Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Protostomia
Cladus: Spiralia
Cladus: Lophotrochozoa
Phylum: Mollusca
Classis: †Helcionelloida
Ordines (4): Helcionellida - Pelagiallifomes - Khairkhaniifomes - Onichochiliformes
Name
Helcionelloida Peel, 1991
References
Peel, J. S. 1991: "Functional morphology of the Class Helcionelloida nov., and the early evolution of the Mollusca". In Simonetta, A. M., Conway Morris, S. The early evolution of Metazoa and the significance of problematic taxa. Cambridge University Press. pp. 157–177. ISBN 978-0-521-40242-2.
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
P. Yu. Parkhaev. 2006: "Adaptive radiation of the Cambrian helcionelloid mollusks (Gastropoda, Archaeobranchia)." In: S.V. Rozhnov (ed.) "Evolution of the biosphere and biodiversity. Towards the 70th anniversary of A. Y. Rozanov". 2006. Moscow, pp. 282-296.
P. Yu. Parkhaev. 2007: "The Cambrian ‘basement’ of gastropod evolution". Geological Society, London, Special Publications 286: 415–421. http://books.google.com/books?id=GA7-8JIh9IwC&pg=PA415
External links
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). http://www.geology.cz/bulletin/contents/art2008.01.023
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.[1]
Anatomy
Further information: Helcionellid § Morphology
These animals were 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"-like opening which was most likely used for breathing.
2005 taxonomy
The taxonomy of the Gastropoda by Bouchet & Rocroi, 2005[2] categorizes members of this taxon within the Paleozoic molluscs of uncertain systematic position, but that taxonomy to not use the name Helcionelloida.
2006-2007 taxonomy
Taxonomy of helcionelloid according to the opinion of P. Yu. Parkhaev:[3][4]
Gastropoda Cuvier, 1797
Subclass Archaeobranchia Parkhaev, 2001
Order Helcionelliformes Golikov & Starobogatov, 1975
Superfamily Helcionelloidea Wenz, 1938
Family Helcionellidae Wenz, 1938
Family Igarkiellidae Parkhaev, 2001
Family Coreospiridae Knight, 1947
Superfamily Yochelcionelloidea Runnegar & Jell, 1976
Family Trenellidae Parkhaev, 2001
Family Yochelcionellidae Runnegar & Jell, 1976
Family Stenothecidae Runnegar & Jell, 1980
Subfamily Stenothecinae Runnegar & Jell, 1980
Subfamily Watsonellinae Parkhaev, 2001
Order Pelagiellifomes MacKinnon, 1985
Family Pelagiellidae Knight, 1952
Family Aldanellidae Linsley et Kier, 1984
Subclass Divasibranchia Minichev & Starobogatov, 1975
Order Khairkhaniiformes Parkhaev, 2001
Family Khairkhaniidae Missarzhevsky, 1989
Subclass Dextrobranchia Minichev & Starobogatov, 1975
Order Onychochiliformes Minichev & Starobogatov, 1975
Family Onychochilidae Koken, 1925
References
Peel, J. S. (1991). "Functional Morphology of the Class Helcionelloida Nov., and the Early Evolution of the Mollusca". In Simonetta, A. M.; Conway Morris, S (eds.). The Early Evolution of Metazoa and the Significance of Problematic Taxa. Cambridge University Press. pp. 157–177. ISBN 978-0-521-40242-2.
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
P. Yu. Parkhaev (2006) "Adaptive radiation of the Cambrian helcionelloid mollusks (Gastropoda, Archaeobranchia). Archived 2015-06-10 at the Wayback Machine" In: S.V. Rozhnov (ed.) "Evolution of the biosphere and biodiversity. Towards the 70th anniversary of A. Y. Rozanov". 2006. Moscow, pp. 282-296.
P. Yu. Parkhaev (2007). "The Cambrian 'basement' of gastropod evolution". Geological Society, London, Special Publications. 286: 415–421. doi:10.1144/SP286.31.
External links
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. - slightly different taxonomic placement of Yochelcionellidae.
https://web.archive.org/
Retrieved from "http://en.wikipedia.org/"
All text is available under the terms of the GNU Free Documentation License
