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Turbonilla acutissima.png
live Turbonilla acutissima
Pyramidella maculosa - D'Orbigny.jpg
Apertural view of a shell of Pyramidella acus
Scientific classification e
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Clade: Heterobranchia
Clade: Euthyneura
Order: Panpulmonata
Superfamily: Pyramidelloidea
Family: Pyramidellidae
J. E. Gray, 1840[1]

Pyramidellidae, common name the pyram family, or pyramid shells, is a voluminous taxonomic family of mostly small and minute ectoparasitic sea snails, marine heterobranch gastropod molluscs. The great majority of species of pyrams are micromolluscs.

The pyram family is distributed worldwide with more than 6,000 named species in more than 350 nominal genera and subgenera.[2]

This family of micromollusks has been little studied and the phylogenetic relationships within the family are not well worked out. There is an absence of a general consensus regarding which species belong to a specific genus or subgenus, contributing to much confusion. Schander (1999) names more than 300 supraspecific names.[3] As there has been no serious generic revision of the genera worldwide, generic polyphyly can be expected to be rampant throughout the family. However, the family itself is deemed monophyletic.[4]

The family is currently divided into 11 subfamilies (Ponder & Lindberg 1997).[5] An alternative interpretation is that the family Pyramidellidae is but one of six families within the superfamily Pyramidelloidea (Schander, van Aartsen & Corgan 1999).[6] Many species are rare or infrequently recorded.


Subfamilies included within the family Pyramidellidae vary according to the taxonomy consulted. The currently leading taxonomy is the taxonomy of Bouchet & Rocroi (2005).

1997 taxonomy[edit]

Taxonomy of Pyramidellidae by Ponder & Lindberg (1997):[5]

1999 taxonomy[edit]

Taxonomy of Pyramidellidae by Schander, Van Aartsen & Corgan (1999):[6]

2005 taxonomy[edit]

Taxonomy of Pyramidellidae by Bouchet & Rocroi (2005):[7]

  • Subfamily Pyramidellinae Gray, 1840
    • Tribe Pyramidellini Gray, 1840 - synonyms: Obeliscidae A. Adams, 1863 (inv.); Plotiidae Focart, 1951 (inv.)
    • Tribe Sayellini Wise, 1996 - formerly subfamily Sayellinae
  • Subfamily Odostomiinae Pelseneer, 1928
    • Tribe Odostomiini Pelseneer, 1928 - synonyms: Ptychostomonidae Locard, 1886; Liostomiini Schander, Halanych, Dahlgren & Sundberg, 2003 (n.a.)
    • Tribe Chrysallidini Saurin, 1958 - formerly subfamily Chrysallidinae, synonyms: Menesthinae Saurin, 1958; Pyrgulininae Saurin, 1959
    • Tribe Cyclostremellini D. R. Moore, 1966 - formerly subfamily Cyclostremellinae
    • Tribe Odostomellini Saurin, 1959 - formerly subfamily Odostomellinae
  • Subfamily Syrnolinae Saurin, 1958 - formerly subfamily Syrnolinae
    • Tribe Syrnolini Saurin, 1958
    • Tribe Tiberiini Saurin, 1958 - formerly subfamily Tiberiinae
  • Subfamily Turbonillinae Bronn, 1849
    • Tribe Turbonillini Bronn, 1849 - synonym: Chemnitziinae Stoliczka, 1868
    • Tribe Cingulinini Saurin, 1958 - formerly subfamily Cingulininae
    • Tribe Eulimellini Saurin, 1958 - formerly subfamily Eulimellinae
  • Pyramidellidae incertae sedis

In 2010 the family Pyramidellidae has been recognized as monophyletic [8]

In 2017 the genus Helodiamea Peñas & Rolán, 2017 of deep-water Pyramidelloidea from the Central and South Pacific, was recognized.[9]

Problematic taxa[edit]

The following genera are currently difficult to place within existing subtaxa of the Pyramidellidae.

The following species is of uncertain placement within Pyramidellidae.


