''Madagasikara johnsoni'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

freshwater snail Freshwater snails are gastropod mollusks which live in fresh water. There are many different families. They are found throughout the world in various habitats, ranging from ephemeral pools to the largest lakes, and from small seeps and springs ...

with a

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

and an operculum, an aquatic

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Pachychilidae Pachychilidae, common name pachychilids, is a taxonomic family of freshwater snails, gastropod molluscs in the clade Sorbeoconcha.Gofas, S. (2014). Pachychilidae. Accessed through: World Register of Marine Species at http://www.marinespecies.org/ ...

.Köhler, F. & Glaubrecht, M. (2010). "Uncovering an overlooked radiation: molecular phylogeny and biogeography of Madagascar’s endemic river snails (Caenogastropoda: Pachychilidae: ''Madagasikara'' gen. nov.). '' Biological Journal of the Linnean Society'' 99: 867-894.

Distribution

This species is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

. The only precisely known locality is in Ankara Sontsitra National Park, West Madagaskar. The type locality was given as " River Kamony, in the north-west of the island", but the thereabouts of this locality has not been exactly determined. The most detailed version of the type locality is that of the Kamoro River drainage in

Mahajanga Province Mahajanga was a former province of Madagascar that had an area of 150,023 km². It had a population of 1,896,000 (2004). Its capital was Mahajanga, the second largest city in Madagascar. Except for Fianarantsoa, Mahajanga Province bordere ...

, north-west Madagascar.

Description

''Madagasikara johnsoni'' was originally discovered and described (under the name ''Melanatria johnsoni'') by Edgar Albert Smith in 1882. The shell is large, elongate-pyramidal, turreted, thick, covered with an olive epidermis. It is closely lineated or strigate with longitudinal lines of a darker tint. The shell has nine

whorls 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). Whorls in nature File:Photograph and axial plane floral d ...

. Whorls are very slightly convex beneath, strongly spirally ribbed and grooved. The ribs are six in number on the upper whorls and rounded; the two above are much more slender than the four beneath; the uppermost borders the suture; the next lies in the concavity at the top of the whorls; and the rest surround the slight convexity, and are three times as broad as the sulci separating them. All the whorls, with the exception of the last four, are coronated at the slight angle below the excavation with very short, hollow, oblique spinules. Some of the spiral grooves exhibit rows of fine granules. The last whorl descends somewhat, giving the shell a slightly distorted appearance. It is girded with about twelve transverse costae, a few at the base being smaller than five principal ones around the middle. The aperture is bluish within, faintly stained with olive-brown near the margins. The peristome widely and deeply sinuated on the outer lip in the concavity of the whorl, arcuate and prominent in the middle, then shallowly sinuated again. Columellar margin is thickened, free, arcuate, reflexed, ending in a distinct basal sinus. The width of the shell is 24–28.9 mm. The height of the shell is 69.9-77.7 mm. The width of the aperture is 14.0-14.2 mm. The height of the aperture is 20.5-21.0 mm. There is not known description of operculum. There is also not known anatomy of this species. Reproduction strategy is also unknown.

References

This article incorporates public domain text from the reference {{Taxonbar, from=Q16985070 Pachychilidae Gastropods described in 1882 Endemic fauna of Madagascar