Devonian

Nautiloids are first known from the late Cambrian Fengshan Formation of northeastern China, where they seem to have been quite diverse (at the time this was a warm shallow sea rich in marine life). However, although four orders have been proposed from the 131 species named, there is no certainty that all of these are valid, and indeed it is likely that these taxa are seriously oversplit. Most of these early forms died out, but a single family, the Ellesmeroceratidae, survived to the early Ordivician, where it ultimately gave rise to a ...

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Nautiloid, Nautiloid - Taxonomic relationships, Nautiloid - Defining Characteristics, Nautiloid - The Recent Nautilus, Nautiloid - Fossil Record, Nautiloid - Evolutionary History, Nautiloid - Classification

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The physical geography of the UK varies greatly. It includes the chalk cliffs of Kent and Dorset, the rolling hills and fields of southeast England, the granite cliffs of Cornwall, the mountains of Wales, the uplands of the Peak District and the Pennines, the lakes and mountains of Cumbria, the Scottish lowlands, highlands and islands, and the fields, lakes and mountains of Northern Ireland. The country can be roughly divided into highland and lowland along the Tees-Exe line. The overall geomorphology of the UK was shaped by the comb ...

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Geography of the United Kingdom, Geography of the United Kingdom - Physical geography, Geography of the United Kingdom - Geology, Geography of the United Kingdom - Mountains and hills, Geography of the United Kingdom - Rivers and lakes, Geography of the United Kingdom - Artificial waterways, Geography of the United Kingdom - Coastline, Geography of the United Kingdom - Islands, Geography of the United Kingdom - Climate, Geography of the United Kingdom - Human geography, Geography of the United Kingdom - Political geography, Geography of the United Kingdom - Demographics, Geography of the United Kingdom - Economic geography, Geography of the United Kingdom - Natural resources, Geography of the United Kingdom - Environment, Geography of the United Kingdom - Current issues, Geography of the United Kingdom - International agreements

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Caithness extends about 40 miles (64 kilometres) north-south and about 30 miles (50 km) east-west. The general aspect of Caithness, which measures in area about 712 square miles (1844 km²), is flat; and this peculiarity is rendered still more striking by the almost total absence of forest. Most of Caithness is old red sandstone to an estimated depth of over 4,000 metres. This consists of the cemented sediments of Lake Orcadie, which is believed to have stretched from Shetland to Grampian during the Devonian period, about 370 million ...

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Caithness, Caithness - Geography, Caithness - History, Caithness - Natural heritage, Caithness - District, Caithness - Area committee, Caithness - Constituency, Caithness - Footnotes

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Most familiar are the multicellular land plants, called embryophytes. They include the vascular plants, plants with full systems of leaves, stems, and roots. They also include a few of their close relatives, often called bryophytes, of which mosses and liverworts are the most common. All of these plants have eukaryotic cells with cell walls composed of cellulose, and most obtain their energy through photosynthesis, using light and carbon dioxide to synthesize food. About three hundred plant species do not photosynthesize but ar ...

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Plant, Plant - Embryophytes, Plant - Algae and Fungi, Plant - Importance, Plant - Growth, Plant - Fossils, Plant - Distribution, Plant - References and further reading

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The classical "Big Five" mass extinctions identified by Raup and Sepkoski (1982) are widely agreed upon as some of the most significant: End Ordovician, Late Devonian, End Permian, End Triassic, and End Cretaceous. These and a selection of other extinction events are highlighted below: 488 million years ago — a series of mass extinctions at the Cambrian-Ordovician transition (the Cambrian-Ordovician extinction events) eliminated many brachiopods and conodonts and severely reduced the number of trilobite species. See also:

Extinction event, Extinction event - Extinction events, Extinction event - Causes for Mass Extinction, Extinction event - Postulated extinction cycles

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Michigan was home to various Native American tribes for centuries before the arrival of Europeans. When the first European explorers arrived, the most populous and influential tribes were the linguistically and ethnically related Ottawa, Chippewa, and Potawatomi. Within Michigan, the Chippewa were the most populous, estimated at between 25,000 and 35,000, and were predominant in the western Upper Peninsula and northern Wisconsin, though they were also present in other areas of the Upper Peninsula and Northern Michigan. The Ottawa primarily i ...