The following genera have become synonyms (but some species in this genera have not yet been reassigned) :

  • Actaeopyramis P. Fischer, 1885: synonym of Monotigma G.B. Sowerby II, 1839
  • Amaura Møller, 1842: synonym of Aartsenia Warén, 1991
  • Auriculina Gray, 1847 accepted as Ondina de Folin, 1870
  • Besla Dall & Bartsch, 1904 accepted as Parthenina Bucquoy, Dautzenberg & Dollfus, 1883
  • Brachystomia Monterosato, 1884: synonym of Odostomia Fleming, 1813
  • Chemnitzia d'Orbigny, 1839: synonym of Turbonilla Risso, 1826
  • Elusa A. Adams, 1861: synonym of Tropaeas Dall & Bartsch, 1904
  • Folinella Dall & Bartsch, 1904: synonym of Chrysallida Carpenter, 1856
  • Iole A. Adams, 1860: synonym of Iolaea A. Adams, 1867
  • Iolina Baily, 1948: synonym of Iolaea A. Adams, 1867
  • Ividella Dall & Bartsch, 1909 accepted as Chrysallida Carpenter, 1856
  • Lonchaeus : synonym of Longchaeus Mörch, 1875
  • Moerchiella Thiele, 1924 : synonym of Moerchia A. Adams, 1860
  • Moerchinella Thiele, 1931 accepted as Moerchia A. Adams, 1860
  • Monoptygma: synonym of Monotigma G.B. Sowerby II, 1839
  • Monotygma G.B. Sowerby II, 1839: synonym of Monotigma G.B. Sowerby II, 1839
  • Noemia de Folin, 1870: synonym of Noemiamea de Folin, 1886
  • Obeliscus Gray, 1847: synonym of Pyramidella Lamarck, 1799
  • Obex Laws, 1940 accepted as Obexomia Laws, 1941
  • Odontostoma Philippi, 1853: synonym of Odostomia Fleming, 1813
  • Odontostomia G.B. Sowerby I, 1839: synonym of Odostomia Fleming, 1813
  • Parthenia Lowe, 1840: synonym of Parthenina Bucquoy, Dautzenberg & Dollfus, 1883
  • Parthenina Bucquoy, Dautzenberg & Dollfus, 1883: synonym of Chrysallida Carpenter, 1856
  • Partulida Schaufuss, 1869: synonym of Chrysallida Carpenter, 1856
  • Planipyrgiscus [sic] accepted as Planpyrgiscus Laws, 1937
  • Plotia Röding, 1798: synonym of Pyramidella Lamarck, 1799
  • Ptychostomon Locard, 1886 accepted as Odostomia Fleming, 1813
  • Pyrgulina A. Adams, 1864: synonym of Chrysallida Carpenter, 1856
  • Raoulostraca Oliver, 1915 accepted as Eulimella Forbes & M'Andrew, 1846
  • Tragula Monterosato, 1884: synonym of Chrysallida Carpenter, 1856
  • Tropeas [sic] accepted as Tropaeas Dall & Bartsch, 1904


This family is found worldwide, but many species are only found in relatively small geographical ranges. The species found at the Cape Verdes are mainly endemic species. [11]

Shell description[edit]

The length of the slender, elongated (turreted or conical) shells varies between 0.5 mm and 3.5 cm, but most species in the family have shells which are smaller than 13 mm.

The texture of these shells is smooth or sculptured in various forms such as ribs and spirals. Their color is mostly white, cream or yellowish, sometimes with red or brown lines.

The shell of these snails has a blunt, heterostrophic (i.e. whorls appear to be coiled in the opposite direction to those of the teleoconch) protoconch, which is often pointed sideways or wrapped up. The teleoconch is dextrally coiled, but the larval shells are sinistral. This results in a sinistrally coiled protoconch.

The columella has usually one, but sometimes several, spiral folds. The aperture is closed by an operculum.

The operculum is ovoid and paucispiral, with the apex anterior, a thread-like arcuate ridge on the proximal side, the inner margin notched in harmony with the plaits of the pillar when prominent.

Life habits[edit]

The Pyramidellidae are ectoparasites, feeding mainly on other molluscs and on annelid worms, but some are known to feed on peanut worms and crustaceans.[12][13] A few species in the family Pyramidellidae, such as Otopleura mitralis, are symbiotic with sea anemones, such as Neoaiptasia morbilla.[14]

They do not have a radula. Instead their long proboscis is used to pierce the skin of its prey and suck up its fluids and soft tissues. The eyes on the grooved tentacles are situated toward the base of the tentacles. These tentacles have a concave surface. Between the head and the propodium (the foremost division of the foot), a lobed process called the mentum (= thin projection) is visible. This mentum is slightly indented in midline.

