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Erik Jarvik
Anders Erik Vilhelm Jarvik (30 November 1907 – 11 January 1998) was a Swedish paleontologist who worked extensively on the sarcopterygian (or lobe-finned) fish ''Eusthenopteron''. In a career that spanned some 60 years, Jarvik produced some of the most detailed anatomical work on this fish, making it arguably the best known fossil vertebrate. Jarvik was born at a farm in Utby Parish near Mariestad in northern Västergötland. He studied botany, zoology, geology, and paleontology at Uppsala University, where he took his licentiate's degree in 1937. In 1942, he completed his PhD with the dissertation ''On the structure of the snout of Crossopterygians and lower Gnathostomes in general''. He participated in the Greenland expedition of Gunnar Säve-Söderbergh in 1932 and was appointed assistant in the Department of Palaeozoology of the Swedish Museum of Natural History in Stockholm in 1937; he eventually succeeded Erik Stensiö as professor and head of the departmen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Osteolepiform
Osteolepiformes, also known as Osteolepidida, is a group of prehistoric lobe-finned fishes which first appeared during the Devonian period. The order contains the families Canowindridae, Megalichthyidae, Osteolepididae and Tristichopteridae. The order is generally considered to be paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ... because the characters that define it are mainly attributes of stem tetrapodomorphs. Below is a cladogram showing the paraphyly of Osteolepiformes compiled and modified from Ahlberg and Johanson (1998). See also Swartz (2012). Osteolepiformes is marked by the green bracket. References External linksTree of Life Tetrapodomorphs Prehistoric fish orders Paraphyletic groups {{paleo-lobefinned-fish-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lepospondyli
Lepospondyli is a diverse taxon of early tetrapods. With the exception of one late-surviving lepospondyl from the Late Permian of Morocco ('' Diplocaulus minumus''), lepospondyls lived from the Early Carboniferous (Mississippian) to the Early Permian and were geographically restricted to what is now Europe and North America. Five major groups of lepospondyls are known: Adelospondyli; Aïstopoda; Lysorophia; Microsauria; and Nectridea. Lepospondyls have a diverse range of body forms and include species with newt-like, eel- or snake-like, and lizard-like forms. Various species were aquatic, semiaquatic, or terrestrial. None were large (the biggest genus, the diplocaulid '' Diplocaulus'', reached a meter in length, but most were much smaller), and they are assumed to have lived in specialized ecological niches not taken by the more numerous temnospondyl amphibians that coexisted with them in the Paleozoic. Lepospondyli was named in 1888 by Karl Alfred von Zittel, who coined the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Batrachomorpha
The Batrachomorpha ("frog forms") are a clade containing recent and extinct amphibians that are more closely related to modern amphibians than they are to mammals and reptiles. According to many analyses they include the extinct Temnospondyli; some show that they include the Lepospondyli instead. The name traditionally indicated a more limited group. The first tetrapods were all amphibians in the physiological sense that they laid their eggs in water, and are colloquially sometimes referred to as labyrinthodonts or stegocephalians. The term "amphibians" can be ambiguous, however. In modern phylogeny, the basalmost tetrapods are discerned from two derived branches, one consisting of the crown group of modern amphibians, the Lissamphibia, and its relatives. In this scheme, the name Batrachomorpha is given to this branch of amphibians, while the name Reptiliomorpha denotes the other branch. While the actual phylogeny of the modern amphibians is not well understood, their ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amphibia
Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial animal, terrestrial, fossorial, arboreal or freshwater aquatic ecosystems. Thus amphibians typically start out as larvae living in water, but some species have developed behavioural adaptations to bypass this. The young generally undergo metamorphosis from larva with gills to an adult air-breathing form with lungs. Amphibians use their skin as a secondary respiratory surface and some small terrestrial salamanders and frogs lack lungs and rely entirely on their skin. They are superficially similar to reptiles like lizards but, along with mammals and birds, reptiles are amniotes and do not require water bodies in which to breed. With their complex reproductive needs and permeable skins, amphibians are often ecological indicators; in re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caecilian