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Michigan, Michigan - History, Michigan - Michigan history timeline, Michigan - Early European history, Michigan - U.S. territorial history, Michigan - U.S. state history, Michigan - Law and Government, Michigan - Geography, Michigan - National parks, Michigan - Economy, Michigan - Demographics, Michigan - Religion, Michigan - Important cities, Michigan - 20 wealthiest places in Michigan, Michigan - Education, Michigan - Colleges and universities, Michigan - Community Colleges and Technical Schools, Michigan - Professional sports teams, Michigan - Other notable sports teams, Michigan - Michigan's Sports Victories, Michigan - State symbols, Michigan - Miscellaneous information, Michigan - Quick trivia

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The Silurian is usually broken into lower ( Llandovery and Wenlock) and upper ( Ludlow and Pridoli) subdivisions (epochs). Nevertheless, some schemes use a lower (Llandovery), middle (Wenlock) and upper (Ludlow and Pridoli) breakdown. These faunal stages are characterized by their index fossils, new species of colonial marine Graptolites that appeared in each. The series and stages from youngest to oldest are: Pridoli Series - no stages defined (Upper Silurian) Ludlow Series divided into See also:

Silurian, Silurian - Historiography, Silurian - Silurian subdivisions, Silurian - Silurian paleogeography, Silurian - Silurian biota, Silurian - Source

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Geology of the Yosemite area - Volcanism. Starting 20 million years ago and lasting until 5 million years ago a now-extinct extension of Cascade Range volcanos erupted, bringing large amounts of igneous material in the area. These igneous deposits blanketed the region north of the Yosemite area. Some lava associated with this activity poured into the Grand Canyon of the Tuolumne and formed Little Devils Postpile (a smaller but much older version of the colum ...

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Geology of the Yosemite area, Geology of the Yosemite area - Formation of exposed rocks, Geology of the Yosemite area - Passive to active margin, Geology of the Yosemite area - Pluton emplacement, Geology of the Yosemite area - Cenozoic activity, Geology of the Yosemite area - Volcanism, Geology of the Yosemite area - Uplift and erosion, Geology of the Yosemite area - Glaciations, Geology of the Yosemite area - Controversy

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Primitive amphibians like Ichthyostega and Acanthostega differed from animals like Crossopterygians (for instance Eusthenopteron or Panderichthys) in that although Crossopterygians had lungs, they used their gills as the primary means of acquiring oxygen. Ichthyostega probably used lungs as its primary means of breathing. Primitive amphibians had a special type of skin that helped them retain bodily fluids and deter desiccation whereas Crossopterygians did not, and a stronger skeletal structure allowed I ...

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Ichthyostega, Ichthyostega - History and Systematics, Ichthyostega - Characteristics, Ichthyostega - Adaptations for land-life

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Geology of the British Isles - Proterozoic Era. The Gneisses, the oldest rocks in Britain or Ireland, date from at least 2,700 Ma (Ma = millions of years ago) in the Archean period of this era, the Earth itself being only about 4,600 Ma old. They are found in the far north west of Scotland and in the Hebrides, with a few small outcrops elsewhere. Formed from rock originally deposited at the surface of the planet, the rocks were later buried d ...

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Geology of the British Isles, Geology of the British Isles - Geological history, Geology of the British Isles - Proterozoic Era, Geology of the British Isles - Paleozoic Era, Geology of the British Isles - Mesozoic Era, Geology of the British Isles - Cenozoic Era, Geology of the British Isles - Geological features, Geology of the British Isles - Geological resources, Geology of the British Isles - Events, Geology of the British Isles - Institutions, Geology of the British Isles - People, Geology of the British Isles - Awards

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Some important terms: A formation is a rock unit that has one or more sediment beds, and a member is a minor unit in a formation. Groups are sets of formations that are related in significant ways, and a supergroup is a sequence of vertically related groups and lone formations. The various kinds of unconformities are gaps in the geologic record. Such gaps can be due to an absence of deposition or due to subsequent erosion removing the rock units.See also:

Geology of the Grand Canyon area, Geology of the Grand Canyon area - Deposition of sediments, Geology of the Grand Canyon area - Vishnu Group, Geology of the Grand Canyon area - Grand Canyon Supergroup, Geology of the Grand Canyon area - Tonto Group, Geology of the Grand Canyon area - Temple Butte Redwall and Surprise Canyon, Geology of the Grand Canyon area - Supai Group, Geology of the Grand Canyon area - Hermit Coconino Toroweap and Kaibab, Geology of the Grand Canyon area - Mesozoic deposition, Geology of the Grand Canyon area - Creation of the Grand Canyon, Geology of the Grand Canyon area - Uplift and nearby extension, Geology of the Grand Canyon area - The Colorado River is born and cuts down, Geology of the Grand Canyon area - Volcanic activity dams the new canyon, Geology of the Grand Canyon area - Recent geology human impact and the future

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This table of formations exposed in the Death Valley area lists and describes the exposed formations of the Death Valley National Park and the surrounding area. System Series Formation Lithology and thickness Characteristic fossils Quaternary Holocene   Fan gravel; silt and salt on floor of playa, less than 100 feet (30 m) thick. None   Pleistocene   Fan gravel; silt ...

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Geology of the Death Valley area, Geology of the Death Valley area - Early sedimentation, Geology of the Death Valley area - Proterozoic complex, Geology of the Death Valley area - Pahrump Group, Geology of the Death Valley area - Crustal thinning and rifting, Geology of the Death Valley area - Passive margin formed, Geology of the Death Valley area - A Carbonate shelf forms, Geology of the Death Valley area - Change to active margin and uplift, Geology of the Death Valley area - Development of a flood plain, Geology of the Death Valley area - Extension creates the Basin and Range, Geology of the Death Valley area - Volcanism and valley-fill sedimentation, Geology of the Death Valley area - Table of formations, Geology of the Death Valley area - Table of salts^[30], Geology of the Death Valley area - Notes

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The hills are home to a number of limestone features, including caves (Wookey Hole), limestone pavements, and a number of gorges, most famously Cheddar Gorge and Burrington Combe. In addition to Carboniferous and some Jurassic limestone, parts of the hills are formed from Devonian sandstone and Silurian volcanic rocks. The latter are quarried for use in road construction and as a concrete aggregate. From the time of the Romans until the late Victorian era, the hill ...

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Mendip Hills, Mendip Hills - Geology, Mendip Hills - Ecology, Mendip Hills - History, Mendip Hills - Notable towns

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In ancient times, it was believed that liverworts cured diseases of the liver, hence the name. In Old English, the word liverwort literally means liver plant. This probably stemed from the superficial appearance of some thalloid liverworts (which resemble a liver in outline), and led to the common name of the group as hepatics, from the Latin word for liver. An unrelated flowering plant, Hepatica, is sometimes also refered to as liverwort because it was ...

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Marchantiophyta, Marchantiophyta - Overview, Marchantiophyta - Description, Marchantiophyta - Life cycle, Marchantiophyta - Classification

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The bodies of trilobites are divided into three parts (tagmata): a cephalon (head), composed of the two preoral and first four postoral segments completely fused together; a thorax composed of freely articulating segments; and a pygidium (tail) composed of the last few segments fused together with the telson. In the most primitive trilobites the pygidia are still fairly rudimentary. The thorax is fairly flexible—fossilised trilobites are often fo ...

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Trilobite, Trilobite - Physical description, Trilobite - Sensory organs, Trilobite - Holochroal eyes, Trilobite - Schizochroal eyes, Trilobite - Abathochroal eyes, Trilobite - Development, Trilobite - Terminology, Trilobite - Extinction, Trilobite - Fossil distribution

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Among the loose beds of ash that cover the slopes of many volcanoes, three classes of materials are represented. In addition to true ashes of the kind described above, there are lumps of the old lavas and tuffs forming the walls of the crater, etc., which have been torn away by the violent outbursts of steam, and pieces of sedimentary rocks from the deeper parts of the volcano that were dislodged by the rising lava and are often intensely baked and recrystallized by the heat t ...

