Omalogyridae is a family of minute and microscopic sea snails, marine gastropod molluscs in the informal group Lower Heterobranchia.Gofas, S. (2012). Omalogyridae. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=1742 on 2012-08-31 Omalogyrids are micromolluscs, among the smallest known, with adult shells usually smaller than 1 millimeter in diameter.
This family is poorly known and is tentatively placed in the unresolved infraclass "Lower Heterobranchia". Studies of this group are sketchy and miss or omit the basic information about taxonomy or distribution. They are globally distributed in shallow marine environments, where they feed on algae.
Description
Omalogyrids are among the smallest gastropods, with adult shells usually less than 1 millimeter in diameter. The omalogyrid Ammonicera minortalis is the smallest gastropod in the United States, with a shell 0.34–0.46 mm in diameter, while Retrotortina fuscata is the smallest gastropod in Europe, with a shell 0.50–0.75 mm in diameter. The shells of Ammonicera and Omalogyra are more or less planispiral, giving them an appearance similar to miniature ammonite shells, while the shell of Retrotortina is hyperstrophic. Ammonicera possess a pair of distinct tentacles, while in Retrotortina and Omalogyra the tentacles are replaced by a pair of flat, semicircular lobes. The eyes are at the bases of the tentacles or lobes. There is considerable variation in the anatomy of the radula in omalogyrids.
Genera Genera within the family Omalogyridae include: Ammonicera Vayssiére, 1893 Omalogyra Jeffreys, 1867 Retrotortina Chaster, 1896 † Schobertinella Nützel & Gründel, 2015 Genera brought into synonymy Ammonicerina O.G. Costa, 1861: synonym of Omalogyra Jeffreys, 1859 Helisalia Laseron, 1954: synonym of Omalogyra Jeffreys, 1859 Homalogyra Jeffreys, 1867: synonym of Omalogyra Jeffreys, 1859
References
Bouchet, P., Rocroi, J.-P. (2005). Classification and nomenclator of gastropod families. Malacologia. 47(1-2): 1-397 .
External links
Powell A. W. B., New Zealand Mollusca, William Collins Publishers Ltd, Auckland, New Zealand 1979 Sars, G.O. (1878). Bidrag til Kundskaben om Norges arktiske Fauna. I. Mollusca Regionis Arcticae Norvegiae. Oversigt over de i Norges arktiske Region Forekommende Bløddyr. Brøgger, Christiania. xiii + 466 pp., pls 1-34 & I-XVIII