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Last Whorl
The body whorl is part of the morphology (biology), morphology of the gastropod shell, shell in those gastropod mollusks that possess a coiled shell. The term is also sometimes used in a similar way to describe the shell of a cephalopod mollusk. In gastropods In gastropods, the body whorl, or last whorl, is the most recently formed and largest Whorl (mollusc), whorl (or revolution) of a spiral or Helix, helical Gastropod shell, shell, terminating in the Aperture (mollusc), aperture. It is called the "body whorl" because most of the body of the soft parts of the animal fits into this whorl. The proportional size of the body whorl in gastropod shells differs greatly according to the actual shell morphology. For shells in which the rate of whorl expansion of each revolution around the axis is very high, the aperture and the body whorl are large, and the shell tends to be low Spire (mollusc), spired. The shell of the abalone is a good example of this kind of shell. The opposite ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tarebia Granifera Shell
''Tarebia'' is a genus of freshwater snails, gastropod mollusks in the subfamily Thiarinae of the family Thiaridae. Species Species within the genus ''Tarebia'' include: * † '' Tarebia acuta'' (J. Sowerby, 1822) * † ''Tarebia bojolaliensis'' (K. Martin, 1905) * † ''Tarebia cardinalis'' (Lapparent, 1938) * † ''Tarebia cerithioides'' (Rolle, 1858) * † ''Tarebia darmavangiensis'' (K. Martin, 1905) * '' Tarebia granifera'' (Lamarck, 1816) * ''Tarebia hainesiana'' * † ''Tarebia issiracensis'' (Fontannes, 1884) * ''Tarebia invieta'' * ''Tarebia lateritia'' * ''Tarebia luzoniensis'' * † ''Tarebia preangerensis'' (K. Martin, 1905) * ''Tarebia semigranosa ''Tarebia'' is a genus of freshwater snails, gastropod mollusks in the subfamily Thiarinae of the family Thiaridae. Species Species within the genus ''Tarebia'' include: * † '' Tarebia acuta'' (J. Sowerby, 1822) * † '' Tarebia bojolal ...'' * † '' Tarebia trimargaritifera'' (Ludwig, 1865) ;Synon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spire (mollusc)
A spire is a part of the coiled shell of molluscs. The spire consists of all of the whorls except for the body whorl. Each spire whorl represents a rotation of 360°. A spire is part of the shell of a snail, a gastropod mollusc, a gastropod shell, and also the whorls of the shell in ammonites, which are fossil shelled cephalopods. In textbook illustrations of gastropod shells, the tradition (with a few exceptions) is to show most shells with the spire uppermost on the page. The spire, when it is not damaged or eroded, includes the protoconch (also called the nuclear whorls or the larval shell), and most of the subsequent teleoconch whorls (also called the postnuclear whorls), which gradually increase in area as they are formed. Thus the spire in most gastropods is pointed, the tip being known as the " apex". The word "spire" is used, in an analogy to a church spire or rock spire, a high, thin, pinnacle. The "spire angle" is the angle, as seen from the apex, at which a sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phragmocone
The phragmocone is the chambered portion of the shell of a cephalopod. It is divided by septa into camerae. In most nautiloids and ammonoids, the phragmocone is a long, straight, curved, or coiled structure, in which the camarae are linked by a siphuncle which determines buoyancy by means of gas exchange. Despite this benefit, such a large shell adds to the mass of the animal, and hence is disadvantageous in catching fast-moving prey. Some nautiloids, such as the Silurian Ascocerida, dropped the phragmocone upon maturity, presumably to increase speed and maneuverability. They thus became the early Paleozoic equivalent of coleoids. The early coleoids and belemnoids adopted a different approach: the phragmocone was retained but became internal and reduced. In general the shell in cephalopods tends to be vestigial or absent. Fossil record Being the only biomineralised part of most cephalopods, the phragmocone is typically the only part to enter the fossil record. It is someti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Septa (biology)
Septa (singular septum) are thin walls or partitions between the internal chambers (camerae) of the shell of a cephalopod, namely nautiloids or ammonoids. As the creature grows, its body moves forward in the shell to a new living chamber, secreting septa behind it. This adds new chambers to the shell, which can be clearly seen in cross-sections of the shell of the living nautilus, or in ammonoid and nautiloid fossils. The septa are attached to the inside wall of the shell, thus dividing the phragmocone into camerae. Where the septum meets the shell a suture line forms; in some ammonoids these lines became extremely complex and elaborate, providing strength without the necessity of added weight. Elaborate sutures allowed for thinner shells, and hence less time needed for shell growth and less time spent in the vulnerable juvenile stage. The nature and structure of the septa, as with the camerae, and siphuncle, and the presence or absence of deposits, are important in classif ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Siphuncle
The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and '' Spirula''. In the case of the cuttlefish, the siphuncle is indistinct and connects all the small chambers of that animal's highly modified shell; in the other cephalopods it is thread-like and passes through small openings in the septa (walls) dividing the camerae (chambers). Some older studies have used the term siphon for the siphuncle, though this naming convention is uncommon in modern studies to prevent confusion with a mollusc organ of the same name. Function The siphuncle is used primarily in emptying water from new chambers as the shell grows. To perform this task, the cephalopod increases the saltiness of the blood in the siphuncle, and the water moves from the more dilute chamber into the blood through osmosis. At the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonoidea
Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) than they are to shelled nautiloids such as the living '' Nautilus'' species. The earliest ammonites appeared during the Devonian, with the last species vanishing during the Cretaceous–Paleogene extinction event. Ammonites are excellent index fossils, and linking the rock layer in which a particular species or genus is found to specific geologic time periods is often possible. Their fossil shells usually take the form of planispirals, although some helically spiraled and nonspiraled forms (known as heteromorphs) have been found. The name "ammonite", from which the scientific term is derived, was inspired by the spiral shape of their fossilized shells, which somewhat resemble tightly coiled rams' horns. Pliny the Elder ( 79 AD n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nautiloid
Nautiloids are a group of marine cephalopods (Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and '' Allonautilus''. Fossil nautiloids are diverse and speciose, with over 2,500 recorded species. They flourished during the early Paleozoic era, when they constituted the main predatory animals. Early in their evolution, nautiloids developed an extraordinary diversity of shell shapes, including coiled morphologies and giant straight-shelled forms (orthocones). Only a handful of rare coiled species, the nautiluses, survive to the present day. In a broad sense, "nautiloid" refers to a major cephalopod subclass or collection of subclasses (Nautiloidea ''sensu lato''). Nautiloids are typically considered one of three main groups of cephalopods, along with the extinct ammonoids (ammonites) and living coleoids (such as squid, octopus, and kin). While ammonoids and coleoids are monophyletic clades with exclusive ancestor-descendant re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Segmentina
''Segmentina'' is a genus of very small, air-breathing, freshwater snails, aquatic gastropod mollusks or micromollusks in the family Planorbidae, the ramshorn snails. Albrecht et al. (2007)Albrecht C., Kuhn K. & Streit B. (2007). "A molecular phylogeny of Planorboidea (Gastropoda, Pulmonata): insights from enhanced taxon sampling". ''Zoologica Scripta'' 36: 27-39. . have confirmed the placement of this genus in the tribe Segmentinini within subfamily Planorbinae. Species Species in this genus include: *'' Segmentina avecenninae'' *'' Segmentina bouilleti'' *''Segmentina bugense'' *'' Segmentina cantori'' *'' Segmentina caucasica'' *''Segmentina chevalieri'' *'' Segmentina congenera'' *'' Segmentina distinguenda'' *'' Segmentina drenici'' *''Segmentina filocincta'' *''Segmentina haueri'' *''Segmentina lartetii'' *''Segmentina loczyi'' *''Segmentina malkae'' *''Segmentina mica'' *''Segmentina molytes'' *''Segmentina montgazoniana'' *'' Segmentina nitida'' * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planorbidae
Planorbidae, common name the ramshorn snails or ram's horn snails, is a family of air-breathing freshwater snails, aquatic pulmonate gastropod molluscs. Unlike most molluscs, the blood of ram's horn snails contains iron-based hemoglobin instead of copper-based hemocyanin. As a result, planorbids are able to breathe oxygen more efficiently than other molluscs. The presence of hemoglobin gives the body a reddish colour. This is especially apparent in albino animals. Being air breathers like other '' Panpulmonata'', planorbids do not have gills, but instead have a lung. The foot and head of planorbids are rather small, while their thread-like tentacles are relatively long. Many of the species in this family have coiled shells that are planispiral, in other words, the shells are more or less coiled flat, rather than having an elevated spire as is the case in most gastropod shells. Although they carry their shell in a way that makes it appear to be dextral, the shell of coiled plan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turritella
''Turritella'' is a genus of medium-sized sea snails with an operculum, marine gastropod mollusks in the family Turritellidae.Vos, C.; Gofas, S. (2013). Turritella Lamarck, 1799. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=138615 on 2013-06-02 They have tightly coiled shells, whose overall shape is basically that of an elongated cone. The name ''Turritella'' comes from the Latin word ''turritus'' meaning "turreted" or "towered" and the diminutive suffix ''-ella''. Species Valid Valid species within the genus ''Turritella'' are listed below. Fossil species are marked with a dagger "†". * ''Turritella acropora'' (Dall, 1889) * '' Turritella albolapis'' Finlay, 1924 * '' Turritella algida'' Melvill & Standen, 1912 * '' Turritella anactor'' Berry, 1957 * ''Turritella annulata'' Kiener, 1843 * † ''Turritella apicalis'' - Pleistocene of Florida * ''Turritella attenuata'' Reeve, 1849 * '' Turritella aurocincta'' Ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Abalone
Abalone ( or ; via Spanish , from Rumsen ''aulón'') is a common name for any of a group of small to very large marine gastropod molluscs in the family Haliotidae. Other common names are ear shells, sea ears, and, rarely, muttonfish or muttonshells in parts of Australia, ormer in the UK, perlemoen in South Africa, and paua in New Zealand. Abalones are marine snails. Their taxonomy puts them in the family Haliotidae, which contains only one genus, '' Haliotis'', which once contained six subgenera. These subgenera have become alternate representations of ''Haliotis''. The number of species recognized worldwide ranges between 30 and 130 with over 230 species-level taxa described. The most comprehensive treatment of the family considers 56 species valid, with 18 additional subspecies. The shells of abalones have a low, open spiral structure, and are characterized by several open respiratory pores in a row near the shell's outer edge. The thick inner layer of the shell is compose ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aperture (mollusc)
The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where the head-foot part of the body of the animal emerges for locomotion, feeding, etc. The term ''aperture'' is used for the main opening in gastropod shells, scaphopod shells, and also for '' Nautilus'' and ammonite shells. The word is not used to describe bivalve shells, where a natural opening between the two shell valves in the closed position is usually called a ''gape''. Scaphopod shells are tubular, and thus they have two openings: a main anterior aperture and a smaller posterior aperture. As well as the aperture, some gastropod shells have additional openings in their shells for respiration; this is the case in some Fissurellidae (keyhole limpets) where the central smaller opening at the apex of the shell is called an orifice, and in the Haliotidae (abalones) where the row of respiratory openings in the shell are also called orifices. In gastropods In some prosob ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
