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Anabarella
''Anabarella'' is a species of bilaterally-flattened monoplacophoran mollusc, with a morphological similarity to the rostroconchs. Its shell preserves evidence of three mineralogical textures on its outer surface: it is polygonal near the crest of the shell, subsequently changing to both spiny and stepwise. Its internal microstructure is calcitic and semi-nacreous. Its name reflects its provenance from Anabar, Siberia. It has been interpreted as ancestral to the rostroconchs, and has been aligned to the Helcionellidae. The genus is closely related to ''Watsonella'', with which it bears many morphological similarities, including a laminar internal shell microstructure said to connect it with the early bivalves ''Fordilla'' and ''Pojetaia ''Pojetaia'' is an extinct genus of early bivalves, one of two genera in the extinct family Fordillidae. The genus is known solely from Early to Middle Cambrian fossils found in North America, Greenland, Europe, North Africa, Asia, and Aus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Watsonella
''Watsonella'' is a genus of 'mollusc' known from early (Terreneuvian) Cambrian strata. The genus is closely related to '' Anabarella'', with which it bears many morphological similarities, including a laminar internal shell microstructure said to connect it with the early bivalves ''Fordilla'' and ''Pojetaia''. Biostratigraphic significance Watsonella has been proposed as an index fossil of the Cambrian, defining a W. crosbyi zone. Notwithstanding the weakness of a first appearance datum as a definition for the base of a period, the species has been proposed as a marker for the base of the presently unratified second stage of the Terreneuvian (i.e. Cambrian Stage 2). However, the species has now been found late in the FOrtunian, drawing back its first occurrence. But that said its occurrence in Australia seems to begin rather near the base of Stage 2. Affinity Widely thought to be a mollusc, the connection between the two 'valves' of Watsonella recalls the configuration ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fordilla
''Fordilla'' is an extinct genus of early bivalves, one of two genera in the extinct family Fordillidae. The genus is known solely from Early Cambrian fossils found in North America, Greenland, Europe, the Middle East, and Asia.The Paleobiology Database ''Fordilla'' entry accessed 4 January 2012 The genus currently contains three described species, ''Fordilla germanica'', ''Fordilla sibirica'', and the type species ''Fordilla troyensis''. Description ''Fordilla'' are small bivalves with that are equal in size and suboval in shape. In size ''Fordilla'' specime ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rostroconch
The Rostroconchia is a class of extinct molluscs dating from the early Cambrian to the Late Permian. They were initially thought to be bivalves, but were later given their own class. They have a single shell in their larval stage, and the adult typically has a single, pseudo-bivalved shell enclosing the mantle and muscular foot. The anterior part of the shell probably pointed downward and had a gap from which the foot could probably emerge. Rostroconchs probably lived a sedentary semi-infaunal lifestyle. There were probably more than 1,000 species of members of this class. Approximately 3 dozen genera and an even greater number of species have been described. Generally, rostroconchs are small, less than two centimeters in length, but larger forms, found in United States Devonian limestones, can grow to a length of 15 cm. Morphology and lifestyle Externally, rostroconchs look much like bivalves and rostroconchs probably had an extendable muscular foot, indicated by a prom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bivalves
Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bivalves have no head and they lack some usual molluscan organs, like the radula and the odontophore. They include the clams, oysters, cockles, mussels, scallops, and numerous other families that live in saltwater, as well as a number of families that live in freshwater. The majority are filter feeders. The gills have evolved into ctenidia, specialised organs for feeding and breathing. Most bivalves bury themselves in sediment, where they are relatively safe from predation. Others lie on the sea floor or attach themselves to rocks or other hard surfaces. Some bivalves, such as the scallops and file shells, can swim. The shipworms bore into wood, clay, or stone and live inside these substances. The shell of a bivalve is composed of calc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pojetaia
''Pojetaia'' is an extinct genus of early bivalves, one of two genera in the extinct family Fordillidae. The genus is known solely from Early to Middle Cambrian fossils found in North America, Greenland, Europe, North Africa, Asia, and Australia.The Paleobiology Database ''Pojetaia'' entry accessed 4 January 2012 The genus currently contains two accepted species, ''Pojetaia runnegari'', the type species, and ''Pojetaia sarhroensis'', though up to seven species have been proposed. The genera ''Buluniella'', ''Jellia'', and ''Oryzoconcha'' are all considered synonyms of ''Pojetaia''. Description ''Pojetaia'' are small bivalves with |
Monoplacophoran
Monoplacophora , meaning "bearing one plate", is a polyphyletic superclass of molluscs with a cap-like shell inhabiting deep sea environments . Extant representatives were not recognized as such until 1952; previously they were known only from the fossil record, and were thought to have become extinct 375 million years ago. Although the shell of many monoplacophorans is limpet-like in shape, they are not gastropods, nor do they have any close relation to gastropods. Definition Discussion about monoplacophorans is made difficult by the slippery definition of the taxon; some authors take it to refer to all non-gastropod mollusks with a single shell, or all single-shelled mollusks with serially repeated units; whereas other workers restrict the definition to cap-shaped forms, excluding spiral and other shapes of shell. The inclusion of the gastropod-like Bellerophontoidea within the group is also contentious. One attempt to resolve this confusion was to separate out the predomina ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anabar Plateau
The Anabar Plateau ( rus, Анабарское плато) is a mountain plateau in Krasnoyarsk Krai and the Sakha Republic (Yakutia), Siberia, Russia. The plateau is in a latitude dominated by permafrost. The permafrost thickness under the Anabar Plateau reaches . Geography The Anabar Plateau is located north of the Arctic Circle in northeastern Krasnoyarsk Krai and northwestern Sakha Republic, SSE of the Taymyr Depression, the central part of the North Siberian Lowland. It is located north of the Vilyuy Plateau and is the northernmost feature of the Central Siberian Plateau, to which it is connected in the southeast. To the southwest it runs into the higher Putorana Mountains, the border between both not being well-defined. The average height of the plateau surface is around . There are slightly higher tableland type elevations running across the plateau area, mostly in a roughly east to west direction. The highest point is a high unnamed summit. The Big Kuonamka, which fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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