''Microdrillia'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of very small

sea snail Sea snails are slow-moving marine (ocean), marine gastropod Mollusca, molluscs, usually with visible external shells, such as whelk or abalone. They share the Taxonomic classification, taxonomic class Gastropoda with slugs, which are distinguishe ...

s, marine

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

s in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Borsoniidae Borsoniidae is a monophyletic family of small to medium-sized sea snails, marine gastropod mollusks in the superfamily Conoidea.Bouchet, P. (2011). Borsoniidae. Accessed through: World Register of Marine Species at http://www.marinespecies.org/ ...

.Bouchet, P.; Gofas, S. (2015). Microdrillia Casey, 1903. In: MolluscaBase (2015). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=137821 on 2016-03-14

Description

The species in this genus are characterized by a well-developed, multispiral, closely coiled

protoconch A protoconch (meaning first or earliest or original shell) is an embryonic or larval shell which occurs in some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod. In older texts it is also called " ...

. One to three of its basal whorls are costulate. The

body whorl The body whorl is part of the morphology (biology), morphology of the gastropod shell, shell in those gastropod mollusks that possess a coiled shell. The term is also sometimes used in a similar way to describe the shell of a cephalopod mollusk ...

is wholly devoid of costae but spirally carinate. The retral sinus is relatively large, circularly rounded and close to the suture. The

aperture In optics, the aperture of an optical system (including a system consisting of a single lens) is the hole or opening that primarily limits light propagated through the system. More specifically, the entrance pupil as the front side image o ...

is oblique. The

columella Lucius Junius Moderatus Columella (, Arabic: ) was a prominent Roman writer on agriculture in the Roman Empire. His in twelve volumes has been completely preserved and forms an important source on Roman agriculture and ancient Roman cuisin ...

is callous, with or without plications. The

siphonal canal The siphonal canal is an anatomical feature of the shells of certain groups of sea snails within the clade Neogastropoda. Some sea marine gastropods have a soft tubular anterior extension of the mantle called a siphon through which water i ...

is short or subobsolete. The following species of this genus are also found as fossils in the age range of 48.6 Ma to 0.781 Ma: ''Microdrillia comatotropis'', ''Microdrillia cossmanni'', ''Microdrillia crispata'', ''Microdrillia harrisi'', ''Microdrillia ouchitae'', ''Microdrillia propetrina'', ''Microdrillia tersa'', ''Microdrillia trina''

Distribution

This marine genus occurs in the

Gulf of Oman The Gulf of Oman or Sea of Oman ( ''khalīj ʿumān''; ''daryâ-ye omân''), also known as Gulf of Makran or Sea of Makran ( ''khalīj makrān''; ''daryâ-ye makrān''), is a gulf in the Indian Ocean that connects the Arabian Sea with th ...

, off

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

and off Australia (

New South Wales New South Wales (commonly abbreviated as NSW) is a States and territories of Australia, state on the Eastern states of Australia, east coast of :Australia. It borders Queensland to the north, Victoria (state), Victoria to the south, and South ...

Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...

Species

* † '' Microdrillia aturensis'' Lozouet, 2017 * '' Microdrillia circumvertens'' (Melvill & Standen, 1901) * '' Microdrillia commentica'' (Hedley, 1915) * '' Microdrillia dinos'' Kilburn, 1986 * '' Microdrillia fastosa'' (Hedley, 1907) * † '' Microdrillia meyeri'' (Cossmann, 1889) * '' Microdrillia niponica'' (E. A. Smith, 1879) * '' Microdrillia optima'' (Thiele, 1925) * † '' Microdrillia pakaurangia'' Powell, 1942 * '' Microdrillia patricia'' (Melvill, 1904) * '' Microdrillia pertinax'' (Hedley, 1922) * '' Microdrillia rhomboidales'' Stahlschmidt, Poppe & Tagaro, 2018 * '' Microdrillia sagamiensis'' Kuroda & Oyama, 1971 * '' Microdrillia sansibarica'' (Thiele, 1925) * † ''

Microdrillia serratula ''Microdrillia'' is a genus of very small sea snails, marine (ocean), marine gastropod mollusks in the family (biology), family Borsoniidae.Bouchet, P.; Gofas, S. (2015). Microdrillia Casey, 1903. In: MolluscaBase (2015). Accessed through: World ...

'' (Bellardi, 1877) * '' Microdrillia stephensensis'' Laseron, 1954 * † '' Microdrillia teretiaeformis'' A.W. Janssen, 1972 Janssen, Mollusken der Twistringer Schichten, N.-Deutschland, Scripta Geol. 10 (1972)
/ref> * '' Microdrillia trina'' Mansfield, 1925 * '' Microdrillia triporcata'' (E. A. Smith, 1879) ; Species brought into synonymy: * ''Microdrillia crispata'' (Cristofori & Jan, 1832): synonym of '' Drilliola crispata'' (De Cristofori & Jan, 1832) * ''Microdrillia difficilis'' (E. A. Smith, 1879): synonym of '' Drilliola difficilis'' (E. A. Smith, 1879) * ''Microdrillia loprestiana'' (Calcara, 1841): synonym of ''

Drilliola loprestiana ''Drilliola loprestiana'' is a species of sea snail, a marine gastropod mollusk in the family Borsoniidae. Taxonomy Figueira & Absalão (2010) used the name ''Drilliola pulchella'' (Verrill, 1880) for the species generally known as ''Drilliola ...

'' (Calcara, 1841) * ''Microdrillia pruina'' (Watson, 1881): synonym of ''

Retidrillia pruina ''Retidrillia pruina'' is a species of sea snail, a marine gastropod mollusk in the family Borsoniidae.Bouchet, P. (2015). Retidrillia pruina (Watson, 1881). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphi ...

'' (Watson, 1881) * ''Microdrillia zeuxippe'' (Dall, 1919): synonym of '' Drilliola zeuxippe'' (Dall, 1919)

References

* Thiele J. (1925). Gastropoden der Deutschen Tiefsee-Expedition. II Teil. Wissenschaftliche Ergebnisse der Deutschen Tiefsee-Expedition auf dem Dampfer "Valdivia" 1898–1899. 17(2): 35-382, pls 13-46 * Kilburn R.N. (1986). Turridae (Mollusca: Gastropoda) of southern Africa and Mozambique. Part 3. Subfamily Borsoniinae. Annals of the Natal Museum. 27: 633–720.

External links

Casey T.L. (1903). ''Notes in the Conrad collection of Vicksburg fossils, with descriptions of new species''. Proceedings of the Academy of Natural Sciences, Philadelphia 55: 261-283

Bouchet P., Kantor Yu.I., Sysoev A. & Puillandre N. (2011) A new operational classification of the Conoidea. Journal of Molluscan Studies 77: 273-308
*
De Jong K.M. & Coomans H.E. (1988) Marine gastropods from Curaçao, Aruba and Bonaire. Leiden: E.J. Brill. 261 pp.
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