Yochelcionella

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
Temporal range:
Drawing of a reconstruction of Yochelcionella cyrano as a snail
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: †Helcionelloida
Order: †Helcionelliformes
Family: †Yochelcionellidae
Genus: †Yochelcionella
Runegar & Pojeta, 1974
Species

See text.

Yochelcionella is the type genus of the family Yochelcionellidae.[1]

Description
flow of water in Yochelcionella – note that the flow was originally interpreted to be in the opposite direction to that illustrated;[2] no source is provided for the reconstruction given here.

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.[3] It has also been interpreted as a precursor to the cephalopod funnel[4] or siphuncle.[5]

The taxonomy of the Gastropoda by Bouchet & Rocroi, 2005[1] categorizes Yochelcionella in the family Yochelcionellidae within the superfamilia Yochelcionelloidea within the Paleozoic molluscs of uncertain position within Mollusca (Gastropoda or Monoplacophora).

For an alternate 2007-2007 taxonomy by P. Yu. Parkhae see Helcionelloida.

Species

Species in the genus Yochelcionella include:

  • Yochelcionella americana Runnegar & Pojeta, 1980[6]
  • Yochelcionella angustiplicata
  • Yochelcionella chinensis Pei, 1985[6]
  • Yochelcionella crassa Zhegallo in Esakova et Zhegallo, 1996
  • Yochelcionella cyrano Runnegar and Pojeta 1974 type species. 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 erecta (Walcott, 1891)[6]
  • Yochelcionella gracilis Atkins & Peel, 2004[6]
  • Yochelcionella greenlandica Atkins & Peel, 2004[6]
  • Yochelcionella ostentata
  • Yochelcionella saginata Vendrasco et al., 2010[7]
  • Yochelcionella snorkorum Vendrasco et al., 2010[7]

References
  1. Bouchet 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. ISBN 3-925919-72-4. ISSN 0076-2997. 397 pp. http://www.vliz.be/Vmdcdata/imis2/ref.php?refid=78278
  2. Webers, G. F.; Yochelson, E. L. (1989). "Late Cambrian molluscan faunas and the origin of the Cephalopoda". In Crame, J. A. (ed.). Origins and Evolution of the Antarctic Biota. pp. 29–42. Bibcode:1989GSLSP..47...29W. doi:10.1144/GSL.SP.1989.047.01.04. S2CID 128682549. {{cite book}}: |journal= ignored (help)
  3. Peel, J. S. (2006). "Scaphopodization in Palaeozoic Molluscs". Palaeontology. 49 (6): 1357–1364. doi:10.1111/j.1475-4983.2006.00599.x.
  4. JELL, P. A. (1976). "Mollusca". McGraw-Hill Encyclopedia of Science and Technology, Yearbook 1976. pp. 269–71.
  5. Pojeta, J. Jr (1980). "Molluscan phylogeny. Tulane Studies in Geology and Paleontology". 16: 55–80. {{cite journal}}: Cite journal requires |journal= (help)
  6. Atkins C. J. & Peel J. S. (2008). "Yochelcionella (Mollusca, Helcionelloida) from the lower Cambrian of North America". Bulletin of Geosciences 83(1): 23-38 (8 figures). doi:10.3140/bull.geosci.2008.01.023.
  7. Vendrasco 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 53(1): 97-135. doi:10.1111/j.1475-4983.2009.00922.x.
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