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Xenacanthus
''Xenacanthus'' (from Ancient Greek wikt:ξένος, ξένος, xénos, 'foreign, alien' + wikt:ἄκανθος, ἄκανθος, akanthos, 'spine') is an extinct genus of Xenacanthida, xenacanth cartilaginous fish. It lived in freshwater environments, and fossils of various species have been found worldwide. Description ''Xenacanthus'' is a relatively small member of its order. ''X. decheni'' reached about , ''X. meisenheimensis'' reached up to , ''X''. (''Expleuracanthus'') ''gaudryi'' reached . ''X. parallelus'' is one of the smallest xenacanths, males reached and females reached , both are fully grown. The dorsal fin was ribbonlike and ran the entire length of the back and round the tail, where it joined with the anal fin. This arrangement resembles that of modern conger eels, and ''Xenacanthus'' probably swam in a similar manner. A distinctive spine projected from the back of the head and gave the genus its name. The spike has even been speculated to have been venomous, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xenacanthus Sp Skull Harvard
''Xenacanthus'' (from Ancient Greek ξένος, xénos, 'foreign, alien' + ἄκανθος, akanthos, 'spine') is an extinct genus of xenacanth cartilaginous fish. It lived in freshwater environments, and fossils of various species have been found worldwide. Description ''Xenacanthus'' is a relatively small member of its order. ''X. decheni'' reached about , ''X. meisenheimensis'' reached up to , ''X''. (''Expleuracanthus'') ''gaudryi'' reached . ''X. parallelus'' is one of the smallest xenacanths, males reached and females reached , both are fully grown. The dorsal fin was ribbonlike and ran the entire length of the back and round the tail, where it joined with the anal fin. This arrangement resembles that of modern conger eels, and ''Xenacanthus'' probably swam in a similar manner. A distinctive spine projected from the back of the head and gave the genus its name. The spike has even been speculated to have been venomous, perhaps in a similar manner to a sting ray. The tee ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xenacanthida
Xenacanthida (or Xenacanthiformes) is an order or superorder of extinct shark-like chondrichthyans (cartilaginous fish) known from the Carboniferous to Triassic. They were native to freshwater, marginal marine and shallow marine habitats. Some xenacanths may have grown to lengths of . Most xenacanths died out at the end of the Permian in the End-Permian Mass Extinction, with only a few forms surviving into the Triassic. Description The foundation of the tooth is prolonged lingually with a circlet button and a basal tubercle on the oral and aboral surfaces individually. The family Xenacanthidae consists of five genera: ''Xenacanthus'', '' Triodus'', '' Plicatodus'', '' Mooreodontus'' and '' Wurdigneria''; all of these are distinguished by cross sections of the points, crown center, length of the median edge, type of vertical cristae, and microscopic anatomy. Xenacanths are divided into two groups based on dental characteristics. Group one has tricuspid crowns containing two sto ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rio Do Rasto Formation
The Rio do Rasto Formation is a Late Permian sedimentary geological formation in the South Region, Brazil, South Region of Brazil. The official name is Rio do Rasto, although in some publications it appears as ''Rio do Rastro''. The strata were deposited between the Wordian and the Wuchiapingian, from about 266 to 254 million years ago. The geology, alongside its paleobiota, indicate that the locality was a fresh water, freshwater environment. Some of the animals discovered in the formation include ''Tiarajudens'', ''Parapytanga'' and ''Pampaphoneus''. Description Geology The Rio do Rasto Formation is found mainly in the Brazilian states of Santa Catarina (state), Santa Catarina, Paraná (state), Paraná, and Rio Grande do Sul. It was formed during the Late Permian and is divided into two members: the lower Serrinha Member and the upper Morro Pelado Member, spanning from the Wordian to Wuchiapingian stages of the Permian. The deposits of the Formation are mainly continental, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Louis Agassiz
Jean Louis Rodolphe Agassiz ( ; ) FRS (For) FRSE (May 28, 1807 – December 14, 1873) was a Swiss-born American biologist and geologist who is recognized as a scholar of Earth's natural history. Spending his early life in Switzerland, he received a PhD at Erlangen and a medical degree in Munich. After studying with Georges Cuvier and Alexander von Humboldt in Paris, Agassiz was appointed professor of natural history at the University of Neuchâtel. He emigrated to the United States in 1847 after visiting Harvard University. He went on to become professor of zoology and geology at Harvard, to head its Lawrence Scientific School, and to found its Museum of Comparative Zoology. Agassiz is known for observational data gathering and analysis. He made institutional and scientific contributions to zoology, geology, and related areas, including multivolume research books running to thousands of pages. He is particularly known for his contributions to ichthyological classification, incl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permian Brazil
The Permian ( ) is a geologic period and System (stratigraphy), 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 Perm Governorate, region of Perm in Russia. The Permian witnessed the diversification of the two groups of amniotes, the synapsids and the Sauropsida, 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prehistoric Fish Of South America
Prehistory, also called pre-literary history, is the period of human history between the first known use of stone tools by hominins million years ago and the beginning of recorded history with the invention of writing systems. The use of symbols, marks, and images appears very early among humans, but the earliest known writing systems appeared years ago. It took thousands of years for writing systems to be widely adopted, with writing having spread to almost all cultures by the 19th century. The end of prehistory therefore came at different times in different places, and the term is less often used in discussing societies where prehistory ended relatively recently. It is based on an old conception of history that without written records there could be no history. The most common conception today is that history is based on evidence, however the concept of prehistory hasn't been completely discarded. In the early Bronze Age, Sumer in Mesopotamia, the Indus Valley Civilis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhaetian Extinctions
The Rhaetian is the latest age (geology), age of the Triassic period (geology), Period (in geochronology) or the uppermost stage (stratigraphy), stage of the Triassic system (stratigraphy), System (in chronostratigraphy). It was preceded by the Norian and succeeded by the Hettangian (the lowermost stage or earliest age of the Jurassic). The base of the Rhaetian lacks a formal Global Boundary Stratotype Section and Point, GSSP, though candidate sections include Steinbergkogel section, Steinbergkogel in Austria (since 2007) and Pignola-Abriola section, Pignola-Abriola in Italy (since 2016). The end of the Rhaetian (and the base of the overlying Hettangian Stage) is more well-defined. According to the current International Commission on Stratigraphy, ICS (International Commission on Stratigraphy) system, the Rhaetian ended ± 0.2 Ma (million years ago). In 2010, the base of the Rhaetian (i.e. the Norian-Rhaetian boundary) was voted to be defined based on the first appearance of ''Mi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permian Cartilaginous Fish
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] |
