercontinent. Without much coastline to moderate the continent''s interior temperature, Pangaea experienced major temperature swings and was covered inrge swaths of desert.


    Yet the region still had a belt of tropical rainforest in regions around the equator, said Brendan Murphy, an earth scientist at St. Francis Xavier University in Antigonish, Canada.