Overview
Heterobranchia, the heterobranchs (meaning "different-gilled snails") or Euthyneura,1] is a taxonomic clade of snails and slugs, which includes species from the sea, the land and freshwater; marine, aquatic and terrestrial gastropod mollusks.
Heterobranchia is one of the main clades of gastropods, containing the largest number of species of any of the main clades. Currently Heterobranchia comprises three informal groups: the Lower Heterobranchia, the Opisthobranchia and the Pulmonata, also known as the lower heterobranchs, the opisthobranchs and the pulmonates.[2]
Diversity
The three subdivisions of this large clade are quite diverse:
- The Lower Heterobranchia includes shelled marine and freshwater species.
- Opisthobranchia are almost all marine species, some shelled and some not. The internal organs of the opisthobranchs have undergone detorsion (unwinding of the viscera that were twisted during torsion).
- The Pulmonata includes the majority of land snails and slugs, many freshwater snails, and a small number of marine species. The mantle cavity of the Pulmonata is modified into an air-breathing organ. They are also characterized by detorsion and a s ymmetrically-arranged nervous system. The pulmonates almost always lack an operculum and are hermaphroditic.
Taxonomy
Older taxonomy
The families currently included in Heterobranchia have historically been placed in many different parts of the taxonomic class of gastropods. Earlier authors (such as J.E. Gray, 1840) considered Heterobranchia to consist of only marine gastropods, and conceptualized it as a borderline category, intermediate between the Opisthobranchia & Pulmonata, and all the other gastropods.[3]
The (sometimes recognized) category Heterostropha within the Heterobranchia, which includes such families as Architectonicidae, the sundial or staircase snails, is primarily characterized by a shell which has a heterostrophic protoconch, in other words the apical whorls are coiled in the opposite plane to the adult whorls. The classification of this group was revis ed by Ponder & War?n in 1988.[4]
According to the older taxonomy of the Gastropoda (Ponder & Lindberg, 1997) the Heterobranchia were ranked as a superorder.
2005 taxonomy
Heterobranchia is currently one of the main clades of gastropods. For a detailed taxonomy, see Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)#Clade Heterobranchia.
2010 taxonomy
J?rger et al. (2010)[5] have redefined major groups within the Heterobranchia: they created the new clades Euopisthobranchia and Panpulmonata.[5]
A cladogram showing phylogenic relations of Heterobranchia as proposed by J?rger et al. (2010):[5]
and conceptualized it as a borderline category, intermediate between the Opisthobranchia & Pulmonata, and all the other gastropods.[3]The (sometimes recognized) category Heterostropha within the Heterobranchia, which includes such families as Architectonicidae, the sundial or staircase snails, is primarily characterized by a shell which has a heterostrophic protoconch, in other words the apical whorls are coiled in the opposite plane to the adult whorls. The classification of this group was revised by Ponder & War?n in 1988.[4]
According to the older taxonomy of the Gastropoda (Ponder & Lindberg, 1997) the Heterobranchia were ranked as a superorder.
2005 taxonomy
Heterobranchia is currently one of the main clades of gastropods. For a detailed taxonomy, see Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)#Clade Heterobranchia.
2010 taxonomy
J?rger et al. (2010)[5] have redefined major groups within the Heterobranchia: they created the new clades Euopisthobranchia and Panpulmonata.[5]
A cladogram showing phylogenic relations of Heterobranchia as proposed by J?rger et al. (2010):[5]
References
- ^ W?gele, H., Klussmann-Kolb, A., Vonnemann, V. & Medina, M.. "Heterobranchia I: the Opisthobranchia.". In Ponder, W.F.. Phylogeny and Evolution of the Mollusca. ISBN 978-0-520-25092-5.
- ^ Bouchet P. & Rocroi J.-P. (Ed.); Fr?da J., Hausdorf B., Ponder W., Valdes A. & War?n 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
- ^ Haszprunar G. (1985). "The Heterobranchia ? a new concept of the phylogeny of the higher Gastropoda". Zeitschrift f?r zoologische Systematik und Evolutionsforschung 23 (1): 15?37. ISSN 0044-3808
- ^ Ponder, W. F. & War?n, A. (1988). "Classification of the Caenogastropoda and Heterostropha- A list of family-group names and higher taxa". Malacological review supplement 4: 288?317.
- ^ a b c d e J?rger K. M., St?ger I., Kano Y., Fukuda H., Knebelsberger T. & Schr?dl M. (2010). "On the origin of Acochlidia and other enigmatic euthyneuran gastropods, with implications for the systematics of Heterobranchia". BMC Evolutionary Biology 10: 323. doi:10.1186/1471-2148-10-323.
Taxonomy
The Order Heterobranchia is further organized into finer groupings including:
- Family (1): Nerineidae
- Species: ZipcodeZoo has pages for 27 species and subspecies in the Order Heterobranchia.
Families
Nerineidae
The Nerineidae is an extinct taxonomic family of fossil sea snails, marine gastropod mollusks in the informal group Lower Heterobranchia. [more]
At least 27 species and subspecies belong to the Family Nerineidae.
More info about the Family Nerineidae may be found here.
References
- ^ W?gele, H., Klussmann-Kolb, A., Vonnemann, V. & Medina, M.. "Heterobranchia I: the Opisthobranchia.". In Ponder, W.F.. Phylogeny and Evolution of the Mollusca. ISBN 978-0-520-25092-5.
- ^ Bouchet P. & Rocroi J.-P. (Ed.); Fr?da J., Hausdorf B., Ponder W., Valdes A. & War?n 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
- ^ Haszprunar G. (1985). "The Heterobranchia ? a new concept of the phyloge ny of the higher Gastropoda". Zeitschrift f?r zoologische Systematik und Evolutionsforschung 23 (1): 15?37. ISSN 0044-3808
- ^ Ponder, W. F. & War?n, A. (1988). "Classification of the Caenogastropoda and Heterostropha- A list of family-group names and higher taxa". Malacological review supplement 4: 288?317.
- ^ a b c d e J?rger K. M., St?ger I., Kano Y., Fukuda H., Knebelsberger T. & Schr?dl M. (2010). "On the origin of Acochlidia and other enigmatic euthyneuran gastropods, with implications for the systematics of Heterob ranchia". BMC Evolutionary Biology 10: 323. doi:10.1186/1471-2148-10-323.
Footnotes
- ^ Cristina Grande, José Templado, J. Lucas Cervera and Rafael Zardoya (2004). "Molecular Phylogeny of Euthyneura (Mollusca: Gastropoda) (full text on line)". Mol. Biol. Evol. 21 (2): 303–313. doi:
Further Reading
- Dinapoli A. (2009). Phylogeny and Evolution of the Heterobranchia (Mollusca, Gastropoda). Thesis, Frankfurt am Main, 176 pp. PDF.
- Dinapoli A. & Klussmann-Kolb A. (2010). "The long way to diversity ? Phylogeny and evolution of the Heterobranchia (Mollusca: Gastropoda)". Molecular Phylogenetics and Evolution 55(1): 60-76. doi:10.1016/j.ympev.2009.09.019.
Sources
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