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Alvania Ismar
''Alvania ismar'' is an extinct species of minute sea snail, a marine gastropod mollusk or micromollusk in the family Rissoidae. Distribution The species occurred at the Strait of Sicily in the Pleistocene at depths of 649 meters. Description The species had a height of 2.87 mm and a width of 1.7 mm. The species had a medium sized, ovate-conical shell, with a spiral sculpture on the whole teleoconch. strong axial ribs doesn't reach the base and the inner side of the outer lip is without denticles, protoconch A protoconch (meaning first or earliest or original shell) is an embryonic or larval shell which occurs in some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod. In older texts it is also called " ... is paucispiral. References ismar Prehistoric gastropods {{paleo-gastropod-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strait Of Sicily
The Strait of Sicily (also known as Sicilian Strait, Sicilian Channel, Channel of Sicily, Sicilian Narrows and Pantelleria Channel; or the ; or , ' or ') is the strait between Sicily and Tunisia. The strait is about wide and divides the Tyrrhenian Sea and the western Mediterranean Sea, from the eastern Mediterranean Sea. The maximum depth is . The island of Pantelleria lies in the middle of the strait. There are regular ferries between Sicily and Tunis across the Strait of Sicily; a tunnel has been proposed to link the two regions. Flows Deep currents in the strait flow from east to west, and the current nearer the surface travels from west to east. This unusual water flow is of interest to oceanographers. Within the Central Mediterranean sea it is one of the topographically complex regions. With a length of 600 km it connects the Eastern and Western Mediterranean basins. The strait is delimited by two systems; at the eastern side it is connected with the Ioni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pleistocene
The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in 2009 by the International Union of Geological Sciences, the cutoff of the Pleistocene and the preceding Pliocene was regarded as being 1.806 million years Before Present (BP). Publications from earlier years may use either definition of the period. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology. The name is a combination of Ancient Greek () 'most' and (; Latinized as ) 'new'. The aridification and cooling trends of the preceding Neogene were continued in the Pleistocene. The climate was strongly variable depending on the glacial cycle, oscillating between cold Glacial period, glacial periods and warmer Interglacial, int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mollusc Shell
The mollusc (or mollusk) shell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes. Not all shelled molluscs live in the sea; many live on the land and in freshwater. The ancestral mollusc is thought to have had a shell, but this has subsequently been lost or reduced on some families, such as the squid, octopus, and some smaller groups such as the caudofoveata and neomeniomorpha, solenogastres. Today, over 100,000 living species bear a shell; there is some dispute as to whether these shell-bearing molluscs form a monophyletic group (conchifera) or whether shell-less molluscs are interleaved into their family tree. Malacology, the scientific study of molluscs as living organisms, has a branch devoted to the study of shells, and this is called conchology—although these terms used to be, and to a minor extent still are, used interchange ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lip (gastropod)
In the shell of gastropod mollusks (a snail shell), the lip is the free margin of the peristome (synonym: peritreme) or aperture (mollusc), aperture (the opening) of the gastropod shell. In dextral (right-handed) shells (most snail shells are right-handed), the right side or outer side of the aperture is known as the outer lip (''labrum''). The left side of the aperture is known as the inner lip or columellar lip (''labium'') if there is a pronounced lip there. In those species where there is no pronounced lip, the part of the body whorl that adjoins the aperture is known as the parietal wall. The outer lip is usually thin and sharp in immature shells, and in some adults (e.g. the land snails ''Helicella'' and ''Bulimulus''). However, in some other land snails and in many marine species the outer lip is ''thickened'' (also called ''callused''), or ''reflected'' (turned outwards). In some other marine species it is curled inwards (''inflected''), as in the cowries such as ''Cypraea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protoconch
A protoconch (meaning first or earliest or original shell) is an embryonic or larval shell which occurs in some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod. In older texts it is also called "nucleus". The protoconch may sometimes consist of several whorl (mollusc), whorls, but when this is the case, the whorls show no growth lines. The whorls of the adult shell, which are formed after the protoconch, are known as the teleoconch. The teleoconch starts forming when the larval gastropod becomes a juvenile, and the protoconch may dissolve. Quite often there is a visible line of demarcation where the protoconch ends and the teleoconch begins, and there may be a noticeable change in Sculpture (mollusc), sculpture, or a sudden appearance of sculpture at that point. In some gastropod groups (such as the Architectonicidae), the teleoconch whorls spiral in the opposite direction to the protoconch. In those cases, the shell is called ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alvania
''Alvania'' is a genus of minute sea snails, marine gastropod mollusks or micromollusks in the family Rissoidae. They form a very diversified group within the Rissoidae family. Description ''Alvania'' as currently used may not be monophyletic. The genus ''Alvinia'' has been synonymized with ''Alvania'', until a consistent phylogenetic scheme emerges for the whole group. , is sometimes considered a separate genus.Gofas, S. (2012). Alvinia Monterosato, 1884. Accessed through: World Register of Marine * At http://www.marinespecies.org/aphia.php?p=taxdetails&id=574680 on 18 June 2012 The genus Alvania comprises species with small shells with heights measuring between 1 mm and 7 mm. Their general shape is ovate-conical, reticulated with axial and spirals elements. They have a continuous peristome. Their coloration is variable. Some species such as '' Alvania sculptilis'' have been named twice with the second naming becoming a junior secondary homonym. However, the genus ''Alv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
