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Blastoidea
Blastoids (class Blastoidea) are an extinct type of stemmed echinoderm, often referred to as sea buds. They first appear, along with many other echinoderm classes, in the Ordovician period, and reached their greatest diversity in the Mississippian subperiod of the Carboniferous period. However, blastoids may have originated in the Cambrian. Blastoids persisted until their extinction at the end of Permian, about 250 million years ago. Although never as diverse as their contemporary relatives, the crinoids, blastoids are common fossils, especially in many Mississippian-age rocks. Description Like most echinoderms, blastoids were protected by a set of interlocking plates of calcium carbonate, which formed the main body, or ''theca''. In life, the theca of a typical blastoid was attached to a stalk or column made up of stacked disc-shaped plates. The other end of the column was attached to the ocean floor by a holdfast, very much like stalked crinoids. The stalk was usually relat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Echinoderm
An echinoderm () is any animal of the phylum Echinodermata (), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as larvae, as adults echinoderms are recognisable by their usually five-pointed radial symmetry (pentamerous symmetry), and are found on the sea bed at every ocean depth from the intertidal zone to the abyssal zone. The phylum contains about 7,600 living species, making it the second-largest group of deuterostomes after the chordates, as well as the largest marine-only phylum. The first definitive echinoderms appeared near the start of the Cambrian. Echinoderms are important both ecologically and geologically. Ecologically, there are few other groupings so abundant in the deep sea, as well as shallower oceans. Most echinoderms are able to reproduce asexually and regenerate tissue, organs and limbs; in some cases, they can undergo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blastozoa
Blastozoa is a subphylum of extinct echinoderms characterized by the presence of specialized respiratory structures and brachiole plates used for feeding. It ranged from the Cambrian to the Permian. Biserial, triradiate, and pentaradiate ambulacral patterns have been identified in blastozoa specimens. The pentaradiate pattern in particular has been associated with several different classes. A significant species has been found at the Zaouïa Formation. References External linksHarvard: Subphylum Blastozoa Blastozoa, Paleozoic echinoderms Cambrian echinoderms Silurian echinoderms Ordovician echinoderms Devonian echinoderms Permian echinoderms Animal subphyla {{paleo-echinoderm-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentremites
''Pentremites'' is an extinct genus of blastoid echinoderm belonging to the family Pentremitidae. Description These stalked echinoderms averaged a height of about but occasionally ranged up to about 3 times that size. They, like other blastoids, superficially resemble their distant relatives, the crinoids or ''sea lilies'', having a near-identical, planktivorous lifestyle living on the sea floor attached by a stalk. As with all other blastoids, species of ''Pentremites'' trapped food floating in the currents by means of tentacle-like appendages. ''Pentremites'' species lived in the early to middle Carboniferous, from 360.7 to 314.6 Ma. Its fossils are known from North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri .... References * ''Fossils'' (Smithsonian Handbooks) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cystoids
Cystoidea was defined as a class (biology), class of extinct paleozoic blastozoan echinoderms established to encompass stalked taxa that were neither crinoids nor blastoids. It was shown to be polyphyletic in the late 1960s but continues to be used even in recent (as of 2022) literature to discuss both rhombiferans and diploporitans. History The concept of Cystoidea has a complex history, with many emendations from its original conception. Early versions included the homalozoans, eocrinoids, paracrinoids, blastoids, and edrioblastoids. By 1967 the modern usage encompassing only rhombiferans and diploporitans had been established, although questions remained regarding the possible inclusion of blastoids. Despite these removals, speculation continued as to whether cystoids were ancestral to blastoids, crinoids, or echinoids. Work published in 1967 and 1968 questioned whether Cystoidea formed a natural group, and in 1972 the former orders Rhombifera and Diploporita were elevated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentremites Glen Dean Fm KY Aboral
''Pentremites'' is an extinct genus of blastoid echinoderm belonging to the family Pentremitidae. Description These stalked echinoderms averaged a height of about but occasionally ranged up to about 3 times that size. They, like other blastoids, superficially resemble their distant relatives, the crinoids or ''sea lilies'', having a near-identical, planktivorous lifestyle living on the sea floor attached by a stalk. As with all other blastoids, species of ''Pentremites'' trapped food floating in the currents by means of tentacle-like appendages. ''Pentremites'' species lived in the early to middle Carboniferous, from 360.7 to 314.6 Ma. Its fossils are known from North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri .... References * ''Fossils'' (Smithsonian Handbooks) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years from the end of the Cambrian Period Megaannum, Ma (million years ago) to the start of the Silurian Period Ma. The Ordovician, named after the Celtic Britons, Welsh tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same Rock (geology), rock beds in North Wales in the Cambrian and Silurian systems, respectively. Lapworth recognized that the fossil fauna in the disputed Stratum, strata were different from those of either the Cambrian or the Silurian systems, and placed them in a system of their own. The Ordovician received international approval in 1960 (forty years after Lapworth's death), when it was adopted as an official per ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ambulacral
