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Asterosteidae
Rhenanida ("Rhine (fish)") is an order of scaly placoderms. Unlike most other placoderms, the rhenanids' armor was made up of a mosaic of unfused scales and tubercles. The patterns and components of this "mosaic" correspond to the plates of armor in other, more advanced placoderms, suggesting that the ancestral placoderm had armor made of unfused components, as well. All rhenanids were flattened, ray-like, bottom-dwelling predators that lived in marine environments. Evolution The rhenanids were once presumed to be the most primitive, or at least the closest to the ancestral placoderm, as their armor was made up of a mosaic of tubercles, as opposed to the solidified plates of "advanced" placoderms, such as antiarchs and arthrodires. Through comparing the skull anatomies of ''Jagorina pandora'' with those of antiarchs, the rhenanids are considered to be the sister group of the antiarchs (together with their respective Acanthothoracid relatives). Presence in the fossil record Th ...
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Nefudina Qalibahensis
''Nefudina qalibahensis'' is a rhenanid Rhenanida ("Rhine (fish)") is an order of scaly placoderms. Unlike most other placoderms, the rhenanids' armor was made up of a mosaic of unfused scales and tubercles. The patterns and components of this "mosaic" correspond to the plates of ar ... placoderm from the early Emsiane during the Early Devonian Epoch of Northeastern Saudi Arabia. It is known from skull fragments and scales.it died out during the end of the emsiane. References https://www.mindat.org/taxon-4842435.html Rhenanida Placoderms of Asia Vertebrates of the Arabian Peninsula Placoderm genera {{placoderm-stub ...
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Bolivosteus Chacomensis
''Bolivosteus chacomensis'' is a rhenanid placoderm from the Eifelian of Bolivia, and is the only placoderm known from the “Malvinokaffric” invertebrate faunas. The Malvinokaffric faunas represent a series of cold-water ecosystems near or at the South Pole during the Middle Devonian, and apparently lacked the presence of ammonoids, bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a ..., or colonial corals. ''B. chacomensis'' is known from skull fragments and scales. References Rhenanida Placoderm genera Placoderms of South America Devonian Bolivia Fossils of Bolivia Fossil taxa described in 1986 {{placoderm-stub ...
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Asterosteus
''Asterosteus'' is genus of rhenanid Rhenanida ("Rhine (fish)") is an order of scaly placoderms. Unlike most other placoderms, the rhenanids' armor was made up of a mosaic of unfused scales and tubercles. The patterns and components of this "mosaic" correspond to the plates of ar ... placoderm from the Eifelian. The type species, ''A. stenocephalus'', is known from an incomplete skull from Middle Devonian strata of Ohio. What may be a second species ("''Asterosteus sp'' Schmidtt 1963") is described from fragments decorated with star-shaped tubercules from the Eifelian-aged Gebze beds of Turkey. References Rhenanida Placoderms of North America Placoderms of Asia Placoderm genera Paleontology in Ohio Eifelian life {{placoderm-stub ...
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Ostracoderm
Ostracoderms () are the armored jawless fish of the Paleozoic Era. The term does not often appear in classifications today because it is paraphyletic (excluding jawed fishes) (may also be polyphyletic if anaspids are closer to cyclostomes) and thus does not correspond to one evolutionary lineage. However, the term is still used as an informal way of loosely grouping together the armored jawless fishes. An innovation of ostracoderms was the use of gills not for feeding, but exclusively for respiration. Earlier chordates with gill precursors used them for both respiration and feeding. Ostracoderms had separate pharyngeal gill pouches along the side of the head, which were permanently open with no protective operculum. Unlike invertebrates that use ciliated motion to move food, ostracoderms used their muscular pharynx to create a suction that pulled small and slow moving prey into their mouths. Swiss anatomist Louis Agassiz received some fossils of bony armored fish from Sco ...
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Ichthyolith
An ichthyolith (from Greek, “fish“ and ”stone”, “rock“, literally "fish- rock") is any disarticulated remains of a fish found in the fossil record, most often a scale, denticle or tooth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, t .... The term was coined by Doyle, Kennedy and Riedel (1974) to denote 'fish skeletal debris'. The term 'stratignathy', proposed in the same paper for the time relationships of ichthyoliths, did not gain currency. References Prehistoric fish Fossil record of animals {{paleo-fish-stub ...
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Genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus. :E.g. '' Panthera leo'' (lion) and '' Panthera onca'' (jaguar) are two species within the genus ''Panthera''. ''Panthera'' is a genus within the family Felidae. The composition of a genus is determined by taxonomists. The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including the idea that a newly defined genus should fulfill these three criteria to be descriptively useful: # monophyly – all descendants of an ancestral taxon are grouped together (i.e. phylogenetic analysis should c ...
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Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, where rocks from this period were first studied. The first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents. By the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. The arthropod groups of myriapods, arachnids and hexapods also became well-established early in this period, after starting their expansion to land at least from the Ordovician period. Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fishes. The placoderms began domina ...
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Species
In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can reproduction, produce Fertility, fertile offspring, typically by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, morphology (biology), morphology, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. The most recent rigorous estimate for the total number of species of eukaryotes is between 8 and 8.7 million. However, only about 14% of these had been described by 2011. All species (except viruses) are given a binomial nomenclature, two-part name, a "binomial". The first part of a binomial is the genus to which the species belongs. The second part is called the specifi ...
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Jagorina Pandora
''Jagorina pandora'' is a rhenanid Rhenanida ("Rhine (fish)") is an order of scaly placoderms. Unlike most other placoderms, the rhenanids' armor was made up of a mosaic of unfused scales and tubercles. The patterns and components of this "mosaic" correspond to the plates of ar ... placoderm of Upper Frasnian Germany. As with other rhenanids, it was a flattened, skate-like fish protected in an armor made up of unfused tubercles, and preyed on other, smaller fish by ambushing them from the sea bottom. Although ''J. pandora'' is known primarily from bone fragments and an intact skull, it is the second most studied rhenanid, after '' Gemuendina stuertzi''. It is from ''Jagorina'' that the details of the skull anatomy of rhenanids are known. Although scientists know of the overall anatomy and bodyplan of rhenanids because of ''G. stuertzi'', very little information has been gleaned from the skulls of ''G. stuertzi'', as all of the specimens of that species have been greatl ...
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Gondwana
Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages of break-up, involving the separation of Antarctica from South America (forming the Drake Passage) and Australia, occurred during the Paleogene. Gondwana was not considered a supercontinent by the earliest definition, since the landmasses of Baltica, Laurentia, and Siberia were separated from it. To differentiate it from the Indian region of the same name (see ), it is also commonly called Gondwanaland. Gondwana was formed by the accretion of several cratons. Eventually, Gondwana became the largest piece of continental crust of the Palaeozoic Era, covering an area of about , about one-fifth of the Earth's surface. During the Carboniferous Period, it merged with Laurasia to form a larger supercontinent called Pangaea. Gondwana ...
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