This MedLibrary.org supplementary page on Heterobranchia is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
| Heterobranchia | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
 The sea butterfly or pteropod gastropod, Clione limacina
|
||||||||||
| Scientific classification | ||||||||||
|
||||||||||
| Orders | ||||||||||
Heterobranchia, the heterobranchs, (meaning "different-gilled snails"), is a taxonomic superorder of sea snails, marine gastropod mollusks.
(Note: Gastropod taxonomy has been in flux for many years, and this is especially true currently, because of new research in molecular phylogeny. Because of all this on-going change, different reliable sources can yield very different classifications. This is especially true within groups which are poorly understood in general.)
This superorder contains a diverse and interesting group of families. The similarity in the structure of the gills within this group makes the various families eligible for membership, despite all the other differences they show.
The families included in this recently established superorder of mollusks1 have historically been placed in many different parts of the taxonomic class of gastropods. Earlier authors (as J.E. Gray, 1840) placed the Heterobranchia as a borderline category intermediate between the Opisthobranchia & Pulmonata, and all the other gastropods.
The (sometimes recognized) order 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 has been revised by Ponder & Warén (1988)2.
(In contrast to the heterobranchs, the bodies of the Opisthobranchia have undergone detorsion (unwinding). They have essentially evolved back to the bilateral symmetry of their ancestors. The mantle cavity of the Pulmonata has modified into an air-breathing organ. They are also characterized by detorsion and a symmetrically-arranged nervous system. The pulmonates usually lack an operculum and are hermaphroditic. The order Pulmonata contains most land snails and slugs, many freshwater snails, and a small number of marine species.)
Taxonomy of the Heterobranchia
Superorder Heterobranchia J.E. Gray, 1840
- Order Heterostropha P. Fischer, 1885 (sometimes Allogastropoda Haszprunar, 1985) (paraphyletic)
- Order Opisthobranchia Milne-Edwards, 1848 (paraphyletic)
- Suborder Cephalaspidea P. Fischer, 1883 (headshield slugs)
- Suborder Sacoglossa Von Ihering, 1876 (sap-suckling slugs)
- Suborder Anaspidea P. Fischer, 1883 (sea hares)
- Suborder Notaspidea P. Fischer, 1883 (sidegill slugs)
- Suborder Thecosomata de Blainville, 1824 (sea butterflies)
- Infraorder Euthecosomata
- Infraorder Pseudothecosomata
- Suborder Gymnosomata de Blainville, 1824 (sea angels)
- Suborder Nudibranchia de Blainville, 1814 (nudibranchs, true sea slugs))
- Infraorder Anthobranchia Férussac, 1819
- Infraorder Cladobranchia Willan & Morton, 1984
- Order Pulmonata Cuvier in Blainville, 1814 (pulmonates)
- Suborder Systellommatophora Pilsbry, 1948
- Suborder Basommatophora Keferstein in Bronn, 1864 (freshwater pulmonates, pond snails)
- Suborder Eupulmonata Haszprunar & Huber, 1990
- Infraorder Acteophila (Dall, 1885 (formerly Archaeopulmonata)
- Infraorder Trimusculiformes Minichev & Starobogatov, 1975
- Infraorder Stylommatophora A. Schmidt, 1856 (land snails)
- Subinfraorder Orthurethra
- Subinfraorder Sigmurethra
New studies, published in 2004, 3 put the monophyletic Pulmonata and the paraphyletic Opisthobranchia together in the clade Euthyneura Spengel 1881. This clade together with the paraphyletic group Heterostropha (pyramidellids and other related groups) define the clade Heterobranchia.
Clade Heterobranchia
- Grade Heterostropha
- Clade Euthyneura
- Grade Opisthobranchia
- Clade Pulmonata
References
- ^ Haszprunar G. (1985). "The Heterobranchia ― a new concept of the phylogeny of the higher Gastropoda". Zeitschrift für zoologische Systematik und Evolutionsforschung 23 (1): 15–37. ISSN 0044-3808
- ^ Ponder, W. F. & Warén, A. (1988). "Classification of the Caenogastropoda and Heterostropha- A list of family-group names and higher taxa". Malacological review supplement 4: 288–317.
- ^ 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:. PMID 14660702, http://mbe.oxfordjournals.org/cgi/content/full/21/2/303.
Wikipedia content modification information:
- This page was last modified on 17 November 2008, at 01:01.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Heterobranchia".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.