Amastra subcornea

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Amastra subcornea
Amastra subcornea 001.jpg
Shell of Amastra subcornea (holotype)
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Order: Stylommatophora
Family: Amastridae
Genus: Amastra
Species:
A. subcornea
Binomial name
Amastra subcornea
Hyatt & Pilsbry, 1911
Synonyms

Amastra (Metamastra) subcorneaHyatt & Pilsbry, 1911 alternative representation

Contents

Amastra subcornea is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusc in the family Amastridae. [1]

Description

The length of the shell attains 12.5 mm, its diameter 6⅓ mm.

(Original description) The shell contains 6½ whorls. This subfossil shell is smaller than Amastra cornea but exhibits a similarly attenuated and biconcave outline near the apex. Its overall appearance resembles that of Leptachatina A. Gould, 1847, particularly due to the rapid expansion of the last three whorls. However, the apex lacks the blunt appearance typical of Leptachatina and does not exhibit the disproportionate growth rates between the nepionic and neanic stages observed in that genus.

The aperture is narrow, resulting from the contraction of the body whorl. The columella is perforated, though the opening is relatively small and nearly sealed in some specimens. The shell surface features prominent growth ridges, while the nepionic stage displays finer, transverse ridges.

The shell's characteristics are intermediate between those of † Amastra cornea(Newcomb, 1854) and the more primitive shells of the *Brevis* series found on the island of Oahu. This strongly suggests that it represents a transitional species, bridging the evolutionary gap between these groups. [2]

Distribution

This species is endemic to Hawaii, occurring on Oahu Island.

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References

  1. ↑ Amastra subcornea Hyatt & Pilsbry, 1911 . 4 December 2024. Retrieved through: World Register of Marine Species .
  2. ↑ 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. 189. Retrieved 3 December 2024.{{cite book}}: CS1 maint: multiple names: authors list (link)PD-icon.svg This article incorporates text from this source, which is in the public domain .
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