| Madagasikara johnsoni | |
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| Apertural view of a shell of Madagasikara johnsoni | |
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| Species: | M. johnsoni
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| Binomial name | |
| Madagasikara johnsoni (
E. A. Smith, 1882)
[1]
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Madagasikara johnsoni is a species of tropical freshwater snail with a gill and an operculum, an aquatic gastropod mollusc in the family Pachychilidae. [2]
Distribution
This species is endemic to Madagascar. [2] The only precisely known locality is in Ankara Sontsitra National Park, West Madagaskar. [2]
The type locality was given as " River Kamony, in the north-west of the island", [1] but the thereabouts of this locality has not been exactly determined. [2] The most detailed version of the type locality is that of the Kamoro River drainage in Mahajanga Province, north-west Madagascar. [2]
Description
Madagasikara johnsoni was originally discovered and described (under the name Melanatria johnsoni) by Edgar Albert Smith in 1882. [1]
The shell is large, elongate-pyramidal, turreted, thick, covered with an olive epidermis. [1] It is closely lineated or strigate with longitudinal lines of a darker tint. [1] The shell has nine whorls. [1] [2] Whorls are very slightly convex beneath, strongly spirally ribbed and grooved. [1] 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. [1] 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. [1] Some of the spiral grooves exhibit rows of fine granules. [1] The last whorl descends somewhat, giving the shell a slightly distorted appearance. [1] It is girded with about twelve transverse costae, a few at the base being smaller than five principal ones around the middle. [1]
The aperture is bluish within, faintly stained with olive-brown near the margins. [1] 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. [1] Columellar margin is thickened, free, arcuate, reflexed, ending in a distinct basal sinus. [1]
The width of the shell is 24–28.9 mm. [1] [2] The height of the shell is 69.9-77.7 mm. [2] The width of the aperture is 14.0-14.2 mm. [2] The height of the aperture is 20.5-21.0 mm. [2]
There is not known description of operculum. [2] There is also not known anatomy of this species. [2] Reproduction strategy is also unknown. [2]
References
This article incorporates public domain text from the reference [1]
- ^ a b c d e f g h i j k l m n o p q Smith E. A. (1882). "A contribution to the Molluscan fauna of Madagascar". Proceedings of the Zoological Society of London 1882: 375-390. pages 383-384, plate 22, figure 6-7.
- ^ a b c d e f g h i j k l m n 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. doi: 10.1111/j.1095-8312.2009.01390.x