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18-551: The park occupies a large plain , which was formed when a depression in Paleozoic crystalline rocks was filled with organic and inorganic sediments , thus creating a sedimentary basin . The uppermost sediment levels are of fluvial and aeolian origin. The eastern parts of the park are dominated by silts and clays , creating less permeable soils, while the western parts contain soils that are coarser and more porous. There are faults that were generated during formation of

36-512: A valley, a plain is enclosed on two sides, but in other cases a plain may be delineated by a complete or partial ring of hills, by mountains, or by cliffs . Where a geological region contains more than one plain, they may be connected by a pass (sometimes termed a gap ). Coastal plains mostly rise from sea level until they run into elevated features such as mountains or plateaus. Plains can be formed from flowing lava ; from deposition of sediment by water, ice, or wind; or formed by erosion by

54-408: Is a flat expanse of land with a layer of grass that generally does not change much in elevation , and is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains , as coastal plains , and as plateaus or uplands . Plains are one of the major landforms on earth, where they are present on all continents, and cover more than one-third of the world's land area. In

72-580: Is adjacent to the Pilcomayo River and its former channels, which are frequently flooded. It is dominated by riparian vegetation. Figs and sweetwood trees can be found there, covered by many species of lianas , vines and epiphytes . The patchy vegetation of the higher lands, forming distinctive "mountain islands", represent the fourth zone. Quebracho trees ( Schinopsis balansae and Aspidosperma quebracho-blanco ) can frequently be found there. Higher lands are inhabited by such mammals as

90-461: Is also capable of making sounds; both grunts and squeaks. Like other callichthyines, Hoplosternum species build bubble nests . Among callichthyines, H. littorale has the most complex nest structure. Hoplosternum is a builder of bubblenests from plant parts, some bottom materials, and bubbles formed by a mouth secretion and air. The male forms a mass of bubbles about 20 cm (8 in.) in diameter and 10 cm (4 in) high. During

108-549: Is derived from the Greek hoplon (weapon) and sternon (chest). There are currently three described species in this genus: Hoplosternum species are found in tropical Central and South America especially in Guyana . It is called "Hassa" by the locals. Hoplosternum is normally found in large schools on the muddy bottoms of slow-moving rivers, pools, drainage ditches, and swampy areas. In water with low oxygen content,

126-453: Is located in a subtropical zone with annual mean temperature of 23 °C (73 °F) and annual mean precipitation of 1,200 millimetres (47 in). Summer temperatures can exceed 40 °C (104 °F), but during winters, frost is not uncommon. Winters are dry, while precipitation peaks in March and November. The area is affected by frequent tornadoes . For the purposes of classifying

144-421: Is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains , as coastal plains , and as plateaus or uplands . Plains are one of the major landforms on earth, being present on all continents and covering more than one-third of the world's land area. Plains in many areas are important for agriculture . There are various types of plains and biomes on them. A plain or flatland

162-490: Is the main watercourse of the area. During the wet season, the river and its tributaries flood the nearby areas, creating large swaths of interconnected lakes and marshes, most of which are temporary. The southern end of the park contains a larger lake called Laguna Blanca, which is a habitat for many waterfowl species and a resting point for migratory bird species coming from the Northern Hemisphere . The park

180-547: The Hoplosternum that can use atmospheric air and thus tolerate droughts that frequently affect shallow water bodies in the area. The snake population is represented by species such as the yellow anaconda ( Eunectes notaeus ) and Hydrodynastes gigas , a large water snake. Plain In geography , a plain , commonly known as flatland , is a flat expanse of land that generally does not change much in elevation , and

198-521: The Andes , lying parallel to the Paraguay River . While the park's territory is gently sloping down from west to east, there is very little variety in elevation. The subtle differences become important in times of heavy rains and floods, when the area becomes inundated with pools of water connected by channels forming in the most low-lying areas. The Pilcomayo River , after which the park is named,

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216-438: The gray brocket , capybara , peccary , howler monkey and puma ; birds include chachalacas and rails . The maned wolf can be found in the lowlands, along with such birds as the greater rhea and seriemas . Aquatic environments are inhabited by storks , herons , roseate spoonbills and ducks . There are two caiman species: the broad-snouted caiman and the yacare caiman . The fish population includes species from

234-647: The Earth. They are structurally depressed areas of the world that make up some of the most extensive natural lowlands on the Earth's surface. Hoplosternum Hoplosternum is a small genus of freshwater catfish in the Callichthyinae subfamily of the armored catfish family. A fossil catfish has been identified as Hoplosternum sp. from the middle Miocene in the La Venta formation, Magdalena River basin, Colombia . The name Hoplosternum

252-404: The agents from hills or mountains. Biomes on plains include grassland ( temperate or subtropical ), steppe ( semi-arid ), savannah ( tropical ) or tundra ( polar ). In a few instances, deserts and rainforests may also be considered plains. Plains in many areas are important for agriculture because where the soils were deposited as sediments they may be deep and fertile , and

270-468: The fish are capable of utilizing atmospheric air by taking in a gulp of air at the surface of the water and passing it back to the hind gut. The walls of the gut are lined with tiny blood vessels into which the oxygen from the air can pass, similar to the function of true lungs. The remaining gasses pass out through the anus. When there is a severe drought, these air breathers are able to traverse short stretches of land seeking better conditions. The fish

288-595: The flatness facilitates mechanization of crop production; or because they support grasslands which provide good grazing for livestock . The types of depositional plains include: Erosional plains have been leveled by various agents of denudation such as running water, rivers, wind and glacier which wear out the rugged surface and smoothens them. Plain resulting from the action of these agents of denudation are called peneplains (almost plain) while plains formed from wind action are called pediplains . Structural plains are relatively undisturbed horizontal surfaces of

306-569: The park's types of plants, the area can be divided into 4 distinct zones. One is savanna , which is dominated by the Caranday wax palm , an unofficial emblem of the area, towering over a dense cover of herbaceous plants (especially from the genus Scirpus ). Other trees include such species as Acacia caven and Prosopis nigra . Wetlands are dominated by aquatic vegetation . Floating plants include water hyacinths , Limnocharitaceae , Nymphoides and Ludwigia . Another distinct zone

324-466: The time of construction, the female is actively chased away or ignored. When the nest construction is complete, the male will accept the female. The eggs (up to several hundred) are deposited into the nest and the male or the pair will actively protect the nest for about four weeks until the fry come out of the nest at the size of 2.5 cm (1 in). Hoplosternum is also known by the nickname hassa in Guyana and other parts of South America . It

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