''Megasurcula'' 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 medium-sized

predatory Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

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 ...

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

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 ...

Pseudomelatomidae Pseudomelatomidae is a family (biology), family of predatory sea snails, marine gastropods included in the superfamily Conoidea (previously Conacea) and part of the Neogastropoda (Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005), Bouchet & Ro ...

, a family previously lumped with others collectively known as turrids.Bouchet P. & Rocroi J.-P. (Ed.); Frýda J., Hausdorf B., Ponder W., Valdes A. & Warén A. 2005. ''Classification and nomenclator of gastropod families''. Malacologia: International Journal of Malacology, 47(1-2). ConchBooks: Hackenheim, Germany. . ISSN 0076-2997. 397 pp. http://www.vliz.be/Vmdcdata/imis2/ref.php?refid=78278 Species within this genus occur in the Eastern

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

MolluscaBase (2020). MolluscaBase. Megasurcula T. L. Casey, 1904. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=432503 on 2020-01-25

Description

(Original description) The embryo in this genus is apparently paucispiral, but conoidal. 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 obsolete. The base of the shell is broadly obtuse. 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 ...

shows an oblique ridge externally. The sinus is large and broadly rounded and very near the suture. The fasciolar surface below the suture is broad and feebly concave. The periphery is obtuse and not very prominent. The suture is simple, without a subjacent elevated collar. The surface is rendered somewhat rough by relatively fine, close-set and irregular spiral lines. There is no longitudinal

sculpture Sculpture is the branch of the visual arts that operates in three dimensions. Sculpture is the three-dimensional art work which is physically presented in the dimensions of height, width and depth. It is one of the plastic arts. Durable sc ...

except lines of growth. The species are large and ponderous, and include ''

Megasurcula carpenteriana ''Megasurcula carpenteriana'' (Gabb, 1865), also known as Carpenter's turrid, is a species of medium-sized predatory sea snail, a marine gastropod mollusc in the family Pseudomelatomidae, a family previously lumped with others collectively kno ...

'' (Gabb, 1865) and ''Surcula tryoni'' Gabb 1865, from the coast of California. ''Megasurcula'' is a widely isolated and strongly characterized genus, belonging exclusively to the living fauna of the Pacific coast of North America as far as known at present. It is, at the same time, a rather direct descendant of the extinct ''Bathytoma'', but the species are of far larger size, ''carpenteriana'' being probably the largest or most ponderous Pleurotomid known. The embryo, which is conoidal and multispiral in Bathytoma, has gradually lost some of its

whorl A whorl ( or ) is an individual circle, oval, volution or equivalent in a whorled pattern, which consists of a spiral or multiple concentric objects (including circles, ovals and arcs). In nature File:Photograph and axial plane floral diagra ...

s, as shown in ''Megasurcula'', which of itself would not be a generic character, but there is in ''Bathytoma'' a broad constriction of 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 ...

below the convexity, forming a short stout beak, which is wholly unobservable in ''Megasurcula'', and 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 much more capacious in the latter, with the anal sinus much larger and different in form and position.Casey T.L. (1904) Notes on the Pleurotomidae with description of some new genera and species. Transactions of the Academy of Science of St. Louis, 14, 123–170
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Species

Species within the genus ''Megasurcula'' include: * ''

'' (Gabb, 1865) * † '' Megasurcula centroamericana'' Landau, Da Silva & Heitz, 2016 * † '' Megasurcula condonana'' (Anderson & Martin, 1914) * † '' Megasurcula cryptoconoides'' Makiyama, 1926 * † '' Megasurcula elongata'' (Hatai, 1940) * † '' Megasurcula guayasensis'' Marks, 1951 * † '' Megasurcula howei'' Hanna and Hertlein, 1938 * † '' Megasurcula kurodai'' (Otuka, 1934) * † '' Megasurcula osawanoensis'' (Tsuda) * † '' Megasurcula rara'' (Nomura & Onishi, 1940) * '' Megasurcula remondii'' (Gabb, 1866) * † '' Megasurcula siogamensis'' (Nomura, 1935) * '' Megasurcula stearnsiana'' (Raymond, 1904) * '' Megasurcula tremperiana'' (Dall, 1911) * † '' Megasurcula wynoocheensis'' (Weaver, 1912) * † '' Megasurcula yokoyamai'' (Otuka, 1934) ;Species brought into synonymy: * † ''Megasurcula etheringtoni'' Weaver, 1943: synonym of † '' Megasurcula howei'' Hanna and Hertlein, 1938 * ''Megasurcula granti'' Bartsch, 1944: synonym of ''Pleurotoma (Surcula) carpenteriana'' Gabb, 1865 * † ''Megasurcula keepi'' (Arnold) Grant and Gale, 1931: synonym of † '' Megasurcula howei'' Hanna and Hertlein, 1938

References

* Grant and Gale (1931)， Plioc．Pleistoc．Mo1L Calif．，p ．495 −（500 ）
Bartsch, P, Some turrid mollusks of Monterey Bay and vicinity; Proceedings of the Biological Society of Washington, v. 57 p. 57-68

External links

*
Bouchet, P.; Kantor, Y. I.; Sysoev, A.; Puillandre, N. (2011). ''A new operational classification of the Conoidea (Gastropoda).'' Journal of Molluscan Studies. 77(3): 273-308

{{Taxonbar, from=Q3169454 Pseudomelatomidae Taxa named by Thomas Lincoln Casey Jr.