Ambulacral is a term typically used in the context of anatomical parts of the phylum Echinodermata or class Asteroidea and Edrioasteroidea. Echinoderms can have ambulacral parts that include ossicles, plates, spines, and suckers. For example, sea stars or "star fish" have an ambulacral groove on their oral side (underside). This ambulacral groove extends from the mouth to the end of each ray or arm. Each groove of each arm in turn has four rows of hollow tube feet that can be extended or withdrawn. Opposite the ambulacral groove is an ambulacral ridge on the aboral side of each ray, known as an ambulacrum. These have interambulacra between them. Etymology From the Latin 'ambulācrum', meaning 'walk planted with trees', 'avenue', 'alley' and 'walking Walking (also known as ambulation) is one of the main gaits of terrestrial locomotion among legged animals. Walking is typically slower than running and other gaits. Walking is defined as an " inverted pendulum" gait in which th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permian Echinoderms
The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the sixth and last period of the Paleozoic Era; the following Triassic Period belongs to the Mesozoic Era. The concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the region of Perm in Russia. The Permian witnessed the diversification of the two groups of amniotes, the synapsids and the sauropsids (reptiles). The world at the time was dominated by the supercontinent Pangaea, which had formed due to the collision of Euramerica and Gondwana during the Carboniferous. Pangaea was surrounded by the superocean Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior. Amniotes, which could better cope with these drier conditions, rose to dominance in place of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Devonian Echinoderms
The Devonian ( ) is a geologic period and system of the Paleozoic era during the Phanerozoic eon, spanning 60.3 million years from the end of the preceding Silurian period at million years ago ( Ma), to the beginning of the succeeding Carboniferous period at Ma. It is the fourth period of both the Paleozoic and the Phanerozoic. It is named after Devon, South West England, where rocks from this period were first studied. The first significant evolutionary radiation of life on land occurred during the Devonian, as free- sporing land plants (pteridophytes) began to spread across dry land, forming extensive coal forests which covered the continents. By the middle of the Devonian, several groups of vascular plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants ( pteridospermatophytes) appeared. This rapid evolution and colonization process, which had begun during the Silurian, is known as the Silurian-Devonian Terrestrial Revo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ordovician Echinoderms
The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era, and the second of twelve periods of the Phanerozoic Eon. The Ordovician spans 41.6 million years from the end of the Cambrian Period Ma (million years ago) to the start of the Silurian Period Ma. The Ordovician, named after the Welsh tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same rock beds in North Wales in the Cambrian and Silurian systems, respectively. Lapworth recognized that the fossil fauna in the disputed strata were different from those of either the Cambrian or the Silurian systems, and placed them in a system of their own. The Ordovician received international approval in 1960 (forty years after Lapworth's death), when it was adopted as an official period of the Paleozoic Era by the International Geological Congress. Life continued to flour ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tennessee
Tennessee (, ), officially the State of Tennessee, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Kentucky to the north, Virginia to the northeast, North Carolina to the east, Georgia (U.S. state), Georgia, Alabama, and Mississippi to the south, Arkansas to the southwest, and Missouri to the northwest. Tennessee is the List of U.S. states and territories by area, 36th-largest by area and the List of U.S. states and territories by population, 15th-most populous of the 50 states. According to the United States Census Bureau, the state's estimated population as of 2024 is 7.22 million. Tennessee is geographically, culturally, and legally divided into three Grand Divisions of Tennessee, Grand Divisions of East Tennessee, East, Middle Tennessee, Middle, and West Tennessee. Nashville, Tennessee, Nashville is the state's capital and largest city, and anchors its largest metropolitan area. Tennessee has dive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continental Shelf
A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island is known as an "''insular shelf''." The continental margin, between the continental shelf and the abyssal plain, comprises a steep continental slope, surrounded by the flatter continental rise, in which sediment from the continent above cascades down the slope and accumulates as a pile of sediment at the base of the slope. Extending as far as 500 km (310 mi) from the slope, it consists of thick sediments deposited by turbidity currents from the shelf and slope. The continental rise's gradient is intermediate between the gradients of the slope and the shelf. Under the United Nations Convention on the Law of the Sea, the name continental shelf was given a legal definition as the stretch of the seabed adjacent to the shores ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