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Tuff, Tuff - Volcanic ash, Tuff - Breccias, Tuff - Igneous rock, Tuff - Welded Tuff, Tuff - Rhyolite tuffs, Tuff - Trachyte tuffs, Tuff - Andesitic tuffs, Tuff - Basaltic tuffs, Tuff - Ultra-basic tuffs, Tuff - Folding and metamorphosis, Tuff - Economic importance

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This classification is based on that of Soleglad & Fet (2003) [2].which replaced the older, unpublished classification of Stockwell [3]. Additional taxonomic changes are from Soleglad et al. (2005) [4]. INFRAORDER Orthosterni Pocock, 1911 PARVORDER Pseudoch ...

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Scorpion, Scorpion - Physical characteristics, Scorpion - Scorpion venom, Scorpion - Reproduction, Scorpion - Birth and development, Scorpion - Origins, Scorpion - Geographical distribution, Scorpion - How scorpions eat, Scorpion - Suicide misconception, Scorpion - Classification, Scorpion - Cultural symbolism

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As the Taconic Orogeny subsided in early Silurian time, uplifts and folds in the Hudson Valley region were beveled by erosion. Upon this surface sediments began to accumulate, derived from remaining uplifts in the New England region. The evidence for this is the Silurian Shawangunk Conglomerate, a massive, ridge-forming quartz sandstone and conglomerate formation, which rests unconformably on a surface of older gently- to steeply-dipping pre-Silurian age strata throughout the region. This ridge of Shawangunk Conglomerate extends southward fr ...

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Taconic orogeny, Taconic orogeny - Aftermath of the Taconic Orogeny

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Ammonite - Basic shell anatomy. The chambered part of the ammonite shell is called a phragmocone. The phragmocone contains a series of progressively larger chambers, called camerae (sing. camera) that are divided by thin walls called septa (sing. septum). Only the last and largest chamber, the body chamber, was occupied by the living animal at any given moment. As it grew, it adde ...

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Ammonite, Ammonite - Classification, Ammonite - Life, Ammonite - Shell anatomy and diversity, Ammonite - Basic shell anatomy, Ammonite - Sexual dimorphism, Ammonite - Variations in shape, Ammonite - The aptychus, Ammonite - Size, Ammonite - Ammonite distribution, Ammonite - Trivia, Ammonite - References and further reading

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In the colonial times the river valley was a major trade route through the hill country of western New York, first for the Iroquois and other Native Americans, and later for the European settlers. In 1779 during the American Revolutionary War, Americans troops of the Sullivan Expedition defeated a combined force of Iroquois, their allies, Tories and British at the Battle of Newtown along the river southeast of Elmira. The victory opened the way for Sullivan to systematically destroy the Native American ...

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Chemung River, Chemung River - Description, Chemung River - History

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Inside the sea star underneath the hepatic caeca are the gonads which are involved in reproduction. The space inside the body not occupied by the internal organs is known as the perivisceral coelom. The body cavity also contains the water vascular system that operates the tube feet, and the hemal system. Hemal channels form rings around the mouth (the oral hemal ring), closer to the top of the starfish (the aboral hemal ring), and around the digestive system (the gastric hemal ring). The axial sinus, a portion of the body cavity, connects the three rings. Each ray also has hemal channels running next to the gonads. < ...

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Sea star, Sea star - Distribution, Sea star - External Anatomy, Sea star - Internal Anatomy, Sea star - Digestion and excretion, Sea star - Nervous System, Sea star - Circulation and respiration, Sea star - Behaviour, Sea star - Reproduction, Sea star - Locomotion, Sea star - Regeneration, Sea star - Geological history

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Scotland is geologically alien to Europe, comprising a lost sliver of the ancient continent of Laurentia (which later formed the bulk of North America). During the Cambrian period the crustal region which became Scotland formed part of the continental shelf of Laurentia, then still south of the equator. Laurentia was separated from the continent of Baltica (which later became Scandinavia and the Baltic region) by the diminishing Iapetus Ocean. The two ancient continents moved toward one another through the Cambrian and Ordovician periods, wi ...

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Prehistoric Scotland, Prehistoric Scotland - The deep prehistory of Scotland, Prehistoric Scotland - Before modern humans, Prehistoric Scotland - Hunter-gatherers, Prehistoric Scotland - Farmers and monument builders, Prehistoric Scotland - Bronze age, Prehistoric Scotland - Iron age, Prehistoric Scotland - Access - guide books

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