Portal:Silurian

Topics Culture Geography Health History Mathematics Nature People Philosophy Religion Society Technology The Silurian Portal The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.8 ± 1.5 million years ago (mya), to the beginning of the Devonian Period, about 419.2 ± 3.2 mya. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by several million years. The base of the Silurian is set at a major extinction event when 60% of marine species were wiped out. SeeOrdovician-Silurian extinction events. A significant evolutionary milestone during the Silurian was the appearance of jawed and bony fish. Life also began to appear on land in the form of small, moss-like, vascular plants which grew beside lakes, streams, and coastlines. However, terrestrial life would not greatly diversify and affect the landscape until the Devonian. (See more…) Template:/box-footer Phoronids (sometimes called horseshoe worms) are a phylum of marine animals that filter-feed with a "crown" of tentacles, and build upright tubes of chitin to support and protect their soft bodies. Most adult phoronids are 2 cm long and about 1.5 mm wide, although the largest are 50 cm long. The bottom end of the body is an a flask-like swelling, which anchors the animal in the tube and enables it to retract its body very quickly when threatened. When the lophophore is extended at the top of the body, little hairs on the sides of the tentacles draw food particles to the mouth, which is inside and slightly to one side of the base of the lophophore. The food then moves down to the stomach, which is in the ampulla. Solid wastes are moved up the intestine and out through the anus, which is outside and slightly below the lophophore. As of 2010 there are no indisputable body fossils of phoronids. There is good evidence that phoronids created trace fossils found in the Silurian, Devonian, Permian, Jurassic and Cretaceous periods, and possibly in the Ordovician and Triassic. Phoronids, brachiopods and bryozoans have collectively been called lophophorates, because all use lophophores to feed. Most researchers now regard phoronids as members of the protostome super-phylum Lophotrochozoa. The relationships between lophotrochozoans are still unclear. Some analyses regard phoronids and brachiopods as sister-groups, while others place phoronids as a sub-group within brachiopoda. (see more...) A Eurypterus fossil. Paleontology or palaeontology (/ˌpeɪlɪɒnˈtɒlədʒi/, /ˌpeɪlɪənˈtɒlədʒi/ or /ˌpælɪɒnˈtɒlədʒi/, /ˌpælɪənˈtɒlədʒi/) is the scientific study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments (their paleoecology). As a "historical science" it attempts to explain causes rather than conduct experiments to observe effects. Paleontological observations have been documented as far back as the 5th century BC. The science became established in the 18th century as a result of Georges Cuvier's work on comparative anatomy, and developed rapidly in the 19th century. The term itself originates from Greek: παλαιός (palaios) meaning "old, ancient," ὄν, ὀντ- (on, ont-), meaning "being, creature" and λόγος (logos), meaning "speech, thought, study". Paleontology lies on the border between biology and geology. It now uses techniques drawn from a wide range of sciences, including biochemistry, mathematics and engineering. Use of all these techniques has enabled paleontologists to discover much of the evolutionary history of life, almost all the way back to when Earth became capable of supporting life, about 3,800 million years ago. As knowledge has increased, paleontology has developed specialized sub-divisions, some of which focus on different types of fossil organisms while others study ecology and environmental history, such as ancient climates. Body fossils and trace fossils are the principal types of evidence about ancient life, and geochemical evidence has helped to decipher the evolution of life before there were organisms large enough to leave fossils. (see more...) Cooksonia, a primitive vascular plant from the Silurian period. Photo credit: Zeimusu ... that a fossil of the extinct sea scorpion Eurypterus (restoration pictured) was once thought to be a catfish? ... that the Paleozoic monoplacophoran Pilina unguis was twice as large as any known living monoplacophoran? ... that the extinct trilobite Bumastus (artist's rendition pictured) was named after its resemblance to large grapes? ...that Ornatifilum is likely to be the oldest known fossil fungus? ...that the Silurian Lau extinction event caused the Earth to temporarily return to a condition similar to how it was before multicellular life evolved? Template:/box-header Epochs - Llandovery - Wenlock - Ludlow - Pridoli Ages - Rhuddanian - Aeronian - Telychian - Sheinwoodian - Homerian - Gorstian - Ludfordian Events - Alice Springs Orogeny - Early Palaeozoic Icehouse - Andean-Saharan glaciation - Caledonian orogeny - Ireviken event - Lau event - Mulde event Geography - Avalonia - Baltica - Gondwana - Laurentia - Euramerica Animals - Acanthodians - Bivalves - Brachiopods - Bryozoa - Cephalopods - Crinoids - Gastropods - Hederelloids - Leeches - Tentaculitoids - Trilobites Plants - Lycopods - Rhyniophytes - Vascular plants Fossil sites - Yea Flora Fossil Site Stratigraphic units - Old Red Sandstone - Shawangunk Formation - Tuscarora Formation Researchers - Increase A. Lapham - Roderick Murchison Culture - List of creatures in the Walking with... series - Walking With Monsters Template:/box-footer Template:/box-header Featured Silurian articles - Fungus Good Silurian articles - Chitinozoan - Ornatifilum Template:/box-footer ▼ Silurian ► Silurian life Here are some tasks awaiting attention: Stubs : Silurian stubs Current Silurian FACs - none currently Template:/box-footer Time Earth sciences Paleontology Extinct and Endangered Species Paleozoic Cambrian Ordovician Silurian Error creating thumbnail: File missing Devonian Carboniferous Permian What are portals? List of portals Featured portals