Caecilians (; ) are a group of limbless, vermiform or serpentine amphibians. They mostly live hidden in the ground and in stream substrates, making them the least familiar order of amphibians. Caecilians are mostly distributed in the tropics of South and Central America, Africa, and southern Asia. Their diet consists of small subterranean creatures such as earthworms. All modern caecilians and their closest fossil relatives are grouped as a clade, Apoda , within the larger group Gymnophiona , which also includes more primitive extinct caecilian-like amphibians. The name derives from the Greek words γυμνος (''gymnos'', naked) and οφις (''ophis'', snake), as the caecilians were originally thought to be related to snakes. The body is cylindrical dark brown or bluish black in colour. The skin is slimy and bears grooves or ringlike markings. Description Caecilians completely lack limbs, making the smaller species resemble worms, while the larger species, with lengths ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Porolepiform
Porolepiformes is an order of prehistoric lobe-finned fish which lived during the Devonian period (about 416 to 359 million years ago). The group contains two families: Holoptychiidae and Porolepididae. Porolepiformes was established by the Swedish paleontologist Erik Jarvik, and were thought to have given rise to the salamanders and caecilians independently of the other tetrapods. He based this conclusion on the shapes of the snouts of the aforementioned groups. This view is no longer in favour in Paleontology. Jarvik also claimed the existence of choanae in porolepiformes which linked them to tetrapods, but this has remained controversial. Recent phylogenetic reconstruction places porolepiformes close to lungfishes. More recent evidence has shown that at least one genus ''Laccognathus'' was most likely amphibious Amphibious means able to use either land or water. In particular it may refer to: Animals * Amphibian, a vertebrate animal of the class Amphibia (many ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caudata
The Caudata are a group of amphibians containing the extant salamanders ( Urodela) and all extinct species of amphibians more closely related to salamanders than to frogs. They are typically characterized by a superficially lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. Disagreement exists between different authorities as to the definition of the terms "Caudata" and "Urodela". Some maintain that Urodela should be restricted to the crown group, with Caudata being used for the total group. Others restrict the name Caudata to the crown group and use Urodela for the total group. The former approach seems to be most widely adopted and is used in this article. Evolution The origins and evolutionary relationships between the three main groups of amphibians ( apodans, urodeles and anurans) is a matter of debate. A 2005 molecular phylogeny, based on rDNA analysis, su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holoptychius Quebecensis -"salamanderfisk"
''Holoptychius'' (from el, όλος , 'whole' and el, πτυχή 'fold') is an extinct genus of porolepiform lobe-finned fish from the Middle Devonian to Carboniferous (Mississippian) periods. It is known from fossils worldwide. The genus was first described by Louis Agassiz in 1839. Description ''Holoptychius'' was a streamlined predator about long (though largest specimen could grew up to ), which fed on other bony fish. Its rounded scales and body form indicate that it could have swum quickly through the water to catch prey. Similar to other rhipidistians, it had fang-like teeth on its palate in addition to smaller teeth on the jaws. Its asymmetrical tail sported a caudal fin on its lower end. To compensate for the downward push caused by this fin placement, the pectoral fins of ''Holoptychius'' were placed high on the body. Species Of the genus ''Holoptychius'' the following species have been described: * ''H. americanus'' * ''H. andersoni'' * ''H. bergmanni'' (Do ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reversal Film
In photography, reversal film or slide film is a type of photographic film that produces a positive image on a transparent base. Instead of negatives and prints, reversal film is processed to produce transparencies or diapositives (abbreviated as "diafilm" or "dia" in some languages like German or Hungarian). Reversal film is produced in various sizes, from 35 mm to roll film to 8×10 inch sheet film. A slide is a specially mounted individual transparency intended for projection onto a screen using a slide projector. This allows the photograph to be viewed by a large audience at once. The most common form is the 35 mm slide, with the image framed in a 2×2 inch cardboard or plastic mount. Some specialized labs produce photographic slides from digital camera images in formats such as JPEG, from computer-generated presentation graphics, and from a wide variety of physical source material such as fingerprints, microscopic sections, paper documents, astronomical i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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