''Yochelcionella'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of basal

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

s which lived during the

Tommotian Stage 2 of the Cambrian is the unnamed upper stage of the Terreneuvian Series. It lies atop the Fortunian and below Stage 3 of the Cambrian. It is commonly referred to as the Tommotian, after the Cambrian stratigraphy of Siberia. Neither the upper ...

epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided by ...

, the first epoch of the

Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...

period. This genus is often reconstructed to resemble

snail A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gastro ...

s. ''Yochelcionella'' is the

type genus In biological taxonomy, the type genus is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearing type of a nominal f ...

of the family

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 ...

Description

This genus of molluscs possessed shells which were shaped like curved caps, with an

exhaust pipe An exhaust system is used to guide reaction exhaust gases away from a controlled combustion inside an engine or stove. The entire system conveys burnt gases from the engine and includes one or more exhaust pipes. Depending on the overall system ...

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

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

Taxonomy

When they were first discovered, they were originally thought to be

monoplacophora 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 ...

ns. 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. & Warén A. 2005. ''Classification and nomenclator of gastropod families''. Malacologia: International Journal of Malacology, 47(1-2). ConchBooks: Hackenheim, Germany. . . 397 pp. http://www.vliz.be/Vmdcdata/imis2/ref.php?refid=78278 categorizes ''Yochelcionella'' in the family

within the superfamilia

Yochelcionelloidea Yochelcionelloidea is an extinct superfamily of paleozoic molluscs of uncertain position ( Gastropoda or Monoplacophora). The earliest yochelcionellids are known from the Middle Tommotian, but they are most diverse from the Botomian through the ...

within the Paleozoic molluscs of uncertain position within Mollusca (Gastropoda or Monoplacophora). For an alternate 2007-2007 taxonomy by P. Yu. Parkhae see

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 ...

Species

Species in the genus ''Yochelcionella'' include: * ''

Yochelcionella americana ''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 Y ...

'' Runnegar & Pojeta, 1980 * '' Yochelcionella angustiplicata'' * '' Yochelcionella chinensis'' Pei, 1985 * ''

Yochelcionella crassa ''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 Y ...

'' Zhegallo in Esakova et Zhegallo, 1996 * ''

Yochelcionella cyrano ''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 Y ...

'' Runnegar and Pojeta 1974

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

. Its type locality is ANU Collection 10352, 16 km northeast of Mootwingee Aboriginal Site, which is in a Solvan carbonate limestone in the Coonigan Formation of Australia.. * ''

Yochelcionella daleki ''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 Y ...

'' * ''

Yochelcionella erecta ''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 Y ...

'' (Walcott, 1891)Atkins C. J. & Peel J. S. (2008). "''Yochelcionella'' (Mollusca, Helcionelloida) from the lower Cambrian of North America". ''

Bulletin of Geosciences The ''Bulletin of Geosciences'' is a peer-reviewed scientific journal publishing original research papers, review articles, and short contributions. It covers all aspects of palaeoenvironmental geology, including palaeontology, stratigraphy, sedime ...

'' 83(1): 23-38 (8 figures). . * ''

Yochelcionella gracilis ''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 Y ...

'' Atkins & Peel, 2004 * ''

Yochelcionella greenlandica ''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 Y ...

'' Atkins & Peel, 2004 * ''

Yochelcionella ostentata ''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 Y ...

'' * ''

Yochelcionella saginata ''Yochelcionella'' is an extinct genus of basal molluscs which lived during the Tommotian Epoch (geology), epoch, the first epoch of the Cambrian period. This genus is often reconstructed to resemble snails. ''Yochelcionella'' is the type genus ...

'' Vendrasco et al., 2010 * ''

Yochelcionella snorkorum ''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 Y ...

'' Vendrasco et al., 2010Vendrasco M. J., Porter S. M., Kouchinsky A., Li G. & Fernandez C. Z. (2010). "New data on molluscs and their shell microstructures from the Middle Cambrian Gowers Formation, Australia". ''

Palaeontology Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

'' 53(1): 97-135. .

References

External links

Yochelcionellidae Palaeos

{{Taxonbar, from=Q16993581 Yochelcionellidae Cambrian molluscs Cambrian animals of North America Fossil taxa described in 1974 Paleozoic life of Newfoundland and Labrador Paleozoic life of the Northwest Territories Paleozoic life of Quebec Cambrian genus extinctions