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Helcionellidae
Helcionellid or Helcionelliformes is an order (biology), order of small fossil Small shelly fauna, shells that are universally interpreted as molluscs, though no sources spell out why this taxonomic interpretation is preferred. These animals are first found about in the late Nemakit-Daldynian Geologic time scale#Terminology, age, which is the earliest part of the Cambrian period. A single species persisted to the Early Ordovician. These fossils are component of the small shelly fossils (SSF) assemblages. These are thought to be early molluscs with rather snail-like shells, although they lack any compelling molluscan synapomorphies and thus may not belong to the group. They have been alleged to represent ancestors of the modern conchiferans, a group that includes all the well-known modern classes – gastropods, cephalopods and bivalves. They have also been considered to represent direct ancestors to the cephalopods. Parkhaev (2006, 2007) considers these animals to be crown-grou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Latouchella
''Latouchella'' is an extinct genus of marine invertebrate animal, that is considered to be a mollusk and which may be a sea snail, a gastropod. It is a helcionellid from the Tommotian epoch of what is now Siberia. Its tightly coiled, spiral shell contains a number of low "walls" running up the front surface of the interior; these would have directed water currents within its shell. Between these walls are a series of furrows, parallel to the shell's aperture, giving casts of the internal structure the appearance of a railway line, with sleepers (created by furrows) tying together paired rails that run towards the apex of the shell. It was named by Edgar Sterling Cobbold in 1921 for the Rev. William Martin Digues La Touche of Wistanstow, Shropshire, England, in whose collection it was found. Description This genus had a curved, segmented shell, and it is often reconstructed as a snail-like creature. Older taxonomy The taxonomy of the genus ''Latouchella'' was originally ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helcionelliformes
Helcionellid or Helcionelliformes is an order of small fossil shells that are universally interpreted as molluscs, though no sources spell out why this taxonomic interpretation is preferred. These animals are first found about in the late Nemakit-Daldynian age, which is the earliest part of the Cambrian period. A single species persisted to the Early Ordovician. These fossils are component of the small shelly fossils (SSF) assemblages. These are thought to be early molluscs with rather snail-like shells, although they lack any compelling molluscan synapomorphies and thus may not belong to the group. They have been alleged to represent ancestors of the modern conchiferans, a group that includes all the well-known modern classes – gastropods, cephalopods and bivalves. They have also been considered to represent direct ancestors to the cephalopods. Parkhaev (2006, 2007) considers these animals to be crown-group gastropods. Previous to the 2006 classification by Parkhaev, helcio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helcionellidae
Helcionellid or Helcionelliformes is an order (biology), order of small fossil Small shelly fauna, shells that are universally interpreted as molluscs, though no sources spell out why this taxonomic interpretation is preferred. These animals are first found about in the late Nemakit-Daldynian Geologic time scale#Terminology, age, which is the earliest part of the Cambrian period. A single species persisted to the Early Ordovician. These fossils are component of the small shelly fossils (SSF) assemblages. These are thought to be early molluscs with rather snail-like shells, although they lack any compelling molluscan synapomorphies and thus may not belong to the group. They have been alleged to represent ancestors of the modern conchiferans, a group that includes all the well-known modern classes – gastropods, cephalopods and bivalves. They have also been considered to represent direct ancestors to the cephalopods. Parkhaev (2006, 2007) considers these animals to be crown-grou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helcionelloidea
Helcionellid or Helcionelliformes is an order of small fossil shells that are universally interpreted as molluscs, though no sources spell out why this taxonomic interpretation is preferred. These animals are first found about in the late Nemakit-Daldynian age, which is the earliest part of the Cambrian period. A single species persisted to the Early Ordovician. These fossils are component of the small shelly fossils (SSF) assemblages. These are thought to be early molluscs with rather snail-like shells, although they lack any compelling molluscan synapomorphies and thus may not belong to the group. They have been alleged to represent ancestors of the modern conchiferans, a group that includes all the well-known modern classes – gastropods, cephalopods and bivalves. They have also been considered to represent direct ancestors to the cephalopods. Parkhaev (2006, 2007) considers these animals to be crown-group gastropods. Previous to the 2006 classification by Parkhaev, helcio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helcionelloida