These gastropods are hermaphrodites, laying eggs in jelly-like masses on the shell of its host. Some species have spermatophores.[3][15][16]

Name derived from shape[edit]

The name of this taxonomic family comes from the shape of the shell, which is like a pyramid.[17] More specifically, the shape is like a right circular cone,[18] which is equivalent to a right pyramid whose base has many sides.[19]


  1. ^ Gray, J. E. (1840). Synopsis of the contents of the British Museum, 42nd edition. London. p. 370 pp. 
  2. ^ Schander, Christoffer; Halanych, Kenneth M.; Dahlgren, Thomas; Sundberg, Per (2003). "Test of the monophyly of Odostomiinae and Turbonilliinae (Gastropoda, Heterobranchia, Pyramidellidae) based on 16S mtDNA sequences". Zoologica Scripta. 32 (3): 243–254. doi:10.1046/j.1463-6409.2003.00112.x. 
  3. ^ a b Schander, Christoffer; Hori, Shigeo; Lundberg, Joakim (2011). "Anatomy, phylogeny and biology of Odostomella and Herviera, with the description of a new species of Odostomella (Mollusca, Heterostropha, Pyramidellidae)". Ophelia. 51 (1): 39–76. doi:10.1080/00785326.1999.10409399. 
  4. ^ Dinapoli, A.; Zinssmeister, C.; Klussmann-Kolb, A. (2010). "New insights into the phylogeny of the Pyramidellidae (Gastropoda)". Journal of Molluscan Studies. 77 (1): 1–7. doi:10.1093/mollus/eyq027. 
  5. ^ a b Ponder, W.F. & Lindberg, D. R. (1997). "Towards a phylogeny of gastropod molluscs: an analysis using morphological characters". Zoological Journal of the Linnean Society. 119 (2): 88–265. doi:10.1111/j.1096-3642.1997.tb00137.x. 
  6. ^ a b Schander, C.; van Aartsen, J.J.; Corgan, J. X. (1999) [1998]. "Families and genera of the Pyramidelloidea (Mollusca: Gastropoda)" (PDF). Bollettino Malacologico. 34 (9-12): 145–166. 
  7. ^ Bouchet, P. & Rocroi, J.-P. (2005). "Classification and Nomenclator of Gastropod Families". Malacologia. 47 (1–2): 1–397. 
  8. ^ Dinapoli, Angela; Carmen Zinnsmeister; Annette Klussmann-Kolb (10 September 2010). "New insights into the phylogeny of the Pyramidellidae (Gastropoda)". Journal of Molluscan Studies. 77 (1): 1–7. doi:10.1093/mollus/eyq027. Retrieved 2011-10-25. 
  9. ^ Bouchet, P. (2017). Helodiamea Peñas & Rolán, 2017. In: MolluscaBase (2017). Accessed through: World Register of Marine Species at on 2017-09-10
  10. ^ WoRMS (2010). Peristichia. In: Bouchet, P.; Gofas, S.; Rosenberg, G. (2010) World Marine Mollusca database. Accessed through: World Register of Marine Species at on 2011-03-15
  11. ^ J.J. van Aartsen, E. Gittenberger & J. Goud, Pyramidellidae (Mollusca, Gastropoda, Heterobranchia) collected during the Dutch CANCAP and MAURITANIA expeditions in the south-eastern part of the North Atlantic Ocean (part 2)
  12. ^ Sneli, J.-A. (1972). "Odostomia turrita found on Hommarus gammarus". Nautilus. 86 (1): 23–24. 
  13. ^ Robertson, R.; Mau-Lastovicka, Terry (1979). "The ectoparasitism of Boonea and Fargoa (Gastropoda: Pyramidellidae)". Biological Bulletin. Marine Biological Laboratory. 157 (2): 320–333. doi:10.2307/1541058. JSTOR 1541058. 
  14. ^ Roger H. Goodwill et. al. (2009), A sea anemone symbiotic with gastropods of eight species in the Mariana Islands; Micronesica 41(1): 117–130, 2009 Archived 2010-06-18 at the Wayback Machine.
  15. ^ Høisæter, T. (1965). "Spermatophores in Chrysallida obtusa (Brown) (Opisthobranchia, Pyramidellidae)". Sarsia. 18: 63–68. 
  16. ^ Robertson, R. (1967). "The life history of Odostomia bisuturalis and Odostomia spermatophores (Gastropoda: Pyramidellidae)". American Philosophical Society Yearbook. 1967: 368–370. 
  17. ^ Tenney, Sanborn and Tenney, Abby. Natural history of animals; Containing brief descriptions of the animals figured on Tenney's Natural history tablets, but complete without the tablets, p. 202 (Scribner, Armstrong & Co., 1875): "The Pyramid-Shells are so named from their shape"
  18. ^ Step, Edward. Shell Life: An Introduction to the British Mollusca, p. 250 (F. Warne & Company, 1901).
  19. ^ Robbins, Edward. Plane and Solid Geometry, p. 349 (American Book Company, 1907).

Further reading[edit]

External links[edit]