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.
This family of micromolluscs 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. 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. However a study in 2011 seems to indicate that this family is deeply nested within the Pulmonata instead of the Heterobranchia.Dinapoli A, Zinssmeister C, Klussman-Kolb A. 2011. New insights into the phylogeny of the Pyramidellidae (Gastropoda). Journal of Molluscan Studies 77:1-7.
The family is currently divided into 11 subfamilies (Ponder & Lindberg 1997). An alternative interpretation is that the family Pyramidellidae is but one of six families within the superfamily Pyramidelloidea (Schander, van Aartsen & Corgan 1999). Many species are rare or infrequently recorded.
Subfamilies 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 Taxonomy of Pyramidellidae by Ponder & Lindberg (1997): Chrysallidinae Saurin, 1958 Cingulininae Saurin, 1959 Cyclostremellinae Moore, 1966 Eulimellinae Saurin, 1958 Odostomellinae Saurin, 1959 Odostomiinae Pelseneer, 1928 Pyramidellinae J.E. Gray, 1840 Sayellinae Wise, 1996 Syrnolinae Saurin, 1958 Tiberiinae Saurin, 1958 Turbonillinae Bronn, 1849
1999 taxonomy Taxonomy of Pyramidellidae by Schander, Van Aartsen & Corgan (1999): Superfamily Pyramidelloidea Gray, 1840 Family Amathinidae Ponder, 1987 Family Ebalidae Warén, 1994 - synonym: Anisocyclidae van Aartsen, 1995 Family Odostomiidae Pelseneer, 1928 Subfamily Odostomiinae Pelseneer, 1928 Subfamily Chrysallidinae Saurin, 1958 Subfamily Odostomellinae Saurin, 1958 Subfamily Cyclostremellinae Moore, 1966 Family Pyramidellidae J. E. Gray, 1840 Subfamily Pyramidellinae J. E. Gray, 1840 Subfamily Sayellinae Wise, 1996 Family Syrnolidae Saurin, 1958 Subfamily Syrnolinae Saurin, 1958 Subfamily Tiberiinae Saurin, 1958 Family Turbonillidae Bronn, 1849 Subfamily Turbonillinae Bronn, 1849 Subfamily Eulimellinae Saurin, 1958 Subfamily Cingulininae Saurin, 1959
2005 taxonomy Taxonomy of Pyramidellidae by Bouchet & Rocroi (2005): 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 Bulimoscilla Robba, 2013 Maricarmenia Peñas & Rolán, 2017 Pyrabinella Faber, 2013 Pyramidellidae incertae sedis insularis Oliver, 1915
In 2010 the family Pyramidellidae has been recognized as monophyleticPeñas A. & Rolán E. (2017). Deep water Pyramidelloidea from the central and South Pacific. The tribe Chrysallidini. ECIMAT (Estación de Ciencias Mariñas de Toralla), Universidade de Vigo. 412 pp.
In 2017 the genera Helodiamea Peñas & Rolán, 2017 of deep-water Pyramidelloidea from the Central and South Pacific, and the Perheida Peñas & Rolán, 2017 were recognized.Bouchet, P. (2017). Helodiamea Peñas & Rolán, 2017. In: MolluscaBase (2017). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=955936 on 2017-09-10
Problematic taxa The following genera are currently difficult to place within existing subtaxa of the Pyramidellidae. Charilda Iredale, 1929 Contraxiala Laseron, 1956 Cossmannica Dall & Bartsch, 1904 Eulimotibera Nomura, 1939 Finlayola Laws, 1937 Morrisonetta Brandt, 1968 Peristichia Dall, 1889WoRMS (2010). Peristichia. In: Bouchet, P.; Gofas, S.; Rosenberg, G. (2010) World Marine Mollusca database. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=415795 on 2011-03-15 Ulfa Dall & Bartsch, 1904 Vagna Dall & Bartsch, 1904
The following species is of uncertain placement within Pyramidellidae. "Epigrus" insularis Oliver, 1915 Pyramidellidae incertae sedis venusta (de Folin, 1872)
Synonyms 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: synonym of Ondina de Folin, 1870 Besla Dall & Bartsch, 1904: synonym of 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: synonym of Chrysallida Carpenter, 1856 Lonchaeus : synonym of Longchaeus Mörch, 1875 Moerchiella Thiele, 1924 : synonym of Moerchia A. Adams, 1860 Moerchinella Thiele, 1931: synonym of 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: synonym of 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]: synonym of Planpyrgiscus Laws, 1937 Plotia Röding, 1798: synonym of Pyramidella Lamarck, 1799 Ptychostomon Locard, 1886: synonym of Odostomia Fleming, 1813 Pyrgulina A. Adams, 1864: synonym of Chrysallida Carpenter, 1856 Raoulostraca Oliver, 1915: synonym of Eulimella Forbes & M'Andrew, 1846 Tragula Monterosato, 1884: synonym of Chrysallida Carpenter, 1856 Tropeas [sic]: synonym of Tropaeas Dall & Bartsch, 1904
Distribution 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.
Shell description 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 oligogyrous 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.
The species are characterized by the lack of jaw or radula, because they are ectoparasites (mostly on polychaetes or other molluscs).
Life habits The Pyramidellidae are ectoparasites, feeding mainly on other molluscs and on annelid worms, but some are known to feed on peanut worms and crustaceans. A few species in the family Pyramidellidae, such as Otopleura mitralis, are symbiotic with sea anemones, such as Neoaiptasia morbilla. 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
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 their hosts. Some species have spermatophores.
Name derived from shape The name of this taxonomic family comes from the shape of the shell, which is like a pyramid.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" More specifically, the shape is like a right circular cone,Step, Edward. Shell Life: An Introduction to the British Mollusca, p. 250 (F. Warne & Company, 1901). which is equivalent to a right pyramid whose base has many sides.Robbins, Edward. Plane and Solid Geometry, p. 349 (American Book Company, 1907).
References
Further reading
External links
Gallery of pyramidellids