| Amastra umbilicata | |
|---|---|
| |
| Shell of Amastra umbilicata | |
| Conservation status | |
 Extinct (IUCN 2.3) | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Gastropoda |
| Order: | Stylommatophora |
| Family: | Amastridae |
| Genus: | Amastra |
| Species: | †A. umbilicata |
| Binomial name | |
| †Amastra umbilicata (L. Pfeiffer, 1856) | |
| Synonyms | |
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Amastra umbilicata was a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusc in the family Amastridae.
- Subspecies
- † Amastra umbilicata arenarum Pilsbry & C. M. Cooke, 1914
- Amastra umbilicata pluscula C. M. Cooke, 1917
- Amastra umbilicata umbilicata (L. Pfeiffer, 1856)
Description
The length of thge shell attains 10 ½ mm, its diameter 5⅔ mm.
The shell is very narrowly but openly umbilicate, dextral, ovate-conic, thin, and striate, with an opaque brown coloration. The spire is slightly concavely conic, terminating in an acute apex.
There are 6 whorls, which are only slightly convex. The body whorl is somewhat shorter than the spire and angular at the base. The aperture is elliptical, with sharp angles at both ends. The columellar fold is compressed, deep, and subtransverse.
The peristome is simple and acute, with the columellar margin slightly dilated and entirely free throughout, adding to the shell's delicate and refined appearance.
This species differs from Amastra petricola in several key features: it has a larger umbilicus, a thinner, unicolored shell, a more slender spire, and a smaller, more oblique columellar fold. Unlike A. petricola, the specimens examined show no sign of thickening within the outer lip, suggesting the two species are not closely related.
The shell color is a rather light brown, becoming darker at the apex. The whorls in the protoconch may be striate when fresh and unworn, but they appear smooth in the specimens available. The whorls are more convex compared to A. petricola.
The umbilicus, when viewed from the base, is circular, deep, and moderately broad, partially overhung by the columellar lip. It is bounded by an obtuse ridge that is accentuated by a shallow spiral excavation near its edge. The aperture is angular where the columellar and basal margins meet. The columellar margin is triangularly dilated and bears a small, highly oblique fold, which emerges more prominently than that of A. petricola, extending nearly to the edge.
Faint traces of a thin, brown outer cuticle are present on the shell surface.
Distribution
This species was endemic to Hawaii and occurred on Oahu Island.
References
- Mollusc Specialist Group (1996). "Amastra umbilicata". IUCN Red List of Threatened Species. 1996: e.T1000A3153045. doi:10.2305/IUCN.UK.1996.RLTS.T1000A3153045.en. Retrieved 17 November 2021.
- "WoRMS - World Register of Marine Species - Amastra umbilicata (L. Pfeiffer, 1856)". www.marinespecies.org. Retrieved 2024-11-19.
- Amastra umbilicata(L. Pfeiffer, 1856). 19 December 2024. Retrieved through: World Register of Marine Species.
- Hyatt, A. & Pilsbry, H. A. (1910–1911). Manual of conchology, structural and systematic, with illustrations of the species. Ser. 2, Pulmonata. Vol. 21: Achatinellidae (Amastrinae). Philadelphia: Conchological Department, Academy of Natural Sciences. p. 183. Retrieved 3 December 2024.
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This article incorporates text from this source, which is in the public domain.
External links
- Pfeiffer, L. (1856). "Descriptions of twenty-three new species of Achatinella, collected by Mr. D. Frick in the Sandwich Islands; from Mr. Cuming's collection". Proceedings of the Zoological Society of London. 23 (297): 204. Retrieved 17 December 2024.
| Taxon identifiers | |
|---|---|
| Amastra umbilicata | |