Helcionelloida is an extinct group of ancient molluscs (phylum Mollusca). These are the oldest known conchiferan molluscs, that is, they had a mineralised shell. Some members of this class were mistaken for Monoplacophorans. The class was erected by Peel in 1991. Anatomy These animals were torsion (gastropod), untorted and they had a coiled, cone-shaped shell. The majority of species were small (shells being about two millimeters in length and or diameter). Modern reconstructions depict them as resembling snails. The shells of some genera, particularly ''Yochelcionella'', also possessed a "Snorkel (anatomy), snorkel"-like opening which was most likely used for breathing. 2005 taxonomy The Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005), taxonomy of the Gastropoda by Bouchet & Rocroi, 2005Bouchet P. & Rocroi J.-P. (Ed.); Frýda J., Hausdorf B., Ponder W., Valdes A. & Warén A. 2005. ''Classification and nomenclator of gastropod families''. Malacologia: International ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mollusc
Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The number of additional fossil species is estimated between 60,000 and 100,000, and the proportion of undescribed species is very high. Many taxa remain poorly studied. Molluscs are the largest marine biology, marine phylum, comprising about 23% of all the named marine organisms. They are highly diverse, not just in size and anatomical structure, but also in behaviour and habitat, as numerous groups are freshwater mollusc, freshwater and even terrestrial molluscs, terrestrial species. The phylum is typically divided into 7 or 8 taxonomy (biology), taxonomic class (biology), classes, of which two are entirely extinct. Cephalopod molluscs, such as squid, cuttlefish, and octopuses, are among the most neurobiology, neurologi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Small Shelly Fauna
The small shelly fauna, small shelly fossils (SSF), or early skeletal fossils (ESF) are mineralized fossils, many only a few millimetres long, with a nearly continuous record from the latest stages of the Ediacaran to the end of the Early Cambrian Period. They are very diverse, and there is no formal definition of "small shelly fauna" or "small shelly fossils". Almost all are from earlier rocks than more familiar fossils such as trilobites. Since most SSFs were preserved by being covered quickly with phosphate and this method of preservation is mainly limited to the late Ediacaran and early Cambrian periods, the animals that made them may actually have arisen earlier and persisted after this time span. Some of the fossils represent the entire skeletons of small organisms, including the mysterious '' Cloudina'' and some snail-like molluscs. However, the bulk of the fossils are fragments or disarticulated remains of larger organisms, including sponges, molluscs, slug-like halkieri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yochelcionella Water Flow
''Yochelcionella'' is an extinct genus of basal molluscs which lived during the Tommotian epoch, the first epoch of the Cambrian period. This genus is often reconstructed to resemble snails. ''Yochelcionella'' is the type genus of the family Yochelcionellidae. Description This genus of molluscs possessed shells which were shaped like curved caps, with an exhaust pipe shaped " snorkel" emanating underneath where the apex (point of the shell) curves over. It is believed that the "snorkel" was used in breathing, allowing waste water to flow away from the gills. Taxonomy When they were first discovered, they were originally thought to be monoplacophorans. Their snorkel may represent a move towards a tubular shell, such as is seen in the modern scaphopods. It has also been interpreted as a precursor to the cephalopod funnel or siphuncle. The taxonomy of the Gastropoda by Bouchet & Rocroi, 2005Bouchet P. & Rocroi J.-P. (Ed.); Frýda J., Hausdorf B., Ponder W., Valdes A. & ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stenothecidae
Stenothecidae is an extinct family of fossil univalved Cambrian molluscs which may be either gastropods or monoplacophorans. The name of this taxon should not be confused with that of the class Stenothecoida, a group of problematic Cambrian invertebrates that have a bivalved (dorsal and ventral) shell. Morphology The group comprises conical laterally compressed shells that may be smooth or ornamented with folds or ribs. The shells are broadly limpet-like, which led to their initial consideration as monoplacophoran molluscs. Taxonomy The taxonomic position of the group is unclear; it has been classified as a Yochelcionelloid or Helcionelloid. It is not obviously in the stem group of any modern molluscan class, and has been referred to the monoplacophora, although the monoplacophora are no longer considered to be a clade, and thus that classification means little more than "primitive mollusc". Genera The family Stenothecidae consists of two subfamilies and the follow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yochelcionellidae
''Yochelcionella'' is an extinct genus of basal molluscs which lived during the Tommotian epoch, the first epoch of the Cambrian period. This genus is often reconstructed to resemble snails. ''Yochelcionella'' is the type genus of the family Yochelcionellidae. Description This genus of molluscs possessed shells which were shaped like curved caps, with an exhaust pipe shaped " snorkel" emanating underneath where the apex (point of the shell) curves over. It is believed that the "snorkel" was used in breathing, allowing waste water to flow away from the gills. Taxonomy When they were first discovered, they were originally thought to be monoplacophorans. Their snorkel may represent a move towards a tubular shell, such as is seen in the modern scaphopods. It has also been interpreted as a precursor to the cephalopod funnel or siphuncle. The taxonomy of the Gastropoda by Bouchet & Rocroi, 2005Bouchet P. & Rocroi J.-P. (Ed.); Frýda J., Hausdorf B., Ponder W., Valdes A. & ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
