Fissurellidae

 ( Taxa Named By John Fleming ) 

This conical shape and the low profile of the shell allow keyhole limpets to withstand wave attack on exposed rocks to which they attach firmly with their strong, muscular foot.

The shell may vary in color and pattern. The shell has a reticulate (= net-like) structure with strong radial ribs and lacks an operculum.

The shell ranges from 3 mm to 13.2 cm. The great keyhole limpet (Megathura crenulata) measures up to 13.2 cm.

For respiration, the shells of fissurellids have a single apical or subapical perforation ("keyhole"). This opening at the top allows a direct exit of exhalant water currents together with waste products from the mantle cavity. The water enters under the edge of the shell near the head and passes over large paired gills. Most young species in this family have a marginal slit in the middle of the anterior end of the spiral shell. Some species possess just a short internal groove at the anterior end. The paired organs in the mantle cavity represent a primitive condition in gastropods.

The soft body consists of a well-developed head, a short muzzle. It has a broad and flat foot and a well-developed mantle. This foot exerts a strong suction, adhering the keyhole limpet to its hard substratum. The mantle extends in some species partly or completely (as in Megathura crenulata) over the shell. The tentacles at the epipodium (the lateral grooves between foot and mantle) are well developed. The species in Medusafissurella have numerous subequal tentacles at the propodium, while the species in Dendrofissurella have an outgrowth with main trunk and side branches at the propodium. The eyes are situated on rudimentary pedicels at their outer bases. The sides are ornamented with short cirri. There are two, symmetrical branchial plumes . The anal siphon occupies the anterior notch or perforated summit of the shell. Tryon G. W. 1873. American marine conchology: or, Descriptions of the shells of the Atlantic coast of the United States from Maine to Florida

In addition to the possession of this hole, slit or groove, keyhole limpets differ in several other ways both internally and externally from true limpets.

A few species in the genera Diodora and Emarginella are carnivorous, feeding on . Puncturella has been reported to digest and detritus. Puncturella aethiopica feeds mainly on Foraminifera. They are also prey for various marine animals, including starfish and some mollusk-eating birds.

• Subfamily Diodorinae Odhner, 1932
• Subfamily Emarginulinae Children, 1834
• Subfamily Fissurellinae Fleming, 1822
• Subfamily Hemitominae Kuroda, Habe & Oyama, 1971: synonym of Zeidorinae Naef, 1913
• Subfamily Zeidorinae Naef, 1913

This classification was based by Bouchet & Rocroi on the studies by Keen (in Moore) (1960), Christiaens (1973) and McMean (1984).

Aktipis S.W., Boehm E. & Giribet G. (2011) then raised the tribe Diodorini to the status of subfamily Diodorinae.Aktipis S.W., Boehm E. & Giribet G. (2011) Another step towards understanding the slit-limpets (Fissurellidae, Fissurelloidea, Vetigastropoda, Gastropoda): a combined five-gene molecular phylogeny. Zoologica Scripta 40: 238-259

• Agariste Monterosato, 1892
• Altrix Palmer, 1942
• Amblychilepas Pilsbry, 1890
• Buchanania Lesson, 1830
• Clathrosepta McLean & Geiger, 1998
• Clypidina Gray, 1847
• Cornisepta McLean & Geiger, 1998
• Cosmetalepas Tom Iredale, 1924
• Cranopsis Adams, 1860
• Dendrofissurella Mclean and Kilburn, 1986
• Diodora Gray, 1821
• Emarginula Lamarck, 1801
• Fissurella Bruguière, 1789
• Fissurellidea d'Orbigny, 1841
• Fissurisepta Seguenza, 1863
• Hemimarginula McLean, 2011
• Hemitoma William Swainson, 1840
• Laeviemarginula Habe In Kuroda, 1953
• Laevinesta Pilsbry and McGinty, 1952
• Leurolepas J. H. McLean, 1970
• Lucapina Sowerby, 1835
• Lucapinella Pilsbry, 1890
• Macroschisma Sowerby, 1839
• Manganesepta McLean & Geiger, 1998
• Medusafissurella Mclean and Kilburn, 1986
• Megathura Pilsbry, 1890
• Monodilepas Finlay, 1927
• Montfortia Récluz, 1843
• Montfortista Tom Iredale, 1929
• Montfortula Tom Iredale, 1915
• Montfortulana Habe, 1961
• Nesta Adams, 1870
• Octomarginula McLean, 2011
• Parmaphorella Strebel, 1907
• Profundisepta McLean & Geiger, 1998
• Puncturella R. T. Lowe, 1827
• Pupillaea Gray In Sowerby, 1835
• Rimula DeFrance, 1827
• Rimulanax Iredale, 1924 (taxon inquerendum)
• Scelidotoma Choe, Yoon and Habe, 1992
• Scutus Montfort, 1810
• Stromboli Berry, 1954
• Tugali Gray in Dieffenbach, 1843
• Tugalina Habe, 1953
• Vacerrena Iredale, 1958
• Variemarginula McLean, 2011
• Zeidora A. Adams, 1860

Genera brought into synonymy

• Austroglyphis Cotton & Godfrey, 1934: synonym of Diodora Gray, 1821
• Aviscutum Tom Iredale, 1940: synonym of Scutus Montfort, 1810
• Capiluna Gray, 1857: synonym of Diodora Gray, 1821
• Cemoria Antoine Risso, 1826 ex: synonym of Puncturella Lowe, 1827
• Cremoria Gray,: synonym of Puncturella Lowe, 1827
• Elegidion Tom Iredale, 1924: synonym of Diodora J. E. Gray, 1821
• Emarginella Pilsbry, 1890: synonym of Emarginula Lamarck, 1801
• Entomella Cotton, 1945: synonym of Emarginula Lamarck, 1801
• Fissuridea Swainson, 1840: synonym of Diodora J. E. Gray, 1821
• Glyphis Carpenter, 1857: synonym of Diodora J. E. Gray, 1821
• Legrandia Beddome, 1883: synonym of Zeidora A. Adams, 1860
• Megatebennus Pilsbry, 1890: synonym of Fissurellidea d'Orbigny, 1839
• Nannoscutum Iredale, 1937: synonym of Scutus Montfort, 1810
• Nesta H. Adams, 1870: synonym of Zeidora A. Adams, 1860
• Notomella Cotton, 1957: synonym of Emarginula Lamarck, 1801
• Parmophoridea Wenz, 1938: synonym of Parmaphorella Strebel, 1907
• Parmophorus Blainville, 1817: synonym of Scutus Montfort, 1810
• Plagiorhytis P. Fischer, 1885: synonym of Montfortula Iredale, 1915
• Scutum P. Fischer, 1885: synonym of Scutus Montfort, 1810
• Semperia Crosse, 1867: synonym of Emarginula Lamarck, 1801
• Sipho T. Brown, 1827: synonym of Puncturella Lowe, 1827
• Siphonella Issel, 1869: synonym of Montfortista Iredale, 1929
• Subemarginula Gray, 1847: synonym of Hemitoma Swainson, 1840
• Subzeidora Iredale, 1924: synonym of Emarginula (Subzeidora) Iredale, 1924
• Tugalia Gray, 1857: synonym of Tugali Gray, 1843
• Vacerra Iredale, 1924: synonym of Puncturella Lowe, 1827
• Zidora P. Fischer, 1885: synonym of Zeidora A. Adams, 1860

• Keyhole limpet hemocyanin

• and J.S. Ryland P.J. Hayward (1996). 9780198540557, Oxford University Press. ISBN 9780198540557

• Sowerby, G.B. Jr. (1862). Monograph of the family Fissurellidae. Reprinted edition (1982). Thesaurus conchyliorum, or monographs of genera of shells. Luis Pisani Burnay: Lisboa, Portugal. 183-206, 9 col. Plates pp.

• Archerd Shell Collection : Fissurellidae
• Aktipis S.W., Boehm E. & Giribet G. (2011) Another step towards understanding the slit-limpets (Fissurellidae, Fissurelloidea, Vetigastropoda, Gastropoda): a combined five-gene molecular phylogeny. Zoologica Scripta 40: 238-259.
• Miocene Gastropods and Biostratigraphy of the Kern River Area, California; United States Geological Survey Professional Paper 642